Make the LiberateCase transformation understand associated types
Consider this FC program:
data family AT a :: *
data instance AT Int = T1 Int Int
f :: AT Int -> Int
f t = case t of DEFAULT -> <body>
We'd like to replace the DEFAULT by a use of T1, so that if
we scrutinise t inside <body> we share the evaluation:
f t = case (t `cast` co) of T1 x y -> <body>
I decided to do this as part of the liberate-case transformation,
which is already trying to avoid redundant evals.
The new transformation requires knowledge of the family instance
environment, so I had to extend ModGuts to carry the fam_inst_env,
and put that envt into the liberate-case environment.
Otherwise it's all pretty straightforward.
projects / ghc-hetmet.git / commit