[PATCH] c++: Fix poor diagnostic for array initializer [PR93710]

[Marek Polacek]

On Mon, Feb 17, 2020 at 02:11:59PM +0100, Christophe Lyon wrote:
> On Wed, 12 Feb 2020 at 21:06, Marek Polacek <polacek@redhat.com> wrote:
> >
> > A small improvement for an error in build_user_type_conversion_1:
> > instead of
> >
> > array-init1.C:11:1: error: conversion from ‘long int’ to ‘A’ is ambiguous
> >    11 | };
> >       | ^
> >
> > we will print
> >
> > array-init1.C:8:3: error: conversion from ‘long int’ to ‘A’ is ambiguous
> >     8 |   0L,
> >       |   ^~
> >
> > Bootstrapped/regtested on x86_64-linux, ok for trunk?
> >
> > 2020-02-12  Marek Polacek  <polacek@redhat.com>
> >
> >         PR c++/93710 - poor diagnostic for array initializer.
> >         * call.c (build_user_type_conversion_1): Use cp_expr_loc_or_input_loc
> >         for an error call.
> >
> >         * g++.dg/diagnostic/array-init1.C: New test.
> > ---
> >  gcc/cp/call.c                                 |  5 +++--
> >  gcc/testsuite/g++.dg/diagnostic/array-init1.C | 11 +++++++++++
> >  2 files changed, 14 insertions(+), 2 deletions(-)
> >  create mode 100644 gcc/testsuite/g++.dg/diagnostic/array-init1.C
> >
> > diff --git a/gcc/cp/call.c b/gcc/cp/call.c
> > index 51621b7dd87..f47f96bf1c2 100644
> > --- a/gcc/cp/call.c
> > +++ b/gcc/cp/call.c
> > @@ -4172,8 +4172,9 @@ build_user_type_conversion_1 (tree totype, tree expr, int flags,
> >        if (complain & tf_error)
> >         {
> >           auto_diagnostic_group d;
> > -         error ("conversion from %qH to %qI is ambiguous",
> > -                fromtype, totype);
> > +         error_at (cp_expr_loc_or_input_loc (expr),
> > +                   "conversion from %qH to %qI is ambiguous",
> > +                   fromtype, totype);
> >           print_z_candidates (location_of (expr), candidates);
> >         }
> >
> > diff --git a/gcc/testsuite/g++.dg/diagnostic/array-init1.C b/gcc/testsuite/g++.dg/diagnostic/array-init1.C
> > new file mode 100644
> > index 00000000000..78580ad6b83
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/diagnostic/array-init1.C
> > @@ -0,0 +1,11 @@
> > +// PR c++/93710 - poor diagnostic for array initializer.
> > +
> > +struct A { A (int); A (char*); int i; };
> > +
> > +int x;
> > +
> > +A a1[] = {
> > +  0L, // { dg-error "3:conversion from .long int. to .A. is ambiguous" }
> > +  &x, // { dg-error "3:invalid conversion from .int\\*. to .int." }
> > +  __builtin_offsetof (A, i) // { dg-error "23:conversion from .long unsigned int. to .A. is ambiguous" }
> 
> Hi,
> 
> This test fails on arm (and i586 according to gcc-testresults:
> /gcc/testsuite/g++.dg/diagnostic/array-init1.C:10:23: error:
> conversion from 'unsigned int' to 'A' is ambiguous
> 
> Note sure if you want to make the dg-error conditional or match '.*
> unsigned int' ?

Sorry about that, fixed now.

Marek