[modules] When we merge together multiple class template specialization

definitions (because some other declaration declares a special member that
isn't present in the canonical definition), we need to search *all* of them; we
can't just stop when we find the requested name in any of the definitions,
because that can fail to find things (and in particular, it can fail to find
the member of the canonical declaration and return a bogus ODR failure).

llvm-svn: 215612

1 files changed, 16 insertions, 3 deletions

diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index e8c3177cb86..55b557c0471 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -3485,9 +3485,22 @@ void ASTWriter::WriteIdentifierTable(Preprocessor &PP,
 /// recent local declaration instead. The chosen declaration will be the most
 /// recent declaration in any module that imports this one.
 static NamedDecl *getDeclForLocalLookup(NamedDecl *D) {
-  for (Decl *Redecl = D; Redecl; Redecl = Redecl->getPreviousDecl())
-    if (!Redecl->isFromASTFile())
-      return cast<NamedDecl>(Redecl);
+  if (!D->isFromASTFile())
+    return D;
+
+  if (Decl *Redecl = D->getPreviousDecl()) {
+    // For Redeclarable decls, a prior declaration might be local.
+    for (; Redecl; Redecl = Redecl->getPreviousDecl())
+      if (!Redecl->isFromASTFile())
+        return cast<NamedDecl>(Redecl);
+  } else if (Decl *First = D->getCanonicalDecl()) {
+    // For Mergeable decls, the first decl might be local.
+    if (!First->isFromASTFile())
+      return cast<NamedDecl>(First);
+  }
+
+  // All declarations are imported. Our most recent declaration will also be
+  // the most recent one in anyone who imports us.
   return D;
 }