使用“proxy s”绑定类型与使用forall绑定类型

在下面的例子中,我不清楚为什么 toto 会失败,而 tata 会起作用。

对此有什么解释吗?

{-# LANGUAGE AllowAmbiguousTypes  #-}
{-# LANGUAGE  TypeFamilies, KindSignatures, FlexibleContexts #-}
{-# LANGUAGE TypeApplications, FunctionalDependencies, MultiParamTypeClasses #-}
{-# LANGUAGE ScopedTypeVariables , GADTs, MultiParamTypeClasses, RankNTypes                #-}
{-# LANGUAGE TypeOperators, UnicodeSyntax, DataKinds              #-}

import Data.Proxy

data KNat where
class ReflectNum (s :: KNat) where

toto ∷ (∀ (s :: KNat). ReflectNum s ⇒ Int) → Int
toto k = toto k

tata ∷ (∀ (s :: KNat). ReflectNum s ⇒ Proxy s -> Int) → Int
tata k = tata (\(p :: Proxy s) -> k p)

误差是

SO.hs:14:15: error:
    • Could not deduce (ReflectNum s0) arising from a use of ‘k’
      from the context: ReflectNum s
        bound by a type expected by the context:
                   forall (s :: KNat). ReflectNum s => Int
        at SO.hs:14:10-15
      The type variable ‘s0’ is ambiguous
    • In the first argument of ‘toto’, namely ‘k’
      In the expression: toto k
      In an equation for ‘toto’: toto k = toto k
   |
14 | toto k = toto k
   |               ^