You are misunderstanding what 'undecidable instances' does.
s/undecidable/incoherent/g
Claus
GHC wants to solve the constraint (D Foo beta) where beta is
as-yet-unconstrained type variable. It finds that one instance *matches*
(by instantiating only the instance declaration, not the constra
You are misunderstanding what 'undecidable instances' does.
GHC wants to solve the constraint (D Foo beta) where beta is
as-yet-unconstrained type variable. It finds that one instance *matches* (by
instantiating only the instance declaration, not the constraint we are solving):
D a b
bu
