fixits: handle per-rule duplicates

[Akim Demaille]

   commit 5879c8dc5a391ce3d9de68f50326121babc8d1be
   Author: Akim Demaille <address@hidden>
   Date:   Thu Jan 17 06:44:51 2019 +0100
      fixits: handle per-rule duplicates
      * src/complain.c (duplicate_rule_directive): Here.
      * tests/actions.at (Invalid uses of %empty): Check it.
   diff --git a/src/complain.c b/src/complain.c
   index d623bb45..82258c62 100644
   --- a/src/complain.c
   +++ b/src/complain.c
   @@ -421,4 +421,5 @@ duplicate_rule_directive (char const *directive,
     complain_indent (&second, complaint, &i, _("only one %s allowed per
   rule"), directive);
     i += SUB_INDENT;
     complain_indent (&first, complaint, &i, _("previous declaration"));
   +  fixits_register (&second, "");
   }
   diff --git a/tests/actions.at b/tests/actions.at
   index e5654a47..aa1eb3aa 100644
   --- a/tests/actions.at
   +++ b/tests/actions.at
   @@ -174,8 +174,35 @@ AT_BISON_CHECK([-fcaret one.y], [1], [],
   one.y:11.3-8:       previous declaration
      %empty {} %empty
      ^~~~~~
   +one.y: warning: fix-its can be applied.  Rerun with option '--update'.
   [-Wother]
   ]])
   +AT_BISON_CHECK([-fcaret -u one.y], [1], [],
   +[[one.y:11.13-18: error: only one %empty allowed per rule
   +   %empty {} %empty
   +             ^~~~~~
   +one.y:11.3-8:       previous declaration
   +   %empty {} %empty
   +   ^~~~~~
   +bison: file 'one.y' was updated (backup: 'one.y~')
   +]])
   +
   +AT_CHECK([cat one.y], [],
   +[[%code top {
   +/* Load config.h, and adjust to the compiler.
   +  We used to do it here, but each time we add a new line,
   +  we have to adjust all the line numbers in error messages.
   +  It's simpler to use a constant include to a varying file.  */
   +#include <testsuite.h>
   +}
   +
   +%%
   +exp:
   +  %empty {} @&t@
   +;
   +]])
   +
   +
   AT_DATA_GRAMMAR([[two.y]],
   [[%%
   exp: