Microsoft/TypeScript

No error for undeclared #private property in `.js` files

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#35,962 opened on Jan 2, 2020

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 (7 comments) (0 reactions) (0 assignees)TypeScript (6,726 forks)batch import
BugDomain: JavaScriptEffort: ModerateHelp Wanted

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Description

class Thing {
    /**
     * @param prop {string}
     */
    constructor(prop) {
        this.#prop = prop;
    }
}

This class assigns to #prop, but it's an error to use #prop without declaring it.

This is reported as a SyntaxError, so this should report an error even outside of checkJs.

Contributor guide

Research direction
Inspect the TypeScript compiler's handling of private fields in .js files. The error should be reported during parsing or binding. Look at the check for pragma and how #private is validated.
Tech stack
typescript
Domain
compilers
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GitTypeScript
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60