[modules] Make NamespaceAliasDecl redeclarable, as it should be. This fixes

merging of namespace aliases across modules and improves source fidelity.
Incidentally also fixes PR20816.

llvm-svn: 217103

1 files changed, 7 insertions, 3 deletions

diff --git a/clang/lib/Serialization/ASTCommon.cpp b/clang/lib/Serialization/ASTCommon.cpp
index ba20f281ea7..13393225b60 100644
--- a/clang/lib/Serialization/ASTCommon.cpp
+++ b/clang/lib/Serialization/ASTCommon.cpp
@@ -151,7 +151,7 @@ bool serialization::isRedeclarableDeclKind(unsigned Kind) {
   switch (static_cast<Decl::Kind>(Kind)) {
   case Decl::TranslationUnit: // Special case of a "merged" declaration.
   case Decl::Namespace:
-  case Decl::NamespaceAlias: // FIXME: Not yet redeclarable, but will be.
+  case Decl::NamespaceAlias:
   case Decl::Typedef:
   case Decl::TypeAlias:
   case Decl::Enum:
@@ -189,8 +189,6 @@ bool serialization::isRedeclarableDeclKind(unsigned Kind) {
   case Decl::MSProperty:
   case Decl::ObjCIvar:
   case Decl::ObjCAtDefsField:
-  case Decl::ImplicitParam:
-  case Decl::ParmVar:
   case Decl::NonTypeTemplateParm:
   case Decl::TemplateTemplateParm:
   case Decl::Using:
@@ -213,6 +211,12 @@ bool serialization::isRedeclarableDeclKind(unsigned Kind) {
   case Decl::Import:
   case Decl::OMPThreadPrivate:
     return false;
+
+  // These indirectly derive from Redeclarable<T> but are not actually
+  // redeclarable.
+  case Decl::ImplicitParam:
+  case Decl::ParmVar:
+    return false;
   }
 
   llvm_unreachable("Unhandled declaration kind");