microsoft / microsoft/TypeScript
compilerOptions support TDZ error option
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Description
According to the PR of #32221 , to prevent such problem like:
(function () {
function cleanup() {
console.log(A); // throw error
}
cleanup();
const A = 1;
}());
this snippet will compile into:
(function () {
function cleanup() {
console.log(A); // log undefined
}
cleanup();
var A = 1;
}());
Error in the first snippet will be ignored, and cause TDZ error. Can tsc support TDZ error enabled option like babel-plugin-transform-block-scoping ? It will notify peoples who write such pattern to prevent further weird problems.
Checklist
My suggestion meets these guidelines:
- This wouldn't be a breaking change in existing TypeScript/JavaScript code
- This wouldn't change the runtime behavior of existing JavaScript code
- This could be implemented without emitting different JS based on the types of the expressions
- This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
- This feature would agree with the rest of TypeScript's Design Goals.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reading the issue's TypeScript and JavaScript examples and the referenced PR #32221. Clarify how a compiler option should report temporal dead zone patterns and what diagnostics it should produce; done means the proposed option is defined well enough to implement and validate without changing existing output by default.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- javascript, typescript
- Domain
- compilers
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 25/100