Data.Vinyl.Utils.Field

Manipulation of constraints that apply to field labels (as opposed to actual types stored in the record).

Documentation

type family FieldAll rs c :: Constraint

Assert that all field labels in a given type list satisfy a given constraint.

Equations

FieldAll `[]` c = ()

FieldAll (r : rs) c = (c r, FieldAll rs c)

data DictProxy c a where

A data type that reifies a constraint. Pattern match on the DictProxy constructor to bring the constraint into scope.

Constructors

DictProxy :: c a => DictProxy c a

getProxy :: DictProxy c a -> Proxy a

Obtain a Proxy from a DictProxy, forgetting its constraint.

reifyFieldConstraint :: FieldAll rs c => proxy c -> Rec Proxy rs -> Rec (DictProxy c) rs

Given a dummy record and a constraint that applies to all field labels, reify the constraint for each field label.