prefer-for-of false positive on interface with length/indexer

[nchen63]

Bug Report

• TSLint version: 4.3.1
• TypeScript version: 2.1.4
• Running TSLint via: (please choose one) vscode

TypeScript code being linted

interface FileList {
    readonly length: number;
    item(index: number): File;
    [index: number]: File;
}

// fileList is an instance of a class that implements FileList
for (let i = 0; i < fileList.length; i++) {
}

with tslint.json configuration:

prefer-for-of: true

Actual behavior

indicates that for loop should be for-of

Expected behavior

fileList is not actually an array and TypeScript errors if you try to make it use for-of

[andy-hanson]

This should wait on microsoft/TypeScript#13502. We would need to check assignability to Iterable.

[ajafff]

FWIW I have a working implementation of prefer-for-of with type information as part of the core rules of the Wotan linter runtime.

[JoshuaKGoldberg]

💀 It's time! 💀

TSLint is deprecated and no longer accepting pull requests other than security fixes. See #4534. ☠️
We recommend you instead use typescript-eslint to lint your TypeScript code with ESLint. ✅

👋 It was a pleasure open sourcing with you!

[JoshuaKGoldberg]

🤖 Beep boop! 👉 TSLint is deprecated 👈 (#4534) and you should switch to typescript-eslint! 🤖

🔒 This issue is being locked to prevent further unnecessary discussions. Thank you! 👋