C++ PATCH for c++/65043, missing narrowing warning with bool

[Jason Merrill]

On Wed, Aug 15, 2018 at 11:30 AM, Marek Polacek <polacek@redhat.com> wrote:
> We weren't complaining about narrowing when converting to bool because
> standard_conversion wasn't setting check_narrowing for the converting to bool
> case; it only sets it at the end of the function.  Moreover, check_narrowing
> wasn't catching real_type -> boolean_type at all, which is wrong;
> [dcl.init.list] says that a narrowing conversion is an implicit conversion from
> a floating-point type to an integer type, and bool is an integer type.
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
>
> 2018-08-14  Marek Polacek  <polacek@redhat.com>
>
>         PR c++/65043
>         * call.c (standard_conversion): Set check_narrowing.
>         * typeck2.c (check_narrowing): Use CP_INTEGRAL_TYPE_P rather
>         than comparing with INTEGER_TYPE.
>
>         * g++.dg/concepts/pr67595.C: Add dg-warning.
>         * g++.dg/cpp0x/Wnarrowing11.C: New test.
>         * g++.dg/cpp0x/Wnarrowing12.C: New test.
>         * g++.dg/cpp0x/rv-cast5.C: Add static_cast.
>
> diff --git gcc/cp/call.c gcc/cp/call.c
> index 62654a9e407..ded279a0f43 100644
> --- gcc/cp/call.c
> +++ gcc/cp/call.c
> @@ -1387,6 +1387,8 @@ standard_conversion (tree to, tree from, tree expr, bool c_cast_p,
>             conv->rank = cr_pbool;
>           if (NULLPTR_TYPE_P (from) && (flags & LOOKUP_ONLYCONVERTING))
>             conv->bad_p = true;
> +         if (flags & LOOKUP_NO_NARROWING)
> +           conv->check_narrowing = true;
>           return conv;
>         }

Hmm, it might be better to fix this section to properly fall through
to the common check_narrowing code below.  OK either way.

Jason