diagnostics: tweak to line-insertion fix-it hints with line-numbering

This commit slightly tweaks line-insertion fix-it hints, so that
with line-numbering, rather than e.g.:

 99 |       x = a;
    |+      break;
110 |     case 'b':
    |     ^~~~~~~~

we fill the margin with "+":

 99 |       x = a;
+++ |+      break;
110 |     case 'b':
    |     ^~~~~~~~

to emphasize that this is a suggested new line, rather than the user's
source.

gcc/ChangeLog:
	* diagnostic-show-locus.c (layout::start_annotation_line): Add
	"margin_char" parameter, defaulting to space.  Use it in place
	of pp_space for the initial part of the margin.
	(layout::print_leading_fixits): Use '+' when filling the margin
	of line-insertion fix-it hints.

gcc/testsuite/ChangeLog:
	* gcc.dg/plugin/diagnostic-test-show-locus-bw-line-numbers.c
	(test_fixit_insert_newline): Update expected output to show '+'
	characters in margin of line-insertion fix-it hint.

From-SVN: r263605

gcc/ChangeLog

+2018-08-16  David Malcolm  <dmalcolm@redhat.com>
+
+	* diagnostic-show-locus.c (layout::start_annotation_line): Add
+	"margin_char" parameter, defaulting to space.  Use it in place
+	of pp_space for the initial part of the margin.
+	(layout::print_leading_fixits): Use '+' when filling the margin
+	of line-insertion fix-it hints.
+
 2018-08-16  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	* config/rs6000/rs6000.md (two unnamed define_insn and define_split):

gcc/diagnostic-show-locus.c

@@ -253,7 +253,7 @@ class layout
   void print_source_line (linenum_type row, const char *line, int line_width,
 			  line_bounds *lbounds_out);
   bool should_print_annotation_line_p (linenum_type row) const;
-  void start_annotation_line () const;
+  void start_annotation_line (char margin_char = ' ') const;
   void print_annotation_line (linenum_type row, const line_bounds lbounds);
   void print_any_labels (linenum_type row);
   void print_trailing_fixits (linenum_type row);
@@ -1330,12 +1330,12 @@ layout::should_print_annotation_line_p (linenum_type row) const
    margin, which is empty for annotation lines.  Otherwise, do nothing.  */
 
 void
-layout::start_annotation_line () const
+layout::start_annotation_line (char margin_char) const
 {
   if (m_show_line_numbers_p)
     {
       for (int i = 0; i < m_linenum_width; i++)
-	pp_space (m_pp);
+	pp_character (m_pp, margin_char);
       pp_string (m_pp, " |");
     }
 }
@@ -1587,7 +1587,7 @@ layout::print_leading_fixits (linenum_type row)
 	     helps them stand out from each other, and from
 	     the surrounding text.  */
 	  m_colorizer.set_normal_text ();
-	  start_annotation_line ();
+	  start_annotation_line ('+');
 	  pp_character (m_pp, '+');
 	  m_colorizer.set_fixit_insert ();
 	  /* Print all but the trailing newline of the fix-it hint.

gcc/testsuite/ChangeLog

+2018-08-16  David Malcolm  <dmalcolm@redhat.com>
+
+	* gcc.dg/plugin/diagnostic-test-show-locus-bw-line-numbers.c
+	(test_fixit_insert_newline): Update expected output to show '+'
+	characters in margin of line-insertion fix-it hint.
+
 2018-08-16  Nathan Sidwell  <nathan@acm.org>
 
 	* gcc.dg/cpp/macsyntx.c: Adjust expected errors.

gcc/testsuite/gcc.dg/plugin/diagnostic-test-show-locus-bw-line-numbers.c

@@ -111,7 +111,7 @@ void test_fixit_insert_newline (void)
       x = b;
     }
 /* { dg-begin-multiline-output "" }
-    |+      break;
++++ |+      break;
 110 |     case 'b':
     |     ^~~~~~~~
    { dg-end-multiline-output "" } */