Drop support for the "ur" string prefix

Parser/tokenizer.c

 
 /* Tokenizer implementation */
 
 #include "Python.h"
 #include "pgenheaders.h"
 
 #include <ctype.h>
 #include <assert.h>
 
 #include "tokenizer.h"
@@ skipping 1394 matching lines @@
             c = tok_nextc(tok);
 
     /* Check for EOF and errors now */
     if (c == EOF) {
         return tok->done == E_EOF ? ENDMARKER : ERRORTOKEN;
     }
 
     /* Identifier (most frequent token!) */
     nonascii = 0;
     if (is_potential_identifier_start(c)) {
-        /* Process b"", r"", u"", br"", rb"" and ur"" */
+        /* Process b"", r"", u"", br"" and rb"" */
         int saw_b = 0, saw_r = 0, saw_u = 0;
         while (1) {
             if (!(saw_b || saw_u) && (c == 'b' || c == 'B'))
                 saw_b = 1;
             /* Since this is a backwards compatibility support literal we don't
                want to support it in arbitrary order like byte literals. */
             else if (!(saw_b || saw_u || saw_r) && (c == 'u' || c == 'U'))
                 saw_u = 1;
-            else if (!saw_r && (c == 'r' || c == 'R'))
+            /* ur"" and ru"" are not supported */
+            else if (!(saw_r || saw_u) && (c == 'r' || c == 'R'))
                 saw_r = 1;
             else
                 break;
             c = tok_nextc(tok);
             if (c == '"' || c == '\'')
                 goto letter_quote;
         }
         while (is_potential_identifier_char(c)) {
             if (c >= 128)
                 nonascii = 1;
@@ skipping 332 matching lines @@
 
 void
 tok_dump(int type, char *start, char *end)
 {
     printf("%s", _PyParser_TokenNames[type]);
     if (type == NAME || type == NUMBER || type == STRING || type == OP)
         printf("(%.*s)", (int)(end - start), start);
 }
 
 #endif