Revert commits related to "[C23] Implement WG14 N3037"

clang/docs/ReleaseNotes.rst

@@ -296,13 +296,6 @@ C23 Feature Support
   scope.
 - Fixed a bug where you could not cast a null pointer constant to type
   ``nullptr_t``. Fixes #GH133644.
-- Implemented `WG14 N3037 <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3037.pdf>`_
-  which allows tag types to be redefined within the same translation unit so
-  long as both definitions are structurally equivalent (same tag types, same
-  tag names, same tag members, etc). As a result of this paper, ``-Wvisibility``
-  is no longer diagnosed in C23 if the parameter is a complete tag type (it
-  does still fire when the parameter is an incomplete tag type as that cannot
-  be completed).
 - Fixed a failed assertion with an invalid parameter to the ``#embed``
   directive. Fixes #GH126940.
 - Fixed a crash when a declaration of a ``constexpr`` variable with an invalid

clang/include/clang/AST/ASTContext.h

@@ -3354,7 +3354,6 @@ class ASTContext : public RefCountedBase<ASTContext> {
   QualType mergeTransparentUnionType(QualType, QualType,
                                      bool OfBlockPointer=false,
                                      bool Unqualified = false);
-  QualType mergeTagDefinitions(QualType, QualType);
 
   QualType mergeObjCGCQualifiers(QualType, QualType);
 

clang/include/clang/AST/ASTStructuralEquivalence.h

@@ -43,9 +43,6 @@ struct StructuralEquivalenceContext {
   /// key: (from, to, IgnoreTemplateParmDepth)
   using NonEquivalentDeclSet = llvm::DenseSet<std::tuple<Decl *, Decl *, int>>;
 
-  /// The language options to use for making a structural equivalence check.
-  const LangOptions &LangOpts;
-
   /// AST contexts for which we are checking structural equivalence.
   ASTContext &FromCtx, &ToCtx;
 
@@ -79,17 +76,15 @@ struct StructuralEquivalenceContext {
   /// Whether to ignore comparing the depth of template param(TemplateTypeParm)
   bool IgnoreTemplateParmDepth;
 
-  StructuralEquivalenceContext(const LangOptions &LangOpts, ASTContext &FromCtx,
-                               ASTContext &ToCtx,
+  StructuralEquivalenceContext(ASTContext &FromCtx, ASTContext &ToCtx,
                                NonEquivalentDeclSet &NonEquivalentDecls,
                                StructuralEquivalenceKind EqKind,
                                bool StrictTypeSpelling = false,
                                bool Complain = true,
                                bool ErrorOnTagTypeMismatch = false,
                                bool IgnoreTemplateParmDepth = false)
-      : LangOpts(LangOpts), FromCtx(FromCtx), ToCtx(ToCtx),
-        NonEquivalentDecls(NonEquivalentDecls), EqKind(EqKind),
-        StrictTypeSpelling(StrictTypeSpelling),
+      : FromCtx(FromCtx), ToCtx(ToCtx), NonEquivalentDecls(NonEquivalentDecls),
+        EqKind(EqKind), StrictTypeSpelling(StrictTypeSpelling),
         ErrorOnTagTypeMismatch(ErrorOnTagTypeMismatch), Complain(Complain),
         IgnoreTemplateParmDepth(IgnoreTemplateParmDepth) {}
 

