Merge pull request #23041 from 333fred/compound-expressions-conversions

Compound expressions conversions

src/Compilers/CSharp/Portable/CSharpExtensions.cs

@@ -706,6 +706,58 @@ public static Conversion GetConversion(this IConversionOperation conversionExpre
             }
         }
 
+        /// <summary>
+        /// Gets the underlying <see cref="Conversion"/> information from this <see cref="ICompoundAssignmentOperation"/>. This
+        /// conversion is applied before the operator is applied to the result of this conversion and <see cref="IAssignmentOperation.Value"/>.
+        /// </summary>
+        /// <remarks>
+        /// This compound assignment must have been created from C# code.
+        /// </remarks>
+        public static Conversion GetInConversion(this ICompoundAssignmentOperation compoundAssignment)
+        {
+            if (compoundAssignment == null)
+            {
+                throw new ArgumentNullException(nameof(compoundAssignment));
+            }
+
+            if (compoundAssignment is BaseCSharpCompoundAssignmentOperation csharpCompoundAssignment)
+            {
+                return csharpCompoundAssignment.InConversionInternal;
+            }
+            else
+            {
+                throw new ArgumentException(string.Format(CSharpResources.ICompoundAssignmentOperationIsNotCSharpCompoundAssignment,
+                                                          nameof(compoundAssignment)),
+                                            nameof(compoundAssignment));
+            }
+        }
+
+        /// <summary>
+        /// Gets the underlying <see cref="Conversion"/> information from this <see cref="ICompoundAssignmentOperation"/>. This
+        /// conversion is applied after the operator is applied, before the result is assigned to <see cref="IAssignmentOperation.Target"/>.
+        /// </summary>
+        /// <remarks>
+        /// This compound assignment must have been created from C# code.
+        /// </remarks>
+        public static Conversion GetOutConversion(this ICompoundAssignmentOperation compoundAssignment)
+        {
+            if (compoundAssignment == null)
+            {
+                throw new ArgumentNullException(nameof(compoundAssignment));
+            }
+
+            if (compoundAssignment is BaseCSharpCompoundAssignmentOperation csharpCompoundAssignemnt)
+            {
+                return csharpCompoundAssignemnt.OutConversionInternal;
+            }
+            else
+            {
+                throw new ArgumentException(string.Format(CSharpResources.ICompoundAssignmentOperationIsNotCSharpCompoundAssignment,
+                                                          nameof(compoundAssignment)),
+                                            nameof(compoundAssignment));
+            }
+        }
+
         public static Conversion GetSpeculativeConversion(this SemanticModel semanticModel, int position, ExpressionSyntax expression, SpeculativeBindingOption bindingOption)
         {
             var csmodel = semanticModel as CSharpSemanticModel;

src/Compilers/CSharp/Portable/CSharpResources.Designer.cs

@@ -10069,6 +10069,15 @@ internal class CSharpResources {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to {0} is not a valid C# compound assignment operation.
+        /// </summary>
+        internal static string ICompoundAssignmentOperationIsNotCSharpCompoundAssignment {
+            get {
+                return ResourceManager.GetString("ICompoundAssignmentOperationIsNotCSharpCompoundAssignment", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to {0} is not a valid C# conversion expression.
         /// </summary>

src/Compilers/CSharp/Portable/CSharpResources.resx

@@ -5207,4 +5207,7 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
   <data name="ERR_RefExtensionMustBeValueTypeOrConstrainedToOne" xml:space="preserve">
     <value>The first parameter of a 'ref' extension method '{0}' must be a value type or a generic type constrained to struct.</value>
   </data>
+  <data name="ICompoundAssignmentOperationIsNotCSharpCompoundAssignment" xml:space="preserve">
+    <value>{0} is not a valid C# compound assignment operation</value>
+  </data>
 </root>
\ No newline at end of file

src/Compilers/CSharp/Portable/Operations/CSharpCompoundAssignmentOperation.cs

+using System;
+using Microsoft.CodeAnalysis.Operations;
+
+namespace Microsoft.CodeAnalysis.CSharp
+{
+    internal abstract class BaseCSharpCompoundAssignmentOperation : BaseCompoundAssignmentExpression
+    {
+        protected BaseCSharpCompoundAssignmentOperation(Conversion inConversion, Conversion outConversion, Operations.BinaryOperatorKind operatorKind, bool isLifted, bool isChecked, IMethodSymbol operatorMethod, SemanticModel semanticModel, SyntaxNode syntax, ITypeSymbol type, Optional<object> constantValue, bool isImplicit) : base(operatorKind, isLifted, isChecked, operatorMethod, semanticModel, syntax, type, constantValue, isImplicit)
+        {
+            InConversionInternal = inConversion;
+            OutConversionInternal = outConversion;
+        }
+
+        internal Conversion InConversionInternal { get; }
+        internal Conversion OutConversionInternal { get; }
+
+        public override CommonConversion InConversion => InConversionInternal.ToCommonConversion();
+        public override CommonConversion OutConversion => OutConversionInternal.ToCommonConversion();
+    }
+
+    internal sealed class CSharpCompoundAssignmentOperation : BaseCSharpCompoundAssignmentOperation
+    {
+        public CSharpCompoundAssignmentOperation(IOperation target, IOperation value, Conversion inConversion, Conversion outConversion, Operations.BinaryOperatorKind operatorKind, bool isLifted, bool isChecked, IMethodSymbol operatorMethod, SemanticModel semanticModel, SyntaxNode syntax, ITypeSymbol type, Optional<object> constantValue, bool isImplicit) :
+            base(inConversion, outConversion, operatorKind, isLifted, isChecked, operatorMethod, semanticModel, syntax, type, constantValue, isImplicit)
+        {
+            TargetImpl = target;
+            ValueImpl = value;
+        }
+
+        protected override IOperation TargetImpl { get; }
+        protected override IOperation ValueImpl { get; }
+    }
+
+    internal sealed class LazyCSharpCompoundAssignmentOperation : BaseCSharpCompoundAssignmentOperation
+    {
+        private readonly Lazy<IOperation> _lazyTarget;
+        private readonly Lazy<IOperation> _lazyValue;
+        public LazyCSharpCompoundAssignmentOperation(Lazy<IOperation> target, Lazy<IOperation> value, Conversion inConversion, Conversion outConversion, Operations.BinaryOperatorKind operatorKind, bool isLifted, bool isChecked, IMethodSymbol operatorMethod, SemanticModel semanticModel, SyntaxNode syntax, ITypeSymbol type, Optional<object> constantValue, bool isImplicit) :
+            base(inConversion, outConversion, operatorKind, isLifted, isChecked, operatorMethod, semanticModel, syntax, type, constantValue, isImplicit)
+        {
+            _lazyTarget = target;
+            _lazyValue = value;
+        }
+
+        protected override IOperation TargetImpl => _lazyTarget.Value;
+        protected override IOperation ValueImpl => _lazyValue.Value;
+    }
+}

src/Compilers/CSharp/Portable/Operations/CSharpOperationCloner.cs

@@ -17,5 +17,11 @@ public override IOperation VisitConversion(IConversionOperation operation, objec
         {
             return new CSharpConversionExpression(Visit(operation.Operand), operation.GetConversion(), operation.IsTryCast, operation.IsChecked, ((Operation)operation).SemanticModel, operation.Syntax, operation.Type, operation.ConstantValue, operation.IsImplicit);
         }
+
+        public override IOperation VisitCompoundAssignment(ICompoundAssignmentOperation operation, object argument)
+        {
+            var compoundAssignment = (BaseCSharpCompoundAssignmentOperation)operation;
+            return new CSharpCompoundAssignmentOperation(Visit(operation.Target), Visit(operation.Value), compoundAssignment.InConversionInternal, compoundAssignment.OutConversionInternal, operation.OperatorKind, operation.IsLifted, operation.IsChecked, operation.OperatorMethod, ((Operation)operation).SemanticModel, operation.Syntax, operation.Type, operation.ConstantValue, operation.IsImplicit);
+        }
     }
 }

src/Compilers/CSharp/Portable/Operations/CSharpOperationFactory.cs

@@ -974,6 +974,8 @@ private ICompoundAssignmentOperation CreateBoundCompoundAssignmentOperatorOperat
             BinaryOperatorKind operatorKind = Helper.DeriveBinaryOperatorKind(boundCompoundAssignmentOperator.Operator.Kind);
             Lazy<IOperation> target = new Lazy<IOperation>(() => Create(boundCompoundAssignmentOperator.Left));
             Lazy<IOperation> value = new Lazy<IOperation>(() => Create(boundCompoundAssignmentOperator.Right));
+            Conversion inConversion = boundCompoundAssignmentOperator.LeftConversion;
+            Conversion outConversion = boundCompoundAssignmentOperator.FinalConversion;
             bool isLifted = boundCompoundAssignmentOperator.Operator.Kind.IsLifted();
             bool isChecked = boundCompoundAssignmentOperator.Operator.Kind.IsChecked();
             IMethodSymbol operatorMethod = boundCompoundAssignmentOperator.Operator.Method;
@@ -981,7 +983,7 @@ private ICompoundAssignmentOperation CreateBoundCompoundAssignmentOperatorOperat
             ITypeSymbol type = boundCompoundAssignmentOperator.Type;
             Optional<object> constantValue = ConvertToOptional(boundCompoundAssignmentOperator.ConstantValue);
             bool isImplicit = boundCompoundAssignmentOperator.WasCompilerGenerated;
-            return new LazyCompoundAssignmentExpression(operatorKind, isLifted, isChecked, target, value, operatorMethod, _semanticModel, syntax, type, constantValue, isImplicit);
+            return new LazyCSharpCompoundAssignmentOperation(target, value, inConversion, outConversion, operatorKind, isLifted, isChecked, operatorMethod, _semanticModel, syntax, type, constantValue, isImplicit);
         }
 
         private IIncrementOrDecrementOperation CreateBoundIncrementOperatorOperation(BoundIncrementOperator boundIncrementOperator)

src/Compilers/CSharp/Portable/PublicAPI.Unshipped.txt

@@ -5,4 +5,6 @@ Microsoft.CodeAnalysis.CSharp.Syntax.RefTypeSyntax.ReadOnlyKeyword.get -> Micros
 Microsoft.CodeAnalysis.CSharp.Syntax.RefTypeSyntax.Update(Microsoft.CodeAnalysis.SyntaxToken refKeyword, Microsoft.CodeAnalysis.SyntaxToken readOnlyKeyword, Microsoft.CodeAnalysis.CSharp.Syntax.TypeSyntax type) -> Microsoft.CodeAnalysis.CSharp.Syntax.RefTypeSyntax
 Microsoft.CodeAnalysis.CSharp.Syntax.RefTypeSyntax.WithReadOnlyKeyword(Microsoft.CodeAnalysis.SyntaxToken readOnlyKeyword) -> Microsoft.CodeAnalysis.CSharp.Syntax.RefTypeSyntax
 static Microsoft.CodeAnalysis.CSharp.CSharpExtensions.GetConversion(this Microsoft.CodeAnalysis.Operations.IConversionOperation conversionExpression) -> Microsoft.CodeAnalysis.CSharp.Conversion
+static Microsoft.CodeAnalysis.CSharp.CSharpExtensions.GetInConversion(this Microsoft.CodeAnalysis.Operations.ICompoundAssignmentOperation compoundAssignment) -> Microsoft.CodeAnalysis.CSharp.Conversion
+static Microsoft.CodeAnalysis.CSharp.CSharpExtensions.GetOutConversion(this Microsoft.CodeAnalysis.Operations.ICompoundAssignmentOperation compoundAssignment) -> Microsoft.CodeAnalysis.CSharp.Conversion
 static Microsoft.CodeAnalysis.CSharp.SyntaxFactory.RefType(Microsoft.CodeAnalysis.SyntaxToken refKeyword, Microsoft.CodeAnalysis.SyntaxToken readOnlyKeyword, Microsoft.CodeAnalysis.CSharp.Syntax.TypeSyntax type) -> Microsoft.CodeAnalysis.CSharp.Syntax.RefTypeSyntax
\ No newline at end of file

src/Compilers/CSharp/Test/Semantic/IOperation/IOperationTests_ICompoundAssignmentOperation.cs

