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.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@134225 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 6 insertions, 1 deletions

diff --git a/include/clang/AST/TemplateBase.h b/include/clang/AST/TemplateBase.h
index 821b4fcbb1..1c693e00c8 100644
--- a/include/clang/AST/TemplateBase.h
+++ b/include/clang/AST/TemplateBase.h
@@ -235,9 +235,14 @@ public:
   bool isNull() const { return Kind == Null; }
 
   /// \brief Whether this template argument is dependent on a template
-  /// parameter.
+  /// parameter such that its result can change from one instantiation to
+  /// another.
   bool isDependent() const;
 
+  /// \brief Whether this template argument is dependent on a template
+  /// parameter.
+  bool isInstantiationDependent() const;
+
   /// \brief Whether this template argument contains an unexpanded
   /// parameter pack.
   bool containsUnexpandedParameterPack() const;