[Bug c++/54548] New: unclear error message for ambiguous type lookup.

["pluto at agmk dot net" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54548

             Bug #: 54548
           Summary: unclear error message for ambiguous type lookup.
    Classification: Unclassified
           Product: gcc
           Version: 4.7.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: pluto@agmk.net


#include <new>
struct X;
namespace { struct X; }
int main()
{
        new X();
}


a gcc error message is unreadable for end-user in case when
the first 'struct X' decl is hidden deeply in the #include forest.

$ LANG=C g++ -Wall t.cpp -c              
t.cpp: In function 'int main()':
t.cpp:6:6: error: expected type-specifier before 'X'
t.cpp:6:6: error: expected ';' before 'X'


clang is more user-friendly and shows problem directly.

$ LANG=C clang++ -Wall t.cpp -c          
t.cpp:6:6: error: reference to 'X' is ambiguous
        new X();
            ^
t.cpp:2:8: note: candidate found by name lookup is 'X'
struct X;
       ^
t.cpp:3:20: note: candidate found by name lookup is '<anonymous namespace>::X'
namespace { struct X; }
                   ^
t.cpp:6:6: error: allocation of incomplete type 'X'
        new X();
            ^
t.cpp:2:8: note: forward declaration of 'X'
struct X;
       ^
2 errors generated.