GC plugin: remove mixin trace override restriction.

tools/clang/blink_gc_plugin/BlinkGCPluginConsumer.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "BlinkGCPluginConsumer.h"
 
 #include <algorithm>
 #include <set>
 
 #include "CheckDispatchVisitor.h"
@@ skipping 131 matching lines @@
     " is not permitted to declare a pure-virtual trace method.";
 
 const char kLeftMostBaseMustBePolymorphic[] =
     "[blink-gc] Left-most base class %0 of derived class %1"
     " must be polymorphic.";
 
 const char kBaseClassMustDeclareVirtualTrace[] =
     "[blink-gc] Left-most base class %0 of derived class %1"
     " must define a virtual trace method.";
 
-const char kClassMustDeclareGCMixinTraceMethod[] =
-    "[blink-gc] Class %0 which inherits from GarbageCollectedMixin must"
-    " locally declare and override trace(Visitor*)";
-
 // Use a local RAV implementation to simply collect all FunctionDecls marked for
 // late template parsing. This happens with the flag -fdelayed-template-parsing,
 // which is on by default in MSVC-compatible mode.
 std::set<FunctionDecl*> GetLateParsedFunctionDecls(TranslationUnitDecl* decl) {
   struct Visitor : public RecursiveASTVisitor<Visitor> {
     bool VisitFunctionDecl(FunctionDecl* function_decl) {
       if (function_decl->isLateTemplateParsed())
         late_parsed_decls.insert(function_decl);
       return true;
     }
@@ skipping 78 matching lines @@
   diag_derives_non_stack_allocated_ =
       diagnostic_.getCustomDiagID(getErrorLevel(), kDerivesNonStackAllocated);
   diag_class_overrides_new_ =
       diagnostic_.getCustomDiagID(getErrorLevel(), kClassOverridesNew);
   diag_class_declares_pure_virtual_trace_ = diagnostic_.getCustomDiagID(
       getErrorLevel(), kClassDeclaresPureVirtualTrace);
   diag_left_most_base_must_be_polymorphic_ = diagnostic_.getCustomDiagID(
       getErrorLevel(), kLeftMostBaseMustBePolymorphic);
   diag_base_class_must_declare_virtual_trace_ = diagnostic_.getCustomDiagID(
       getErrorLevel(), kBaseClassMustDeclareVirtualTrace);
-  diag_class_must_declare_gc_mixin_trace_method_ =
-      diagnostic_.getCustomDiagID(getErrorLevel(),
-                                  kClassMustDeclareGCMixinTraceMethod);
 
   // Register note messages.
   diag_base_requires_tracing_note_ = diagnostic_.getCustomDiagID(
       DiagnosticsEngine::Note, kBaseRequiresTracingNote);
   diag_field_requires_tracing_note_ = diagnostic_.getCustomDiagID(
       DiagnosticsEngine::Note, kFieldRequiresTracingNote);
   diag_raw_ptr_to_gc_managed_class_note_ = diagnostic_.getCustomDiagID(
       DiagnosticsEngine::Note, kRawPtrToGCManagedClassNote);
   diag_ref_ptr_to_gc_managed_class_note_ = diagnostic_.getCustomDiagID(
       DiagnosticsEngine::Note, kRefPtrToGCManagedClassNote);
@@ skipping 170 matching lines @@
       ReportClassContainsInvalidFields(info, &visitor.invalid_fields());
   }
 
   if (info->IsGCDerived()) {
     if (!info->IsGCMixin()) {
       CheckLeftMostDerived(info);
       CheckDispatch(info);
       if (CXXMethodDecl* newop = info->DeclaresNewOperator())
         if (!Config::IsIgnoreAnnotated(newop))
           ReportClassOverridesNew(info, newop);
-      if (info->IsGCMixinInstance()) {
-        // Require that declared GCMixin implementations
-        // also provide a trace() override.
-        if (info->DeclaresGCMixinMethods()
-            && !info->DeclaresLocalTraceMethod())
-          ReportClassMustDeclareGCMixinTraceMethod(info);
-      }
     }
 
     {
       CheckGCRootsVisitor visitor;
       if (visitor.ContainsGCRoots(info))
         ReportClassContainsGCRoots(info, &visitor.gc_roots());
     }
 
     if (info->NeedsFinalization())
       CheckFinalization(info);
@@ skipping 646 matching lines @@
       << info->record();
 }
 
 void BlinkGCPluginConsumer::ReportClassDoesNotRequireFinalization(
     RecordInfo* info) {
   ReportDiagnostic(info->record()->getInnerLocStart(),
                    diag_class_does_not_require_finalization_)
       << info->record();
 }
 
-void BlinkGCPluginConsumer::ReportClassMustDeclareGCMixinTraceMethod(
-    RecordInfo* info) {
-  ReportDiagnostic(info->record()->getInnerLocStart(),
-                   diag_class_must_declare_gc_mixin_trace_method_)
-      << info->record();
-}
-
 void BlinkGCPluginConsumer::ReportOverriddenNonVirtualTrace(
     RecordInfo* info,
     CXXMethodDecl* trace,
     CXXMethodDecl* overridden) {
   ReportDiagnostic(trace->getLocStart(), diag_overridden_non_virtual_trace_)
       << info->record() << overridden->getParent();
   NoteOverriddenNonVirtualTrace(overridden);
 }
 
 void BlinkGCPluginConsumer::ReportMissingTraceDispatchMethod(RecordInfo* info) {
@@ skipping 129 matching lines @@
 void BlinkGCPluginConsumer::NoteField(FieldDecl* field, unsigned note) {
   ReportDiagnostic(field->getLocStart(), note) << field;
 }
 
 void BlinkGCPluginConsumer::NoteOverriddenNonVirtualTrace(
     CXXMethodDecl* overridden) {
   ReportDiagnostic(overridden->getLocStart(),
                    diag_overridden_non_virtual_trace_note_)
       << overridden;
 }