Added tests for unbound lambdas in the operation tree.

src/Compilers/CSharp/Test/Semantic/CSharpCompilerSemanticTest.csproj

@@ -65,6 +65,7 @@
     <Compile Include="IOperation\IOperationTests_IArgument.cs" />
     <Compile Include="IOperation\IOperationTests_IIfStatement.cs" />
     <Compile Include="IOperation\IOperationTests_IFieldReferenceExpression.cs" />
+    <Compile Include="IOperation\IOperationTests_ILambdaExpression.cs" />
     <Compile Include="IOperation\IOperationTests_IObjectCreationExpression.cs" />
     <Compile Include="IOperation\IOperationTests_IParameterReferenceExpression.cs" />
     <Compile Include="IOperation\IOperationTests_IReturnStatement.cs" />

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

+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Test.Utilities;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.CSharp.UnitTests
+{
+    internal partial class IOperationTests : SemanticModelTestBase
+    {
+        [Fact]
+        public void ILambdaExpression_BoundLambda_HasValidLambdaExpressionTree()
+        {
+            string source = @"
+using System;
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        Action x /*<bind>*/= () => F()/*</bind>*/;
+    }
+
+    static void F()
+    {
+    }
+}
+";
+            string expectedOperationTree = @"
+IVariableDeclarationStatement (1 declarations) (OperationKind.VariableDeclarationStatement) (Syntax: 'Action x /* ... *</bind>*/;')
+  IVariableDeclaration (1 variables) (OperationKind.VariableDeclaration) (Syntax: 'Action x /* ... *</bind>*/;')
+    Variables: Local_1: System.Action x
+    Initializer: IConversionExpression (ConversionKind.CSharp, Implicit) (OperationKind.ConversionExpression, Type: System.Action) (Syntax: '() => F()')
+        ILambdaExpression (Signature: lambda expression) (OperationKind.LambdaExpression, Type: null) (Syntax: '() => F()')
+          IBlockStatement (2 statements) (OperationKind.BlockStatement) (Syntax: 'F()')
+            IExpressionStatement (OperationKind.ExpressionStatement) (Syntax: 'F()')
+              IInvocationExpression (static void Program.F()) (OperationKind.InvocationExpression, Type: System.Void) (Syntax: 'F()')
+            IReturnStatement (OperationKind.ReturnStatement) (Syntax: 'F()')
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            VerifyOperationTreeAndDiagnosticsForTest<EqualsValueClauseSyntax>(source, expectedOperationTree, expectedDiagnostics);
+        }
+
+        [Fact]
+        public void ILambdaExpression_UnboundLambdaAsVar_HasValidLambdaExpressionTree()
+        {
+            string source = @"
+using System;
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        var x /*<bind>*/= () => F()/*</bind>*/;
+    }
+
+    static void F()
+    {
+    }
+}
+";
+            string expectedOperationTree = @"
+IVariableDeclarationStatement (1 declarations) (OperationKind.VariableDeclarationStatement, IsInvalid) (Syntax: 'var x /*<bi ... *</bind>*/;')
+  IVariableDeclaration (1 variables) (OperationKind.VariableDeclaration) (Syntax: 'var x /*<bi ... *</bind>*/;')
+    Variables: Local_1: var x
+    Initializer: ILambdaExpression (Signature: lambda expression) (OperationKind.LambdaExpression, Type: null) (Syntax: '() => F()')
+        IBlockStatement (1 statements) (OperationKind.BlockStatement) (Syntax: 'F()')
+          IExpressionStatement (OperationKind.ExpressionStatement) (Syntax: 'F()')
+            IInvocationExpression (static void Program.F()) (OperationKind.InvocationExpression, Type: System.Void) (Syntax: 'F()')
+";
+            var expectedDiagnostics = new DiagnosticDescription[] {
+                // CS0815: Cannot assign lambda expression to an implicitly-typed variable
+                //         var x /*<bind>*/= () => F()/*</bind>*/;
+                Diagnostic(ErrorCode.ERR_ImplicitlyTypedVariableAssignedBadValue, "x /*<bind>*/= () => F()").WithArguments("lambda expression").WithLocation(8, 13),
+            };
+
+            VerifyOperationTreeAndDiagnosticsForTest<EqualsValueClauseSyntax>(source, expectedOperationTree, expectedDiagnostics);
+        }
+
+        [Fact]
+        public void ILambdaExpression_UnboundLambdaAsDelegate_HasValidLambdaExpressionTree()
+        {
+            string source = @"
+using System;
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        Action<int> x /*<bind>*/= () => F()/*</bind>*/;
+    }
+
+    static void F()
+    {
+    }
+}
+";
+            string expectedOperationTree = @"
+IVariableDeclarationStatement (1 declarations) (OperationKind.VariableDeclarationStatement, IsInvalid) (Syntax: 'Action<int> ... *</bind>*/;')
+  IVariableDeclaration (1 variables) (OperationKind.VariableDeclaration, IsInvalid) (Syntax: 'Action<int> ... *</bind>*/;')
+    Variables: Local_1: System.Action<System.Int32> x
+    Initializer: IConversionExpression (ConversionKind.Invalid, Implicit) (OperationKind.ConversionExpression, Type: System.Action<System.Int32>, IsInvalid) (Syntax: '() => F()')
+        ILambdaExpression (Signature: lambda expression) (OperationKind.LambdaExpression, Type: null) (Syntax: '() => F()')
+          IBlockStatement (1 statements) (OperationKind.BlockStatement) (Syntax: 'F()')
+            IExpressionStatement (OperationKind.ExpressionStatement) (Syntax: 'F()')
+              IInvocationExpression (static void Program.F()) (OperationKind.InvocationExpression, Type: System.Void) (Syntax: 'F()')
+";
+            var expectedDiagnostics = new DiagnosticDescription[] {
+                // CS1593: Delegate 'Action<int>' does not take 0 arguments
+                //         Action<int> x /*<bind>*/= () => F()/*</bind>*/;
+                Diagnostic(ErrorCode.ERR_BadDelArgCount, "() => F()").WithArguments("System.Action<int>", "0").WithLocation(8, 35)
+            };
+
+            VerifyOperationTreeAndDiagnosticsForTest<EqualsValueClauseSyntax>(source, expectedOperationTree, expectedDiagnostics);
+        }
+    }
+}