GHC.Tc.Gen.HsType

Typecheck the class in a default declaration, checking that:

• it is indeed a class (not e.g. a type family),

• that the class expects some invisible arguments followed by a single visible argument.

Like tcHsSigType, but for the ...deriving( C ty1 ty2 ) clause

Returns a class constraint with the last argument missing, and the expected kind of the remaining argument.

E.g.:

class C (a::*) (b::k->k) data T a b = ... deriving( C Int )

This function returns (C, [k], [k, Int], k->k).

Return values are fully zonked

Typecheck a deriving strategy. For most deriving strategies, this is a no-op, but for the via strategy, this requires typechecking the via type.

Type-check a visible type application

UserTypeCtxt describes the origin of the polymorphic type in the places where we need an expression to have that type

Skolemise the HsTyVarBndrs in an HsForAllTelescope with the supplied TcTyMode.

Bring into scope the binders of a PolyTcTyCon Used for the type variables of a type or class decl in the "kind checking" and "type checking" pass, but not in the initial-kind run.

Describes the kind expected in a certain context.

• Specialised version of kindGeneralizeSome, but with empty WantedConstraints, so no filtering is needed i.e. kindGeneraliseAll = kindGeneralizeSome emptyWC

Checks that the return kind in a data declaration's kind signature is permissible. There are three cases:

If dealing with a data, newtype, data instance, or newtype instance declaration, check that the return kind is Type.

If the declaration is a newtype or newtype instance and the UnliftedNewtypes extension is enabled, this check is slightly relaxed so that a return kind of the form TYPE r (for some r) is permitted. See Note [Implementation of UnliftedNewtypes] in GHC.Tc.TyCl.

If dealing with a data family declaration, check that the return kind is either of the form:

1. TYPE r (for some r), or

2. k (where k is a bare kind variable; see #12369)

See also Note [Datatype return kinds] in GHC.Tc.TyCl

A description of whether something is a

• data or newtype (DataDeclSort)

• data instance or newtype instance (DataInstanceSort)

• data family (DataFamilySort)

At present, this data type is only consumed by checkDataKindSig.

Checks that the result kind of a class is exactly Constraint, rejecting type synonyms and type families that reduce to Constraint. See #16826.