Re: [PATCH v2 3/3] c++: note other candidates when diagnosing deletedness

[Jason Merrill <jason@redhat.com>]

On 10/23/23 19:51, Patrick Palka wrote:
> With the previous two patches in place, we can now extend our
> deletedness diagnostic to note the other considered candidates, e.g.:
> 
>    deleted16.C: In function 'int main()':
>    deleted16.C:10:4: error: use of deleted function 'void f(int)'
>       10 |   f(0);
>          |   ~^~~
>    deleted16.C:5:6: note: declared here
>        5 | void f(int) = delete;
>          |      ^
>    deleted16.C:5:6: note: candidate: 'void f(int)' (deleted)
>    deleted16.C:6:6: note: candidate: 'void f(...)'
>        6 | void f(...);
>          |      ^
>    deleted16.C:7:6: note: candidate: 'void f(int, int)'
>        7 | void f(int, int);
>          |      ^
>    deleted16.C:7:6: note:   candidate expects 2 arguments, 1 provided
> 
> For now, these these notes are disabled when a deleted special member
> function is selected because it introduces a lot of new "cannot bind
> reference" errors in the testsuite when noting non-viable candidates,
> e.g. in cpp0x/initlist-opt1.C we would need to expect an error when
> noting unviability of A(A&&).  (It'd be nice if we could downgrade such
> errors into notes when noting candidates...)

What about my suggestion to make printing the other candidates an 
opt-in, with the normal output just suggesting the use of that option 
for more information, like -ftemplate-backtrace-limit?

Jason