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

[Jason Merrill]

On 2/12/20 9:05 PM, Marek Polacek 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?

OK.

2020-02-12  Marek Polacek  <pola...@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" }
+};

base-commit: 5bfc8303ffe2d86e938d45f13cd99a39469dac4f