+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+
+using System;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Operations;
+using Microsoft.CodeAnalysis.Test.Utilities;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.CSharp.UnitTests
+{
+    public partial class IOperationTests : SemanticModelTestBase
+    {
+        [CompilerTrait(CompilerFeature.IOperation)]
+        [Fact]
+        public void ICompoundAssignment_NullArgumentToGetConversionThrows()
+        {
+            ICompoundAssignmentOperation nullAssignment = null;
+            Assert.Throws<ArgumentNullException>("compoundAssignment", () => nullAssignment.GetInConversion());
+            Assert.Throws<ArgumentNullException>("compoundAssignment", () => nullAssignment.GetOutConversion());
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation)]
+        [Fact]
+        public void ICompoundAssignment_BinaryOperatorInOutConversion()
+        {
+            string source = @"
+class C
+{
+    static void M()
+    {
+        var c = new C();
+        var x = 1;
+        /*<bind>*/c += x/*</bind>*/;
+    }
+
+    public static implicit operator C(int i)
+    {
+        return null;
+    }
+
+    public static implicit operator int(C c)
+    {
+        return 0;
+    }
+}
+";
+            string expectedOperationTree = @"
+ICompoundAssignmentOperation (BinaryOperatorKind.Add) (OperationKind.CompoundAssignment, Type: C) (Syntax: 'c += x')
+  InConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: System.Int32 C.op_Implicit(C c))
+  OutConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: C C.op_Implicit(System.Int32 i))
+  Left: 
+    ILocalReferenceOperation: c (OperationKind.LocalReference, Type: C) (Syntax: 'c')
+  Right: 
+    ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            VerifyOperationTreeAndDiagnosticsForTest<AssignmentExpressionSyntax>(source, expectedOperationTree, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation)]
+        [Fact]
+        public void ICompoundAssignment_BinaryOperatorInConversion_InvalidMissingOutConversion()
+        {
+            string source = @"
+class C
+{
+    static void M()
+    {
+        var c = new C();
+        var x = 1;
+        /*<bind>*/c += x/*</bind>*/;
+    }
+
+    public static implicit operator int(C c)
+    {
+        return 0;
+    }
+}
+";
+            string expectedOperationTree = @"
+ICompoundAssignmentOperation (BinaryOperatorKind.Add) (OperationKind.CompoundAssignment, Type: C, IsInvalid) (Syntax: 'c += x')
+  InConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: System.Int32 C.op_Implicit(C c))
+  OutConversion: CommonConversion (Exists: False, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+  Left: 
+    ILocalReferenceOperation: c (OperationKind.LocalReference, Type: C, IsInvalid) (Syntax: 'c')
+  Right: 
+    ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'x')
+";
+            var expectedDiagnostics = new DiagnosticDescription[] {
+                // CS0029: Cannot implicitly convert type 'int' to 'C'
+                //         /*<bind>*/c += x/*</bind>*/;
+                Diagnostic(ErrorCode.ERR_NoImplicitConv, "c += x").WithArguments("int", "C").WithLocation(8, 19)
+            };
+
+            VerifyOperationTreeAndDiagnosticsForTest<AssignmentExpressionSyntax>(source, expectedOperationTree, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation)]
+        [Fact]
+        public void ICompoundAssignment_BinaryOperatorOutConversion_InvalidMissingInConversion()
+        {
+            string source = @"
+class C
+{
+    static void M()
+    {
+        var c = new C();
+        var x = 1;
+        /*<bind>*/c += x/*</bind>*/;
+    }
+
+    public static implicit operator C(int i)
+    {
+        return null;
+    }
+}
+";
+            string expectedOperationTree = @"
+ICompoundAssignmentOperation (BinaryOperatorKind.None) (OperationKind.CompoundAssignment, Type: ?, IsInvalid) (Syntax: 'c += x')
+  InConversion: CommonConversion (Exists: False, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+  OutConversion: CommonConversion (Exists: False, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+  Left: 
+    ILocalReferenceOperation: c (OperationKind.LocalReference, Type: C, IsInvalid) (Syntax: 'c')
+  Right: 
+    ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'x')
+";
+            var expectedDiagnostics = new DiagnosticDescription[] {
+                // CS0019: Operator '+=' cannot be applied to operands of type 'C' and 'int'
+                //         /*<bind>*/c += x/*</bind>*/;
+                Diagnostic(ErrorCode.ERR_BadBinaryOps, "c += x").WithArguments("+=", "C", "int").WithLocation(8, 19)
+            };
+
+            VerifyOperationTreeAndDiagnosticsForTest<AssignmentExpressionSyntax>(source, expectedOperationTree, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation)]
+        [Fact]
+        public void ICompoundAssignment_UserDefinedBinaryOperator_InConversion()
+        {
+            string source = @"
+class C
+{
+    static void M()
+    {
+        var c = new C();
+        var x = 1;
+        /*<bind>*/c += x/*</bind>*/;
+    }
+
+    public static implicit operator C(int i)
+    {
+        return null;
+    }
+
+    public static implicit operator int(C c)
+    {
+        return 0;
+    }
+
+    public static C operator +(int c1, C c2)
+    {
+        return null;
+    }
+}
+";
+            string expectedOperationTree = @"
+ICompoundAssignmentOperation (BinaryOperatorKind.Add) (OperatorMethod: C C.op_Addition(System.Int32 c1, C c2)) (OperationKind.CompoundAssignment, Type: C) (Syntax: 'c += x')
+  InConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: System.Int32 C.op_Implicit(C c))
+  OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+  Left: 
+    ILocalReferenceOperation: c (OperationKind.LocalReference, Type: C) (Syntax: 'c')
+  Right: 
+    IConversionOperation (TryCast: False, Unchecked) (OperatorMethod: C C.op_Implicit(System.Int32 i)) (OperationKind.Conversion, Type: C, IsImplicit) (Syntax: 'x')
+      Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: C C.op_Implicit(System.Int32 i))
+      Operand: 
+        ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            VerifyOperationTreeAndDiagnosticsForTest<AssignmentExpressionSyntax>(source, expectedOperationTree, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation)]
+        [Fact]
+        public void ICompoundAssignment_UserDefinedBinaryOperator_OutConversion()
+        {
+            string source = @"
+class C
+{
+    static void M()
+    {
+        var c = new C();
+        var x = 1;
+        /*<bind>*/c += x/*</bind>*/;
+    }
+
+    public static implicit operator C(int i)
+    {
+        return null;
+    }
+
+    public static implicit operator int(C c)
+    {
+        return 0;
+    }
+
+    public static int operator +(C c1, C c2)
+    {
+        return 0;
+    }
+}
+";
+            string expectedOperationTree = @"
+ICompoundAssignmentOperation (BinaryOperatorKind.Add) (OperatorMethod: System.Int32 C.op_Addition(C c1, C c2)) (OperationKind.CompoundAssignment, Type: C) (Syntax: 'c += x')
+  InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+  OutConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: C C.op_Implicit(System.Int32 i))
+  Left: 
+    ILocalReferenceOperation: c (OperationKind.LocalReference, Type: C) (Syntax: 'c')
+  Right: 
+    IConversionOperation (TryCast: False, Unchecked) (OperatorMethod: C C.op_Implicit(System.Int32 i)) (OperationKind.Conversion, Type: C, IsImplicit) (Syntax: 'x')
+      Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: C C.op_Implicit(System.Int32 i))
+      Operand: 
+        ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            VerifyOperationTreeAndDiagnosticsForTest<AssignmentExpressionSyntax>(source, expectedOperationTree, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation)]
+        [Fact]
+        public void ICompoundAssignment_UserDefinedBinaryOperator_InOutConversion()
+        {
+            string source = @"
+class C
+{
+    static void M()
+    {
+        var c = new C();
+        var x = 1;
+        /*<bind>*/c += x/*</bind>*/;
+    }
+
+    public static implicit operator C(int i)
+    {
+        return null;
+    }
+
+    public static implicit operator int(C c)
+    {
+        return 0;
+    }
+
+    public static int operator +(int c1, C c2)
+    {
+        return 0;
+    }
+}
+";
+            string expectedOperationTree = @"
+ICompoundAssignmentOperation (BinaryOperatorKind.Add) (OperatorMethod: System.Int32 C.op_Addition(System.Int32 c1, C c2)) (OperationKind.CompoundAssignment, Type: C) (Syntax: 'c += x')
+  InConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: System.Int32 C.op_Implicit(C c))
+  OutConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: C C.op_Implicit(System.Int32 i))
+  Left: 
+    ILocalReferenceOperation: c (OperationKind.LocalReference, Type: C) (Syntax: 'c')
+  Right: 
+    IConversionOperation (TryCast: False, Unchecked) (OperatorMethod: C C.op_Implicit(System.Int32 i)) (OperationKind.Conversion, Type: C, IsImplicit) (Syntax: 'x')
+      Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: C C.op_Implicit(System.Int32 i))
+      Operand: 
+        ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            VerifyOperationTreeAndDiagnosticsForTest<AssignmentExpressionSyntax>(source, expectedOperationTree, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation)]
+        [Fact]
+        public void ICompoundAssignment_UserDefinedBinaryOperator_InvalidMissingInConversion()
+        {
+            string source = @"
+class C
+{
+    static void M()
+    {
+        var c = new C();
+        var x = 1;
+        /*<bind>*/c += x/*</bind>*/;
+    }
+
+    public static implicit operator C(int i)
+    {
+        return null;
+    }
+
+    public static int operator +(int c1, C c2)
+    {
+        return 0;
+    }
+}
+";
+            string expectedOperationTree = @"
+ICompoundAssignmentOperation (BinaryOperatorKind.None) (OperationKind.CompoundAssignment, Type: ?, IsInvalid) (Syntax: 'c += x')
+  InConversion: CommonConversion (Exists: False, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+  OutConversion: CommonConversion (Exists: False, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+  Left: 
+    ILocalReferenceOperation: c (OperationKind.LocalReference, Type: C, IsInvalid) (Syntax: 'c')
+  Right: 
+    ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'x')
+";
+            var expectedDiagnostics = new DiagnosticDescription[] {
+                // CS0019: Operator '+=' cannot be applied to operands of type 'C' and 'int'
+                //         /*<bind>*/c += x/*</bind>*/;
+                Diagnostic(ErrorCode.ERR_BadBinaryOps, "c += x").WithArguments("+=", "C", "int").WithLocation(8, 19)
+            };
+
+            VerifyOperationTreeAndDiagnosticsForTest<AssignmentExpressionSyntax>(source, expectedOperationTree, expectedDiagnostics);
+        }
+
+        [CompilerTrait(CompilerFeature.IOperation)]
+        [Fact]
+        public void ICompoundAssignment_UserDefinedBinaryOperator_InvalidMissingOutConversion()
+        {
+            string source = @"
+class C
+{
+    static void M()
+    {
+        var c = new C();
+        var x = 1;
+        /*<bind>*/c += x/*</bind>*/;
+    }
+
+    public static implicit operator int(C c)
+    {
+        return 0;
+    }
+
+    public static int operator +(int c1, C c2)
+    {
+        return 0;
+    }
+}
+";
+            string expectedOperationTree = @"
+ICompoundAssignmentOperation (BinaryOperatorKind.Add) (OperationKind.CompoundAssignment, Type: C, IsInvalid) (Syntax: 'c += x')
+  InConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: System.Int32 C.op_Implicit(C c))
+  OutConversion: CommonConversion (Exists: False, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+  Left: 
+    ILocalReferenceOperation: c (OperationKind.LocalReference, Type: C, IsInvalid) (Syntax: 'c')
+  Right: 
+    ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'x')
+";
+            var expectedDiagnostics = new DiagnosticDescription[] {
+                // CS0029: Cannot implicitly convert type 'int' to 'C'
+                //         /*<bind>*/c += x/*</bind>*/;
+                Diagnostic(ErrorCode.ERR_NoImplicitConv, "c += x").WithArguments("int", "C").WithLocation(8, 19)
+            };
+
+            VerifyOperationTreeAndDiagnosticsForTest<AssignmentExpressionSyntax>(source, expectedOperationTree, expectedDiagnostics);
+        }
+    }
+}

src/Compilers/CSharp/Test/Semantic/IOperation/IOperationTests_IWhileUntilLoopStatement.cs

@@ -45,6 +45,8 @@ static void Main()
       IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'sum += ids[i];')
         Expression: 
           ICompoundAssignmentOperation (BinaryOperatorKind.Add) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'sum += ids[i]')
+            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Left: 
               ILocalReferenceOperation: sum (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'sum')
             Right: 
@@ -100,6 +102,8 @@ static int SumWhile()
       IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'sum += i;')
         Expression: 
           ICompoundAssignmentOperation (BinaryOperatorKind.Add) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'sum += i')
+            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Left: 
               ILocalReferenceOperation: sum (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'sum')
             Right: 

