microsoft / microsoft/TypeScript

Unexpected TS4094 with the build parameter `declaration: true`

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Bug Domain: Declaration Emit Needs Human Review
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Description

TypeScript Version: 2.4.1

Code

var Foo = class Foo {
    private _message = "Hi";
    hi() { return this._message; }
}

tsc test.ts -t es2017 -d

Expected behavior: -d should not cause this message: test.ts(1,5): error TS4094: Property '_message' of exported class expression may not be private or protected.

Actual behavior: It does.

There should at least be a suppression parameter to ignore this error.

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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

Start by reproducing the report with the TypeScript 2.4.1 command tsc test.ts -t es2017 -d and the class expression shown in test.ts. Trace declaration generation and the TS4094 diagnostic for exported class expressions, then identify the relevant compiler test entry point. Done means the reported declaration build no longer emits the unexpected error, or the requested suppression behavior is covered by a regression test.

Written by the indexing model from the issue text.

Assessment

Tech stack
typescript
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Active
Clarity
Mostly clear
Newbie friendliness
52/100

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