From: Douglas Gregor <dgregor@apple.com>
Date: Wed, 29 Sep 2010 21:14:36 +0000 (+0000)
Subject: When performing template argument deduction of a function template
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=fbb6fad63acac2bef36cfa13e0706fa3e2a1ed7d;p=clang

When performing template argument deduction of a function template
against a function type, be sure to check the type of the resulting
function template specialization against the desired function type
after substituting the deduced/defaulted template arguments. Fixes PR8196.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@115086 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index 919aea8d02..92d68bba66 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -6348,8 +6348,8 @@ 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.
+        // Template argument deduction ensures that we have an exact match.
+        // This function template specicalization works.
         assert(FunctionType
                  == Context.getCanonicalType(Specialization->getType()));
         Matches.push_back(std::make_pair(I.getPair(),
diff --git a/lib/Sema/SemaTemplateDeduction.cpp b/lib/Sema/SemaTemplateDeduction.cpp
index 5c77ed6106..f3ffa716f1 100644
--- a/lib/Sema/SemaTemplateDeduction.cpp
+++ b/lib/Sema/SemaTemplateDeduction.cpp
@@ -1865,10 +1865,20 @@ Sema::DeduceTemplateArguments(FunctionTemplateDecl *FunctionTemplate,
                                       Deduced, 0))
       return Result;
   }
-  
-  return FinishTemplateArgumentDeduction(FunctionTemplate, Deduced,
-                                         NumExplicitlySpecified,
-                                         Specialization, Info);
+
+  if (TemplateDeductionResult Result 
+        = FinishTemplateArgumentDeduction(FunctionTemplate, Deduced,
+                                          NumExplicitlySpecified,
+                                          Specialization, Info))
+    return Result;
+
+  // If the requested function type does not match the actual type of the
+  // specialization, template argument deduction fails.
+  if (!ArgFunctionType.isNull() &&
+      !Context.hasSameType(ArgFunctionType, Specialization->getType()))
+    return TDK_NonDeducedMismatch;
+
+  return TDK_Success;
 }
 
 /// \brief Deduce template arguments for a templated conversion
diff --git a/test/SemaCXX/addr-of-overloaded-function.cpp b/test/SemaCXX/addr-of-overloaded-function.cpp
index 46bdf8e6b6..ab80d8f141 100644
--- a/test/SemaCXX/addr-of-overloaded-function.cpp
+++ b/test/SemaCXX/addr-of-overloaded-function.cpp
@@ -104,3 +104,15 @@ namespace PR8033 {
   // expected-error{{cannot initialize a variable of type}}
 
 }
+
+namespace PR8196 {
+  template <typename T> struct mcdata {
+    typedef int result_type;
+  };
+  template <class T> 
+    typename mcdata<T>::result_type wrap_mean(mcdata<T> const&);
+  void add_property(double(*)(mcdata<double> const &)); // expected-note{{candidate function not viable: no overload of 'wrap_mean' matching}}
+  void f() {
+    add_property(&wrap_mean); // expected-error{{no matching function for call to 'add_property'}}
+  }
+}