src/Compilers/CSharp/Test/Semantic/Semantics/OperatorTests.cs

@@ -2043,6 +2043,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a += b;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Add) (OperatorMethod: S S.op_Addition(S x, S y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a += b')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2050,6 +2052,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a -= c;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Subtract) (OperatorMethod: S S.op_Subtraction(S x, S y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a -= c')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2057,6 +2061,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a *= d;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Multiply) (OperatorMethod: S S.op_Multiply(S x, S y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a *= d')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2064,6 +2070,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a /= e;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Divide) (OperatorMethod: S S.op_Division(S x, S y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a /= e')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2071,6 +2079,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a %= f;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Remainder) (OperatorMethod: S S.op_Modulus(S x, S y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a %= f')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2078,6 +2088,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a <<= 10;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.LeftShift) (OperatorMethod: S S.op_LeftShift(S x, System.Int32 y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a <<= 10')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2085,6 +2097,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a >>= 20;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.RightShift) (OperatorMethod: S S.op_RightShift(S x, System.Int32 y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a >>= 20')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2092,6 +2106,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a &= g;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.And) (OperatorMethod: S S.op_BitwiseAnd(S x, S y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a &= g')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2099,6 +2115,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a |= h;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Or) (OperatorMethod: S S.op_BitwiseOr(S x, S y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a |= h')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2106,6 +2124,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a ^= i;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.ExclusiveOr) (OperatorMethod: S S.op_ExclusiveOr(S x, S y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a ^= i')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2162,6 +2182,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a += b;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Add) (OperatorMethod: S S.op_Addition(S x, S y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a += b')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2169,6 +2191,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a -= c;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Subtract) (OperatorMethod: S S.op_Subtraction(S x, S y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a -= c')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2176,6 +2200,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a *= d;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Multiply) (OperatorMethod: S S.op_Multiply(S x, S y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a *= d')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2183,6 +2209,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a /= e;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Divide) (OperatorMethod: S S.op_Division(S x, S y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a /= e')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2190,6 +2218,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a %= f;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Remainder) (OperatorMethod: S S.op_Modulus(S x, S y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a %= f')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2197,6 +2227,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a <<= 10;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.LeftShift) (OperatorMethod: S S.op_LeftShift(S x, System.Int32 y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a <<= 10')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2204,6 +2236,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a >>= 20;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.RightShift) (OperatorMethod: S S.op_RightShift(S x, System.Int32 y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a >>= 20')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2211,6 +2245,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a &= g;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.And) (OperatorMethod: S S.op_BitwiseAnd(S x, S y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a &= g')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2218,6 +2254,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a |= h;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Or) (OperatorMethod: S S.op_BitwiseOr(S x, S y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a |= h')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2225,6 +2263,8 @@ static void Main(S a, S b, S c, S d, S e, S f, S g, S h, S i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a ^= i;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.ExclusiveOr) (OperatorMethod: S S.op_ExclusiveOr(S x, S y)) (OperationKind.CompoundAssignment, Type: S) (Syntax: 'a ^= i')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: S) (Syntax: 'a')
         Right: 
@@ -2262,6 +2302,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a += b;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Add) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a += b')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
         Right: 
@@ -2269,6 +2311,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a -= c;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Subtract) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a -= c')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
         Right: 
@@ -2276,6 +2320,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a *= d;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Multiply) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a *= d')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
         Right: 
@@ -2283,6 +2329,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a /= e;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Divide) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a /= e')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
         Right: 
@@ -2290,6 +2338,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a %= f;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Remainder) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a %= f')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
         Right: 
@@ -2297,6 +2347,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a <<= 10;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.LeftShift) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a <<= 10')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
         Right: 
@@ -2304,6 +2356,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a >>= 20;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.RightShift) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a >>= 20')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
         Right: 
@@ -2311,6 +2365,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a &= g;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.And) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a &= g')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
         Right: 
@@ -2318,6 +2374,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a |= h;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Or) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a |= h')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
         Right: 
@@ -2325,6 +2383,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a ^= i;')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.ExclusiveOr) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a ^= i')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
         Right: 
@@ -2350,6 +2410,8 @@ static void M(int a, int? b)
 ";
             string expectedOperationTree = @"
 ICompoundAssignmentOperation (BinaryOperatorKind.Add, IsLifted) (OperationKind.CompoundAssignment, Type: System.Int32, IsInvalid) (Syntax: 'a += b')
+  InConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+  OutConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
   Left: 
     IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32, IsInvalid) (Syntax: 'a')
   Right: 
@@ -2395,6 +2457,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
     IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a += b;')
       Expression: 
         ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a += b')
+          InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+          OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
           Left: 
             IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
           Right: 
@@ -2402,6 +2466,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
     IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a -= c;')
       Expression: 
         ICompoundAssignmentOperation (BinaryOperatorKind.Subtract, Checked) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a -= c')
+          InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+          OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
           Left: 
             IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
           Right: 
@@ -2409,6 +2475,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
     IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a *= d;')
       Expression: 
         ICompoundAssignmentOperation (BinaryOperatorKind.Multiply, Checked) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a *= d')
+          InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+          OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
           Left: 
             IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
           Right: 
@@ -2416,6 +2484,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
     IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a /= e;')
       Expression: 
         ICompoundAssignmentOperation (BinaryOperatorKind.Divide, Checked) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a /= e')
+          InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+          OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
           Left: 
             IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
           Right: 
@@ -2423,6 +2493,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
     IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a %= f;')
       Expression: 
         ICompoundAssignmentOperation (BinaryOperatorKind.Remainder) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a %= f')
+          InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+          OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
           Left: 
             IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
           Right: 
@@ -2430,6 +2502,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
     IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a <<= 10;')
       Expression: 
         ICompoundAssignmentOperation (BinaryOperatorKind.LeftShift) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a <<= 10')
+          InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+          OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
           Left: 
             IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
           Right: 
@@ -2437,6 +2511,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
     IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a >>= 20;')
       Expression: 
         ICompoundAssignmentOperation (BinaryOperatorKind.RightShift) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a >>= 20')
+          InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+          OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
           Left: 
             IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
           Right: 
@@ -2444,6 +2520,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
     IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a &= g;')
       Expression: 
         ICompoundAssignmentOperation (BinaryOperatorKind.And) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a &= g')
+          InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+          OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
           Left: 
             IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
           Right: 
@@ -2451,6 +2529,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
     IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a |= h;')
       Expression: 
         ICompoundAssignmentOperation (BinaryOperatorKind.Or) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a |= h')
+          InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+          OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
           Left: 
             IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
           Right: 
@@ -2458,6 +2538,8 @@ static void M(int a, int b, int c, int d, int e, int f, int g, int h, int i)
     IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a ^= i;')
       Expression: 
         ICompoundAssignmentOperation (BinaryOperatorKind.ExclusiveOr) (OperationKind.CompoundAssignment, Type: System.Int32) (Syntax: 'a ^= i')
+          InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+          OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
           Left: 
             IParameterReferenceOperation: a (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'a')
           Right: 

src/Compilers/Core/Portable/Generated/Operations.xml.Generated.cs

@@ -1127,6 +1127,8 @@ internal abstract partial class BaseCompoundAssignmentExpression : AssignmentExp
         /// Operator method used by the operation, null if the operation does not use an operator method.
         /// </summary>
         public IMethodSymbol OperatorMethod { get; }
+        public abstract CommonConversion InConversion { get; }
+        public abstract CommonConversion OutConversion { get; }
 
         public override void Accept(OperationVisitor visitor)
         {
@@ -1138,39 +1140,6 @@ public override void Accept(OperationVisitor visitor)
         }
     }
 
-    /// <summary>
-    /// Represents an assignment expression that includes a binary operation.
-    /// </summary>
-    internal sealed partial class CompoundAssignmentExpression : BaseCompoundAssignmentExpression, ICompoundAssignmentOperation
-    {
-        public CompoundAssignmentExpression(BinaryOperatorKind operatorKind, bool isLifted, bool isChecked, IOperation target, IOperation value, IMethodSymbol operatorMethod, SemanticModel semanticModel, SyntaxNode syntax, ITypeSymbol type, Optional<object> constantValue, bool isImplicit) :
-            base(operatorKind, isLifted, isChecked, operatorMethod, semanticModel, syntax, type, constantValue, isImplicit)
-        {
-            TargetImpl = target;
-            ValueImpl = value;
-        }
-        protected override IOperation TargetImpl { get; }
-        protected override IOperation ValueImpl { get; }
-    }
-
-    /// <summary>
-    /// Represents an assignment expression that includes a binary operation.
-    /// </summary>
-    internal sealed partial class LazyCompoundAssignmentExpression : BaseCompoundAssignmentExpression, ICompoundAssignmentOperation
-    {
-        private readonly Lazy<IOperation> _lazyTarget;
-        private readonly Lazy<IOperation> _lazyValue;
-
-        public LazyCompoundAssignmentExpression(BinaryOperatorKind operatorKind, bool isLifted, bool isChecked, Lazy<IOperation> target, Lazy<IOperation> value, IMethodSymbol operatorMethod, SemanticModel semanticModel, SyntaxNode syntax, ITypeSymbol type, Optional<object> constantValue, bool isImplicit) :
-            base(operatorKind, isLifted, isChecked, operatorMethod, semanticModel, syntax, type, constantValue, isImplicit)
-        {
-            _lazyTarget = target ?? throw new System.ArgumentNullException(nameof(target));
-            _lazyValue = value ?? throw new System.ArgumentNullException(nameof(value));
-        }
-        protected override IOperation TargetImpl => _lazyTarget.Value;
-        protected override IOperation ValueImpl => _lazyValue.Value;
-    }
-
     /// <summary>
     /// Represents an expression that includes a ? or ?. conditional access instance expression.
     /// </summary>

src/Compilers/Core/Portable/Operations/ICompoundAssignmentOperation.cs

@@ -35,5 +35,16 @@ public interface ICompoundAssignmentOperation : IAssignmentOperation
         /// <code>true</code> if overflow checking is performed for the arithmetic operation.
         /// </summary>
         bool IsChecked { get; }
+
+        /// <summary>
+        /// Conversion applied to <see cref="IAssignmentOperation.Target"/> before the operation occurs.
+        /// </summary>
+        CommonConversion InConversion { get; }
+
+        /// <summary>
+        /// Conversion applied to the result of the binary operation, before it is assigned back to
+        /// <see cref="IAssignmentOperation.Target"/>.
+        /// </summary>
+        CommonConversion OutConversion { get; }
     }
 }

src/Compilers/Core/Portable/Operations/OperationCloner.cs

@@ -385,11 +385,6 @@ public override IOperation VisitDeclarationExpression(IDeclarationExpressionOper
             return new DeclarationExpression(Visit(operation.Expression), ((Operation)operation).SemanticModel, operation.Syntax, operation.Type, operation.ConstantValue, operation.IsImplicit);
         }
 
-        public override IOperation VisitCompoundAssignment(ICompoundAssignmentOperation operation, object argument)
-        {
-            return new CompoundAssignmentExpression(operation.OperatorKind, operation.IsLifted, operation.IsChecked, Visit(operation.Target), Visit(operation.Value), operation.OperatorMethod, ((Operation)operation).SemanticModel, operation.Syntax, operation.Type, operation.ConstantValue, operation.IsImplicit);
-        }
-
         public override IOperation VisitIncrementOrDecrement(IIncrementOrDecrementOperation operation, object argument)
         {
             bool isDecrement = operation.Kind == OperationKind.Decrement;

src/Compilers/Core/Portable/Operations/OperationFactory.cs

@@ -32,25 +32,6 @@ public static IExpressionStatementOperation CreateSimpleAssignmentExpressionStat
             return new ExpressionStatement(expression, semanticModel, syntax, type: null, constantValue: default(Optional<object>), isImplicit: isImplicit);
         }
 
-        public static IExpressionStatementOperation CreateCompoundAssignmentExpressionStatement(
-            IOperation target, IOperation value, BinaryOperatorKind operatorKind, bool isLifted, bool isChecked, IMethodSymbol operatorMethod, SemanticModel semanticModel, SyntaxNode syntax, bool isImplicit)
-        {
-            var expression = new CompoundAssignmentExpression(
-                     operatorKind,
-                     isLifted,
-                     isChecked,
-                     target,
-                     value,
-                     operatorMethod,
-                     semanticModel,
-                     syntax,
-                     target.Type,
-                     default(Optional<object>),
-                     isImplicit);
-
-            return new ExpressionStatement(expression, semanticModel, syntax, type: null, constantValue: default(Optional<object>), isImplicit: isImplicit);
-        }
-
         public static ILiteralOperation CreateLiteralExpression(long value, ITypeSymbol resultType, SemanticModel semanticModel, SyntaxNode syntax, bool isImplicit)
         {
             return new LiteralExpression(semanticModel, syntax, resultType, constantValue: new Optional<object>(value), isImplicit: isImplicit);

src/Compilers/Core/Portable/PublicAPI.Unshipped.txt

@@ -245,10 +245,12 @@ Microsoft.CodeAnalysis.Operations.ICollectionElementInitializerOperation.AddMeth
 Microsoft.CodeAnalysis.Operations.ICollectionElementInitializerOperation.Arguments.get -> System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.IOperation>
 Microsoft.CodeAnalysis.Operations.ICollectionElementInitializerOperation.IsDynamic.get -> bool
 Microsoft.CodeAnalysis.Operations.ICompoundAssignmentOperation
+Microsoft.CodeAnalysis.Operations.ICompoundAssignmentOperation.InConversion.get -> Microsoft.CodeAnalysis.Operations.CommonConversion
 Microsoft.CodeAnalysis.Operations.ICompoundAssignmentOperation.IsChecked.get -> bool
 Microsoft.CodeAnalysis.Operations.ICompoundAssignmentOperation.IsLifted.get -> bool
 Microsoft.CodeAnalysis.Operations.ICompoundAssignmentOperation.OperatorKind.get -> Microsoft.CodeAnalysis.Operations.BinaryOperatorKind
 Microsoft.CodeAnalysis.Operations.ICompoundAssignmentOperation.OperatorMethod.get -> Microsoft.CodeAnalysis.IMethodSymbol
+Microsoft.CodeAnalysis.Operations.ICompoundAssignmentOperation.OutConversion.get -> Microsoft.CodeAnalysis.Operations.CommonConversion
 Microsoft.CodeAnalysis.Operations.IConditionalAccessInstanceOperation
 Microsoft.CodeAnalysis.Operations.IConditionalAccessOperation
 Microsoft.CodeAnalysis.Operations.IConditionalAccessOperation.Operation.get -> Microsoft.CodeAnalysis.IOperation

src/Compilers/VisualBasic/Portable/Binding/Binder_Statements.vb

@@ -1997,16 +1997,17 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
 
             Dim placeholder As BoundCompoundAssignmentTargetPlaceholder = Nothing
 
-            If Not isError Then
-                placeholder = New BoundCompoundAssignmentTargetPlaceholder(left.Syntax, targetType).MakeCompilerGenerated()
-                right = BindBinaryOperator(node, placeholder, right, operatorTokenKind, operatorKind, isOperandOfConditionalBranch:=False, diagnostics:=diagnostics)
-                right.SetWasCompilerGenerated()
-                right = ApplyImplicitConversion(node, targetType, right, diagnostics)
-            Else
-                ' Try to reclassify 'right' if we still can.
-                right = MakeRValueAndIgnoreDiagnostics(right)
+            If isError Then
+                ' Suppress all additional diagnostics. This ensures that we still generate the appropriate tree shape
+                ' even in error scenarios
+                diagnostics = New DiagnosticBag()
             End If
 
+            placeholder = New BoundCompoundAssignmentTargetPlaceholder(left.Syntax, targetType).MakeCompilerGenerated()
+            right = BindBinaryOperator(node, placeholder, right, operatorTokenKind, operatorKind, isOperandOfConditionalBranch:=False, diagnostics:=diagnostics)
+            right.SetWasCompilerGenerated()
+            right = ApplyImplicitConversion(node, targetType, right, diagnostics)
+
             left = left.SetGetSetAccessKindIfAppropriate()
 
             Return New BoundAssignmentOperator(node, left, placeholder, right, False, hasErrors:=isError)

src/Compilers/VisualBasic/Portable/BoundTree/Expression.vb

@@ -11,6 +11,14 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
         End Property
     End Class
 
