No overload matches this call. Overload 1 of 4, '(iterable?: Iterable<readonly [unknown, unknown]> | null | undefined): Map<unknown, unknown>'

[albertkao9]

🔎 Search Terms

"No overload matches this call" '(iterable?: Iterable<readonly [unknown, unknown]> | null | undefined): Map<unknown, unknown>'

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about this.

⏯ Playground Link

https://www.typescriptlang.org/play?#code/MYewdgzgLgBAlmADgV1gXhmApgdxgWQENEAKAbRjIHJjEAbLKgGioCcsATKgXScqoBGhMMMLMqATyx06IHDxjcAlAG4AsAChseIqTIA6QwhRRu+gLbESWMFFYSYaAHwwbdifvYA3LKwhYSJSCVIA

💻 Code

const input = new Map([ ['apple','red'], ['banana','yellow'] ]);
new Map([...input].map(entry => entry.reverse()));

🙁 Actual behavior

compile error:
No overload matches this call.
Overload 1 of 4, '(iterable?: Iterable<readonly [unknown, unknown]> | null | undefined): Map<unknown, unknown>', gave the following error.
Argument of type 'string[][]' is not assignable to parameter of type 'Iterable<readonly [unknown, unknown]>'.
The types returned by 'Symbol.iterator.next(...)' are incompatible between these types.
Type 'IteratorResult<string[], any>' is not assignable to type 'IteratorResult<readonly [unknown, unknown], any>'.
Type 'IteratorYieldResult<string[]>' is not assignable to type 'IteratorResult<readonly [unknown, unknown], any>'.
Type 'IteratorYieldResult<string[]>' is not assignable to type 'IteratorYieldResult<readonly [unknown, unknown]>'.
Type 'string[]' is not assignable to type 'readonly [unknown, unknown]'.
Target requires 2 element(s) but source may have fewer.
Overload 2 of 4, '(entries?: readonly (readonly [unknown, unknown])[] | null | undefined): Map<unknown, unknown>', gave the following error.
Argument of type 'string[][]' is not assignable to parameter of type 'readonly (readonly [unknown, unknown])[]'.
Type 'string[]' is not assignable to type 'readonly [unknown, unknown]'.

🙂 Expected behavior

No compile error

Additional information about the issue

This JavaScript code has no compile error at https://developer.mozilla.org/en-US/play .
i.e. It works.

[nmain]

So you want .reverse() to change the type [T, U] into [U, T]? I can't find a specific issue for this, but this is closely related to things like #44309 and the other tickets linked from that.

Edit: And if you want it on reverse() and not just toReversed() I think you'd also need #41339?

[RyanCavanaugh]

There's currently no type constructor that reflects the type of reverse(), so we don't "know" how many elements are in it

[sukima]

EDIT: never mind, Unable to reproduce in playground.

I ran into this error for a different reason. It has to do that TS expects the constructor for Map to take an Array when in fact per the spec it should be an Iterable. this line I think should be:

--- a	2024-01-09 20:14:25.893721728 -0500
+++ b	2024-01-09 20:15:27.910665078 -0500
@@ -29,7 +29,7 @@
 
 interface MapConstructor {
     new (): Map<any, any>;
-    new <K, V>(entries?: readonly (readonly [K, V])[] | null): Map<K, V>;
+    new <K, V>(entries?: readonly Iterable<readonly [K, V]> | null): Map<K, V>;
     readonly prototype: Map<any, any>;
 }
 declare var Map: MapConstructor;