Don't give duplicate member error for explicit implementations of dif…

…ferent file-local interfaces with same source name
dotnet · May 27, 2023 · c8889b1 · c8889b1
1 parent 32b9156
commit c8889b1
Show file tree

Hide file tree

Showing 2 changed files with 492 additions and 3 deletions.
diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberContainerSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberContainerSymbol.cs
@@ -1948,10 +1948,23 @@ private void CheckMemberNameConflicts(BindingDiagnosticBag diagnostics)
                         {
                             if (symbol.Kind != SymbolKind.Field || !symbol.IsImplicitlyDeclared)
                             {
-                                // The type '{0}' already contains a definition for '{1}'
-                                if (Locations.Length == 1 || IsPartial)
+                                var explicitImplementations = symbol.GetExplicitInterfaceImplementations();
+                                var lastExplicitImplementations = lastSym.GetExplicitInterfaceImplementations();
+
+                                // Source symbols can only explicitly implement at most 1 member
+                                Debug.Assert(explicitImplementations.Length is 0 or 1 && explicitImplementations.Length == lastExplicitImplementations.Length);
+
+                                // Sometimes two non-overloadable members can have exactly the same source name, but be explicit implementations of different members.
+                                // For example, when explicitly implementing members of file-local interfaces.
+                                // We don't consider such members to be duplicates.
+                                if (explicitImplementations.Length == 0
+                                    || explicitImplementations[0].Equals(lastExplicitImplementations[0], TypeCompareKind.AllIgnoreOptions))
                                 {
-                                    diagnostics.Add(ErrorCode.ERR_DuplicateNameInClass, symbol.GetFirstLocation(), this, symbol.Name);
+                                    // The type '{0}' already contains a definition for '{1}'
+                                    if (Locations.Length == 1 || IsPartial)
+                                    {
+                                        diagnostics.Add(ErrorCode.ERR_DuplicateNameInClass, symbol.GetFirstLocation(), this, symbol.Name);
+                                    }
                                 }
                             }