The big problem with ScopedTypeVariables is that it changes the meaning of existing code by unifying type variables that are not unified today in standardized Haskell.<p>It&#x27;s one of those things that you&#x27;d probably do if you were starting with a blank slate, but it&#x27;s not worth breaking existing code for when you can instead get the functionality through an opt-in extension. GHC Haskell&#x27;s language extensions are pretty nice that way, but it would be nice to standardize the extensions to open the (extended) language back up to alternative implementations.