clang/include/clang/Basic/DiagnosticASTKinds.td

@@ -480,23 +480,16 @@ def warn_odr_function_type_inconsistent : Warning<
   "external function %0 declared with incompatible types in different "
   "translation units (%1 vs. %2)">,
   InGroup<ODR>;
-def warn_odr_tag_type_with_attributes : Warning<
-  "type %0 has %select{an attribute|a member with an attribute}1 which "
-  "currently causes the types to be treated as though they are incompatible">,
-  InGroup<ODR>, DefaultError;
-def note_odr_attr_here : Note<"attribute %0 here">;
 def err_odr_tag_type_inconsistent
-    : Error<"type %0 has incompatible definitions%select{| in different "
-            "translation units}1">;
+    : Error<"type %0 has incompatible definitions in different translation "
+            "units">;
 def warn_odr_tag_type_inconsistent
-    : Warning<"type %0 has incompatible definitions%select{| in different "
-              "translation units}1">,
+    : Warning<"type %0 has incompatible definitions in different translation "
+              "units">,
       InGroup<ODR>;
 def note_odr_tag_kind_here: Note<
   "%0 is a %select{struct|interface|union|class|enum}1 here">;
 def note_odr_field : Note<"field %0 has type %1 here">;
-def note_odr_field_bit_width : Note<"bit-field %0 has bit-width %1 here">;
-def note_odr_field_not_bit_field : Note<"field %0 is not a bit-field">;
 def note_odr_field_name : Note<"field has name %0 here">;
 def note_odr_missing_field : Note<"no corresponding field here">;
 def note_odr_base : Note<"class has base type %0">;
@@ -507,14 +500,6 @@ def note_odr_number_of_bases : Note<
   "class has %0 base %plural{1:class|:classes}0">;
 def note_odr_enumerator : Note<"enumerator %0 with value %1 here">;
 def note_odr_missing_enumerator : Note<"no corresponding enumerator here">;
-def note_odr_incompatible_fixed_underlying_type : Note<
-  "enumeration %0 declared with incompatible fixed underlying types (%1 vs. "
-  "%2)">;
-def note_odr_fixed_underlying_type : Note<
-  "enumeration %0 has fixed underlying type here">;
-def note_odr_missing_fixed_underlying_type : Note<
-  "enumeration %0 missing fixed underlying type here">;
-
 def err_odr_field_type_inconsistent : Error<
   "field %0 declared with incompatible types in different "
   "translation units (%1 vs. %2)">;

clang/include/clang/Parse/Parser.h

@@ -1964,21 +1964,6 @@ class Parser : public CodeCompletionHandler {
                           const ParsedTemplateInfo &TemplateInfo,
                           AccessSpecifier AS, DeclSpecContext DSC);
 
-  /// ParseEnumBody - Parse a {} enclosed enumerator-list.
-  /// \verbatim
-  ///       enumerator-list:
-  ///         enumerator
-  ///         enumerator-list ',' enumerator
-  ///       enumerator:
-  ///         enumeration-constant attributes[opt]
-  ///         enumeration-constant attributes[opt] '=' constant-expression
-  ///       enumeration-constant:
-  ///         identifier
-  /// \endverbatim
-  ///
-  void ParseEnumBody(SourceLocation StartLoc, Decl *TagDecl,
-                     SkipBodyInfo *SkipBody = nullptr);
-
   /// ParseStructUnionBody
   /// \verbatim
   ///       struct-contents:
@@ -1991,6 +1976,7 @@ class Parser : public CodeCompletionHandler {
   /// [OBC]   '@' 'defs' '(' class-name ')'
   /// \endverbatim
   ///
+  void ParseEnumBody(SourceLocation StartLoc, Decl *TagDecl);
   void ParseStructUnionBody(SourceLocation StartLoc, DeclSpec::TST TagType,
                             RecordDecl *TagDecl);
 

clang/include/clang/Sema/Sema.h

@@ -4811,8 +4811,7 @@ class Sema final : public SemaBase {
   Decl *ActOnEnumConstant(Scope *S, Decl *EnumDecl, Decl *LastEnumConstant,
                           SourceLocation IdLoc, IdentifierInfo *Id,
                           const ParsedAttributesView &Attrs,
-                          SourceLocation EqualLoc, Expr *Val,
-                          SkipBodyInfo *SkipBody = nullptr);
+                          SourceLocation EqualLoc, Expr *Val);
   void ActOnEnumBody(SourceLocation EnumLoc, SourceRange BraceRange,
                      Decl *EnumDecl, ArrayRef<Decl *> Elements, Scope *S,
                      const ParsedAttributesView &Attr);

clang/lib/AST/ASTContext.cpp

@@ -16,7 +16,6 @@
 #include "clang/AST/APValue.h"
 #include "clang/AST/ASTConcept.h"
 #include "clang/AST/ASTMutationListener.h"
-#include "clang/AST/ASTStructuralEquivalence.h"
 #include "clang/AST/ASTTypeTraits.h"
 #include "clang/AST/Attr.h"
 #include "clang/AST/AttrIterator.h"
@@ -12358,28 +12357,6 @@ static QualType mergeEnumWithInteger(ASTContext &Context, const EnumType *ET,
   return {};
 }
 
