-- Strip off existing lambdas and casts
-- Note [Eta expansion and SCCs]
go 0 expr = expr
- go n (Lam v body) | isTyVar v = Lam v (go n body)
+ go n (Lam v body) | isTyCoVar v = Lam v (go n body)
| otherwise = Lam v (go (n-1) body)
go n (Cast expr co) = Cast (go n expr) co
go n expr = -- pprTrace "ee" (vcat [ppr orig_expr, ppr expr, ppr etas]) $
etaInfoApp subst (Lam v1 e) (EtaVar v2 : eis)
= etaInfoApp subst' e eis
where
- subst' | isTyVar v1 = CoreSubst.extendTvSubst subst v1 (mkTyVarTy v2)
+ subst' | isTyCoVar v1 = CoreSubst.extendTvSubst subst v1 (mkTyVarTy v2)
| otherwise = CoreSubst.extendIdSubst subst v1 (Var v2)
etaInfoApp subst (Cast e co1) eis
-- coerce T (\x::[T] -> (coerce ([T]->Int) e) x)
go n subst ty' (EtaCo (Type.substTy subst co) : eis)
- | otherwise -- We have an expression of arity > 0,
+ | otherwise -- We have an expression of arity > 0,
+ -- but its type isn't a function.
= WARN( True, ppr orig_n <+> ppr orig_ty )
- (getTvInScope subst, reverse eis) -- but its type isn't a function.
+ (getTvInScope subst, reverse eis)
-- This *can* legitmately happen:
-- e.g. coerce Int (\x. x) Essentially the programmer is
-- playing fast and loose with types (Happy does this a lot).