+    Partial Friend Class BoundAssignmentOperator
+        Protected Overrides ReadOnly Property Children As ImmutableArray(Of BoundNode)
+            Get
+                Return ImmutableArray.Create(Of BoundNode)(Me.Left, Me.Right)
+            End Get
+        End Property
+    End Class
+
     Partial Friend Class BoundDelegateCreationExpression
         Protected Overrides ReadOnly Property Children As ImmutableArray(Of BoundNode)
             Get

src/Compilers/VisualBasic/Portable/Operations/VisualBasicCompoundAssigmentOperation.vb

+' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+
+Imports System.Runtime.CompilerServices
+Imports Microsoft.CodeAnalysis.Operations
+
+Namespace Microsoft.CodeAnalysis.VisualBasic
+    Friend MustInherit Class BaseVisualBasicCompoundAssignmentOperation
+        Inherits BaseCompoundAssignmentExpression
+
+        Protected Sub New(inConversion As Conversion, outConversion As Conversion, operatorKind As Operations.BinaryOperatorKind, isLifted As Boolean, isChecked As Boolean, operatorMethod As IMethodSymbol, semanticModel As SemanticModel, syntax As SyntaxNode, type As ITypeSymbol, constantValue As [Optional](Of Object), isImplicit As Boolean)
+            MyBase.New(operatorKind, isLifted, isChecked, operatorMethod, semanticModel, syntax, type, constantValue, isImplicit)
+            InConversionInternal = inConversion
+            OutConversionInternal = outConversion
+        End Sub
+
+        Friend ReadOnly Property InConversionInternal As Conversion
+        Friend ReadOnly Property OutConversionInternal As Conversion
+
+        Public Overrides ReadOnly Property InConversion As CommonConversion
+            Get
+                Return InConversionInternal.ToCommonConversion()
+            End Get
+        End Property
+
+        Public Overrides ReadOnly Property OutConversion As CommonConversion
+            Get
+                Return OutConversionInternal.ToCommonConversion()
+            End Get
+        End Property
+    End Class
+
+    Friend NotInheritable Class VisualBasicCompoundAssignmentOperation
+        Inherits BaseVisualBasicCompoundAssignmentOperation
+
+        Public Sub New(target As IOperation, value As IOperation, inConversion As Conversion, outConversion As Conversion, operatorKind As Operations.BinaryOperatorKind, isLifted As Boolean, isChecked As Boolean, operatorMethod As IMethodSymbol, semanticModel As SemanticModel, syntax As SyntaxNode, type As ITypeSymbol, constantValue As [Optional](Of Object), isImplicit As Boolean)
+            MyBase.New(inConversion, outConversion, operatorKind, isLifted, isChecked, operatorMethod, semanticModel, syntax, type, constantValue, isImplicit)
+
+            TargetImpl = target
+            ValueImpl = value
+        End Sub
+
+        Protected Overrides ReadOnly Property TargetImpl As IOperation
+
+        Protected Overrides ReadOnly Property ValueImpl As IOperation
+    End Class
+
+    Friend NotInheritable Class LazyVisualBasicCompoundAssignmentOperation
+        Inherits BaseVisualBasicCompoundAssignmentOperation
+
+        Private ReadOnly _lazyTarget As Lazy(Of IOperation)
+        Private ReadOnly _lazyValue As Lazy(Of IOperation)
+
+        Public Sub New(target As Lazy(Of IOperation), value As Lazy(Of IOperation), inConversion As Conversion, outConversion As Conversion, operatorKind As Operations.BinaryOperatorKind, isLifted As Boolean, isChecked As Boolean, operatorMethod As IMethodSymbol, semanticModel As SemanticModel, syntax As SyntaxNode, type As ITypeSymbol, constantValue As [Optional](Of Object), isImplicit As Boolean)
+            MyBase.New(inConversion, outConversion, operatorKind, isLifted, isChecked, operatorMethod, semanticModel, syntax, type, constantValue, isImplicit)
+
+            _lazyTarget = target
+            _lazyValue = value
+        End Sub
+
+        Protected Overrides ReadOnly Property TargetImpl As IOperation
+            Get
+                Return _lazyTarget.Value
+            End Get
+        End Property
+
+        Protected Overrides ReadOnly Property ValueImpl As IOperation
+            Get
+                Return _lazyValue.Value
+            End Get
+        End Property
+    End Class
+End Namespace

src/Compilers/VisualBasic/Portable/Operations/VisualBasicOperationCloner.vb

@@ -14,5 +14,10 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
         Public Overrides Function VisitConversion(operation As IConversionOperation, argument As Object) As IOperation
             Return New VisualBasicConversionExpression(Visit(operation.Operand), operation.GetConversion(), operation.IsTryCast, operation.IsChecked, DirectCast(operation, Operation).SemanticModel, operation.Syntax, operation.Type, operation.ConstantValue, operation.IsImplicit)
         End Function
+
+        Public Overrides Function VisitCompoundAssignment(operation As ICompoundAssignmentOperation, argument As Object) As IOperation
+            Dim baseType = DirectCast(operation, BaseVisualBasicCompoundAssignmentOperation)
+            Return New VisualBasicCompoundAssignmentOperation(Visit(operation.Target), Visit(operation.Value), baseType.InConversionInternal, baseType.OutConversionInternal, operation.OperatorKind, operation.IsLifted, operation.IsChecked, operation.OperatorMethod, DirectCast(operation, Operation).SemanticModel, operation.Syntax, operation.Type, operation.ConstantValue, operation.IsImplicit)
+        End Function
     End Class
 End Namespace

src/Compilers/VisualBasic/Portable/Operations/VisualBasicOperationFactory.vb

@@ -272,28 +272,15 @@ Namespace Microsoft.CodeAnalysis.Operations
         End Function
 
         Private Function CreateBoundAssignmentOperatorOperation(boundAssignmentOperator As BoundAssignmentOperator) As IOperation
-            Dim kind = GetAssignmentKind(boundAssignmentOperator)
-            Dim isImplicit As Boolean = boundAssignmentOperator.WasCompilerGenerated
-            If kind = OperationKind.CompoundAssignment Then
-                ' convert Right to IOperation temporarily. we do this to get right operand, operator method and etc
-                Dim temporaryRight = DirectCast(Create(boundAssignmentOperator.Right), IBinaryOperation)
-
-                Dim operatorKind As BinaryOperatorKind = temporaryRight.OperatorKind
-                Dim target As Lazy(Of IOperation) = New Lazy(Of IOperation)(Function() Create(boundAssignmentOperator.Left))
-
-                ' right now, parent of right operand is set to the temporary IOperation, reset the parent
-                ' we basically need to do this since we skip BoundAssignmentOperator.Right from IOperation tree
-                Dim rightOperand = Operation.ResetParentOperation(temporaryRight.RightOperand)
-                Dim value As Lazy(Of IOperation) = New Lazy(Of IOperation)(Function() rightOperand)
-
-                Dim operatorMethod As IMethodSymbol = temporaryRight.OperatorMethod
-                Dim syntax As SyntaxNode = boundAssignmentOperator.Syntax
-                Dim type As ITypeSymbol = boundAssignmentOperator.Type
-                Dim constantValue As [Optional](Of Object) = ConvertToOptional(boundAssignmentOperator.ConstantValueOpt)
-                Dim isLifted As Boolean = boundAssignmentOperator.Type.IsNullableType()
-                Dim isChecked As Boolean = temporaryRight.IsChecked
-                Return New LazyCompoundAssignmentExpression(operatorKind, isLifted, isChecked, target, value, operatorMethod, _semanticModel, syntax, type, constantValue, isImplicit)
+            If boundAssignmentOperator.Syntax.IsKind(SyntaxKind.MidAssignmentStatement) Then
+                ' We don't support mid statements currently. Return a none operation for them
+                Dim constantValue As [Optional](Of Object) = ConvertToOptional(boundAssignmentOperator?.ConstantValueOpt)
+                Dim isImplicit As Boolean = boundAssignmentOperator.WasCompilerGenerated
+                Return Operation.CreateOperationNone(_semanticModel, boundAssignmentOperator.Syntax, constantValue, Function() GetIOperationChildren(boundAssignmentOperator), isImplicit)
+            ElseIf boundAssignmentOperator.LeftOnTheRightOpt IsNot Nothing Then
+                Return CreateCompoundAssignment(boundAssignmentOperator)
             Else
+                Dim isImplicit As Boolean = boundAssignmentOperator.WasCompilerGenerated
                 Dim target As Lazy(Of IOperation) = New Lazy(Of IOperation)(Function() Create(boundAssignmentOperator.Left))
                 Dim value As Lazy(Of IOperation) = New Lazy(Of IOperation)(Function() Create(boundAssignmentOperator.Right))
                 Dim isRef As Boolean = False
@@ -447,33 +434,31 @@ Namespace Microsoft.CodeAnalysis.Operations
         End Function
 
         Private Function CreateBoundBinaryOperatorOperation(boundBinaryOperator As BoundBinaryOperator) As IBinaryOperation
-            Dim operatorKind As BinaryOperatorKind = Helper.DeriveBinaryOperatorKind(boundBinaryOperator.OperatorKind, boundBinaryOperator.Left)
-            Dim leftOperand As Lazy(Of IOperation) = New Lazy(Of IOperation)(Function() Create(boundBinaryOperator.Left))
-            Dim rightOperand As Lazy(Of IOperation) = New Lazy(Of IOperation)(Function() Create(boundBinaryOperator.Right))
-            Dim operatorMethod As IMethodSymbol = Nothing
+            Dim binaryOperatorInfo = GetBinaryOperatorInfo(boundBinaryOperator)
+            Dim leftOperand As Lazy(Of IOperation) = New Lazy(Of IOperation)(Function() Create(binaryOperatorInfo.LeftOperand))
+            Dim rightOperand As Lazy(Of IOperation) = New Lazy(Of IOperation)(Function() Create(binaryOperatorInfo.RightOperand))
             Dim syntax As SyntaxNode = boundBinaryOperator.Syntax
             Dim type As ITypeSymbol = boundBinaryOperator.Type
             Dim constantValue As [Optional](Of Object) = ConvertToOptional(boundBinaryOperator.ConstantValueOpt)
-            Dim isLifted As Boolean = (boundBinaryOperator.OperatorKind And VisualBasic.BinaryOperatorKind.Lifted) <> 0
-            Dim isChecked As Boolean = boundBinaryOperator.Checked
-            Dim isCompareText As Boolean = (boundBinaryOperator.OperatorKind And VisualBasic.BinaryOperatorKind.CompareText) <> 0
             Dim isImplicit As Boolean = boundBinaryOperator.WasCompilerGenerated
-            Return New LazyBinaryOperatorExpression(operatorKind, leftOperand, rightOperand, isLifted, isChecked, isCompareText, operatorMethod, _semanticModel, syntax, type, constantValue, isImplicit)
+            Return New LazyBinaryOperatorExpression(binaryOperatorInfo.OperatorKind, leftOperand, rightOperand, binaryOperatorInfo.IsLifted,
+                                                    binaryOperatorInfo.IsChecked, binaryOperatorInfo.IsCompareText, binaryOperatorInfo.OperatorMethod,
+                                                    _semanticModel, syntax, type, constantValue, isImplicit)
         End Function
 
         Private Function CreateBoundUserDefinedBinaryOperatorOperation(boundUserDefinedBinaryOperator As BoundUserDefinedBinaryOperator) As IBinaryOperation
-            Dim operatorKind As BinaryOperatorKind = Helper.DeriveBinaryOperatorKind(boundUserDefinedBinaryOperator.OperatorKind, leftOpt:=Nothing)
-            Dim leftOperand As Lazy(Of IOperation) = New Lazy(Of IOperation)(Function() GetUserDefinedBinaryOperatorChild(boundUserDefinedBinaryOperator, 0))
-            Dim rightOperand As Lazy(Of IOperation) = New Lazy(Of IOperation)(Function() GetUserDefinedBinaryOperatorChild(boundUserDefinedBinaryOperator, 1))
-            Dim operatorMethod As IMethodSymbol = If(boundUserDefinedBinaryOperator.UnderlyingExpression.Kind = BoundKind.Call, boundUserDefinedBinaryOperator.Call.Method, Nothing)
+            Dim binaryOperatorInfo = GetUserDefinedBinaryOperatorInfo(boundUserDefinedBinaryOperator)
+            Dim leftOperand As Lazy(Of IOperation) =
+                New Lazy(Of IOperation)(Function() GetUserDefinedBinaryOperatorChild(boundUserDefinedBinaryOperator, binaryOperatorInfo.LeftOperand))
+            Dim rightOperand As Lazy(Of IOperation) =
+                New Lazy(Of IOperation)(Function() GetUserDefinedBinaryOperatorChild(boundUserDefinedBinaryOperator, binaryOperatorInfo.RightOperand))
             Dim syntax As SyntaxNode = boundUserDefinedBinaryOperator.Syntax
             Dim type As ITypeSymbol = boundUserDefinedBinaryOperator.Type
             Dim constantValue As [Optional](Of Object) = ConvertToOptional(boundUserDefinedBinaryOperator.ConstantValueOpt)
-            Dim isLifted As Boolean = (boundUserDefinedBinaryOperator.OperatorKind And VisualBasic.BinaryOperatorKind.Lifted) <> 0
-            Dim isChecked As Boolean = boundUserDefinedBinaryOperator.Checked
-            Dim isCompareText As Boolean = False
             Dim isImplicit As Boolean = boundUserDefinedBinaryOperator.WasCompilerGenerated
-            Return New LazyBinaryOperatorExpression(operatorKind, leftOperand, rightOperand, isLifted, isChecked, isCompareText, operatorMethod, _semanticModel, syntax, type, constantValue, isImplicit)
+            Return New LazyBinaryOperatorExpression(binaryOperatorInfo.OperatorKind, leftOperand, rightOperand, binaryOperatorInfo.IsLifted,
+                                                    binaryOperatorInfo.IsChecked, binaryOperatorInfo.IsCompareText, binaryOperatorInfo.OperatorMethod,
+                                                    _semanticModel, syntax, type, constantValue, isImplicit)
         End Function
 
