Default code action for unused function parameter (6133) in non-final position should not delete

[midgleyc]

TypeScript Version: 3.9.6

Search Terms:
6133, unused parameter, quick fix, code action, tsserver

Code

const express = require('express')
const unusedImport = require('fs')
const anotherUnusedImport = require('util')
const app = express()
const port = 3000

app.get('/', helloWorld)
app.get('/used', (req, res) => res.send('used'))

function helloWorld(unusedReq, res) {
    return res.send('Hello World!');
}

function unusedFunction() {
}

app.listen(port, () => console.log(`Example app listening at http://localhost:${port}`))

Expected behavior:

If I apply the code action "Delete all unused declarations" to "unusedImport", it, "anotherUnusedImport" and "unusedFunction" should be deleted, but nothing else.

Actual behavior:

The parameter "unusedReq" in helloWorld is also deleted, but the line app.get('/', helloWorld) is not modified.

The unread req parameter in app.get('/used', (req, res) => res.send('used')) is correctly not removed.

If I were to change the line to app.get('/', (req, res, next) => helloWorld(req, res, next)) it would be adjusted correctly, but using the function directly with a changed parameter set changes the behaviour.

Playground Link:

Related Issues:

[a-tarasyuk]

The fixUnusedIdentifier doesn't check where or how a function was used

TypeScript/src/services/codefixes/fixUnusedIdentifier.ts

Lines 251 to 252 in 87a3b42

	case SyntaxKind.FunctionDeclaration:
	return true;

I'm thinking about the following ways, however, not sure which way will be correct.

1. Forbid changing parameters in function declarations for fixAll action
2. Try to find all references by the function name, if some of them used in a call expression then forbid remove unused parameters