Implement name lookup for conversion function template specializations

(C++ [temp.mem]p5-6), which involves template argument deduction based
on the type named, e.g., given

  struct X { template<typename T> operator T*(); } x;

when we call

  x.operator int*();

we perform template argument deduction to determine that T=int. This
template argument deduction is needed for template specialization and
explicit instantiation, e.g.,

  template<> X::operator float*() { /* ... */ }

and when calling or otherwise naming a conversion function (as in the
first example). 

This fixes PR5742 and PR5762, although there's some remaining ugliness
that's causing out-of-line definitions of conversion function
templates to fail. I'll look into that separately.

llvm-svn: 93162

1 files changed, 4 insertions, 2 deletions

diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index ecb89edcf7d..5ca8bfde80f 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -4540,8 +4540,10 @@ Sema::DeclResult Sema::ActOnExplicitInstantiation(Scope *S,
       if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Prev)) {
         if (Context.hasSameUnqualifiedType(Method->getType(), R)) {
           Matches.clear();
+
           Matches.push_back(Method);
-          break;
+          if (Method->getTemplateSpecializationKind() == TSK_Undeclared)
+            break;
         }
       }
     }
@@ -4553,7 +4555,7 @@ Sema::DeclResult Sema::ActOnExplicitInstantiation(Scope *S,
     TemplateDeductionInfo Info(Context);
     FunctionDecl *Specialization = 0;
     if (TemplateDeductionResult TDK
-          = DeduceTemplateArguments(FunTmpl,
+          = DeduceTemplateArguments(FunTmpl, 
                                (HasExplicitTemplateArgs ? &TemplateArgs : 0),
                                     R, Specialization, Info)) {
       // FIXME: Keep track of almost-matches?