microsoft / microsoft/TypeScript-TmLanguage

String Literal Param in Default Type Definition in Interface Function Causes Breakage

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Dominant language
TypeScript
Stars
471
Forks
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PR merge metrics
No merged PRs in 30d

Description

Code

let var1;

interface MyInterface {
  func<T = Lowercase<'StringLiteral'>>(): T;
}

let var2;

JavaScript and TypeScript Nightly version: 5.6.0-dev.20240623

Screenshot 2024-06-24 at 12 33 28 PM

Breakage continues for many other keywords at the same block level such as: let, const, export, for, while, interface etc. class itself seems to overcome the breakage.

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First steps

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  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the interface snippet in VS Code with the TypeScript Nightly extension, then inspect the TypeScript TextMate grammar files in this repository. Check how the default type definition and nested string literal affect block-level keyword scopes. Done means the snippet and the listed keywords no longer cause syntax highlighting to break.

Written by the indexing model from the issue text.

Assessment

Tech stack
typescript
Domain
tooling
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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