[LLVMbugs] [Bug 16859] New: Member function pointer resolution confused by templates

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=16859

            Bug ID: 16859
           Summary: Member function pointer resolution confused by
                    templates
           Product: clang
           Version: 3.3
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++11
          Assignee: unassignedclangbugs at nondot.org
          Reporter: llvm-bugs at quasiparticle.net
                CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 11019
  --> http://llvm.org/bugs/attachment.cgi?id=11019&action=edit
Templated member function pointer resolution testcase

Member function pointer resolution in function calls seems to be confused by
templates. Given a class with two members:

struct X {
    int x(int, int) { return 1; }

    template<int>
    int x(int) { return 2; }
};

and a resolution template that matches only on member function pointers with
two arguments:

template<class R, class C, class Arg1, class Arg2>
auto fn2(R (C::*p)(Arg1, Arg2))
    -> R (C::*)(Arg1, Arg2)
{
    return p;
}

I cannot resolve a member function pointer of X using fn2, e.g. fn2(&X::x)
results in a compile-time error. Qualifying the member function pointer
beforehand, i.e. fn2((int (X::*)(int, int)) &X::x) compiles fine.

GCC resolves the member function pointer as expected, i.e. the expression above
yields a pointer-to-member with two function arguments.

See the attached file for full testcase.
Expected output: 11
Actual output: compile time error

test.cpp:21:12: error: no matching function for call to 'fn2'
        auto fn = fn2(&X::x);
                  ^~~
test.cpp:12:6: note: candidate template ignored: couldn't infer template
argument 'R'
auto fn2(R (C::*p)(Arg1, Arg2))
     ^
1 error generated.

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