lib Fix Part 4/6 – String.replaceAll and related changes

[graphemecluster]

General Information

PR separated out from #49855, because there might be some members expecting smaller PRs. As mentioned in the comments from the big PR, whether to review a single, large PR or 6 smaller PRs is up to the TypeScript Team to decide. I couldn't have found a better way for this; hopefully this will not bring any trouble to the Team.

This PR partially fixes #49773.
For details and the track list about the changes, please see #49773.

Part 4/6, String.replaceAll and related changes

Most of them are documentation changes.

Fix #36299
Fix #38595

[sandersn]

@typescript-bot run dt
@typescript-bot user test this
@typescript-bot test top100

[typescript-bot]

Heya @sandersn, I've started to run the parallelized Definitely Typed test suite on this PR at ba0601e. You can monitor the build here.

[typescript-bot]

Heya @sandersn, I've started to run the diff-based top-repos suite on this PR at ba0601e. You can monitor the build here.

Update: The results are in!

[typescript-bot]

Heya @sandersn, I've started to run the diff-based user code test suite on this PR at ba0601e. You can monitor the build here.

Update: The results are in!

[typescript-bot]

@sandersn Here are the results of running the user test suite comparing main and refs/pull/50452/merge:

Everything looks good!

[typescript-bot]

@sandersn Here are the results of running the top-repos suite comparing main and refs/pull/50452/merge:

Something interesting changed - please have a look.

Details

microsoft/vscode

3 of 54 projects failed to build with the old tsc and were ignored

src/tsconfig.json

• error TS2345: Argument of type 'string' is not assignable to parameter of type '"NFC" | "NFD" | "NFKC" | "NFKD" | undefined'.
  • src/vs/base/common/normalization.ts#L31

src/tsconfig.monaco.json

• error TS2345: Argument of type 'string' is not assignable to parameter of type '"NFC" | "NFD" | "NFKC" | "NFKD" | undefined'.
  • src/vs/base/common/normalization.ts#L31

src/tsconfig.tsec.json

• error TS2345: Argument of type 'string' is not assignable to parameter of type '"NFC" | "NFD" | "NFKC" | "NFKD" | undefined'.
  • src/vs/base/common/normalization.ts#L31

[ArshVermaGit]

This PR continues the incremental approach of splitting the broader changes from #49855 into smaller, more reviewable units, which should make it easier for the TypeScript team to evaluate and discuss specific concerns in isolation. Focusing on String.replaceAll and related updates, the changes are largely documentation-oriented, helping clarify behavior and improve consistency across the standard library definitions. Addressing long-standing issues like #36299 and #38595 adds tangible value while keeping the scope manageable, and the decision to structure the work as part 4/6 demonstrates thoughtful consideration for review workflow and maintainability. Overall, this feels like a practical and considerate contribution that improves clarity without introducing unnecessary risk.