ghc-9.0.2: The GHC API

GHC.Rename.HsType

Synopsis

# Documentation

Constructors

 AlwaysBind Always bind any free tyvars of the given type, regardless of whether we have a forall at the top.For pattern type sigs, we do want to bring those type variables into scope, even if there's a forall at the top which usually stops that happening, e.g:\ (x :: forall a. a -> b) -> eHere we do bring b into scope.RULES can also use AlwaysBind, such as in the following example:{-# RULES \"f\" forall (x :: forall a. a -> b). f x = ... b ... #-}This only applies to RULES that do not explicitly bind their type variables. If a RULE explicitly quantifies its type variables, then NeverBind is used instead. See also Note [Pattern signature binders and scoping] in GHC.Hs.Type. BindUnlessForall Unless there's forall at the top, do the same thing as AlwaysBind. This is only ever used in places where the "forall-or-nothing" rule is in effect. See Note [forall-or-nothing rule]. NeverBind Never bind any free tyvars. This is used for RULES that have both explicit type and term variable binders, e.g.:{-# RULES \"const\" forall a. forall (x :: a) y. const x y = x #-}The presence of the type variable binder forall a. implies that the free variables in the types of the term variable binders x and y are not bound. In the example above, there are no such free variables, but if the user had written (y :: b) instead of y in the term variable binders, then b would be rejected for being out of scope. See also Note [Pattern signature binders and scoping] in GHC.Hs.Type.

Constructors

 ReassociateNegation KeepNegationIntact

Should GHC warn if a quantified type variable goes unused? Usually, the answer is "yes", but in the particular case of binding LHsQTyVars, we avoid emitting warnings. See Note [Suppress -Wunused-foralls when binding LHsQTyVars].

Constructors

 WarnUnusedForalls NoWarnUnusedForalls

#### Instances

Instances details
 Source # Instance detailsDefined in GHC.Rename.HsType Methods

Arguments

 :: Maybe assoc Just _ => an associated type decl -> FreeKiTyVars Surface-syntax free vars that we will implicitly bind. May have duplicates, which are removed here. -> ([Name] -> RnM (a, FreeVars)) -> RnM (a, FreeVars)

extractHsTyRdrTyVars finds the type/kind variables of a HsType/HsKind. It's used when making the foralls explicit. See Note [Kind and type-variable binders]

Extracts the free type/kind variables from the kind signature of a HsType. This is used to implicitly quantify over k in type T = Nothing :: Maybe k. The left-to-right order of variables is preserved. See Note [Kind and type-variable binders] and Note [Ordering of implicit variables] and Note [Implicit quantification in type synonyms].

Extracts free type and kind variables from types in a list. When the same name occurs multiple times in the types, all occurrences are returned.

Get type/kind variables mentioned in the kind signature, preserving left-to-right order:

• data T a (b :: k1) :: k2 -> k1 -> k2 -> Type -- result: [k2,k1]
• data T a (b :: k1) -- result: []

See Note [Ordering of implicit variables].

Arguments

 :: Bool True = explicit forall E.g. f :: forall a. a->b we do not want to bring b into scope, hence True But f :: a -> b we want to bring both a and b into scope, hence False -> FreeKiTyVars Free vars of the type -> RnM FreeKiTyVars

See Note [forall-or-nothing rule]. This tiny little function is used (rather than its small body inlined) to indicate that we are implementing that rule.

nubL :: Eq a => [Located a] -> [Located a] Source #