let's get the discussion going about proposal #155 (https://github.com/goldfirere/ghc-proposals/blob/type-lambda/proposals/0000-type-lambda.rst).

Summary:

the idea is pretty simple:  allow functions to name their type arguments explicitly, so that they can be used in type signatures within the function's definition.   The notation for a type argument is `@a`, and such type arguments can be used only when functions have an explicit type signature (technically, when GHC is doing "checking" rather then "inference").

This proposal provides an alternative to "ScopedTypeVariables" to refer to type parameters, which I think is a step in the right direction, as using the `forall` to introduce type variables always felt a bit hacky to me (now, there's a technical argument :)

I am a bit concerned with the notation though:  in other places where we use `@a`, (e.g., #126 type application in patterns, and TypeApplications) the `a` is a type, while in this use it must be a variable.   I wonder if this punning might be confusing.   I don't really have an alternative suggestion though.

What does everyone else thing?

-Iavor