Destructuring an existential with let reports "this switch" #9069

Destructuring a GADT constructor with an existential type in a let reports a switch that isn't in the source:

type rec any = Any('a, 'a => string): any

let get = value => {
  let Any(x, _) = value
  x
}

This has type: $Any_'a
But this switch is expected to return: 'a
The type constructor $Any_'a would escape its scope

All branches in a switch must return the same type.
To fix this, change your branch to return the expected type.

The let is checked as a match internally, but the hint about switch branches doesn't apply here. (See also the $Any_'a naming in the related issue.)