-tcAddScopedTyVars :: [RenamedHsType] -> TcM a -> TcM a
--- Find the not-already-in-scope signature type variables,
--- kind-check them, and bring them into scope
---
--- We no longer specify that these type variables must be univerally
--- quantified (lots of email on the subject). If you want to put that
--- back in, you need to
--- a) Do a checkSigTyVars after thing_inside
--- b) More insidiously, don't pass in expected_ty, else
--- we unify with it too early and checkSigTyVars barfs
--- Instead you have to pass in a fresh ty var, and unify
--- it with expected_ty afterwards
-tcAddScopedTyVars sig_tys thing_inside
- = tcGetEnv `thenNF_Tc` \ env ->
- let
- all_sig_tvs = foldr (unionNameSets . extractHsTyVars) emptyNameSet sig_tys
- sig_tvs = filter not_in_scope (nameSetToList all_sig_tvs)
- not_in_scope tv = not (tcInLocalScope env tv)
- in
- tcScopedTyVars sig_tvs (kcHsSigTypes sig_tys) thing_inside
-