Hi,

This does not appear to be related to ImplicitParameters, rather `MonoLocalBinds` is not working as expected.

Here is an example without implicit parameters that compiles just fine, but would be rejected if `p` was monomorphic:

{-# LANGUAGE NoMonomorphismRestriction, MonoLocalBinds #-}

class C a where

f :: a -> ()

instance C Bool where f = const ()

instance C Char where f = const ()

g = let p = f

in (p 'a', p True)

-Iavor

On Fri, Mar 22, 2013 at 1:39 AM, Roman Cheplyaka <roma@ro-che.info> wrote:

The value of the following expression

let ?y = 2 in
let p = ?y in
let ?y = 1 in
p

depends on whether the second binding is generalised.

MonomorphismRestriction makes it not generalise, hence the value is 2.

What surprises me is that MonoLocalBinds doesn't have this effect.

Prelude> :set -XImplicitParams -XNoMonomorphismRestriction -XMonoLocalBinds
Prelude> let ?y = 2 in let p = ?y in let ?y = 1 in p
1

What's going on here?

Roman

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