noUnusedLocals checks don't work with private modifier

[falsandtru]

TypeScript Version: master

Code

class C {
  constructor(private parent: void) {
    parent;
  }
}

Expected behavior:

pass

Actual behavior:

$ node built/local/tsc.js --noEmit --noUnusedLocals index.ts
index.ts(2,23): error TS6138: Property 'parent' is declared but never used.

[mhegazy]

this.parent is never used.

[falsandtru]

constructor(public/protected parent: void) and constructor(parent: void) work correctly. Only constructor(private parent: void) throws an error. At least you should arrange the behaviors.

[mhegazy]

constructor(public/protected parent: void) => public/ protected properties can be used outside the class, so they are not flagged as unused. the same applies to exported declarations in a module.

constructor(parent: void) => parent is a parameter, you use it inside the constructor, no error here..

constructor(private parent: void) => is equivalent to:

class C {
  private parent;
  constructor(parent: void) {
  }
}

if you never use this.parent why did you declare it as a property.

[falsandtru]

parent is a parameter

node built/local/tsc.js --noEmit --noUnusedParameters --noUnusedLocals index.ts doesn't throw an error with constructor(parent: void). But throws an error if I add private modifier. It is odd.

[mhegazy]

private parent declares two things....

1. a parameter to this function, which you have used ..
2. a property on the class, which you have not used. hence the error: Property 'parent' ....

I suggest you read more about parameter properties in http://www.typescriptlang.org/docs/handbook/classes.html#parameter-properties

[falsandtru]

two things

I understood now, thanks. But it is confusing and it can be resolved. I think almost all users will expect resolving this issue.

[falsandtru]

In the following code, noUnusedParameters checks resolved by noUnusedLocals. But the converse is not.

class C {
  constructor(private parent: void) {
    this.parent;
  }
}

Compiler should resolve these two checks bidirectionally.

[mhegazy]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.