WIP implementation of explicit function template specialization. This

first implementation recognizes when a function declaration is an
explicit function template specialization (based on the presence of a
template<> header), performs template argument deduction + ambiguity
resolution to determine which template is being specialized, and hooks

There are many caveats here:
  - We completely and totally drop any explicitly-specified template
  arguments on the floor
  - We don't diagnose any of the extra semantic things that we should
  diagnose. 
  - I haven't looked to see that we're getting the right linkage for
  explicit specializations

On a happy note, this silences a bunch of errors that show up in
libstdc++'s <iostream>, although Clang still can't get through the
entire header.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@82728 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 3 insertions, 0 deletions

diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index edb854ccdd..6200beb863 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -4055,6 +4055,7 @@ Sema::ResolveAddressOfOverloadedFunction(Expr *From, QualType ToType,
       //   resulting template argument list is used to generate a single
       //   function template specialization, which is added to the set of
       //   overloaded functions considered.
+      // FIXME: We don't really want to build the specialization here, do we?
       FunctionDecl *Specialization = 0;
       TemplateDeductionInfo Info(Context);
       if (TemplateDeductionResult Result
@@ -4064,6 +4065,8 @@ Sema::ResolveAddressOfOverloadedFunction(Expr *From, QualType ToType,
         // FIXME: make a note of the failed deduction for diagnostics.
         (void)Result;
       } else {
+        // FIXME: If the match isn't exact, shouldn't we just drop this as
+        // a candidate? Find a testcase before changing the code.
         assert(FunctionType
                  == Context.getCanonicalType(Specialization->getType()));
         Matches.insert(