[LLVMbugs] [Bug 10672] New: Unhelpful error message for out-of-line definition of template class's member function template

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=10672

           Summary: Unhelpful error message for out-of-line definition of
                    template class's member function template
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C++
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: david at rothlis.net
                CC: llvmbugs at cs.uiuc.edu, dgregor at apple.com


For the following invalid C++ code:

    template <typename T>
    struct A {
        template <typename U>
        void f();
    };
    template <typename T, typename U>
    void A<T>::f() { }

Clang's error message is:
test.cpp:6:1: error: too many template parameters in template redeclaration
template <typename T, typename U>
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
test.cpp:1:1: note: previous template declaration is here
template <typename T>
^~~~~~~~~~~~~~~~~~~~~
test.cpp:7:12: error: out-of-line definition of 'f' does not match any
declaration in 'A<T>'
void A<T>::f() {
     ~~~~~~^
2 errors generated.

GCC's error message is actually much *more* helpful:
test.cpp:7: error: prototype for ‘void A<T>::f()’ does not match any in class
‘A<T>’
test.cpp:4: error: candidate is: template<class T> template<class U> void
A::f()
test.cpp:7: error: template definition of non-template ‘void A<T>::f()’

in that it shows the desired syntax: template<class T> template <class U> void
A::f() { ...

Most people are unlikely to get this syntax right on the first try, so I think
the error message is important.

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