[Bug c++/80684] poor error message and fix-it hint for a function with an argument of undeclared type

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80684

Eric Gallager <egallager at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2017-08-18
                 CC|                            |egallager at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Eric Gallager <egallager at gcc dot gnu.org> ---
For me the fix-it is just:

$ /usr/local/bin/g++ -S -Wall -Wextra -pedantic 80684.cc
80684.cc:1:15: error: variable or field ‘f’ declared void
 void f (string);
               ^
80684.cc:1:9: error: ‘string’ was not declared in this scope
 void f (string);
         ^~~~~~
80684.cc:1:9: note: suggested alternative: ‘__strong’
 void f (string);
         ^~~~~~
         __strong
$

When I include the header, the message is:

$ /usr/local/bin/g++ -S -Wall -Wextra -pedantic 80684.cc
80684.cc:3:15: error: variable or field ‘f’ declared void
 void f (string);
               ^
80684.cc:3:9: error: ‘string’ was not declared in this scope
 void f (string);
         ^~~~~~
80684.cc:3:9: note: suggested alternative:
In file included from /usr/local/include/c++/8.0.0/string:39:0,
                 from 80684.cc:1:
/usr/local/include/c++/8.0.0/bits/stringfwd.h:74:33: note:  
‘std::__cxx11::string’
   typedef basic_string<char>    string;
                                 ^~~~~~
$

It seems like in this second case where <string> is already included, the ideal
fix-it would be to suggest inserting the 'std::' prefix before 'string', or
adding a "using namespace std;" directive earlier in the file. Thus,
confirming.