Allow function type in untagged variants

[fhammerschmidt]

Just tried to bind the MUI SxProps with untagged variants.

This is the TS definition:

export type SxProps<Theme extends object = {}> =
  | SystemStyleObject<Theme>
  | ((theme: Theme) => SystemStyleObject<Theme>)
  | ReadonlyArray<
      boolean | SystemStyleObject<Theme> | ((theme: Theme) => SystemStyleObject<Theme>)
    >;

and this is my attempt in ReScript:

module SxProps = {
  type theme = {primaryColor?: string}
  type systemStyleObject = {mr?: int, color?: string}

  @unboxed
  type rec t =
    | @as(false) False
    | @as(true) True
    | Object(systemStyleObject)
    | Array(array<t>)
    | Callback(callback)
  and callback = theme => systemStyleObject
}

which, aside from the fact that it's simplified because the array should not be nested and the booleans should only be nested, does not work, because one cannot use a function (the Callback variant in this example) type here.

Would it be possible to add that? Since you can check that easily with typeof == "function".

[cristianoc]

Do you have references to example TS code that uses that?
Just curious, not important. The description is already clear.

[fhammerschmidt]

Yes, here: https://mui.com/system/getting-started/the-sx-prop/#callback-values

[cristianoc]

Yes, here: https://mui.com/system/getting-started/the-sx-prop/#callback-values

Thanks, so it looks like a case where one wants to construct values rather than doing pattern matching on.
While the internal implementation of material UI is the one that does "pattern matching", in the sense of detecting different shapes used.

[fhammerschmidt]

That is true. Looks like in this case a bunch of externals with %identity is still the way to go.

However, I still wonder if it would be a useful addition in other cases.

[zth]

This pattern, providing either an object or a function to produce that object, is quite common in TS I'd say.

[cknitt]

    | Bool(bool)

instead of

    | @as(false) False
    | @as(true) True

would be nice, too. (Wasn't there a discussion about that somewhere else? Can't find the issue.)

[zth]

    | Bool(bool)

instead of

    | @as(false) False
    | @as(true) True

would be nice, too. (Wasn't there a discussion about that somewhere else? Can't find the issue.)

Here: #6231