Imported record field access can trigger type checker exception

[peblair]

When deleting the : MatchResult annotation on this line, this error is raised:

 λ grain git:(regexp) ✗ > grain compiler/test/stdlib/regex.test.gr
/Users/pblair/views/grain/cli/bin/grainc.exe: internal error, uncaught exception:
                                              (Failure "Impossible: deprecated error type in typetexp")

This is not ideal. We should either correctly unify the type information to preclude an error altogether (preferable), or, if that is not possible for some reason, provide a better error message.
cc @ospencer

[ospencer]

Fixed in #1200