Reverted IsImplicit to original code to be able to handle lowered bound trees in the future.

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

@@ -796,7 +796,7 @@ private IConversionOperation CreateBoundAsOperatorOperation(BoundAsOperator boun
             bool isChecked = false;
             ITypeSymbol type = boundAsOperator.Type;
             Optional<object> constantValue = ConvertToOptional(boundAsOperator.ConstantValue);
-            bool isImplicit = false; // as expressions can never be implicitly created
+            bool isImplicit = boundAsOperator.WasCompilerGenerated;
             return new LazyCSharpConversionExpression(operand, conversion, isTryCast, isChecked, _semanticModel, syntax, type, constantValue, isImplicit);
         }
 

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

@@ -517,7 +517,7 @@ Namespace Microsoft.CodeAnalysis.Operations
         Private Function CreateBoundTryCastOperation(boundTryCast As BoundTryCast) As IOperation
             Dim syntax As SyntaxNode = boundTryCast.Syntax
             Dim type As ITypeSymbol = boundTryCast.Type
-            Dim isImplicit As Boolean = False ' Try Cast can never be an implicit operation
+            Dim isImplicit As Boolean = boundTryCast.WasCompilerGenerated
 
             Dim constantValue As [Optional](Of Object) = ConvertToOptional(boundTryCast.ConstantValueOpt)
             Dim conversionInformation = CreateConversionOperand(boundTryCast.Operand, boundTryCast.ConversionKind, boundTryCast.Syntax, boundTryCast.Type)
@@ -540,7 +540,7 @@ Namespace Microsoft.CodeAnalysis.Operations
             Dim syntax As SyntaxNode = boundDirectCast.Syntax
             Dim type As ITypeSymbol = boundDirectCast.Type
             Dim constantValue As [Optional](Of Object) = ConvertToOptional(boundDirectCast.ConstantValueOpt)
-            Dim isImplicit As Boolean = False ' Direct Cast can never be an implicit operation
+            Dim isImplicit As Boolean = boundDirectCast.WasCompilerGenerated
 
             Dim conversionInformation = CreateConversionOperand(boundDirectCast.Operand, boundDirectCast.ConversionKind, boundDirectCast.Syntax, boundDirectCast.Type)
             Dim operand As Lazy(Of IOperation) = conversionInformation.Operation