Documentation

Type family that maps a constraint to its first class representation - should be generally used instead of its concrete result for consistency.

Reflect a constraint as a dictionary value.

You can use TypeApplications to make the constraint c explicit. Dict is injective, so c may be inferred sometimes.

Reify a dictionary to resolve a constraint required by the second operand.

For example, this lets us use + on a type that doesn't have a top-level Num instance.

>>> newtype Foo = Foo Int deriving Show
>>> (coerce (dict @(Num Int)) :: Dict (Num Foo)) ==> Foo 1 + Foo 2
Foo 3

This function is extremely unsafe. It breaks the global property that there is at most one instance for each constraint. For example, sets and maps in containers rely on that property to maintain their invariants.

Use at your own risk.