When a template-id refers to a single function template, and the

explicitly-specified template arguments are enough to determine the
instantiation, and either template argument deduction fails or is not
performed in that context, we can resolve the template-id down to a
function template specialization (so sayeth C++0x
[temp.arg.explicit]p3). Fixes PR5811.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@91852 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 69 insertions, 22 deletions

diff --git a/lib/Sema/SemaTemplateDeduction.cpp b/lib/Sema/SemaTemplateDeduction.cpp
index 5434beaef1..11798c468a 100644
--- a/lib/Sema/SemaTemplateDeduction.cpp
+++ b/lib/Sema/SemaTemplateDeduction.cpp
@@ -1506,15 +1506,39 @@ Sema::DeduceTemplateArguments(FunctionTemplateDecl *FunctionTemplate,
                               ParamType->getAs<PointerType>()->getPointeeType())))
       TDF |= TDF_DerivedClass;
 
+    // FIXME: C++0x [temp.deduct.call] paragraphs 6-9 deal with function
+    // pointer parameters.
+    
+    if (Context.hasSameUnqualifiedType(ArgType, Context.OverloadTy)) {
+      // We know that template argument deduction will fail if the argument is
+      // still an overloaded function. Check whether we can resolve this 
+      // argument as a single function template specialization per
+      // C++ [temp.arg.explicit]p3.
+      FunctionDecl *ExplicitSpec
+        = ResolveSingleFunctionTemplateSpecialization(Args[I]);
+      Expr *ResolvedArg = 0;
+      if (ExplicitSpec)
+        ResolvedArg = FixOverloadedFunctionReference(Args[I], ExplicitSpec);
+      if (!ExplicitSpec || !ResolvedArg) {
+        // Template argument deduction fails if we can't resolve the overloaded
+        // function.
+        return TDK_FailedOverloadResolution;
+      }
+      
+      // Get the type of the resolved argument.
+      ArgType = ResolvedArg->getType();
+      if (ArgType->isPointerType() || ArgType->isMemberPointerType())
+        TDF |= TDF_IgnoreQualifiers;
+      
+      ResolvedArg->Destroy(Context);
+    }
+    
     if (TemplateDeductionResult Result
         = ::DeduceTemplateArguments(Context, TemplateParams,
                                     ParamType, ArgType, Info, Deduced,
                                     TDF))
       return Result;
 
-    // FIXME: C++0x [temp.deduct.call] paragraphs 6-9 deal with function
-    // pointer parameters.
-
     // FIXME: we need to check that the deduced A is the same as A,
     // modulo the various allowed differences.
   }
@@ -1524,24 +1548,19 @@ Sema::DeduceTemplateArguments(FunctionTemplateDecl *FunctionTemplate,
 }
 
 /// \brief Deduce template arguments when taking the address of a function
-/// template (C++ [temp.deduct.funcaddr]) or matching a 
+/// template (C++ [temp.deduct.funcaddr]) or matching a specialization to
+/// a template.
 ///
 /// \param FunctionTemplate the function template for which we are performing
 /// template argument deduction.
 ///
-/// \param HasExplicitTemplateArgs whether any template arguments were
-/// explicitly specified.
-///
-/// \param ExplicitTemplateArguments when @p HasExplicitTemplateArgs is true,
-/// the explicitly-specified template arguments.
-///
-/// \param NumExplicitTemplateArguments when @p HasExplicitTemplateArgs is true,
-/// the number of explicitly-specified template arguments in
-/// @p ExplicitTemplateArguments. This value may be zero.
+/// \param ExplicitTemplateArguments the explicitly-specified template 
+/// arguments.
 ///
 /// \param ArgFunctionType the function type that will be used as the
 /// "argument" type (A) when performing template argument deduction from the
-/// function template's function type.
+/// function template's function type. This type may be NULL, if there is no
+/// argument type to compare against, in C++0x [temp.arg.explicit]p3.
 ///
 /// \param Specialization if template argument deduction was successful,
 /// this will be set to the function template specialization produced by
@@ -1578,14 +1597,16 @@ Sema::DeduceTemplateArguments(FunctionTemplateDecl *FunctionTemplate,
   // Trap any errors that might occur.
   SFINAETrap Trap(*this);
 
-  // Deduce template arguments from the function type.
-  Deduced.resize(TemplateParams->size());
-  if (TemplateDeductionResult Result
-        = ::DeduceTemplateArguments(Context, TemplateParams,
-                                    FunctionType, ArgFunctionType, Info,
-                                    Deduced, 0))
-    return Result;
-
+  if (!ArgFunctionType.isNull()) {
+    // Deduce template arguments from the function type.
+    Deduced.resize(TemplateParams->size());
+    if (TemplateDeductionResult Result
+          = ::DeduceTemplateArguments(Context, TemplateParams,
+                                      FunctionType, ArgFunctionType, Info,
+                                      Deduced, 0))
+      return Result;
+  }
+  
   return FinishTemplateArgumentDeduction(FunctionTemplate, Deduced,
                                          Specialization, Info);
 }
@@ -1694,6 +1715,32 @@ Sema::DeduceTemplateArguments(FunctionTemplateDecl *FunctionTemplate,
   return Result;
 }
 
+/// \brief Deduce template arguments for a function template when there is
+/// nothing to deduce against (C++0x [temp.arg.explicit]p3).
+///
+/// \param FunctionTemplate the function template for which we are performing
+/// template argument deduction.
+///
+/// \param ExplicitTemplateArguments the explicitly-specified template 
+/// arguments.
+///
+/// \param Specialization if template argument deduction was successful,
+/// this will be set to the function template specialization produced by
+/// template argument deduction.
+///
+/// \param Info the argument will be updated to provide additional information
+/// about template argument deduction.
+///
+/// \returns the result of template argument deduction.
+Sema::TemplateDeductionResult
+Sema::DeduceTemplateArguments(FunctionTemplateDecl *FunctionTemplate,
+                           const TemplateArgumentListInfo *ExplicitTemplateArgs,
+                              FunctionDecl *&Specialization,
+                              TemplateDeductionInfo &Info) {
+  return DeduceTemplateArguments(FunctionTemplate, ExplicitTemplateArgs,
+                                 QualType(), Specialization, Info);
+}
+
 /// \brief Stores the result of comparing the qualifiers of two types.
 enum DeductionQualifierComparison { 
   NeitherMoreQualified = 0,