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GHC 9.10.3 · lts/ghc-9.10.x · 248f8f0 · 2026-10-05

Moduleghc-9.10.3GHC2021

GHC.Core.Class

  • 7 types
  • 25 values
  • Packageghc-9.10.3
  • Exports32
  • LanguageGHC2021
  • LicenceBSD-3-Clause
  • SourceClass.hs
datadata Class
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Instances5Eq, Data, NamedThing, Outputable, Uniquable
datadata TyFamEqnValidityInfo
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Information about a type family equation, used for validity checking of closed type family equations and associated type family default equations.

This type exists to delay validity-checking after typechecking type declaration groups, to avoid cyclic evaluation inside the typechecking knot.

See Note [Type-checking default assoc decls] in GHC.Tc.TyCl.

Constructors

  • NoVI

    Used for equations which don't need any validity checking, for example equations imported from another module.

  • VI

    Information necessary for validity checking of a type family equation.

    • vi_loc :: SrcSpan
    • vi_qtvs :: [TcTyVar]

      LHS quantified type variables

    • vi_non_user_tvs :: TyVarSet

      non-user-written type variables (for error message reporting)

      Example: with -XPolyKinds, typechecking type instance forall a. F = () introduces the kind variable k for the kind of a. See #23734.

    • vi_pats :: [Type]

      LHS patterns

    • vi_rhs :: Type

      RHS of the equation

      NB: for associated type family default declarations, this is the RHS *before* applying the substitution from Note [Type-checking default assoc decls] in GHC.Tc.TyCl.

typetype FunDep a = ([a], [a])
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