http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51277
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-11-23 12:05:00 UTC --- (In reply to comment #0) > - in the first case, the location of the using-declaration or using- > directive (if there are several, any one of them should suffice) > // What I would like to see > test.cpp: In function 'int main()': > test.cpp:12:9: error: call of overloaded 'foo(int)' is ambiguous > test.cpp:12:9: note: candidates are: > test.cpp:3:10: note: void n1::foo(double) > test.cpp:6:13: note: visible in global namespace because of using-declaration > located here Should 'global namespace' refer to the scope containing the using-declaration or the scope containing the ambiguous call? (They're both the global namespace in your example, but don't have to be.) A using-directive can also appear at block scope and a using-declaration can also appear at block scope and class scope, so the note would have to be able to decide between printing "global namespace" vs "namespace X" vs "current scope" vs ...? A using-declaration /declares/ the name in that scope as a synonym for the other entity, it doesn't just make it visible. A using-directive just makes the names visible. To keep the diagnostics simpler maybe the note could just say: test.cpp:6:13: note: found due to using-declaration here or test.cpp:6:13: note: found due to using-directive here I think that still conveys enough information, without having to worry about whether it's at namespace scope (and global vs named vs unnamed) or block scope or class scope. > // What I would like to see > test.cpp: In function 'int main()': > test.cpp:12:20: error: call of overloaded 'foo(int, n1::Bar)' is ambiguous > test.cpp:12:20: note: candidates are: > test.cpp:8:6: note: void foo(float, n1::Bar) > test.cpp:5:10: note: void n1::foo(double, n1::Bar) > test.cpp:3:14: note: found by argument-dependent lookup because second > argument > is of type n1::Bar Printing "argument 2" is easier than "second argument" (or the diagnostic machinery needs to be able to print ordinal numbers for any value in any language!) Would that note still be useful if it said "is of type X<Y<n1::Bar>>" ? What about if it said "is of type Derived" where that type has n1::Bar as an indirect base class? Would it help to add "so n1 is an associated namespace" or would that make it too long? test.cpp:3:14: note: found by argument-dependent lookup because 'n1' is an associated namespace of argument 2 of type 'n1::Bar' > Does this sound doable? I have no idea :)
