Enc: async/iterator editing regression fix

src/EditorFeatures/CSharpTest/EditAndContinue/ActiveStatementTests.cs

@@ -7856,6 +7856,76 @@ static async void F()
             edits.VerifyRudeDiagnostics(active);
         }
 
+        [Fact]
+        public void AsyncMethodEdit_Semantics()
+        {
+            string src1 = @"
+using System;
+using System.Threading.Tasks;
+
+class C
+{
+    static async Task<int> F()
+    {
+        Console.WriteLine(1);
+        return await Task.FromResult(1);
+    }
+}
+";
+            string src2 = @"
+using System;
+using System.Threading.Tasks;
+
+class C
+{
+    static async Task<int> F()
+    {
+        Console.WriteLine(2);
+        return await Task.FromResult(1);
+    }
+}
+";
+            var edits = GetTopEdits(src1, src2);
+            var active = GetActiveStatements(src1, src2);
+
+            edits.VerifySemanticDiagnostics();
+        }
+
+        [Fact]
+        public void IteratorMethodEdit_Semantics()
+        {
+            string src1 = @"
+using System;
+using System.Collections.Generic;
+
+class C
+{
+    static IEnumerable<int> F()
+    {
+        Console.WriteLine(1);
+        yield return 1;
+    }
+}
+";
+            string src2 = @"
+using System;
+using System.Collections.Generic;
+
+class C
+{
+    static IEnumerable<int> F()
+    {
+        Console.WriteLine(2);
+        yield return 2;
+    }
+}
+";
+            var edits = GetTopEdits(src1, src2);
+            var active = GetActiveStatements(src1, src2);
+
+            edits.VerifySemanticDiagnostics();
+        }
+
         #endregion
 
         #region Misplaced AS 

src/Features/Core/Portable/EditAndContinue/AbstractEditAndContinueAnalyzer.cs

@@ -2312,7 +2312,7 @@ public ConstructorEdit(INamedTypeSymbol oldType)
                             {
                                 var updatedMember = updatedMembers[updatedMemberIndex];
 
-                                ReportStateMachineRudeEdits(updatedMember, oldSymbol, diagnostics);
+                                ReportStateMachineRudeEdits(oldModel.Compilation, updatedMember, oldSymbol, diagnostics);
 
                                 bool newBodyHasLambdas;
                                 ReportLambdaAndClosureRudeEdits(
@@ -3703,6 +3703,7 @@ private bool AreEquivalentClosureScopes(SyntaxNode oldScopeOpt, SyntaxNode newSc
         #region State Machines
 
         private void ReportStateMachineRudeEdits(
+            Compilation oldCompilation,
             UpdatedMemberInfo updatedInfo, 
             ISymbol oldMember, 
             List<RudeEditDiagnostic> diagnostics)
@@ -3719,7 +3720,7 @@ private bool AreEquivalentClosureScopes(SyntaxNode oldScopeOpt, SyntaxNode newSc
 
             // We assume that the attributes, if exist, are well formed.
             // If not an error will be reported during EnC delta emit.
-            if (oldMember.ContainingAssembly.GetTypeByMetadataName(stateMachineAttributeQualifiedName) == null)
+            if (oldCompilation.GetTypeByMetadataName(stateMachineAttributeQualifiedName) == null)
             {
                 diagnostics.Add(new RudeEditDiagnostic(
                     RudeEditKind.UpdatingStateMachineMethodMissingAttribute,