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, 9 insertions, 0 deletions

diff --git a/clang/lib/AST/TemplateName.cpp b/clang/lib/AST/TemplateName.cpp
index b22e4b4c0d6..1f7b19aae47 100644
--- a/clang/lib/AST/TemplateName.cpp
+++ b/clang/lib/AST/TemplateName.cpp
@@ -99,6 +99,15 @@ bool TemplateName::isDependent() const {
   return true;
 }
 
+bool TemplateName::isInstantiationDependent() const {
+  if (QualifiedTemplateName *QTN = getAsQualifiedTemplateName()) {
+    if (QTN->getQualifier()->isInstantiationDependent())
+      return true;
+  }
+  
+  return isDependent();
+}
+
 bool TemplateName::containsUnexpandedParameterPack() const {
   if (TemplateDecl *Template = getAsTemplateDecl()) {
     if (TemplateTemplateParmDecl *TTP