Flow: $Shape does not preserve covariance

[ForbesLindesay]

e.g.

/* @flow */

type State= {+foo: number};
function setState(state: $Shape<State>) {
}
setState(({foo: 10}: State));

produces the error:

4: function setState(state: $Shape<State>) {
                                   ^ object type. Covariant property `foo` incompatible with contravariant use in
4: function setState(state: $Shape<State>) {
                                   ^ State

Even though all usage of the foo property is covariant.

[nmn]

$Shape is an experimental feature for very specific use-cases.

[ForbesLindesay]

Yes, but it's used internally by React, so this prevents you marking parts of your state as co-variant. I get that $Shape is only for special use cases, but the inconsistencies when using things like $Shape<T>, $Exact<T> and ReactClass<T> are causing a lot of pain for me. It's death from a thousand cuts. I get that they each seem low-priority, but collectively they have a big impact on the developer experience.

[TrySound]

Seems like fixed
https://flow.org/try/#0PQKgBAAgZgNg9gdzCYAoVAXAngBwKZgDKGAhhngLxgDeA1FHHAFxgB2ArgLYBGeATgF8A3KijtWAYwwBLOKzABnPBmJk8ACgWlyLACSEAFiXwAeVeQB8AShqoBqJSu0b11BszABGAAwCW5vCsrISA