Consistent rules of automatic binding of types and values in patterns

[ppolesiuk]

If a constructor pattern or a polymorphic actual parameter does not mention some named parameter, it could be introduced to the environment or not. Currently implemented rules are not very consistent:

data T = C of {`n : Int}
let f C = `n (* is valid, because `n was implicitly introduced *)
let g (C { module M }) = `n (* Unbound implicit `n *)

nor intuitive:

let f (g : ({x} -> _) -> _) = g x (* is valid, since x was implicitly introduced *)

We should develop more clear, consistent, and intuitive rules how this feature should behave.