Safe Haskell	None
Language	Haskell98

Language.Haskell.TH.ExpandSyns

Contents

Expand synonyms
Misc utilities

Synopsis

expandSyns :: Type -> Q Type
expandSynsWith :: SynonymExpansionSettings -> Type -> Q Type
data SynonymExpansionSettings
noWarnTypeFamilies :: SynonymExpansionSettings
substInType :: (Name, Type) -> Type -> Type
substInCon :: (Name, Type) -> Con -> Con
evades :: Data t => [Name] -> t -> [Name]
evade :: Data d => Name -> d -> Name

Expand synonyms

expandSyns :: Type -> Q Type Source #

Calls expandSynsWith with the default settings.

expandSynsWith :: SynonymExpansionSettings -> Type -> Q Type Source #

Expands all type synonyms in the given type. Type families currently won't be expanded (but will be passed through).

data SynonymExpansionSettings Source #

Instances

Semigroup SynonymExpansionSettings Source #
Instance details Defined in Language.Haskell.TH.ExpandSyns Methods (<>) :: SynonymExpansionSettings -> SynonymExpansionSettings -> SynonymExpansionSettings # sconcat :: NonEmpty SynonymExpansionSettings -> SynonymExpansionSettings # stimes :: Integral b => b -> SynonymExpansionSettings -> SynonymExpansionSettings #
Monoid SynonymExpansionSettings Source #	Default settings (`mempty`): Warn if type families are encountered. (The `mappend` is currently rather useless; the monoid instance is intended for additional settings in the future).
Instance details Defined in Language.Haskell.TH.ExpandSyns Methods mempty :: SynonymExpansionSettings # mappend :: SynonymExpansionSettings -> SynonymExpansionSettings -> SynonymExpansionSettings # mconcat :: [SynonymExpansionSettings] -> SynonymExpansionSettings #

noWarnTypeFamilies :: SynonymExpansionSettings Source #

Suppresses the warning that type families are unsupported.

Misc utilities

substInType :: (Name, Type) -> Type -> Type Source #

Capture-free substitution

substInCon :: (Name, Type) -> Con -> Con Source #

Capture-free substitution

evades :: Data t => [Name] -> t -> [Name] Source #

Make a list of names (based on the first arg) such that every name in the result is distinct from every name in the second arg, and from the other results

evade :: Data d => Name -> d -> Name Source #

Make a name (based on the first arg) that's distinct from every name in the second arg

Example why this is necessary:

type E x = forall y. Either x y

... expandSyns [t| forall y. y -> E y |]

The example as given may actually work correctly without any special capture-avoidance depending on how GHC handles the ys, but in any case, the input type to expandSyns may be an explicit AST using mkName to ensure a collision.