Introduce a new expression type, UnresolvedDeclRefExpr, that describes

dependent qualified-ids such as

  Fibonacci<N - 1>::value

where N is a template parameter. These references are "unresolved"
because the name is dependent and, therefore, cannot be resolved to a
declaration node (as we would do for a DeclRefExpr or
QualifiedDeclRefExpr). UnresolvedDeclRefExprs instantiate to
DeclRefExprs, QualifiedDeclRefExprs, etc.

Also, be a bit more careful about keeping only a single set of
specializations for a class template, and instantiating from the
definition of that template rather than a previous declaration. In
general, we need a better solution for this for all TagDecls, because
it's too easy to accidentally look at a declaration that isn't the
definition.

We can now process a simple Fibonacci computation described as a
template metaprogram.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@67308 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 0 deletions

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 483b79a098..18d55d92f4 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -52,6 +52,20 @@ std::string Sema::getDeclName(DeclTy *d) {
 /// and then return NULL.
 Sema::TypeTy *Sema::getTypeName(IdentifierInfo &II, SourceLocation NameLoc,
                                 Scope *S, const CXXScopeSpec *SS) {
+  // C++ [temp.res]p3:
+  //   A qualified-id that refers to a type and in which the
+  //   nested-name-specifier depends on a template-parameter (14.6.2)
+  //   shall be prefixed by the keyword typename to indicate that the
+  //   qualified-id denotes a type, forming an
+  //   elaborated-type-specifier (7.1.5.3).
+  //
+  // We therefore do not perform any name lookup up SS is a dependent
+  // scope name. FIXME: we will need to perform a special kind of
+  // lookup if the scope specifier names a member of the current
+  // instantiation.
+  if (SS && isDependentScopeSpecifier(*SS))
+    return 0;
+
   NamedDecl *IIDecl = 0;
   LookupResult Result = LookupParsedName(S, SS, &II, LookupOrdinaryName, 
                                          false, false);