ExPatFail.hs:12:15: error:
• Couldn't match expected type ‘p’ with actual type ‘a’
‘a’ is a rigid type variable bound by
a pattern with constructor:
MkT :: forall a. Integral a => a -> Int -> T,
in a pattern binding
at ExPatFail.hs:12:11-17
‘p’ is a rigid type variable bound by
the inferred type of f :: T -> p
at ExPatFail.hs:(12,1)-(13,10)
• In the pattern: MkT y _
In a pattern binding: MkT y _ = x
In the expression: let MkT y _ = x in y
• Relevant bindings include
f :: T -> p (bound at ExPatFail.hs:12:1)