diff options
Diffstat (limited to 'libraries/template-haskell')
| -rw-r--r-- | libraries/template-haskell/Language/Haskell/TH/Syntax.hs | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/libraries/template-haskell/Language/Haskell/TH/Syntax.hs b/libraries/template-haskell/Language/Haskell/TH/Syntax.hs index aacc8c3db1..3087c69504 100644 --- a/libraries/template-haskell/Language/Haskell/TH/Syntax.hs +++ b/libraries/template-haskell/Language/Haskell/TH/Syntax.hs @@ -1833,6 +1833,35 @@ data DecidedStrictness = DecidedLazy | DecidedUnpack deriving (Show, Eq, Ord, Data, Generic) +-- | A single data constructor. +-- +-- The constructors for 'Con' can roughly be divided up into two categories: +-- those for constructors with \"vanilla\" syntax ('NormalC', 'RecC', and +-- 'InfixC'), and those for constructors with GADT syntax ('GadtC' and +-- 'RecGadtC'). The 'ForallC' constructor, which quantifies additional type +-- variables and class contexts, can surround either variety of constructor. +-- However, the type variables that it quantifies are different depending +-- on what constructor syntax is used: +-- +-- * If a 'ForallC' surrounds a constructor with vanilla syntax, then the +-- 'ForallC' will only quantify /existential/ type variables. For example: +-- +-- @ +-- data Foo a = forall b. MkFoo a b +-- @ +-- +-- In @MkFoo@, 'ForallC' will quantify @b@, but not @a@. +-- +-- * If a 'ForallC' surrounds a constructor with GADT syntax, then the +-- 'ForallC' will quantify /all/ type variables used in the constructor. +-- For example: +-- +-- @ +-- data Bar a b where +-- MkBar :: (a ~ b) => c -> MkBar a b +-- @ +-- +-- In @MkBar@, 'ForallC' will quantify @a@, @b@, and @c@. data Con = NormalC Name [BangType] -- ^ @C Int a@ | RecC Name [VarBangType] -- ^ @C { v :: Int, w :: a }@ | InfixC BangType Name BangType -- ^ @Int :+ a@ |