Documentation

This instance must not overlap another

Silently ignore this instance if you find a more specific one that matches the constraint you are trying to resolve

Example: constraint (Foo [Int]) instances (Foo [Int]) (Foo [a]) OverlapOk Since the second instance has the OverlapOk flag, the first instance will be chosen (otherwise its ambiguous which to choose)

Like OverlapOk, but also ignore this instance if it doesn't match the constraint you are trying to resolve, but could match if the type variables in the constraint were instantiated

Example: constraint (Foo [b]) instances (Foo [Int]) Incoherent (Foo [a]) Without the Incoherent flag, we'd complain that instantiating b would change which instance was chosen