microsoft / microsoft/TypeScript-TmLanguage

Highlighting breaks when casting a variable called `type`

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Dominant language
TypeScript
Stars
471
Forks
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Description

JavaScript and TypeScript Nightly version: v5.3.20230923

Hi there, an issue occurs when both using <> and as casting.

Code

Using <> casting with newline after <:

export function main() {
  const type = ``;
  const variable = <
  'dog' | 'cat'>type;

  return;
}

The remaining lines Highlights weirdly, or even stops:

current behavior expected behavior
image image

Using as casting with already declared variable:

export function main() {
  const type = ``;
  let variable = ``;
  variable = type as 'dog' | 'cat';
  return;
}
current behavior expected behavior
image image

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  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 two TypeScript examples in a VS Code highlighting environment, comparing the current and expected behavior shown in the issue. Then inspect the repository's TypeScript TextMate grammar rules for angle-bracket and as casting, and verify that highlighting continues correctly after both forms, including when a variable is named type.

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
42/100

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