`RegExp#[Symbol.matchAll]` should return iterable of `RegExpExecArray` instead of `RegExpMatchArray`

[lionel-rowe]

🔎 Search Terms

RegExp, matchAll, Symbol.matchAll, RegExpExecArray, RegExpMatchArray

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about RegExp, matchAll, Symbol.matchAll, RegExpExecArray, RegExpMatchArray

⏯ Playground Link

https://www.typescriptlang.org/play/?target=99#code/MYewdgzgLgBATgUxgXhgegHRoOYChSSzRwowDkAhgEbBm64BmIJAFAdDALYwgMzEZOFKMAAWAQQA2klogCUcmAG9cMNejQ8A1jBYIAHgAcEwKAgAm8BBACukqHNXr2sAJYAuGGBucqCEqicGK5g5gbqMLgAvvRMrC5cPHyIANoAygCeviCSgsJiUpIAuizECspOamiaACoZxuTevv4wAD4wNqEIDCEWZDCuEF4gsBQQEK7YYNSSSFAgMFD1SGRNfnBkGJUwCR5ePuukQSFh+tG4QA

💻 Code

const re = /./g
const str = 'abc'

for (const m of str.matchAll(re)) {
    // ok (expected result)
    const i: number = m.index    
}

for (const m of re[Symbol.matchAll](str)) {
    // Type 'number | undefined' is not assignable to type 'number'.
    const i: number = m.index
}

🙁 Actual behavior

While String#matchAll now correctly returns RegExpStringIterator<RegExpExecArray> (#36788, fixed in #55565), the identically-behaving RegExp#[Symbol.matchAll] still returns the incorrect type RegExpStringIterator<RegExpMatchArray>

🙂 Expected behavior

String#matchAll and RegExp#[Symbol.matchAll] to behave identically at compile time as well as runtime, i.e. both String#matchAll and RegExp#[Symbol.matchAll] to consistently return RegExpStringIterator<RegExpExecArray>.

Additional information about the issue

No response