Polymorphic type annotations generalize weak polymorphic variables

[thierry-martinez]

Polymorphic type annotations generalize weak polymorphic variables, making such programs type check and segfault:

let f x =
  let ref : type a . a option ref = ref None in
  ref := Some x;
  Option.get !ref

let () = print_string (f 0)

This program is rejected by OCaml 4.10 but is accepted by OCaml 4.11 and trunk. Bisection points to the commit c272447.

[gasche]

Woops! Looks like an opportunity for a 4.11.1.

[lpw25]

Fixed by #9857