Optional Iterator parameter "incorrectly" accepts spread arguments

declare const strs1: string[];
declare const strs2: IterableIterator<string>;

declare function badFoo(x?: Iterable<string>): void

// This function is BAD.
// The last two calls are INCORRECTLY accepted.

badFoo(strs1); // accepted - fine
badFoo(strs2); // accepted - fine

badFoo(...strs1); // accepted, BAD ❌
badFoo(...strs2); // accepted, BAD ❌

Playground Link

[jakebailey]

@bschnurr thanks 😄

[DanielRosenwasser]

Ultimately I think it’s a case where strings being at all compatible with Iterable<string> is extremely suspicious unless it’s made explicit with a type assertion. Seems a bit heavy-handed, but I can’t think of the last time I needed to spread a string except for emoji examples.