Merge pull request #9625 from DustinCampbell/issue-9576

Fix null ref in C# expander when adding cast to lambda return statement

src/EditorFeatures/CSharpTest/CodeActions/InlineTemporary/InlineTemporaryTests.cs

@@ -3888,5 +3888,45 @@ static void N(int x, int y)
 }";
             await TestAsync(initial, expected, compareTokens: false);
         }
+
+        [WorkItem(9576, "https://github.com/dotnet/roslyn/issues/9576")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsInlineTemporary)]
+        public async Task InlineIntoLambdaWithReturnStatementWithNoExpression()
+        {
+            const string initial = @"
+using System;
+class C
+{
+    static void M(Action a) { }
+
+    static void N()
+    {
+        var [||]x = 42;
+        M(() =>
+        {
+            Console.WriteLine(x);
+            return;
+        });
+    }
+}";
+
+            const string expected = @"
+using System;
+class C
+{
+    static void M(Action a) { }
+
+    static void N()
+    {
+        M(() =>
+        {
+            Console.WriteLine(42);
+            return;
+        });
+    }
+}";
+
+            await TestAsync(initial, expected, compareTokens: false);
+        }
     }
 }

src/Workspaces/CSharp/Portable/Simplification/CSharpSimplificationService.Expander.cs

@@ -141,17 +141,19 @@ public override SyntaxNode VisitReturnStatement(ReturnStatementSyntax node)
                 if (newNode is ReturnStatementSyntax)
                 {
                     var newReturnStatement = (ReturnStatementSyntax)newNode;
-
-                    var parentLambda = node.FirstAncestorOrSelf<LambdaExpressionSyntax>();
-                    if (parentLambda != null)
+                    if (newReturnStatement.Expression != null)
                     {
-                        var returnType = (_semanticModel.GetSymbolInfo(parentLambda).Symbol as IMethodSymbol)?.ReturnType;
-                        if (returnType != null)
+                        var parentLambda = node.FirstAncestorOrSelf<LambdaExpressionSyntax>();
+                        if (parentLambda != null)
                         {
-                            ExpressionSyntax newExpressionWithCast;
-                            if (TryCastTo(returnType, node.Expression, newReturnStatement.Expression, out newExpressionWithCast))
+                            var returnType = (_semanticModel.GetSymbolInfo(parentLambda).Symbol as IMethodSymbol)?.ReturnType;
+                            if (returnType != null)
                             {
-                                newNode = newReturnStatement.WithExpression(newExpressionWithCast);
+                                ExpressionSyntax newExpressionWithCast;
+                                if (TryCastTo(returnType, node.Expression, newReturnStatement.Expression, out newExpressionWithCast))
+                                {
+                                    newNode = newReturnStatement.WithExpression(newExpressionWithCast);
+                                }
                             }
                         }
                     }