Introduce the notion of instantiation dependence into Clang's AST. A

type/expression/template argument/etc. is instantiation-dependent if
it somehow involves a template parameter, even if it doesn't meet the
requirements for the more common kinds of dependence (dependent type,
type-dependent expression, value-dependent expression).

When we see an instantiation-dependent type, we know we always need to
perform substitution into that instantiation-dependent type. This
keeps us from short-circuiting evaluation in places where we
shouldn't, and lets us properly implement C++0x [temp.type]p2.

In theory, this would also allow us to properly mangle
instantiation-dependent-but-not-dependent decltype types per the
Itanium C++ ABI, but we aren't quite there because we still mangle
based on the canonical type in cases like, e.g.,

  template<unsigned> struct A { };
  template<typename T>
    void f(A<sizeof(sizeof(decltype(T() + T())))>) { }
  template void f<int>(A<sizeof(sizeof(int))>);

and therefore get the wrong answer.

llvm-svn: 134225

1 files changed, 5 insertions, 2 deletions

diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index d88b7857624..a7034aa7712 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -1898,6 +1898,7 @@ QualType Sema::CheckTemplateIdType(TemplateName Name,
 
   QualType CanonType;
 
+  bool InstantiationDependent = false;
   if (TypeAliasTemplateDecl *AliasTemplate
         = dyn_cast<TypeAliasTemplateDecl>(Template)) {
     // Find the canonical type for this type alias template specialization.
@@ -1923,7 +1924,7 @@ QualType Sema::CheckTemplateIdType(TemplateName Name,
       return QualType();
   } else if (Name.isDependent() ||
              TemplateSpecializationType::anyDependentTemplateArguments(
-               TemplateArgs)) {
+               TemplateArgs, InstantiationDependent)) {
     // This class template specialization is a dependent
     // type. Therefore, its canonical type is another class template
     // specialization type that contains all of the converted
@@ -4833,10 +4834,12 @@ Sema::ActOnClassTemplateSpecialization(Scope *S, unsigned TagSpec,
                                          Converted))
       return true;
 
+    bool InstantiationDependent;
     if (!Name.isDependent() &&
         !TemplateSpecializationType::anyDependentTemplateArguments(
                                              TemplateArgs.getArgumentArray(),
-                                                         TemplateArgs.size())) {
+                                                         TemplateArgs.size(),
+                                                     InstantiationDependent)) {
       Diag(TemplateNameLoc, diag::err_partial_spec_fully_specialized)
         << ClassTemplate->getDeclName();
       isPartialSpecialization = false;