egison-5.1.0: test/type-error/52-missing-signature-constraint.egi

-- A definition whose body requires a type-class constraint that its
-- signature does not declare must be rejected (the signature is the
-- contract; if the body needs {Ord a}, the signature must say so).
--
-- Here <= is an Ord method used at the signature's type variable `a`,
-- but the signature declares no {Ord a}.

def needsOrd {a} (x: a) (y: a) : Bool := x <= y