Properly support tuple field accessors typing about mlscript HOT 4 CLOSED

Related JS-gen issue: #65 (comment)

from mlscript.

I realize the right way of doing this is to change the way field removal types act on tuples (and arrays).

Currently it leaves tuples untouched:

We should add a field in TupleType and ArrayType to remember which fields have been hidden by a Without type applied on such types.

(Cc @Meowcolm024.)

from mlscript.

Another improvement request: properly reason about intersected tuple-record types, as mentioned in #79 (comment).

For example:

def test: (string, 1) & { _1: "hello" }
//│ test: (string, 1,) & {_1: "hello", _2: 1}

The above should simplify to test: ("hello", 1,).

Moreover in:

test: { _1: 'a }
//│ res: {_1: "hello"}

test: ('a, 1)
//│ res: (string, 1,)

I would have expected to get type ("hello", 1,) for the latter.

Similarly, the following could "simplify" to res: Array[1] & {_1: 1}:

error: Array[1] & { _1: int }
//│ res: Array[1] & {_1: int}

from mlscript.

I realize the right way of doing this is to change the way field removal types act on tuples (and arrays).

Note: To make things simpler, we didn't go with this approach. Instead, we just convert these types to records upon removing fields from them, which is not optimal ((1, 2) with {_1 = 3} is typed as {_1: 3, _2: 2} whereas it could be typed as (3, 2)), but probably sufficient for now.

from mlscript.