Elaborated EOF char message a little

parse.y

@@ -6209,7 +6209,7 @@ lex_goto_eol(struct parser_params *p)
     for (; pcur < pend; pcur++) {
         const char *eof = eof_char(*pcur);
         if (eof) {
-            rb_warning1("encountered %s in comment, just ignored in this version", WARN_S(eof));
+            rb_warning1("encountered EOF char(%s) in comment, just ignored in this version", WARN_S(eof));
             break;
         }
     }

test/ruby/test_parse.rb

@@ -722,7 +722,7 @@ x = __ENCODING__
 
   def test_embedded_rd_warning
     [["\0", "\\0"], ["\C-d", "^D"], ["\C-z", "^Z"]].each do |eof, mesg|
-      mesg = /encountered #{Regexp.quote(mesg)}/
+      mesg = /encountered EOF char\(#{Regexp.quote(mesg)}\)/
       assert_warning(mesg) {eval("=begin\n#{eof}\n=end")}
       assert_warning(mesg) {eval("=begin#{eof}\n=end")}
       assert_warning(mesg) {eval("=begin\n=end#{eof}\n")}

test/ruby/test_syntax.rb

@@ -944,9 +944,9 @@ eom
   end
 
   def test_warning_for_eof_in_comment
-    assert_warning(/encountered \\0/) {eval("#\0")}
-    assert_warning(/encountered \^D/) {eval("#\C-d")}
-    assert_warning(/encountered \^Z/) {eval("#\C-z")}
+    assert_warning(/encountered EOF char\(\\0\)/) {eval("#\0")}
+    assert_warning(/encountered EOF char\(\^D\)/) {eval("#\C-d")}
+    assert_warning(/encountered EOF char\(\^Z\)/) {eval("#\C-z")}
   end
 
   def test_unexpected_fraction