Recommit my change to how C++ does elaborated type lookups, now with
two bugfixes which fix selfhost and (hopefully) the nightly tests.
llvm-svn: 102198
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index c9001f1..cc57bdd 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -5000,7 +5000,8 @@
SearchDC = SearchDC->getEnclosingNamespaceContext();
}
- // In C++, look for a shadow friend decl.
+ // In C++, we need to do a redeclaration lookup to properly
+ // diagnose some problems.
if (getLangOptions().CPlusPlus) {
Previous.setRedeclarationKind(ForRedeclaration);
LookupQualifiedName(Previous, SearchDC);
@@ -5009,6 +5010,30 @@
if (!Previous.empty()) {
NamedDecl *PrevDecl = (*Previous.begin())->getUnderlyingDecl();
+
+ // It's okay to have a tag decl in the same scope as a typedef
+ // which hides a tag decl in the same scope. Finding this
+ // insanity with a redeclaration lookup can only actually happen
+ // in C++.
+ //
+ // This is also okay for elaborated-type-specifiers, which is
+ // technically forbidden by the current standard but which is
+ // okay according to the likely resolution of an open issue;
+ // see http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#407
+ if (getLangOptions().CPlusPlus) {
+ if (TypedefDecl *TD = dyn_cast<TypedefDecl>(PrevDecl)) {
+ if (const TagType *TT = TD->getUnderlyingType()->getAs<TagType>()) {
+ TagDecl *Tag = TT->getDecl();
+ if (Tag->getDeclName() == Name &&
+ Tag->getDeclContext()->Equals(TD->getDeclContext())) {
+ PrevDecl = Tag;
+ Previous.clear();
+ Previous.addDecl(Tag);
+ }
+ }
+ }
+ }
+
if (TagDecl *PrevTagDecl = dyn_cast<TagDecl>(PrevDecl)) {
// If this is a use of a previous tag, or if the tag is already declared
// in the same scope (so that the definition/declaration completes or
@@ -5100,23 +5125,61 @@
// If we get here, we're going to create a new Decl. If PrevDecl
// is non-NULL, it's a definition of the tag declared by
// PrevDecl. If it's NULL, we have a new definition.
+
+
+ // Otherwise, PrevDecl is not a tag, but was found with tag
+ // lookup. This is only actually possible in C++, where a few
+ // things like templates still live in the tag namespace.
} else {
- // PrevDecl is a namespace, template, or anything else
- // that lives in the IDNS_Tag identifier namespace.
- if (TUK == TUK_Reference || TUK == TUK_Friend ||
- isDeclInScope(PrevDecl, SearchDC, S)) {
- // The tag name clashes with a namespace name, issue an error and
- // recover by making this tag be anonymous.
+ assert(getLangOptions().CPlusPlus);
+
+ // Use a better diagnostic if an elaborated-type-specifier
+ // found the wrong kind of type on the first
+ // (non-redeclaration) lookup.
+ if ((TUK == TUK_Reference || TUK == TUK_Friend) &&
+ !Previous.isForRedeclaration()) {
+ unsigned Kind = 0;
+ if (isa<TypedefDecl>(PrevDecl)) Kind = 1;
+ else if (isa<ClassTemplateDecl>(PrevDecl)) Kind = 2;
+ Diag(NameLoc, diag::err_tag_reference_non_tag) << Kind;
+ Diag(PrevDecl->getLocation(), diag::note_declared_at);
+ Invalid = true;
+
+ // Otherwise, only diagnose if the declaration is in scope.
+ } else if (!isDeclInScope(PrevDecl, SearchDC, S)) {
+ // do nothing
+
+ // Diagnose implicit declarations introduced by elaborated types.
+ } else if (TUK == TUK_Reference || TUK == TUK_Friend) {
+ unsigned Kind = 0;
+ if (isa<TypedefDecl>(PrevDecl)) Kind = 1;
+ else if (isa<ClassTemplateDecl>(PrevDecl)) Kind = 2;
+ Diag(NameLoc, diag::err_tag_reference_conflict) << Kind;
+ Diag(PrevDecl->getLocation(), diag::note_previous_decl) << PrevDecl;
+ Invalid = true;
+
+ // Otherwise it's a declaration. Call out a particularly common
+ // case here.
+ } else if (isa<TypedefDecl>(PrevDecl)) {
+ Diag(NameLoc, diag::err_tag_definition_of_typedef)
+ << Name
+ << cast<TypedefDecl>(PrevDecl)->getUnderlyingType();
+ Diag(PrevDecl->getLocation(), diag::note_previous_decl) << PrevDecl;
+ Invalid = true;
+
+ // Otherwise, diagnose.
+ } else {
+ // The tag name clashes with something else in the target scope,
+ // issue an error and recover by making this tag be anonymous.
Diag(NameLoc, diag::err_redefinition_different_kind) << Name;
Diag(PrevDecl->getLocation(), diag::note_previous_definition);
Name = 0;
- Previous.clear();
Invalid = true;
- } else {
- // The existing declaration isn't relevant to us; we're in a
- // new scope, so clear out the previous declaration.
- Previous.clear();
}
+
+ // The existing declaration isn't relevant to us; we're in a
+ // new scope, so clear out the previous declaration.
+ Previous.clear();
}
}
@@ -5187,28 +5250,6 @@
New->addAttr(::new (Context) PragmaPackAttr(Alignment * 8));
}
- if (getLangOptions().CPlusPlus && SS.isEmpty() && Name && !Invalid) {
- // C++ [dcl.typedef]p3:
- // [...] Similarly, in a given scope, a class or enumeration
- // shall not be declared with the same name as a typedef-name
- // that is declared in that scope and refers to a type other
- // than the class or enumeration itself.
- LookupResult Lookup(*this, Name, NameLoc, LookupOrdinaryName,
- ForRedeclaration);
- LookupName(Lookup, S);
- TypedefDecl *PrevTypedef = Lookup.getAsSingle<TypedefDecl>();
- NamedDecl *PrevTypedefNamed = PrevTypedef;
- if (PrevTypedef && isDeclInScope(PrevTypedefNamed, SearchDC, S) &&
- Context.getCanonicalType(Context.getTypeDeclType(PrevTypedef)) !=
- Context.getCanonicalType(Context.getTypeDeclType(New))) {
- Diag(Loc, diag::err_tag_definition_of_typedef)
- << Context.getTypeDeclType(New)
- << PrevTypedef->getUnderlyingType();
- Diag(PrevTypedef->getLocation(), diag::note_previous_definition);
- Invalid = true;
- }
- }
-
// If this is a specialization of a member class (of a class template),
// check the specialization.
if (isExplicitSpecialization && CheckMemberSpecialization(New, Previous))