Re: [Haskell-cafe] Applying typed hole proposal leads to compilation failure

On Fri, Aug 24, 2018 at 06:25:34PM -0400, Brandon Allbery wrote:

Note that this also requires ScopedTypeVariables; the Haskell standard specifies that type variables are only in scope within the type signature, not the accompanying binding. Which is also why the explicit "forall" is required, to tell it to use the modified rules here, which otherwise could cause other code that expects standard Haskell behavior to fail to compile if it happens to reuse type variables from the signature.

I had thought of mentioning this but their original snippet included the extension so I thought they already knew.