         Private Function CreateBoundBinaryConditionalExpressionOperation(boundBinaryConditionalExpression As BoundBinaryConditionalExpression) As ICoalesceOperation
@@ -530,7 +515,7 @@ Namespace Microsoft.CodeAnalysis.Operations
                 Return New LazyDelegateCreationExpression(operand, _semanticModel, syntax, type, constantValue, isImplicit)
             End If
 
-            Dim conversion As Conversion = New Conversion(New KeyValuePair(Of ConversionKind, MethodSymbol)(boundTryCast.ConversionKind, Nothing))
+            Dim conversion As Conversion = CreateConversion(boundTryCast)
             Dim isTryCast As Boolean = True
             Dim isChecked As Boolean = False
             Return New LazyVisualBasicConversionExpression(operand, conversion, isTryCast, isChecked, _semanticModel, syntax, type, constantValue, isImplicit)
@@ -552,7 +537,7 @@ Namespace Microsoft.CodeAnalysis.Operations
                 Return New LazyDelegateCreationExpression(operand, _semanticModel, syntax, type, constantValue, isImplicit)
             End If
 
-            Dim conversion As Conversion = New Conversion(New KeyValuePair(Of ConversionKind, MethodSymbol)(boundDirectCast.ConversionKind, Nothing))
+            Dim conversion As Conversion = CreateConversion(boundDirectCast)
             Dim isTryCast As Boolean = False
             Dim isChecked As Boolean = False
             Return New LazyVisualBasicConversionExpression(operand, conversion, isTryCast, isChecked, _semanticModel, syntax, type, constantValue, isImplicit)
@@ -578,8 +563,9 @@ Namespace Microsoft.CodeAnalysis.Operations
             Dim constantValue As [Optional](Of Object) = ConvertToOptional(boundConversion.ConstantValueOpt)
             Dim isImplicit As Boolean = boundConversion.WasCompilerGenerated OrElse Not boundConversion.ExplicitCastInCode
 
-            Dim conversionInformation = CreateConversionOperand(boundConversion.Operand, boundConversion.ConversionKind, boundConversion.Syntax, boundConversion.Type)
-            Dim methodSymbol As MethodSymbol = conversionInformation.MethodSymbol
+            Dim conversionOperandAndMethod = GetConversionInfo(boundConversion)
+            Dim conversionInformation = CreateConversionOperand(conversionOperandAndMethod.Operand, boundConversion.ConversionKind, boundConversion.Syntax, boundConversion.Type)
+            Dim methodSymbol As MethodSymbol = conversionOperandAndMethod.Method
             Dim operand As Lazy(Of IOperation) = conversionInformation.Operation
             Dim isDelegateCreation As Boolean = conversionInformation.IsDelegateCreation
 
@@ -589,7 +575,7 @@ Namespace Microsoft.CodeAnalysis.Operations
                 Return New LazyDelegateCreationExpression(operand, _semanticModel, syntax, type, constantValue, isImplicit)
             End If
 
-            Dim conversion = New Conversion(New KeyValuePair(Of VisualBasic.ConversionKind, MethodSymbol)(boundConversion.ConversionKind, methodSymbol))
+            Dim conversion As Conversion = CreateConversion(boundConversion)
             Dim isTryCast As Boolean = False
             Dim isChecked As Boolean = False
             Return New LazyVisualBasicConversionExpression(operand, conversion, isTryCast, isChecked, _semanticModel, syntax, type, constantValue, isImplicit)

src/Compilers/VisualBasic/Portable/Operations/VisualBasicOperationFactory_Methods.vb

@@ -12,40 +12,115 @@ Namespace Microsoft.CodeAnalysis.Operations
             Return If(value Is Nothing OrElse value.IsBad, New [Optional](Of Object)(), New [Optional](Of Object)(value.Value))
         End Function
 
-        Private Shared Function GetAssignmentKind(value As BoundAssignmentOperator) As OperationKind
-            If value.LeftOnTheRightOpt IsNot Nothing Then
-                Select Case value.Right.Kind
-                    Case BoundKind.BinaryOperator
-                        Dim rightBinary As BoundBinaryOperator = DirectCast(value.Right, BoundBinaryOperator)
-                        If rightBinary.Left Is value.LeftOnTheRightOpt Then
-                            Return OperationKind.CompoundAssignment
-                        End If
-                    Case BoundKind.UserDefinedBinaryOperator
-                        Dim rightOperatorBinary As BoundUserDefinedBinaryOperator = DirectCast(value.Right, BoundUserDefinedBinaryOperator)
-
-                        ' It is not permissible to access the Left property of a BoundUserDefinedBinaryOperator unconditionally,
-                        ' because that property can throw an exception if the operator expression is semantically invalid.
-                        ' get it through helper method
-                        Dim leftOperand = GetUserDefinedBinaryOperatorChildBoundNode(rightOperatorBinary, 0)
-                        If leftOperand Is value.LeftOnTheRightOpt Then
-                            Return OperationKind.CompoundAssignment
-                        End If
-                End Select
+        Private Function CreateCompoundAssignment(boundAssignment As BoundAssignmentOperator) As ICompoundAssignmentOperation
+            Debug.Assert(boundAssignment.LeftOnTheRightOpt IsNot Nothing)
+            Dim binaryOperator As BoundExpression = Nothing
+            Dim inConversion = New Conversion(Conversions.Identity)
+            Dim outConversion As Conversion = inConversion
+            Select Case boundAssignment.Right.Kind
+                Case BoundKind.Conversion
+                    Dim inConversionNode = DirectCast(boundAssignment.Right, BoundConversion)
+                    Dim conversionInfo = GetConversionInfo(inConversionNode)
+                    binaryOperator = conversionInfo.Operand
+                    outConversion = CreateConversion(inConversionNode)
+                Case BoundKind.UserDefinedBinaryOperator, BoundKind.BinaryOperator
+                    binaryOperator = boundAssignment.Right
+                Case Else
+                    Throw ExceptionUtilities.UnexpectedValue(boundAssignment)
+            End Select
+
+            Dim operatorInfo As BinaryOperatorInfo
+            Dim rightOperand As Lazy(Of IOperation)
+            Select Case binaryOperator.Kind
+                Case BoundKind.BinaryOperator
+                    operatorInfo = GetBinaryOperatorInfo(DirectCast(binaryOperator, BoundBinaryOperator))
+                    rightOperand = New Lazy(Of IOperation)(Function() Create(operatorInfo.RightOperand))
+                Case BoundKind.UserDefinedBinaryOperator
+                    Dim userDefinedOperator = DirectCast(binaryOperator, BoundUserDefinedBinaryOperator)
+                    operatorInfo = GetUserDefinedBinaryOperatorInfo(userDefinedOperator)
+                    rightOperand = New Lazy(Of IOperation)(Function() GetUserDefinedBinaryOperatorChild(userDefinedOperator, operatorInfo.RightOperand))
+                Case Else
+                    Throw ExceptionUtilities.UnexpectedValue(boundAssignment)
+            End Select
+
+            Dim leftOnTheRight As BoundExpression = operatorInfo.LeftOperand
+            If leftOnTheRight.Kind = BoundKind.Conversion Then
+                Dim outConversionNode = DirectCast(leftOnTheRight, BoundConversion)
+                Dim conversionInfo = GetConversionInfo(outConversionNode)
+                inConversion = CreateConversion(outConversionNode)
+                leftOnTheRight = conversionInfo.Operand
             End If
 
-            Return OperationKind.SimpleAssignment
+            Debug.Assert(leftOnTheRight Is boundAssignment.LeftOnTheRightOpt)
+
+            Dim leftOperand As Lazy(Of IOperation) = New Lazy(Of IOperation)(Function() Create(boundAssignment.Left))
+            Dim syntax As SyntaxNode = boundAssignment.Syntax
+            Dim type As ITypeSymbol = boundAssignment.Type
+            Dim constantValue As [Optional](Of Object) = ConvertToOptional(boundAssignment.ConstantValueOpt)
+            Dim isImplicit As Boolean = boundAssignment.WasCompilerGenerated
+
+            Return New LazyVisualBasicCompoundAssignmentOperation(leftOperand, rightOperand, inConversion, outConversion, operatorInfo.OperatorKind,
+                                                                  operatorInfo.IsLifted, operatorInfo.IsChecked, operatorInfo.OperatorMethod,
+                                                                  _semanticModel, syntax, type, constantValue, isImplicit)
+        End Function
+
+        Private Structure BinaryOperatorInfo
+            Public Sub New(leftOperand As BoundExpression,
+                           rightOperand As BoundExpression,
+                           binaryOperatorKind As BinaryOperatorKind,
+                           operatorMethod As MethodSymbol,
+                           isLifted As Boolean,
+                           isChecked As Boolean,
+                           isCompareText As Boolean)
+                Me.LeftOperand = leftOperand
+                Me.RightOperand = rightOperand
+                Me.OperatorKind = binaryOperatorKind
+                Me.OperatorMethod = operatorMethod
+                Me.IsLifted = isLifted
+                Me.IsChecked = isChecked
+                Me.IsCompareText = isCompareText
+            End Sub
+
+            Public ReadOnly LeftOperand As BoundExpression
+            Public ReadOnly RightOperand As BoundExpression
+            Public ReadOnly OperatorKind As BinaryOperatorKind
+            Public ReadOnly OperatorMethod As MethodSymbol
+            Public ReadOnly IsLifted As Boolean
+            Public ReadOnly IsChecked As Boolean
+            Public ReadOnly IsCompareText As Boolean
+        End Structure
+
+        Private Shared Function GetBinaryOperatorInfo(boundBinaryOperator As BoundBinaryOperator) As BinaryOperatorInfo
+            Return New BinaryOperatorInfo(
+                leftOperand:=boundBinaryOperator.Left,
+                rightOperand:=boundBinaryOperator.Right,
+                binaryOperatorKind:=Helper.DeriveBinaryOperatorKind(boundBinaryOperator.OperatorKind, boundBinaryOperator.Left),
+                operatorMethod:=Nothing,
+                isLifted:=(boundBinaryOperator.OperatorKind And VisualBasic.BinaryOperatorKind.Lifted) <> 0,
+                isChecked:=boundBinaryOperator.Checked,
+                isCompareText:=(boundBinaryOperator.OperatorKind And VisualBasic.BinaryOperatorKind.CompareText) <> 0)
+        End Function
+
+        Private Shared Function GetUserDefinedBinaryOperatorInfo(boundUserDefinedBinaryOperator As BoundUserDefinedBinaryOperator) As BinaryOperatorInfo
+            Return New BinaryOperatorInfo(
+                leftOperand:=GetUserDefinedBinaryOperatorChildBoundNode(boundUserDefinedBinaryOperator, 0),
+                rightOperand:=GetUserDefinedBinaryOperatorChildBoundNode(boundUserDefinedBinaryOperator, 1),
+                binaryOperatorKind:=Helper.DeriveBinaryOperatorKind(boundUserDefinedBinaryOperator.OperatorKind, leftOpt:=Nothing),
+                operatorMethod:=If(boundUserDefinedBinaryOperator.UnderlyingExpression.Kind = BoundKind.Call, boundUserDefinedBinaryOperator.Call.Method, Nothing),
+                isLifted:=(boundUserDefinedBinaryOperator.OperatorKind And VisualBasic.BinaryOperatorKind.Lifted) <> 0,
+                isChecked:=boundUserDefinedBinaryOperator.Checked,
+                isCompareText:=False)
         End Function
 
-        Private Function GetUserDefinedBinaryOperatorChild([operator] As BoundUserDefinedBinaryOperator, index As Integer) As IOperation
-            Dim child = Create(GetUserDefinedBinaryOperatorChildBoundNode([operator], index))
+        Private Function GetUserDefinedBinaryOperatorChild([operator] As BoundUserDefinedBinaryOperator, child As BoundExpression) As IOperation
             If child IsNot Nothing Then
-                Return child
+                Return Create(child)
             End If
-            Dim isImplicit As Boolean = [operator].WasCompilerGenerated
+            Dim isImplicit As Boolean = [operator].UnderlyingExpression.WasCompilerGenerated
             Return OperationFactory.CreateInvalidExpression(_semanticModel, [operator].UnderlyingExpression.Syntax, ImmutableArray(Of IOperation).Empty, isImplicit)
         End Function
 
-        Private Shared Function GetUserDefinedBinaryOperatorChildBoundNode([operator] As BoundUserDefinedBinaryOperator, index As Integer) As BoundNode
+        Private Shared Function GetUserDefinedBinaryOperatorChildBoundNode([operator] As BoundUserDefinedBinaryOperator, index As Integer) As BoundExpression
             If [operator].UnderlyingExpression.Kind = BoundKind.Call Then
                 If index = 0 Then
                     Return [operator].Left
@@ -80,6 +155,10 @@ Namespace Microsoft.CodeAnalysis.Operations
                     method = DirectCast(conversion.Operand, BoundUserDefinedConversion).Call.Method
                 End If
                 Return New Conversion(KeyValuePair.Create(conversionKind, method))
+            ElseIf expression.Kind = BoundKind.TryCast Then
+                Return New Conversion(KeyValuePair.Create(Of ConversionKind, MethodSymbol)(DirectCast(expression, BoundTryCast).ConversionKind, Nothing))
+            ElseIf expression.Kind = BoundKind.DirectCast Then
+                Return New Conversion(KeyValuePair.Create(Of ConversionKind, MethodSymbol)(DirectCast(expression, BoundDirectCast).ConversionKind, Nothing))
             End If
             Return New Conversion(Conversions.Identity)
         End Function
@@ -192,13 +271,10 @@ Namespace Microsoft.CodeAnalysis.Operations
             Return OperationFactory.CreateInvalidExpression(_semanticModel, parent.Syntax, ImmutableArray(Of IOperation).Empty, isImplicit)
         End Function
 
