Re: [Haskell-cafe] Solved but strange error in type inference

On Wed, Jan 4, 2012 at 12:44 AM, Yves Parès wrote:

Remove subsome type signature. You are redeclaring type variables which obviously cannot match those of legSome. This cannot work without scoped type variables (and ad-hoc foralls to bring them to scope, of course).

That subsome type signature is from the original code. I wonder why the redeclared type variables cannot match those of legSome? p.s. I just realized that my changed code missed the line:

import qualified Data.Map as M