[modules] Track all default template arguments for a given parameter across

modules, and allow use of a default template argument if any of the parameters
providing it is visible.

llvm-svn: 239485

1 files changed, 26 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index d0a55b57c61..147b81bc597 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -1228,6 +1228,8 @@ Module *Sema::getOwningModule(Decl *Entity) {
 }
 
 void Sema::makeMergedDefinitionVisible(NamedDecl *ND, SourceLocation Loc) {
+  // FIXME: If ND is a template declaration, make the template parameters
+  // visible too. They're not (necessarily) within its DeclContext.
   if (auto *M = PP.getModuleContainingLocation(Loc))
     Context.mergeDefinitionIntoModule(ND, M);
   else
@@ -1282,6 +1284,30 @@ bool Sema::hasVisibleMergedDefinition(NamedDecl *Def) {
   return false;
 }
 
+template<typename ParmDecl>
+static bool hasVisibleDefaultArgument(Sema &S, const ParmDecl *D) {
+  if (!D->hasDefaultArgument())
+    return false;
+
+  while (D) {
+    auto &DefaultArg = D->getDefaultArgStorage();
+    if (!DefaultArg.isInherited() && S.isVisible(D))
+      return true;
+
+    // If there was a previous default argument, maybe its parameter is visible.
+    D = DefaultArg.getInheritedFrom();
+  }
+  return false;
+}
+
+bool Sema::hasVisibleDefaultArgument(const NamedDecl *D) {
+  if (auto *P = dyn_cast<TemplateTypeParmDecl>(D))
+    return ::hasVisibleDefaultArgument(*this, P);
+  if (auto *P = dyn_cast<NonTypeTemplateParmDecl>(D))
+    return ::hasVisibleDefaultArgument(*this, P);
+  return ::hasVisibleDefaultArgument(*this, cast<TemplateTemplateParmDecl>(D));
+}
+
 /// \brief Determine whether a declaration is visible to name lookup.
 ///
 /// This routine determines whether the declaration D is visible in the current