-        Private Shared Function GetChildOfBadExpressionBoundNode(parent As BoundNode, index As Integer) As BoundNode
+        Private Shared Function GetChildOfBadExpressionBoundNode(parent As BoundNode, index As Integer) As BoundExpression
             Dim badParent As BoundBadExpression = TryCast(parent, BoundBadExpression)
             If badParent?.ChildBoundNodes.Length > index Then
-                Dim child As BoundNode = badParent.ChildBoundNodes(index)
-                If child IsNot Nothing Then
-                    Return child
-                End If
+                Return badParent.ChildBoundNodes(index)
             End If
 
             Return Nothing
@@ -394,12 +470,8 @@ Namespace Microsoft.CodeAnalysis.Operations
         ''' is actually a delegate creation.
         ''' </summary>
         Private Function CreateConversionOperand(operand As BoundNode, conversionKind As ConversionKind, conversionSyntax As SyntaxNode, targetType As TypeSymbol
-                                                   ) As (MethodSymbol As MethodSymbol, Operation As Lazy(Of IOperation), IsDelegateCreation As Boolean)
-            If (conversionKind And VisualBasic.ConversionKind.UserDefined) = VisualBasic.ConversionKind.UserDefined Then
-                Dim userDefinedConversion As BoundUserDefinedConversion = DirectCast(operand, BoundUserDefinedConversion)
-                Return (userDefinedConversion.Call.Method, New Lazy(Of IOperation)(Function() Create(userDefinedConversion.Operand)), IsDelegateCreation:=False)
-            ElseIf IsDelegateCreation(conversionKind, conversionSyntax, operand, targetType) Then
-                Dim methodSymbol As MethodSymbol = Nothing
+                                                 ) As (Operation As Lazy(Of IOperation), IsDelegateCreation As Boolean)
+            If IsDelegateCreation(conversionKind, conversionSyntax, operand, targetType) Then
                 Dim operandLazy As Lazy(Of IOperation)
                 If operand.Kind = BoundKind.DelegateCreationExpression Then
                     ' If the child is a BoundDelegateCreationExpression, we don't want to generate a nested IDelegateCreationExpression.
@@ -413,10 +485,22 @@ Namespace Microsoft.CodeAnalysis.Operations
                     ' Delegate to standard operation handling for this.
                     operandLazy = New Lazy(Of IOperation)(Function() Create(operand))
                 End If
-                Return (methodSymbol, operandLazy, IsDelegateCreation:=True)
+                Return (operandLazy, IsDelegateCreation:=True)
             Else
                 Dim methodSymbol As MethodSymbol = Nothing
-                Return (methodSymbol, New Lazy(Of IOperation)(Function() Create(operand)), IsDelegateCreation:=False)
+                Return (New Lazy(Of IOperation)(Function() Create(operand)), IsDelegateCreation:=False)
+            End If
+        End Function
+
+        ''' <summary>
+        ''' Gets the operand and method symbol from a BoundConversion, compensating for if the conversion is a user-defined conversion
+        ''' </summary>
+        Private Shared Function GetConversionInfo(boundConversion As BoundConversion) As (Operand As BoundExpression, Method As MethodSymbol)
+            If (boundConversion.ConversionKind And ConversionKind.UserDefined) = ConversionKind.UserDefined Then
+                Dim userDefinedConversion = DirectCast(boundConversion.Operand, BoundUserDefinedConversion)
+                Return (Operand:=userDefinedConversion.Operand, Method:=userDefinedConversion.Call.Method)
+            Else
+                Return (Operand:=boundConversion.Operand, Method:=Nothing)
             End If
         End Function
 

src/Compilers/VisualBasic/Portable/PublicAPI.Unshipped.txt

@@ -2,4 +2,6 @@ Microsoft.CodeAnalysis.VisualBasic.Conversion.ToCommonConversion() -> Microsoft.
 Microsoft.CodeAnalysis.VisualBasic.LanguageVersion.VisualBasic15_5 = 1505 -> Microsoft.CodeAnalysis.VisualBasic.LanguageVersion
 Microsoft.CodeAnalysis.VisualBasic.VisualBasicExtensions.GetConversion(conversionExpression As Microsoft.CodeAnalysis.Operations.IConversionOperation) -> Microsoft.CodeAnalysis.VisualBasic.Conversion
 Microsoft.CodeAnalysis.VisualBasic.VisualBasicExtensions.GetInConversion(argument As Microsoft.CodeAnalysis.Operations.IArgumentOperation) -> Microsoft.CodeAnalysis.VisualBasic.Conversion
+Microsoft.CodeAnalysis.VisualBasic.VisualBasicExtensions.GetInConversion(compoundAssignment As Microsoft.CodeAnalysis.Operations.ICompoundAssignmentOperation) -> Microsoft.CodeAnalysis.VisualBasic.Conversion
 Microsoft.CodeAnalysis.VisualBasic.VisualBasicExtensions.GetOutConversion(argument As Microsoft.CodeAnalysis.Operations.IArgumentOperation) -> Microsoft.CodeAnalysis.VisualBasic.Conversion
+Microsoft.CodeAnalysis.VisualBasic.VisualBasicExtensions.GetOutConversion(compoundAssignment As Microsoft.CodeAnalysis.Operations.ICompoundAssignmentOperation) -> Microsoft.CodeAnalysis.VisualBasic.Conversion

src/Compilers/VisualBasic/Portable/VBResources.Designer.vb

@@ -12288,6 +12288,15 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
             End Get
         End Property
         
+        '''<summary>
+        '''  Looks up a localized string similar to {0} is not a valid Visual Basic compound assignment operation.
+        '''</summary>
+        Friend ReadOnly Property ICompoundAssignmentOperationIsNotVisualBasicCompoundAssignment() As String
+            Get
+                Return ResourceManager.GetString("ICompoundAssignmentOperationIsNotVisualBasicCompoundAssignment", resourceCulture)
+            End Get
+        End Property
+        
         '''<summary>
         '''  Looks up a localized string similar to {0} is not a valid Visual Basic conversion expression.
         '''</summary>

src/Compilers/VisualBasic/Portable/VBResources.resx

@@ -5521,4 +5521,7 @@
   <data name="FEATURE_LeadingDigitSeparator" xml:space="preserve">
     <value>leading digit separator</value>
   </data>
-</root>
+  <data name="ICompoundAssignmentOperationIsNotVisualBasicCompoundAssignment" xml:space="preserve">
+    <value>{0} is not a valid Visual Basic compound assignment operation</value>
+  </data>
+</root>
\ No newline at end of file

src/Compilers/VisualBasic/Portable/VisualBasicExtensions.vb

@@ -1415,6 +1415,52 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
             End If
         End Function
 
+        ''' <summary>
+        ''' Gets the underlying <see cref="Conversion"/> information from this <see cref="ICompoundAssignmentOperation"/>. This
+        ''' conversion is applied before the operator is applied to the result of this conversion and <see cref="IAssignmentOperation.Value"/>.
+        ''' </summary>
+        ''' <remarks>
+        ''' This compound assignment must have been created from Visual Basic code.
+        ''' </remarks>
+        <Extension>
+        Public Function GetInConversion(compoundAssignment As ICompoundAssignmentOperation) As Conversion
+            If compoundAssignment Is Nothing Then
+                Throw New ArgumentNullException(NameOf(compoundAssignment))
+            End If
+
+            Dim basicCompoundOperation = TryCast(compoundAssignment, BaseVisualBasicCompoundAssignmentOperation)
+            If basicCompoundOperation IsNot Nothing Then
+                Return basicCompoundOperation.InConversionInternal
+            Else
+                Throw New ArgumentException(String.Format(VBResources.ICompoundAssignmentOperationIsNotVisualBasicCompoundAssignment,
+                                                          NameOf(compoundAssignment)),
+                                            NameOf(compoundAssignment))
+            End If
+        End Function
+
+        ''' <summary>
+        ''' Gets the underlying <see cref="Conversion"/> information from this <see cref="ICompoundAssignmentOperation"/>. This
+        ''' conversion is applied after the operator is applied, before the result is assigned to <see cref="IAssignmentOperation.Target"/>.
+        ''' </summary>
+        ''' <remarks>
+        ''' This compound assignment must have been created from Visual Basic code.
+        ''' </remarks>
+        <Extension>
+        Public Function GetOutConversion(compoundAssignment As ICompoundAssignmentOperation) As Conversion
+            If compoundAssignment Is Nothing Then
+                Throw New ArgumentNullException(NameOf(compoundAssignment))
+            End If
+
+            Dim basicCompoundOperation = TryCast(compoundAssignment, BaseVisualBasicCompoundAssignmentOperation)
+            If basicCompoundOperation IsNot Nothing Then
+                Return basicCompoundOperation.OutConversionInternal
+            Else
+                Throw New ArgumentException(String.Format(VBResources.ICompoundAssignmentOperationIsNotVisualBasicCompoundAssignment,
+                                                          NameOf(compoundAssignment)),
+                                            NameOf(compoundAssignment))
+            End If
+        End Function
+
         <Extension>
         Public Function GetSpeculativeConversion(semanticModel As SemanticModel, position As Integer, expression As ExpressionSyntax, bindingOption As SpeculativeBindingOption) As Conversion
             Dim vbmodel = TryCast(semanticModel, VBSemanticModel)

src/Compilers/VisualBasic/Test/Semantic/IOperation/IOperationTests.vb

@@ -198,6 +198,8 @@ End Module
 IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x += y')
   Expression: 
     ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x += y')
+      InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+      OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
       Left: 
         ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
       Right: 
@@ -225,6 +227,8 @@ IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (S
 IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a += b')
   Expression: 
     ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperatorMethod: Function B2.op_Addition(x As B2, y As B2) As B2) (OperationKind.CompoundAssignment, Type: B2, IsImplicit) (Syntax: 'a += b')
+      InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+      OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
       Left: 
         ILocalReferenceOperation: a (OperationKind.LocalReference, Type: B2) (Syntax: 'a')
       Right: 

src/Compilers/VisualBasic/Test/Semantic/IOperation/IOperationTests_IBinaryOperatorExpression.vb

