When we perform dependent name lookup during template instantiation, it's not

sufficient to only consider names visible at the point of instantiation,
because that may not include names that were visible when the template was
defined. More generally, if the instantiation backtrace goes through a module
M, then every declaration visible within M should be available to the
instantiation. Any of those declarations might be part of the interface that M
intended to export to a template that it instantiates.

The fix here has two parts:

1) If we find a non-visible declaration during name lookup during template
instantiation, check whether the declaration was visible from the defining
module of all entities on the active template instantiation stack. The defining
module is not the owning module in all cases: we look at the module in which a
template was defined, not the module in which it was first instantiated.

2) Perform pending instantiations at the end of a module, not at the end of the
translation unit. This is general goodness, since it significantly cuts down
the amount of redundant work that is performed in every TU importing a module,
and also implicitly adds the module containing the point of instantiation to
the set of modules checked for declarations in a lookup within a template
instantiation.

There's a known issue here with template instantiations performed while
building a module, if additional imports are added later on. I'll fix that
in a subsequent commit.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@187167 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 15 insertions, 12 deletions

diff --git a/include/clang/Sema/Lookup.h b/include/clang/Sema/Lookup.h
index 3e7e3a16eb..c47771e4b5 100644
--- a/include/clang/Sema/Lookup.h
+++ b/include/clang/Sema/Lookup.h
@@ -283,33 +283,36 @@ public:
 
   /// \brief Determine whether the given declaration is visible to the
   /// program.
-  static bool isVisible(NamedDecl *D) {
+  static bool isVisible(Sema &SemaRef, NamedDecl *D) {
     // If this declaration is not hidden, it's visible.
     if (!D->isHidden())
       return true;
-    
-    // FIXME: We should be allowed to refer to a module-private name from 
-    // within the same module, e.g., during template instantiation.
-    // This requires us know which module a particular declaration came from.
-    return false;
+
+    if (SemaRef.ActiveTemplateInstantiations.empty())
+      return false;
+
+    // During template instantiation, we can refer to hidden declarations, if
+    // they were visible in any module along the path of instantiation.
+    return isVisibleSlow(SemaRef, D);
   }
-  
+
   /// \brief Retrieve the accepted (re)declaration of the given declaration,
   /// if there is one.
   NamedDecl *getAcceptableDecl(NamedDecl *D) const {
     if (!D->isInIdentifierNamespace(IDNS))
       return 0;
-    
-    if (isHiddenDeclarationVisible() || isVisible(D))
+
+    if (isHiddenDeclarationVisible() || isVisible(SemaRef, D))
       return D;
-    
+
     return getAcceptableDeclSlow(D);
   }
-  
+
 private:
+  static bool isVisibleSlow(Sema &SemaRef, NamedDecl *D);
   NamedDecl *getAcceptableDeclSlow(NamedDecl *D) const;
+
 public:
-  
   /// \brief Returns the identifier namespace mask for this lookup.
   unsigned getIdentifierNamespace() const {
     return IDNS;