Make tag declarations redeclarable. This change has three purposes:

  1) Allow the Index library (and any other interested client) to walk
  the set of declarations for a given tag (enum, union, class,
  whatever). At the moment, this information is not readily available.

  2) Reduce our dependence on TagDecl::TypeForDecl being mapped down
  to a TagType (for which getDecl() will return the tag definition, if
  one exists). This property won't exist for class template partial
  specializations.

  3) Make the canonical declaration of a TagDecl actually canonical,
  e.g., so that it does not change when the tag is defined.

llvm-svn: 77523

2 files changed, 3 insertions, 0 deletions

diff --git a/clang/lib/Frontend/PCHReaderDecl.cpp b/clang/lib/Frontend/PCHReaderDecl.cpp
index 99a1a16835a..65da7dc4517 100644
--- a/clang/lib/Frontend/PCHReaderDecl.cpp
+++ b/clang/lib/Frontend/PCHReaderDecl.cpp
@@ -112,6 +112,8 @@ void PCHDeclReader::VisitTypedefDecl(TypedefDecl *TD) {
 
 void PCHDeclReader::VisitTagDecl(TagDecl *TD) {
   VisitTypeDecl(TD);
+  TD->setPreviousDeclaration(
+                        cast_or_null<TagDecl>(Reader.GetDecl(Record[Idx++])));
   TD->setTagKind((TagDecl::TagKind)Record[Idx++]);
   TD->setDefinition(Record[Idx++]);
   TD->setTypedefForAnonDecl(
diff --git a/clang/lib/Frontend/PCHWriterDecl.cpp b/clang/lib/Frontend/PCHWriterDecl.cpp
index 4239798ac80..fd7ea421dd1 100644
--- a/clang/lib/Frontend/PCHWriterDecl.cpp
+++ b/clang/lib/Frontend/PCHWriterDecl.cpp
@@ -109,6 +109,7 @@ void PCHDeclWriter::VisitTypedefDecl(TypedefDecl *D) {
 
 void PCHDeclWriter::VisitTagDecl(TagDecl *D) {
   VisitTypeDecl(D);
+  Writer.AddDeclRef(D->getPreviousDeclaration(), Record);
   Record.push_back((unsigned)D->getTagKind()); // FIXME: stable encoding
   Record.push_back(D->isDefinition());
   Writer.AddDeclRef(D->getTypedefForAnonDecl(), Record);