patch 8.2.2931: Vim9: line continuation comment uses legacy syntax

Problem:    Vim9: line continuation comment still uses legacy syntax in one
            place.
Solution:   Check for #\ instead of "\ earlier. (closes #8316)

src/scriptfile.c

@@ -1788,6 +1788,8 @@ getsourceline(
     if (line != NULL && options != GETLINE_NONE
 				      && vim_strchr(p_cpo, CPO_CONCAT) == NULL)
     {
+	int comment_char = in_vim9script() ? '#' : '"';
+
 	// compensate for the one line read-ahead
 	--sp->sourcing_lnum;
 
@@ -1800,7 +1802,8 @@ getsourceline(
 	sp->nextline = get_one_sourceline(sp);
 	if (sp->nextline != NULL
 		&& (*(p = skipwhite(sp->nextline)) == '\\'
-			      || (p[0] == '"' && p[1] == '\\' && p[2] == ' ')
+			      || (p[0] == comment_char
+						&& p[1] == '\\' && p[2] == ' ')
 			      || (do_vim9_all && (*p == NUL
 						     || vim9_comment_start(p)))
 			      || (do_bar_cont && p[0] == '|' && p[1] != '|')))
@@ -1842,7 +1845,7 @@ getsourceline(
 			ga_concat(&ga, p);
 		    }
 		}
-		else if (!(p[0] == (in_vim9script() ? '#' : '"')
+		else if (!(p[0] == (comment_char)
 						&& p[1] == '\\' && p[2] == ' ')
 		     && !(do_vim9_all && (*p == NUL || vim9_comment_start(p))))
 		    break;

src/testdir/test_vim9_script.vim

@@ -3081,6 +3081,9 @@ def Test_vim9_comment()
       \ start='foo'
       #\ comment
       \ end='bar'
+      syn region Text start='foo'
+      #\ comment
+      \ end='bar'
   END
   CheckScriptSuccess(lines)
 

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2931,
 /**/
     2930,
 /**/