internal error instead of type error on "some_vector.some_field_name"

[paulstansifer]

Trying to compile the file:

fn f() {
  auto v = vec(1);
  log v.some_field_name; //type error
}

Results in the error message:
6:6:6:23: error: internal compiler error: unimplemented base type for expr_field in typeck.check_expr: vec[int]