Variadic parameter error persists after type is inferred

[Chriscbr]

I tried this:

let g = (x: Array<num>): num => {
  return x.at(0);
};

let f = (...y) => {
  return g(y);
};

When I hover over y in my IDE, it tells me that y has type Array<num>

This happened:

error: Variadic parameters must be type Array or MutArray.
  --> inference.w:5:13
  |
5 | let f = (...y) => {
  |             ^ Variadic parameters must be type Array or MutArray.

I expected this:

I expected the example to compile, or to get an error that I need a type annotation for ...y

Is there a workaround?

No response

Component

Compiler

Wing Version

0.25.14

Node.js Version

18.14.1

Platform(s)

MacOS

Anything else?

No response

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[MarkMcCulloh]

I think there are two options here, assuming we keep the current inference mechanism:

1. When encountering (...y), the type checker will infer y as Array<inference(0)> instead of just inference(0). This will ensure that it will be valid for variadic purposes and that any further inferencing must match that shape
2. Simply require type annotations on variadic args

While I enjoy the ergonomics of (1), it will likely be surprising when this does not work (note mutarray):

let g = (x: MutArray<num>): num => {
  return x.at(0);
};

let f = (...y) => {
  return g(y);
         //^ Expected type to be "MutArray<num>", but got "Array<unknown>" instead
};

With the current inferencing algorithm, it can't apply a constraint that has more than one type (e.g. both Array and MutArray), so we would have to pick one.

[github-actions]

Hi,

This issue hasn't seen activity in 60 days. Therefore, we are marking this issue as stale for now. It will be closed after 7 days.
Feel free to re-open this issue when there's an update or relevant information to be added.
Thanks!

[github-actions]

Hi,

This issue hasn't seen activity in 90 days. Therefore, we are marking this issue as stale for now. It will be closed after 7 days.
Feel free to re-open this issue when there's an update or relevant information to be added.
Thanks!

[github-actions]

Hi,

This issue hasn't seen activity in 90 days. Therefore, we are marking this issue as stale for now. It will be closed after 7 days.
Feel free to re-open this issue when there's an update or relevant information to be added.
Thanks!