GHC.Core.Predicate

A predicate in the solver. The solver tries to prove Wanted predicates from Given ones.

A choice of equality relation. This is separate from the type Role because Phantom does not define a (non-trivial) equality relation.

Does this type classify a core (unlifted) Coercion? At either role nominal or representational (t1 ~# t2) or (t1 ~R# t2) See Note [Types for coercions, predicates, and evidence] in GHC.Core.TyCo.Rep

Get the equality relation relevant for a pred type Returns NomEq for dictionary predicates, etc

Creates a primitive nominal type equality predicate. t1 ~# t2 Invariant: the types are not Coercions

Creates a primitive representational type equality predicate. t1 ~R# t2 Invariant: the types are not Coercions

Makes a lifted equality predicate at the given role

Makes a lifted equality predicate at the given role

Is the type *guaranteed* to determine the value? Might say No even if the type does determine the value. See Note [Type determines value]

mightMentionIP str_cond ty_cond cls tys returns True if:

• cls tys is of the form IP str ty, where str_cond str and ty_cond ty are both True,

• or any superclass of cls tys has this property.

See Note [Local implicit parameters]

Take a type (IP sym ty), where IP is the built in IP class and return (ip, MkIP, [sym,ty]), where ip is the class-op for class IP MkIP is the data constructor for class IP

Is a type a CallStack?

Is a PredType a CallStack implicit parameter?

If so, return the name of the parameter.

Is a PredType an ExceptionContext implicit parameter?

If so, return the name of the parameter.

Is a type an ExceptionContext?

Decomposes a predicate if it is an implicit parameter. Does not look in superclasses. See also [Local implicit parameters].

Dictionary Identifier

Do a topological sort on a list of tyvars, so that binders occur before occurrences E.g. given [ a::k, k::Type, b::k ] it'll return a well-scoped list [ k::Type, a::k, b::k ].

This is a deterministic sorting operation (that is, doesn't depend on Uniques).

It is also meant to be stable: that is, variables should not be reordered unnecessarily. This is specified in Note [ScopedSort] See also Note [Ordering of implicit variables] in GHC.Rename.HsType

Get the free vars of a type in scoped order

Get the free vars of types in scoped order

A CanEqLHS is a type that can appear on the left of a canonical equality: a type variable or exactly-saturated type family application.

Is a type a canonical LHS? That is, is it a tyvar or an exactly-saturated type family application? Does not look through type synonyms.

Retrieve the kind of a CanEqLHS

Convert a CanEqLHS back into a Type

Are two CanEqLHSs equal?