[gspell] InlineCheckerTextBuffer: add more assertions

[Sébastien Wilmet <swilmet src gnome org>]

commit 043609960097f80d99ce4c166892b291df06aae3
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Wed Feb 22 16:16:09 2017 +0100

    InlineCheckerTextBuffer: add more assertions
    
    Let's see if it fails earlier.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=778883

 gspell/gspell-inline-checker-text-buffer.c |   27 ++++++++++++++++++++++-----
 1 files changed, 22 insertions(+), 5 deletions(-)
---
diff --git a/gspell/gspell-inline-checker-text-buffer.c b/gspell/gspell-inline-checker-text-buffer.c
index 58ae1b5..73997e4 100644
--- a/gspell/gspell-inline-checker-text-buffer.c
+++ b/gspell/gspell-inline-checker-text-buffer.c
@@ -242,19 +242,36 @@ check_subregion (GspellInlineCheckerTextBuffer *spell,
                                    start,
                                    end);
 
-       word_start = *start;
-       if (!_gspell_text_iter_starts_word (&word_start))
+       if (_gspell_text_iter_starts_word (start))
        {
-               _gspell_text_iter_forward_word_end (&word_start);
+               word_start = *start;
+       }
+       else
+       {
+               GtkTextIter next_word_end;
+
+               /* Based on adjust_iters() code. */
+               g_assert (!_gspell_text_iter_inside_word (start));
 
-               /* Didn't move, there is no words after @start. */
-               if (gtk_text_iter_equal (&word_start, start))
+               next_word_end = *start;
+               _gspell_text_iter_forward_word_end (&next_word_end);
+
+               /* Didn't move, there are no words after @start. */
+               if (gtk_text_iter_equal (&next_word_end, start))
                {
                        return;
                }
 
+               g_assert (_gspell_text_iter_ends_word (&next_word_end));
+               g_assert_cmpint (gtk_text_iter_compare (start, &next_word_end), <, 0);
+
+               word_start = next_word_end;
                _gspell_text_iter_backward_word_start (&word_start);
                g_assert (_gspell_text_iter_starts_word (&word_start));
+
+               /* This assertion has failed in some cases, see:
+                * https://bugzilla.gnome.org/show_bug.cgi?id=778883
+                */
                g_assert_cmpint (gtk_text_iter_compare (start, &word_start), <, 0);
        }