Fix issue with EE scenario

dotnet · Nov 5, 2016 · 31e9421 · 31e9421
1 parent ecce74d
commit 31e9421
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Showing 2 changed files with 19 additions and 3 deletions.
diff --git a/src/ExpressionEvaluator/CSharp/Source/ExpressionCompiler/CompilationContext.cs b/src/ExpressionEvaluator/CSharp/Source/ExpressionCompiler/CompilationContext.cs
@@ -53,7 +53,7 @@ internal sealed class CompilationContext
             MethodDebugInfo<TypeSymbol, LocalSymbol> methodDebugInfo,
             CSharpSyntaxNode syntax)
         {
-            Debug.Assert((syntax == null) || (syntax is ExpressionSyntax) || (syntax is LocalDeclarationStatementSyntax));
+            Debug.Assert((syntax == null) || (syntax is ExpressionSyntax) || (syntax is LocalDeclarationStatementSyntax) || (syntax is ExpressionStatementSyntax));
 
             // TODO: syntax.SyntaxTree should probably be added to the compilation,
             // but it isn't rooted by a CompilationUnitSyntax so it doesn't work (yet).

diff --git a/src/ExpressionEvaluator/CSharp/Source/ExpressionCompiler/EvaluationContext.cs b/src/ExpressionEvaluator/CSharp/Source/ExpressionCompiler/EvaluationContext.cs
@@ -12,6 +12,7 @@
 using System.Threading;
 using Microsoft.CodeAnalysis.CSharp.Symbols;
 using Microsoft.CodeAnalysis.CSharp.Symbols.Metadata.PE;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Emit;
 using Microsoft.CodeAnalysis.ExpressionEvaluator;
 using Microsoft.DiaSymReader;
@@ -301,11 +302,17 @@ private static MethodSymbol GetSynthesizedMethod(CommonPEModuleBuilder moduleBui
                 Debug.Assert((statementSyntax == null) || !statementDiagnostics.HasAnyErrors());
                 statementDiagnostics.Free();
 
-                if (statementSyntax != null && !statementSyntax.IsKind(SyntaxKind.ExpressionStatement)) // Prefer to parse expression statements as expressions.
+                // Prefer to parse expression statements (except deconstruction-declarations) as expressions.
+                var isExpressionStatement = statementSyntax.IsKind(SyntaxKind.ExpressionStatement);
+                var isDeconstructionDeclaration = isExpressionStatement &&
+                                                  IsDeconstructionDeclaration((ExpressionStatementSyntax)statementSyntax);
+
+                if (statementSyntax != null && (!isExpressionStatement || isDeconstructionDeclaration))
                 {
                     formatSpecifiers = null;
 
-                    if (statementSyntax.IsKind(SyntaxKind.LocalDeclarationStatement))
+                    if (statementSyntax.IsKind(SyntaxKind.LocalDeclarationStatement) ||
+                        isDeconstructionDeclaration)
                     {
                         return statementSyntax;
                     }
@@ -318,6 +325,15 @@ private static MethodSymbol GetSynthesizedMethod(CommonPEModuleBuilder moduleBui
             return expr.ParseExpression(diagnostics, allowFormatSpecifiers: true, formatSpecifiers: out formatSpecifiers);
         }
 
+        private static bool IsDeconstructionDeclaration(ExpressionStatementSyntax expressionStatement)
+        {
+            if (!expressionStatement.Expression.IsKind(SyntaxKind.SimpleAssignmentExpression))
+            {
+                return false;
+            }
+            return ((AssignmentExpressionSyntax)expressionStatement.Expression).IsDeconstructionDeclaration();
+        }
+
         internal override CompileResult CompileAssignment(
             string target,
             string expr,