Ariel Ben-Yehuda 8aeaaac654 add a fast-path to resolve_type_vars_if_possible
this avoids needless substituting

before:
577.76user 4.27system 7:36.13elapsed 127%CPU (0avgtext+0avgdata 1141608maxresident)k

after:
573.01user 4.04system 7:33.86elapsed 127%CPU (0avgtext+0avgdata 1141656maxresident)k
2015-08-18 00:24:16 +03:00
..
2015-08-13 15:42:14 -04:00
2015-08-15 19:35:52 -07:00