1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
|
module GHC.Tc.Types.Rank (Rank(..)) where
import GHC.Base (Bool)
import GHC.Utils.Outputable (Outputable, (<+>), parens, ppr, text)
{-
Note [Higher rank types]
~~~~~~~~~~~~~~~~~~~~~~~~
Technically
Int -> forall a. a->a
is still a rank-1 type, but it's not Haskell 98 (#5957). So the
validity checker allow a forall after an arrow only if we allow it
before -- that is, with Rank2Types or RankNTypes
-}
data Rank = ArbitraryRank -- Any rank ok
| LimitedRank -- Note [Higher rank types]
Bool -- Forall ok at top
Rank -- Use for function arguments
-- Monotypes that could be a polytype through an extension
| MonoTypeRankZero -- RankNTypes
| MonoTypeTyConArg -- ImpredicativeTypes
| MonoTypeSynArg -- LiberalTypeSynonyms
| MonoTypeConstraint -- QuantifiedConstraints
--
| MustBeMonoType -- Monotype regardless of flags
instance Outputable Rank where
ppr ArbitraryRank = text "ArbitraryRank"
ppr (LimitedRank top_forall_ok r)
= text "LimitedRank" <+> ppr top_forall_ok
<+> parens (ppr r)
ppr MonoTypeRankZero = text "MonoTypeRankZero"
ppr MonoTypeTyConArg = text "MonoTypeTyConArg"
ppr MonoTypeSynArg = text "MonoTypeSynArg"
ppr MonoTypeConstraint = text "MonoTypeConstraint"
ppr MustBeMonoType = text "MustBeMonoType"
|