-QualType ASTContext::mergeTagDefinitions(QualType LHS, QualType RHS) {
-  // C17 and earlier and C++ disallow two tag definitions within the same TU
-  // from being compatible.
-  if (LangOpts.CPlusPlus || !LangOpts.C23)
-    return {};
-
-  // Nameless tags are comparable only within outer definitions. At the top
-  // level they are not comparable.
-  const TagDecl *LTagD = LHS->getAsTagDecl(), *RTagD = RHS->getAsTagDecl();
-  if (!LTagD->getIdentifier() || !RTagD->getIdentifier())
-    return {};
-
-  // C23, on the other hand, requires the members to be "the same enough", so
-  // we use a structural equivalence check.
-  StructuralEquivalenceContext::NonEquivalentDeclSet NonEquivalentDecls;
-  StructuralEquivalenceContext Ctx(
-      getLangOpts(), *this, *this, NonEquivalentDecls,
-      StructuralEquivalenceKind::Default, /*StrictTypeSpelling=*/false,
-      /*Complain=*/false, /*ErrorOnTagTypeMismatch=*/true);
-  return Ctx.IsEquivalent(LHS, RHS) ? LHS : QualType{};
-}
-
 QualType ASTContext::mergeTypes(QualType LHS, QualType RHS, bool OfBlockPointer,
                                 bool Unqualified, bool BlockReturnType,
                                 bool IsConditionalOperator) {
@@ -12701,7 +12678,7 @@ QualType ASTContext::mergeTypes(QualType LHS, QualType RHS, bool OfBlockPointer,
                               /*AllowCXX=*/false, IsConditionalOperator);
   case Type::Record:
   case Type::Enum:
-    return mergeTagDefinitions(LHS, RHS);
+    return {};
   case Type::Builtin:
     // Only exactly equal builtin types are compatible, which is tested above.
     return {};

clang/lib/AST/ASTImporter.cpp

@@ -2723,9 +2723,8 @@ bool ASTNodeImporter::IsStructuralMatch(Decl *From, Decl *To, bool Complain,
   }
 
   StructuralEquivalenceContext Ctx(
-      Importer.getToContext().getLangOpts(), Importer.getFromContext(),
-      Importer.getToContext(), Importer.getNonEquivalentDecls(),
-      getStructuralEquivalenceKind(Importer),
+      Importer.getFromContext(), Importer.getToContext(),
+      Importer.getNonEquivalentDecls(), getStructuralEquivalenceKind(Importer),
       /*StrictTypeSpelling=*/false, Complain, /*ErrorOnTagTypeMismatch=*/false,
       IgnoreTemplateParmDepth);
   return Ctx.IsEquivalent(From, To);
@@ -4587,8 +4586,7 @@ static bool IsEquivalentFriend(ASTImporter &Importer, FriendDecl *FD1,
 
   ASTImporter::NonEquivalentDeclSet NonEquivalentDecls;
   StructuralEquivalenceContext Ctx(
-      Importer.getToContext().getLangOpts(), FD1->getASTContext(),
-      FD2->getASTContext(), NonEquivalentDecls,
+      FD1->getASTContext(), FD2->getASTContext(), NonEquivalentDecls,
       StructuralEquivalenceKind::Default,
       /* StrictTypeSpelling = */ false, /* Complain = */ false);
   return Ctx.IsEquivalent(FD1, FD2);
@@ -10885,8 +10883,8 @@ bool ASTImporter::IsStructurallyEquivalent(QualType From, QualType To,
     }
   }
 
-  StructuralEquivalenceContext Ctx(
-      getToContext().getLangOpts(), FromContext, ToContext, NonEquivalentDecls,
-      getStructuralEquivalenceKind(*this), false, Complain);
+  StructuralEquivalenceContext Ctx(FromContext, ToContext, NonEquivalentDecls,
+                                   getStructuralEquivalenceKind(*this), false,
+                                   Complain);
   return Ctx.IsEquivalent(From, To);
 }