-- It's important to add the in-scope tyvars to the global tyvar set
-- as well. Consider
-- f (_::r) = let g y = y::r in ...
-- Here, g mustn't be generalised. This is also important during
-- class and instance decls, when we mustn't generalise the class tyvars
-- when typechecking the methods.
-- It's important to add the in-scope tyvars to the global tyvar set
-- as well. Consider
-- f (_::r) = let g y = y::r in ...
-- Here, g mustn't be generalised. This is also important during
-- class and instance decls, when we mustn't generalise the class tyvars
-- when typechecking the methods.