diagnostics: remove redundancy

[Akim Demaille]

commit 27104acdbee1e234c5d88eb139509e2fb57071d7
Author: Akim Demaille <address@hidden>
Date:   Mon Jan 21 20:03:19 2019 +0100

    diagnostics: remove redundancy
    
    Don't repeat the name of the warning in the sub messages.  E.g.,
    remove the second "[-Wother]" in the following message
    
        foo.y:2.1-27: warning: %define variable 'parse.error' redefined 
[-Wother]
         %define parse.error verbose
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
        foo.y:1.1-27:     previous definition [-Wother]
         %define parse.error verbose
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
    
    * src/complain.c (error_message): Don't print the warning type when
    it's indented.
    Adjust test cases.

diff --git a/src/complain.c b/src/complain.c
index c177e202..a4ab0a1f 100644
--- a/src/complain.c
+++ b/src/complain.c
@@ -279,15 +279,18 @@ error_message (const location *loc, warnings flags, const 
char *prefix,
         *indent_ptr = pos;
       else if (*indent_ptr > pos)
         fprintf (stderr, "%*s", *indent_ptr - pos, "");
-      indent_ptr = 0;
+      indent_ptr = NULL;
     }
 
   if (prefix)
     fprintf (stderr, "%s: ", prefix);
 
   vfprintf (stderr, message, args);
-  if (! (flags & silent))
+  /* Print the type of warning, only if this is not a sub message
+     (in which case the prefix is null).  */
+  if (! (flags & silent) && prefix)
     warnings_print_categories (flags, stderr);
+
   {
     size_t l = strlen (message);
     if (l < 2 || message[l - 2] != ':' || message[l - 1] != ' ')
diff --git a/tests/input.at b/tests/input.at
index bce75b97..22bcfe87 100644
--- a/tests/input.at
+++ b/tests/input.at
@@ -2523,15 +2523,15 @@ fix-it:"input.y":{12:1-12:11}:"%expect-rr"
 input.y:13.1-14: warning: deprecated directive: '%file-prefix =', use 
'%file-prefix' [-Wdeprecated]
 fix-it:"input.y":{13:1-13:15}:"%file-prefix"
 input.y:14.1-16.5: warning: duplicate directive: '%file-prefix\n =' [-Wother]
-input.y:13.1-20:       previous declaration [-Wother]
+input.y:13.1-20:       previous declaration
 fix-it:"input.y":{14:1-16:6}:""
 input.y:17.1-19: warning: deprecated directive: '%fixed-output_files', use 
'%fixed-output-files' [-Wdeprecated]
 fix-it:"input.y":{17:1-17:20}:"%fixed-output-files"
 input.y:18.1-19: warning: duplicate directive: '%fixed_output-files' [-Wother]
-input.y:17.1-19:     previous declaration [-Wother]
+input.y:17.1-19:     previous declaration
 fix-it:"input.y":{18:1-18:20}:""
 input.y:19.1-19: warning: duplicate directive: '%fixed-output-files' [-Wother]
-input.y:17.1-19:     previous declaration [-Wother]
+input.y:17.1-19:     previous declaration
 fix-it:"input.y":{19:1-19:20}:""
 input.y:20.1-19: warning: deprecated directive: '%name-prefix= "foo"', use 
'%define api.prefix {foo}' [-Wdeprecated]
 fix-it:"input.y":{20:1-20:20}:"%define api.prefix {foo}"
@@ -2551,7 +2551,7 @@ input.y:27.1-14: error: %define variable 'parse.error' 
redefined
 input.y:11.1-14:     previous definition
 fix-it:"input.y":{27:1-27:15}:""
 input.y:29.1-18: warning: duplicate directive: '%name-prefix "bar"' [-Wother]
-input.y:13.1-20:     previous declaration [-Wother]
+input.y:13.1-20:     previous declaration
 fix-it:"input.y":{29:1-29:19}:""
 input.y: warning: fix-its can be applied.  Rerun with option '--update'. 
[-Wother]
 ]])
@@ -2669,7 +2669,7 @@ AT_DATA_GRAMMAR([[input.y]],
 
 AT_BISON_CHECK([[input.y]], [[0]], [[]],
 [[input.y:14.1-15.5: warning: duplicate directive: '%file-prefix' [-Wother]
-input.y:13.1-18:       previous declaration [-Wother]
+input.y:13.1-18:       previous declaration
 input.y: warning: %expect-rr applies only to GLR parsers [-Wother]
 input.y: warning: fix-its can be applied.  Rerun with option '--update'. 
[-Wother]
 ]])