[EnC] Allow renaming methods, properties, events etc.

src/Compilers/CSharp/Portable/Emitter/EditAndContinue/EmitHelpers.cs

@@ -198,10 +198,10 @@ internal static class EmitHelpers
                 currentSynthesizedMembers,
                 currentDeletedMembers);
 
-            var mappedSynthesizedMembers = matcher.MapSynthesizedMembers(previousGeneration.SynthesizedMembers, currentSynthesizedMembers);
+            var mappedSynthesizedMembers = matcher.MapSynthesizedOrDeletedMembers(previousGeneration.SynthesizedMembers, currentSynthesizedMembers, isDeletedMemberMapping: false);
 
             // Deleted members are mapped the same way as synthesized members, so we can just call the same method.
-            var mappedDeletedMembers = matcher.MapSynthesizedMembers(previousGeneration.DeletedMembers, currentDeletedMembers);
+            var mappedDeletedMembers = matcher.MapSynthesizedOrDeletedMembers(previousGeneration.DeletedMembers, currentDeletedMembers, isDeletedMemberMapping: true);
 
             // TODO: can we reuse some data from the previous matcher?
             var matcherWithAllSynthesizedMembers = new CSharpSymbolMatcher(

src/Compilers/CSharp/Test/Emit/Emit/EditAndContinue/EditAndContinueTest.GenerationVerifier.cs

@@ -65,6 +65,12 @@ internal void VerifyPropertyDefNames(params string[] expected)
                 AssertEx.Equal(expected, actual, message: GetAssertMessage("PropertyDefs don't match"));
             }
 
+            internal void VerifyDeletedMembers(params string[] expected)
+            {
+                var actual = _generationInfo.Baseline.DeletedMembers.Select(e => e.Key.ToString() + ": {" + string.Join(", ", e.Value.Select(v => v.Name)) + "}");
+                AssertEx.SetEqual(expected, actual, itemSeparator: ",\r\n", itemInspector: s => $"\"{s}\"");
+            }
+
             internal void VerifyTableSize(TableIndex table, int expected)
             {
                 AssertEx.AreEqual(expected, _metadataReader.GetTableRowCount(table), message: GetAssertMessage($"{table} table size doesnt't match"));

src/Compilers/CSharp/Test/Emit/Emit/EditAndContinue/EditAndContinueTest.cs

@@ -7,6 +7,7 @@
 using System.Collections.Immutable;
 using System.Linq;
 using System.Reflection.Metadata;
+using System.Runtime.InteropServices;
 using Microsoft.CodeAnalysis.CSharp.Test.Utilities;
 using Microsoft.CodeAnalysis.Emit;
 using Microsoft.CodeAnalysis.Test.Utilities;
@@ -112,7 +113,11 @@ private ImmutableArray<SemanticEdit> GetSemanticEdits(SemanticEditDescription[]
 
         public void Dispose()
         {
-            Assert.True(_hasVerified, "No Verify call since the last AddGeneration call.");
+            // If the test has thrown an exception, or the test host has crashed, we don't want to assert here
+            // or we'll hide it, so we need to do this dodgy looking thing.
+            var isInException = Marshal.GetExceptionPointers() != IntPtr.Zero;
+
+            Assert.True(isInException || _hasVerified, "No Verify call since the last AddGeneration call.");
             foreach (var disposable in _disposables)
             {
                 disposable.Dispose();

src/Compilers/CSharp/Test/Emit/Emit/EditAndContinue/EditAndContinueTests.cs

@@ -13624,7 +13624,7 @@ class C
                         }
                         """,
                     edits: new[] {
-                        Edit(SemanticEditKind.Delete, symbolProvider: c => c.GetMember("C.M2"), newSymbolProvider: c=>c.GetMember("C")),
+                        Edit(SemanticEditKind.Delete, symbolProvider: c => c.GetMember("C.M2"), newSymbolProvider: c => c.GetMember("C")),
                     },
                     validator: g =>
                     {
@@ -13679,7 +13679,7 @@ class C
                         }
                         """,
                     edits: new[] {
-                        Edit(SemanticEditKind.Delete, symbolProvider: c => c.GetMember("C.M1"), newSymbolProvider: c=>c.GetMember("C")),
+                        Edit(SemanticEditKind.Delete, symbolProvider: c => c.GetMember("C.M1"), newSymbolProvider: c => c.GetMember("C")),
                     },
                     validator: g =>
                     {
@@ -13781,7 +13781,7 @@ class C
                         }
                         """,
                     edits: new[] {
-                        Edit(SemanticEditKind.Delete, symbolProvider: c => c.GetMember("C.M1"), newSymbolProvider: c=>c.GetMember("C")),
+                        Edit(SemanticEditKind.Delete, symbolProvider: c => c.GetMember("C.M1"), newSymbolProvider: c => c.GetMember("C")),
                     },
                     validator: g =>
                     {
@@ -13958,7 +13958,7 @@ class C
                         }
                         """,
                     edits: new[] {
-                        Edit(SemanticEditKind.Delete, symbolProvider: c => c.GetMember("C.M1"), newSymbolProvider: c=>c.GetMember("C")),
+                        Edit(SemanticEditKind.Delete, symbolProvider: c => c.GetMember("C.M1"), newSymbolProvider: c => c.GetMember("C")),
                     },
                     validator: g =>
                     {
@@ -14039,6 +14039,63 @@ .maxstack  1
                 .Verify();
         }
 
+        [Fact]
+        public void Method_Rename_Multiple()
+        {
+            using var test = new EditAndContinueTest(options: TestOptions.DebugDll, targetFramework: TargetFramework.NetStandard20)
+                .AddGeneration(
+                    source: $$"""
+                        class C
+                        {
+                            int M1() { return 0; }
+                        }
+                        """,
+                    validator: g =>
+                    {
+                        g.VerifyTypeDefNames("<Module>", "C");
+                        g.VerifyMethodDefNames("M1", ".ctor");
+                        g.VerifyMemberRefNames(/*CompilationRelaxationsAttribute.*/".ctor", /*RuntimeCompatibilityAttribute.*/".ctor", /*Object.*/".ctor", /*DebuggableAttribute*/".ctor");
+                    });
+
+            for (int i = 0; i < 10; i++)
+            {
+                test.AddGeneration(
+                    source: @$"
+class C
+{{
+    int M2() {{ return {i}; }}
+}}",
+                    edits: new[] {
+                        Edit(SemanticEditKind.Delete, symbolProvider: c => c.GetMember("C.M1"), newSymbolProvider: c => c.GetMember("C")),
+                        Edit(SemanticEditKind.Insert, symbolProvider: c => c.GetMember("C.M2")),
+                    },
+                    validator: g =>
+                    {
+                        g.VerifyTypeDefNames();
+                        g.VerifyMethodDefNames("M1", "M2");
+                        g.VerifyDeletedMembers("C: {M1}");
+                    })
+                .AddGeneration(
+                    source: @$"
+class C
+{{
+    int M1() {{ return {i}; }}
+}}",
+                    edits: new[] {
+                        Edit(SemanticEditKind.Delete, symbolProvider: c => c.GetMember("C.M2"), newSymbolProvider: c => c.GetMember("C")),
+                        Edit(SemanticEditKind.Insert, symbolProvider: c => c.GetMember("C.M1")),
+                    },
+                    validator: g =>
+                    {
+                        g.VerifyTypeDefNames();
+                        g.VerifyMethodDefNames("M1", "M2");
+                        g.VerifyDeletedMembers("C: {M2}");
+                    });
+            }
+
+            test.Verify();
+        }
+
         [Fact]
         public void FileTypes_01()
         {

src/Compilers/Core/Portable/Emit/EditAndContinue/DeltaMetadataWriter.cs

@@ -190,6 +190,9 @@ internal EmitBaseline GetDelta(Compilation compilation, Guid encId, MetadataSize
             // otherwise members from the current compilation have already been merged into the baseline.
             var synthesizedMembers = (_previousGeneration.Ordinal == 0) ? module.GetAllSynthesizedMembers() : _previousGeneration.SynthesizedMembers;
 
+            Debug.Assert(module.EncSymbolChanges is not null);
+            var deletedMembers = (_previousGeneration.Ordinal == 0) ? module.EncSymbolChanges.GetAllDeletedMethods() : _previousGeneration.DeletedMembers;
+
             var currentGenerationOrdinal = _previousGeneration.Ordinal + 1;
 
             var addedTypes = _typeDefs.GetAdded();
@@ -231,7 +234,7 @@ internal EmitBaseline GetDelta(Compilation compilation, Guid encId, MetadataSize
                 anonymousDelegates: ((IPEDeltaAssemblyBuilder)module).GetAnonymousDelegates(),
                 anonymousDelegatesWithFixedTypes: ((IPEDeltaAssemblyBuilder)module).GetAnonymousDelegatesWithFixedTypes(),
                 synthesizedMembers: synthesizedMembers,
-                deletedMembers: _previousGeneration.DeletedMembers,
+                deletedMembers: deletedMembers,
                 addedOrChangedMethods: AddRange(_previousGeneration.AddedOrChangedMethods, addedOrChangedMethodsByIndex),
                 debugInformationProvider: _previousGeneration.DebugInformationProvider,
                 localSignatureProvider: _previousGeneration.LocalSignatureProvider);