@@ -1200,6 +1200,8 @@ IBlockOperation (12 statements, 2 locals) (OperationKind.Block, Type: null) (Syn
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x += y')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x += y')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 
@@ -1207,6 +1209,8 @@ IBlockOperation (12 statements, 2 locals) (OperationKind.Block, Type: null) (Syn
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x -= y')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Subtract, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x -= y')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 
@@ -1214,80 +1218,62 @@ IBlockOperation (12 statements, 2 locals) (OperationKind.Block, Type: null) (Syn
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x *= y')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Multiply, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x *= y')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 
           ILocalReferenceOperation: y (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'y')
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x /= y')
     Expression: 
-      ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x /= y')
+      ICompoundAssignmentOperation (BinaryOperatorKind.Divide, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x /= y')
+        InConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 
-          IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Int32, IsImplicit) (Syntax: 'x /= y')
+          IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Double, IsImplicit) (Syntax: 'y')
             Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Operand: 
-              IBinaryOperation (BinaryOperatorKind.Divide, Checked) (OperationKind.BinaryOperator, Type: System.Double, IsImplicit) (Syntax: 'x /= y')
-                Left: 
-                  IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Double, IsImplicit) (Syntax: 'x')
-                    Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-                    Operand: 
-                      IOperation:  (OperationKind.None, Type: null, IsImplicit) (Syntax: 'x')
-                Right: 
-                  IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Double, IsImplicit) (Syntax: 'y')
-                    Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-                    Operand: 
-                      ILocalReferenceOperation: y (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'y')
+              ILocalReferenceOperation: y (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'y')
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x \= y')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.IntegerDivide, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x \= y')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 
           ILocalReferenceOperation: y (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'y')
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x ^= y')
     Expression: 
-      ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x ^= y')
+      ICompoundAssignmentOperation (BinaryOperatorKind.Power, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x ^= y')
+        InConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 
-          IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Int32, IsImplicit) (Syntax: 'x ^= y')
+          IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Double, IsImplicit) (Syntax: 'y')
             Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Operand: 
-              IBinaryOperation (BinaryOperatorKind.Power, Checked) (OperationKind.BinaryOperator, Type: System.Double, IsImplicit) (Syntax: 'x ^= y')
-                Left: 
-                  IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Double, IsImplicit) (Syntax: 'x')
-                    Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-                    Operand: 
-                      IOperation:  (OperationKind.None, Type: null, IsImplicit) (Syntax: 'x')
-                Right: 
-                  IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Double, IsImplicit) (Syntax: 'y')
-                    Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-                    Operand: 
-                      ILocalReferenceOperation: y (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'y')
+              ILocalReferenceOperation: y (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'y')
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x &= y')
     Expression: 
-      ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x &= y')
+      ICompoundAssignmentOperation (BinaryOperatorKind.Concatenate, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x &= y')
+        InConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 
-          IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Int32, IsImplicit) (Syntax: 'x &= y')
+          IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.String, IsImplicit) (Syntax: 'y')
             Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Operand: 
-              IBinaryOperation (BinaryOperatorKind.Concatenate, Checked) (OperationKind.BinaryOperator, Type: System.String, IsImplicit) (Syntax: 'x &= y')
-                Left: 
-                  IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.String, IsImplicit) (Syntax: 'x')
-                    Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-                    Operand: 
-                      IOperation:  (OperationKind.None, Type: null, IsImplicit) (Syntax: 'x')
-                Right: 
-                  IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.String, IsImplicit) (Syntax: 'y')
-                    Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-                    Operand: 
-                      ILocalReferenceOperation: y (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'y')
+              ILocalReferenceOperation: y (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'y')
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x <<= 2')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.LeftShift, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x <<= 2')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 
@@ -1295,6 +1281,8 @@ IBlockOperation (12 statements, 2 locals) (OperationKind.Block, Type: null) (Syn
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x >>= 3')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.RightShift, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x >>= 3')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 
@@ -1354,6 +1342,8 @@ IBlockOperation (12 statements, 2 locals) (OperationKind.Block, Type: null) (Syn
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x += y')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Add) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x += y')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 
@@ -1361,6 +1351,8 @@ IBlockOperation (12 statements, 2 locals) (OperationKind.Block, Type: null) (Syn
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x -= y')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Subtract) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x -= y')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 
@@ -1368,80 +1360,62 @@ IBlockOperation (12 statements, 2 locals) (OperationKind.Block, Type: null) (Syn
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x *= y')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.Multiply) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x *= y')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 
           ILocalReferenceOperation: y (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'y')
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x /= y')
     Expression: 
-      ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x /= y')
+      ICompoundAssignmentOperation (BinaryOperatorKind.Divide) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x /= y')
+        InConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 
-          IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Int32, IsImplicit) (Syntax: 'x /= y')
+          IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Double, IsImplicit) (Syntax: 'y')
             Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Operand: 
-              IBinaryOperation (BinaryOperatorKind.Divide) (OperationKind.BinaryOperator, Type: System.Double, IsImplicit) (Syntax: 'x /= y')
-                Left: 
-                  IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Double, IsImplicit) (Syntax: 'x')
-                    Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-                    Operand: 
-                      IOperation:  (OperationKind.None, Type: null, IsImplicit) (Syntax: 'x')
-                Right: 
-                  IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Double, IsImplicit) (Syntax: 'y')
-                    Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-                    Operand: 
-                      ILocalReferenceOperation: y (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'y')
+              ILocalReferenceOperation: y (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'y')
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x \= y')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.IntegerDivide) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x \= y')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 
           ILocalReferenceOperation: y (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'y')
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x ^= y')
     Expression: 
-      ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x ^= y')
+      ICompoundAssignmentOperation (BinaryOperatorKind.Power) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x ^= y')
+        InConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 
-          IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Int32, IsImplicit) (Syntax: 'x ^= y')
+          IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Double, IsImplicit) (Syntax: 'y')
             Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Operand: 
-              IBinaryOperation (BinaryOperatorKind.Power) (OperationKind.BinaryOperator, Type: System.Double, IsImplicit) (Syntax: 'x ^= y')
-                Left: 
-                  IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Double, IsImplicit) (Syntax: 'x')
-                    Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-                    Operand: 
-                      IOperation:  (OperationKind.None, Type: null, IsImplicit) (Syntax: 'x')
-                Right: 
-                  IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Double, IsImplicit) (Syntax: 'y')
-                    Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-                    Operand: 
-                      ILocalReferenceOperation: y (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'y')
+              ILocalReferenceOperation: y (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'y')
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x &= y')
     Expression: 
-      ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x &= y')
+      ICompoundAssignmentOperation (BinaryOperatorKind.Concatenate) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x &= y')
+        InConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 
-          IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Int32, IsImplicit) (Syntax: 'x &= y')
+          IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.String, IsImplicit) (Syntax: 'y')
             Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Operand: 
-              IBinaryOperation (BinaryOperatorKind.Concatenate) (OperationKind.BinaryOperator, Type: System.String, IsImplicit) (Syntax: 'x &= y')
-                Left: 
-                  IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.String, IsImplicit) (Syntax: 'x')
-                    Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-                    Operand: 
-                      IOperation:  (OperationKind.None, Type: null, IsImplicit) (Syntax: 'x')
-                Right: 
-                  IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.String, IsImplicit) (Syntax: 'y')
-                    Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-                    Operand: 
-                      ILocalReferenceOperation: y (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'y')
+              ILocalReferenceOperation: y (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'y')
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x <<= 2')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.LeftShift) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x <<= 2')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 
@@ -1449,6 +1423,8 @@ IBlockOperation (12 statements, 2 locals) (OperationKind.Block, Type: null) (Syn
   IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x >>= 3')
     Expression: 
       ICompoundAssignmentOperation (BinaryOperatorKind.RightShift) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x >>= 3')
+        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
         Left: 
           ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
         Right: 

src/Compilers/VisualBasic/Test/Semantic/IOperation/IOperationTests_ICompoundAssignmentOperation.vb

+' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+
+Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
+Imports Microsoft.CodeAnalysis.Test.Utilities
+Imports Microsoft.CodeAnalysis.Operations
+
+Namespace Microsoft.CodeAnalysis.VisualBasic.UnitTests.Semantics
+
+    Partial Public Class IOperationTests
+        Inherits SemanticModelTestBase
+
+        <CompilerTrait(CompilerFeature.IOperation)>
+        <Fact()>
+        Public Sub CompoundAssignment_NullArgumentToGetConversionThrows()
+            Dim nullAssignment As ICompoundAssignmentOperation = Nothing
+            Assert.Throws(Of ArgumentNullException)("compoundAssignment", Function() nullAssignment.GetInConversion())
+            Assert.Throws(Of ArgumentNullException)("compoundAssignment", Function() nullAssignment.GetOutConversion())
+        End Sub
+
+        <CompilerTrait(CompilerFeature.IOperation)>
+        <Fact()>
+        Public Sub CompoundAssignmentOperation_UserDefinedOperatorInConversion()
+            Dim source = <![CDATA[
+Module Module1
+
+    Sub Main()
+        Dim a As New C, x As New Integer
+        a += x'BIND:"a += x"
+    End Sub
+
+    Class C
+        Public Shared Widening Operator CType(i As Integer) As C
+            Return Nothing
+        End Operator
+        Public Shared Widening Operator CType(c As C) As Integer
+            Return 1
+        End Operator
+        Public Shared Operator +(c As Integer, i As C) As C
+            Return 0
+        End Operator
+    End Class
+End Module]]>.Value
+
+            Dim expectedOperationTree = <![CDATA[
+IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a += x')
+  Expression: 
+    ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperatorMethod: Function Module1.C.op_Addition(c As System.Int32, i As Module1.C) As Module1.C) (OperationKind.CompoundAssignment, Type: Module1.C, IsImplicit) (Syntax: 'a += x')
+      InConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: Function Module1.C.op_Implicit(c As Module1.C) As System.Int32)
+      OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+      Left: 
+        ILocalReferenceOperation: a (OperationKind.LocalReference, Type: Module1.C) (Syntax: 'a')
+      Right: 
+        IConversionOperation (TryCast: False, Unchecked) (OperatorMethod: Function Module1.C.op_Implicit(i As System.Int32) As Module1.C) (OperationKind.Conversion, Type: Module1.C, IsImplicit) (Syntax: 'x')
+          Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: Function Module1.C.op_Implicit(i As System.Int32) As Module1.C)
+          Operand: 
+            ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
+]]>.Value
+
+            Dim expectedDiagnostics = String.Empty
+
+            VerifyOperationTreeAndDiagnosticsForTest(Of AssignmentStatementSyntax)(source, expectedOperationTree, expectedDiagnostics)
+        End Sub
+
+        <CompilerTrait(CompilerFeature.IOperation)>
+        <Fact()>
+        Public Sub CompoundAssignmentOperation_UserDefinedOperatorOutConversion()
+            Dim source = <![CDATA[
+Module Module1
+
+    Sub Main()
+        Dim a As New C, x As New Integer
+        a += x'BIND:"a += x"
+    End Sub
+
+    Class C
+        Public Shared Widening Operator CType(i As Integer) As C
+            Return Nothing
+        End Operator
+        Public Shared Widening Operator CType(c As C) As Integer
+            Return 1
+        End Operator
+        Public Shared Operator +(c As C, i As Integer) As Integer
+            Return 0
+        End Operator
+    End Class
+End Module]]>.Value
+
+            Dim expectedOperationTree = <![CDATA[
+IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a += x')
+  Expression: 
+    ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperatorMethod: Function Module1.C.op_Addition(c As Module1.C, i As System.Int32) As System.Int32) (OperationKind.CompoundAssignment, Type: Module1.C, IsImplicit) (Syntax: 'a += x')
+      InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+      OutConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: Function Module1.C.op_Implicit(i As System.Int32) As Module1.C)
+      Left: 
+        ILocalReferenceOperation: a (OperationKind.LocalReference, Type: Module1.C) (Syntax: 'a')
+      Right: 
+        ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
+]]>.Value
+
+            Dim expectedDiagnostics = String.Empty
+
+            VerifyOperationTreeAndDiagnosticsForTest(Of AssignmentStatementSyntax)(source, expectedOperationTree, expectedDiagnostics)
+        End Sub
+
+        <CompilerTrait(CompilerFeature.IOperation)>
+        <Fact()>
+        Public Sub CompoundAssignmentOperation_UserDefinedOperatorInOutConversion()
+            Dim source = <![CDATA[
+Module Module1
+
+    Sub Main()
+        Dim a As New C, x As New Integer
+        a += x'BIND:"a += x"
+    End Sub
+
+    Class C
+        Public Shared Widening Operator CType(i As Integer) As C
+            Return Nothing
+        End Operator
+        Public Shared Widening Operator CType(c As C) As Integer
+            Return 1
+        End Operator
+        Public Shared Operator +(c As Integer, i As C) As Integer
+            Return 0
+        End Operator
+    End Class
+End Module]]>.Value
+
+            Dim expectedOperationTree = <![CDATA[
+IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'a += x')
+  Expression: 
+    ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperatorMethod: Function Module1.C.op_Addition(c As System.Int32, i As Module1.C) As System.Int32) (OperationKind.CompoundAssignment, Type: Module1.C, IsImplicit) (Syntax: 'a += x')
+      InConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: Function Module1.C.op_Implicit(c As Module1.C) As System.Int32)
+      OutConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: Function Module1.C.op_Implicit(i As System.Int32) As Module1.C)
+      Left: 
+        ILocalReferenceOperation: a (OperationKind.LocalReference, Type: Module1.C) (Syntax: 'a')
+      Right: 
+        IConversionOperation (TryCast: False, Unchecked) (OperatorMethod: Function Module1.C.op_Implicit(i As System.Int32) As Module1.C) (OperationKind.Conversion, Type: Module1.C, IsImplicit) (Syntax: 'x')
+          Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: Function Module1.C.op_Implicit(i As System.Int32) As Module1.C)
+          Operand: 
+            ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
+]]>.Value
+
+            Dim expectedDiagnostics = String.Empty
+
+            VerifyOperationTreeAndDiagnosticsForTest(Of AssignmentStatementSyntax)(source, expectedOperationTree, expectedDiagnostics)
+        End Sub
+
+        <CompilerTrait(CompilerFeature.IOperation)>
+        <Fact()>
+        Public Sub CompoundAssignmentExpression_BuiltInOperatorInOutConversion()
+            Dim source = <![CDATA[
+Module Module1
+
+    Sub Main()
+        Dim x, y As New Integer
+        x /= y'BIND:"x /= y"
+    End Sub
+End Module]]>.Value
+
+            Dim expectedOperationTree = <![CDATA[
+IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'x /= y')
+  Expression: 
+    ICompoundAssignmentOperation (BinaryOperatorKind.Divide, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'x /= y')
+      InConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+      OutConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+      Left: 
+        ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
+      Right: 
+        IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Double, IsImplicit) (Syntax: 'y')
+          Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+          Operand: 
+            ILocalReferenceOperation: y (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'y')
+]]>.Value
+
+            Dim expectedDiagnostics = String.Empty
+
+            VerifyOperationTreeAndDiagnosticsForTest(Of AssignmentStatementSyntax)(source, expectedOperationTree, expectedDiagnostics)
+        End Sub
+
+        <CompilerTrait(CompilerFeature.IOperation)>
+        <Fact()>
+        Public Sub CompoundAssignmentExpression_InvalidNoOperator()
+            Dim source = <![CDATA[
+Module Module1
+
+    Sub Main()
+        Dim a As New C, x As New Integer
+        a += x'BIND:"a += x"
+    End Sub
+
+    Class C
+        Public Shared Widening Operator CType(i As Integer) As C
+            Return Nothing
+        End Operator
+        Public Shared Widening Operator CType(c As C) As Integer
+            Return 1
+        End Operator
+    End Class
+End Module]]>.Value
+
+            Dim expectedOperationTree = <![CDATA[
+IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null, IsInvalid) (Syntax: 'a += x')
+  Expression: 
+    ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: Module1.C, IsInvalid, IsImplicit) (Syntax: 'a += x')
+      InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+      OutConversion: CommonConversion (Exists: False, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+      Left: 
+        ILocalReferenceOperation: a (OperationKind.LocalReference, Type: Module1.C, IsInvalid) (Syntax: 'a')
+      Right: 
+        ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'x')
+]]>.Value
+
+            Dim expectedDiagnostics = <![CDATA[
+BC30452: Operator '+' is not defined for types 'Module1.C' and 'Integer'.
+        a += x'BIND:"a += x"
+        ~~~~~~
+]]>.Value
+
+            VerifyOperationTreeAndDiagnosticsForTest(Of AssignmentStatementSyntax)(source, expectedOperationTree, expectedDiagnostics)
+        End Sub
+
+        <CompilerTrait(CompilerFeature.IOperation)>
+        <Fact()>
+        Public Sub CompoundAssignmentExpression_InvalidNoOutConversion()
+            Dim source = <![CDATA[
+Module Module1
+
+    Sub Main()
+        Dim a As New C, x As New Integer
+        a += x'BIND:"a += x"
+    End Sub
+
+    Class C
+        Public Shared Widening Operator CType(c As C) As Integer
+            Return 1
+        End Operator
+        Public Shared Operator +(c As C, i As Integer) As Integer
+            Return 1
+        End Operator
+    End Class
+End Module]]>.Value
+
+            Dim expectedOperationTree = <![CDATA[
+IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null, IsInvalid) (Syntax: 'a += x')
+  Expression: 
+    ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperatorMethod: Function Module1.C.op_Addition(c As Module1.C, i As System.Int32) As System.Int32) (OperationKind.CompoundAssignment, Type: Module1.C, IsInvalid, IsImplicit) (Syntax: 'a += x')
+      InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+      OutConversion: CommonConversion (Exists: False, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+      Left: 
+        ILocalReferenceOperation: a (OperationKind.LocalReference, Type: Module1.C, IsInvalid) (Syntax: 'a')
+      Right: 
+        ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'x')
+]]>.Value
+
+            Dim expectedDiagnostics = <![CDATA[
+BC30311: Value of type 'Integer' cannot be converted to 'Module1.C'.
+        a += x'BIND:"a += x"
+        ~~~~~~
+]]>.Value
+
+            VerifyOperationTreeAndDiagnosticsForTest(Of AssignmentStatementSyntax)(source, expectedOperationTree, expectedDiagnostics)
+        End Sub
+
+        <CompilerTrait(CompilerFeature.IOperation)>
+        <Fact()>
+        Public Sub CompoundAssignmentExpression_InvalidNoInConversion()
+            Dim source = <![CDATA[
+Module Module1
+
+    Sub Main()
+        Dim a As New C, x As New Integer
+        a += x'BIND:"a += x"
+    End Sub
+
+    Class C
+        Public Shared Widening Operator CType(c As Integer) As C
+            Return 1
+        End Operator
+        Public Shared Operator +(c As Integer, i As C) As Integer
+            Return 1
+        End Operator
+    End Class
+End Module]]>.Value
+
+            Dim expectedOperationTree = <![CDATA[
+IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null, IsInvalid) (Syntax: 'a += x')
+  Expression: 
+    ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: Module1.C, IsInvalid, IsImplicit) (Syntax: 'a += x')
+      InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+      OutConversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: True) (MethodSymbol: Function Module1.C.op_Implicit(c As System.Int32) As Module1.C)
+      Left: 
+        ILocalReferenceOperation: a (OperationKind.LocalReference, Type: Module1.C, IsInvalid) (Syntax: 'a')
+      Right: 
+        ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'x')
+]]>.Value
+
+            Dim expectedDiagnostics = <![CDATA[
+BC30311: Value of type 'Module1.C' cannot be converted to 'Integer'.
+        a += x'BIND:"a += x"
+        ~
+BC42004: Expression recursively calls the containing Operator 'Public Shared Widening Operator CType(c As Integer) As Module1.C'.
+            Return 1
+                   ~
+]]>.Value
+
+            VerifyOperationTreeAndDiagnosticsForTest(Of AssignmentStatementSyntax)(source, expectedOperationTree, expectedDiagnostics)
+        End Sub
+
+        <CompilerTrait(CompilerFeature.IOperation)>
+        <Fact()>
+        Public Sub CompoundAssignmentExpression_InvalidNoOperatorOrConversions()
+            Dim source = <![CDATA[
+Module Module1
+
+    Sub Main()
+        Dim a As New C, x As New Integer
+        a += x'BIND:"a += x"
+    End Sub
+
+    Class C
+    End Class
+End Module]]>.Value
+
+            Dim expectedOperationTree = <![CDATA[
+IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null, IsInvalid) (Syntax: 'a += x')
+  Expression: 
+    ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: Module1.C, IsInvalid, IsImplicit) (Syntax: 'a += x')
+      InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+      OutConversion: CommonConversion (Exists: False, IsIdentity: False, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+      Left: 
+        ILocalReferenceOperation: a (OperationKind.LocalReference, Type: Module1.C, IsInvalid) (Syntax: 'a')
+      Right: 
+        ILocalReferenceOperation: x (OperationKind.LocalReference, Type: System.Int32, IsInvalid) (Syntax: 'x')
+]]>.Value
+
+            Dim expectedDiagnostics = <![CDATA[
+BC30452: Operator '+' is not defined for types 'Module1.C' and 'Integer'.
+        a += x'BIND:"a += x"
+        ~~~~~~
+]]>.Value
+
+            VerifyOperationTreeAndDiagnosticsForTest(Of AssignmentStatementSyntax)(source, expectedOperationTree, expectedDiagnostics)
+        End Sub
+
+
+
+    End Class
+End Namespace

src/Compilers/VisualBasic/Test/Semantic/IOperation/IOperationTests_IParameterReferenceExpression.vb

@@ -672,18 +672,17 @@ End Class]]>.Value
             Dim expectedOperationTree = <![CDATA[
 IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'Mid(str, st ... ngth) = str')
   Expression: 
-    ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Void, IsImplicit) (Syntax: 'Mid(str, st ... ngth) = str')
-      Left: 
-        IParameterReferenceOperation: str (OperationKind.ParameterReference, Type: System.String) (Syntax: 'str')
-      Right: 
-        IOperation:  (OperationKind.None, Type: null, IsImplicit) (Syntax: 'Mid(str, st ... ngth) = str')
-          Children(4):
-              IParenthesizedOperation (OperationKind.Parenthesized, Type: System.String) (Syntax: 'Mid(str, start, length)')
-                Operand: 
-                  IOperation:  (OperationKind.None, Type: null, IsImplicit) (Syntax: 'str')
-              IParameterReferenceOperation: start (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'start')
-              IParameterReferenceOperation: length (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'length')
-              IParameterReferenceOperation: str (OperationKind.ParameterReference, Type: System.String) (Syntax: 'str')
+    IOperation:  (OperationKind.None, Type: null, IsImplicit) (Syntax: 'Mid(str, st ... ngth) = str')
+      Children(2):
+          IParameterReferenceOperation: str (OperationKind.ParameterReference, Type: System.String) (Syntax: 'str')
+          IOperation:  (OperationKind.None, Type: null, IsImplicit) (Syntax: 'Mid(str, st ... ngth) = str')
+            Children(4):
+                IParenthesizedOperation (OperationKind.Parenthesized, Type: System.String) (Syntax: 'Mid(str, start, length)')
+                  Operand: 
+                    IOperation:  (OperationKind.None, Type: null, IsImplicit) (Syntax: 'str')
+                IParameterReferenceOperation: start (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'start')
+                IParameterReferenceOperation: length (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'length')
+                IParameterReferenceOperation: str (OperationKind.ParameterReference, Type: System.String) (Syntax: 'str')
 ]]>.Value
 
             Dim expectedDiagnostics = String.Empty

src/Compilers/VisualBasic/Test/Semantic/IOperation/IOperationTests_IWhileUntilLoopStatement.vb

@@ -41,6 +41,8 @@ IWhileLoopOperation (ConditionIsTop: False, ConditionIsUntil: False) (LoopKind.W
       IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'sum += ids(i)')
         Expression: 
           ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'sum += ids(i)')
+            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Left: 
               ILocalReferenceOperation: sum (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'sum')
             Right: 
@@ -52,6 +54,8 @@ IWhileLoopOperation (ConditionIsTop: False, ConditionIsUntil: False) (LoopKind.W
       IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'i += 1')
         Expression: 
           ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'i += 1')
+            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Left: 
               ILocalReferenceOperation: i (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'i')
             Right: 
@@ -211,6 +215,8 @@ IWhileLoopOperation (ConditionIsTop: True, ConditionIsUntil: False) (LoopKind.Wh
       IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'sum += i')
         Expression: 
           ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'sum += i')
+            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Left: 
               ILocalReferenceOperation: sum (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'sum')
             Right: 
@@ -218,6 +224,8 @@ IWhileLoopOperation (ConditionIsTop: True, ConditionIsUntil: False) (LoopKind.Wh
       IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'i += 1')
         Expression: 
           ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'i += 1')
+            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Left: 
               ILocalReferenceOperation: i (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'i')
             Right: 
@@ -458,6 +466,8 @@ IWhileLoopOperation (ConditionIsTop: True, ConditionIsUntil: False) (LoopKind.Wh
       IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'value -= 1')
         Expression: 
           ICompoundAssignmentOperation (BinaryOperatorKind.Subtract, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'value -= 1')
+            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Left: 
               ILocalReferenceOperation: value (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'value')
             Right: 
@@ -547,6 +557,8 @@ IWhileLoopOperation (ConditionIsTop: True, ConditionIsUntil: False) (LoopKind.Wh
       IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'number += 1')
         Expression: 
           ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'number += 1')
+            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Left: 
               IParameterReferenceOperation: number (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'number')
             Right: 
@@ -606,6 +618,8 @@ IWhileLoopOperation (ConditionIsTop: True, ConditionIsUntil: False) (LoopKind.Wh
       IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'number += 1')
         Expression: 
           ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'number += 1')
+            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Left: 
               IParameterReferenceOperation: number (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'number')
             Right: 
@@ -751,6 +765,8 @@ IWhileLoopOperation (ConditionIsTop: True, ConditionIsUntil: False) (LoopKind.Wh
       IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'i += 1')
         Expression: 
           ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'i += 1')
+            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Left: 
               ILocalReferenceOperation: i (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'i')
             Right: 
@@ -822,6 +838,8 @@ IWhileLoopOperation (ConditionIsTop: True, ConditionIsUntil: False) (LoopKind.Wh
       IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'i += 1')
         Expression: 
           ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'i += 1')
+            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Left: 
               ILocalReferenceOperation: i (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'i')
             Right: 
@@ -877,6 +895,8 @@ IWhileLoopOperation (ConditionIsTop: True, ConditionIsUntil: False) (LoopKind.Wh
       IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'i += 1')
         Expression: 
           ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'i += 1')
+            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Left: 
               ILocalReferenceOperation: i (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'i')
             Right: 
@@ -902,6 +922,8 @@ IWhileLoopOperation (ConditionIsTop: True, ConditionIsUntil: False) (LoopKind.Wh
             IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'j += 1')
               Expression: 
                 ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'j += 1')
+                  InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                  OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                   Left: 
                     ILocalReferenceOperation: j (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'j')
                   Right: 
@@ -970,6 +992,8 @@ IWhileLoopOperation (ConditionIsTop: True, ConditionIsUntil: False) (LoopKind.Wh
       IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'i += 1')
         Expression: 
           ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'i += 1')
+            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Left: 
               ILocalReferenceOperation: i (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'i')
             Right: 
@@ -995,6 +1019,8 @@ IWhileLoopOperation (ConditionIsTop: True, ConditionIsUntil: False) (LoopKind.Wh
             IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'j += 1')
               Expression: 
                 ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'j += 1')
+                  InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                  OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
                   Left: 
                     ILocalReferenceOperation: j (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'j')
                   Right: 
@@ -1115,6 +1141,8 @@ IWhileLoopOperation (ConditionIsTop: True, ConditionIsUntil: False) (LoopKind.Wh
       IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'i += 1')
         Expression: 
           ICompoundAssignmentOperation (BinaryOperatorKind.Add, Checked) (OperationKind.CompoundAssignment, Type: System.Int32, IsImplicit) (Syntax: 'i += 1')
+            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
             Left: 
               ILocalReferenceOperation: i (OperationKind.LocalReference, Type: System.Int32) (Syntax: 'i')
             Right: 

src/Test/Utilities/Portable/Compilation/OperationTreeVerifier.cs

@@ -1321,6 +1321,12 @@ public override void VisitCompoundAssignment(ICompoundAssignmentOperation operat
             LogString($" ({kindStr})");
             LogHasOperatorMethodExpressionCommon(operation.OperatorMethod);
             LogCommonPropertiesAndNewLine(operation);
+            Indent();
+            LogConversion(operation.InConversion, "InConversion");
+            LogNewLine();
+            LogConversion(operation.OutConversion, "OutConversion");
+            LogNewLine();
+            Unindent();
 
             Visit(operation.Target, "Left");
             Visit(operation.Value, "Right");

src/Test/Utilities/Portable/Compilation/TestOperationWalker.cs

 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
+using System;
 using System.Collections.Immutable;
 using System.Diagnostics;
 using Microsoft.CodeAnalysis.CSharp;
@@ -539,6 +540,23 @@ public override void VisitCompoundAssignment(ICompoundAssignmentOperation operat
         {
             var operatorMethod = operation.OperatorMethod;
             var binaryOperationKind = operation.OperatorKind;
+            var inConversion = operation.InConversion;
+            var outConversion = operation.OutConversion;
+
+            if (operation.Syntax.Language == LanguageNames.CSharp)
+            {
+                Assert.Throws<ArgumentException>("compoundAssignment", () => VisualBasic.VisualBasicExtensions.GetInConversion(operation));
+                Assert.Throws<ArgumentException>("compoundAssignment", () => VisualBasic.VisualBasicExtensions.GetOutConversion(operation));
+                var inConversionInteranl = CSharp.CSharpExtensions.GetInConversion(operation);
+                var outConversionInteranl = CSharp.CSharpExtensions.GetOutConversion(operation);
+            }
+            else
+            {
+                Assert.Throws<ArgumentException>("compoundAssignment", () => CSharp.CSharpExtensions.GetInConversion(operation));
+                Assert.Throws<ArgumentException>("compoundAssignment", () => CSharp.CSharpExtensions.GetOutConversion(operation));
+                var inConversionInternal = VisualBasic.VisualBasicExtensions.GetInConversion(operation);
+                var outConversionInternal = VisualBasic.VisualBasicExtensions.GetOutConversion(operation);
+            }
 
             base.VisitCompoundAssignment(operation);
         }