Commit 899fd7fb authored by's avatar
Browse files

Add comments about invariants

parent 957b762c
......@@ -54,11 +54,14 @@ data Instance
= Instance { is_cls :: Name -- Class name
-- Used for "rough matching"; see note below
-- INVARIANT: is_tcs = roughMatchTcs is_tys
, is_tcs :: [Maybe Name] -- Top of type args
-- Used for "proper matching"; see note
, is_tvs :: TyVarSet -- Template tyvars for full match
, is_tys :: [Type] -- Full arg types
-- INVARIANT: is_dfun Id has type
-- forall is_tvs. (...) => is_cls is_tys
, is_dfun :: DFunId
, is_flag :: OverlapFlag -- See detailed comments with
......@@ -88,7 +91,7 @@ In is_tcs,
The "proper-match" fields
The is_tvs, is_tys fields are simply cahced values, pulled
The is_tvs, is_tys fields are simply cached values, pulled
out (lazily) from the dfun id. They are cached here simply so
that we don't need to decompose the DFunId each time we want
to match it. The hope is that the fast-match fields mean
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