src/Compilers/Core/Portable/Emit/EditAndContinue/SymbolMatcher.cs

@@ -146,8 +146,8 @@ internal abstract class SymbolMatcher
         }
 
         /// <summary>
-        /// Merges synthesized members generated during lowering of the current compilation with aggregate synthesized members 
-        /// from all previous source generations (gen >= 1).
+        /// Merges synthesized or deleted members generated during lowering, or emit, of the current compilation with aggregate
+        /// synthesized or deleted members from all previous source generations (gen >= 1).
         /// </summary>
         /// <remarks>
         /// Suppose {S -> {A, B, D}, T -> {E, F}} are all synthesized members in previous generations,
@@ -159,9 +159,10 @@ internal abstract class SymbolMatcher
         /// Then the resulting collection shall have the following entries:
         /// {S' -> {A', B', C, D}, U -> {G, H}, T -> {E, F}}
         /// </remarks>
-        internal ImmutableDictionary<ISymbolInternal, ImmutableArray<ISymbolInternal>> MapSynthesizedMembers(
+        internal ImmutableDictionary<ISymbolInternal, ImmutableArray<ISymbolInternal>> MapSynthesizedOrDeletedMembers(
             ImmutableDictionary<ISymbolInternal, ImmutableArray<ISymbolInternal>> previousMembers,
-            ImmutableDictionary<ISymbolInternal, ImmutableArray<ISymbolInternal>> newMembers)
+            ImmutableDictionary<ISymbolInternal, ImmutableArray<ISymbolInternal>> newMembers,
+            bool isDeletedMemberMapping)
         {
             // Note: we can't just return previous members if there are no new members, since we still need to map the symbols to the new compilation.
 
@@ -174,11 +175,8 @@ internal abstract class SymbolMatcher
 
             synthesizedMembersBuilder.AddRange(newMembers);
 
-            foreach (var pair in previousMembers)
+            foreach (var (previousContainer, members) in previousMembers)
             {
-                var previousContainer = pair.Key;
-                var members = pair.Value;
-
                 var mappedContainer = MapDefinitionOrNamespace(previousContainer);
                 if (mappedContainer == null)
                 {
@@ -207,7 +205,11 @@ internal abstract class SymbolMatcher
                         // If the matcher found a member in the current compilation corresponding to previous memberDef,
                         // then the member has to be synthesized and produced as a result of a method update 
                         // and thus already contained in newSynthesizedMembers.
-                        Debug.Assert(newSynthesizedMembers.Contains(mappedMember));
+                        // However, because this method is also used to map deleted members, it's possible that a method
+                        // could be renamed in the previous generation, and renamed back in this generation, which would
+                        // mean it could be mapped, but isn't in the newSynthesizedMembers list, so we allow the flag to
+                        // override this behaviour for deleted methods.
+                        Debug.Assert(isDeletedMemberMapping || newSynthesizedMembers.Contains(mappedMember));
                     }
                     else
                     {

src/Compilers/VisualBasic/Portable/Emit/EditAndContinue/EmitHelpers.vb

@@ -135,8 +135,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Emit
                 currentSynthesizedMembers,
                 currentDeletedMembers)
 
-            Dim mappedSynthesizedMembers = matcher.MapSynthesizedMembers(previousGeneration.SynthesizedMembers, currentSynthesizedMembers)
-            Dim mappedDeletedMembers = matcher.MapSynthesizedMembers(previousGeneration.DeletedMembers, currentDeletedMembers)
+            Dim mappedSynthesizedMembers = matcher.MapSynthesizedOrDeletedMembers(previousGeneration.SynthesizedMembers, currentSynthesizedMembers, isDeletedMemberMapping:=False)
+            Dim mappedDeletedMembers = matcher.MapSynthesizedOrDeletedMembers(previousGeneration.DeletedMembers, currentDeletedMembers, isDeletedMemberMapping:=True)
 
             ' TODO can we reuse some data from the previous matcher?
             Dim matcherWithAllSynthesizedMembers = New VisualBasicSymbolMatcher(

src/EditorFeatures/CSharpTest/EditAndContinue/ActiveStatementTests.Methods.cs

@@ -52,8 +52,43 @@ static void Main(string[] args)
                 new[] { edits },
                 new[]
                 {
-                    DocumentResults(active,
-                    new[] { SemanticEdit(SemanticEditKind.Delete, c => c.GetMember("C.Goo"), deletedSymbolContainerProvider: c => c.GetMember("C")) })
+                    DocumentResults(
+                        active,
+                        diagnostics: new[] { Diagnostic(RudeEditKind.Delete, "class C", DeletedSymbolDisplay(FeaturesResources.method, "Goo(int a)")) })
+                });
+        }
+
+        [Fact]
+        public void Method_Rename_Leaf1()
+        {
+            var src1 = @"
+class C
+{
+    static void Goo(int a)
+    {
+        <AS:0>Console.WriteLine(a);</AS:0>
+    }
+}";
+            var src2 = @"
+class C
+{
+    static void Boo(int a)
+    {
+        <AS:0>Console.WriteLine(a);</AS:0>
+    }
+}
+";
+
+            var edits = GetTopEdits(src1, src2);
+            var active = GetActiveStatements(src1, src2);
+
+            EditAndContinueValidation.VerifySemantics(
+                new[] { edits },
+                new[]
+                {
+                    DocumentResults(
+                        active,
+                        diagnostics: new[] {Diagnostic(RudeEditKind.UpdateAroundActiveStatement, "static void Boo(int a)", FeaturesResources.method) })
                 });
         }