Dot patterns in arguments corresponding to module parameters should not be allowed

[Jesper Cockx]

open import Haskell.Prelude

module _ where

cast : {a b : Set} → @0 a ≡ b → a → b 
cast {a} {b} = cast'
  where
  cast' : @0 a ≡ b → a → b
  cast' refl x = x

{-# COMPILE AGDA2HS cast #-}

This is currently accepted, but compiles to invalid Haskell code:

cast :: a -> b
cast = cast'
  where
    cast' :: a -> b
    cast' x = x