[LLVMbugs] [Bug 22192] New: When printing an ambiguous-overload error that causes a substitution failure, print the candidates

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=22192

            Bug ID: 22192
           Summary: When printing an ambiguous-overload error that causes
                    a substitution failure, print the candidates
           Product: clang
           Version: 3.5
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: zeratul976 at hotmail.com
                CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Consider the following (invalid) code:

    void foo(double);
    void foo(long);

    template <typename T>
    decltype(foo(T())) bar(T);

    int main()
    {
        bar(3);
    }

The error message clang prints for this is:

    test.cpp:9:5: error: no matching function for call to 'bar'
        bar(3);
        ^~~
    test.cpp:5:20: note: candidate template ignored: substitution failure [with
T = int]: call to 'foo' is ambiguous
    decltype(foo(T())) bar(T);
             ~~~       ^

The error message talks about an overload ambiguity, but doesn't print the
candidates.

Compare the error given by gcc:

    test.cpp: In function 'int main()':
    test.cpp:9:10: error: no matching function for call to 'bar(int)'
         bar(3);
              ^
    test.cpp:9:10: note: candidate is:
    test.cpp:5:20: note: template<class T> decltype (foo(T())) bar(T)
     decltype(foo(T())) bar(T);
                        ^
    test.cpp:5:20: note:   template argument deduction/substitution failed:
    test.cpp: In substitution of 'template<class T> decltype (foo(T())) bar(T) 
   [with T = int]':
    test.cpp:9:10:   required from here
    test.cpp:5:17: error: call of overloaded 'foo(int)' is ambiguous
     decltype(foo(T())) bar(T);
                     ^
    test.cpp:5:17: note: candidates are:
    test.cpp:1:6: note: void foo(double)
     void foo(double);
          ^
    test.cpp:2:6: note: void foo(long int)
     void foo(long);
          ^

which lists the candidates. 

I think it's important to list the candidates, so the user can understand the
error and fix the ambiguity more efficiently.

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20150111/a872dcc0/attachment.html>