Overloaded method signatures failing on certain eslint rules

[ismail-syed]

What version of TypeScript are you using?
2.5.2

What version of typescript-eslint-parser are you using?
8.0.0

What code were you trying to parse?

export class Test {
  constructor() {
  }
  public test(param1: Number): Test;
  public test(param1: Test): Test;
  public test(param1: any): Test {
      return new Test();
    }
}

What did you expect to happen?
With the following rules enabled, I would expect the code above to be parsed. The issue seems to be that parsing overloaded method signatures, with the following eslint rules enabled fails.

    "rules": {
      "array-callback-return": "error",
      "getter-return": "error",
      "strict": "error",
      "lines-around-directive": "error",
      "no-empty-function": "error"
    }

Turning off all those rules, and enabling them individually fails as well.

What happened?

$ eslint . --ext .ts --max-warnings 0
Cannot read property 'type' of null
TypeError: Cannot read property 'type' of null
    at EventEmitter.onCodePathStart (/Users/ismailsyed/src/github.com/ismail-syed/typescript-eslint-parser-example/node_modules/eslint/lib/rules/array-callback-return.js:193:34)
n.js:193:34)
    at emitTwo (events.js:130:20)
    at EventEmitter.emit (events.js:213:7)                                                                                                                           lyzer.js:360:30)
    at processCodePathToEnter (/Users/ismailsyed/src/github.com/ismail-syed/typescript-eslint-parser-example/node_modules/eslint/lib/code-path-analysis/code-path-ana-analyzer.js:603:9)
lyzer.js:360:30)
    at CodePathAnalyzer.enterNode (/Users/ismailsyed/src/github.com/ismail-syed/typescript-eslint-parser-example/node_modules/eslint/lib/code-path-analysis/code-path
-analyzer.js:603:9)
    at Traverser.enter (/Users/ismailsyed/src/github.com/ismail-syed/typescript-eslint-parser-example/node_modules/eslint/lib/linter.js:962:32)    at Traverser.__execute (/Users/ismailsyed/src/github.com/ismail-syed/typescript-eslint-parser-example/node_modules/estraverse/estraverse.js:397:31)
    at Traverser.traverse (/Users/ismailsyed/src/github.com/ismail-syed/typescript-eslint-parser-example/node_modules/estraverse/estraverse.js:501:28)
    at Traverser.traverse (/Users/ismailsyed/src/github.com/ismail-syed/typescript-eslint-parser-example/node_modules/eslint/lib/util/traverser.js:31:22)
    at Linter._verifyWithoutProcessors (/Users/ismailsyed/src/github.com/ismail-syed/typescript-eslint-parser-example/node_modules/eslint/lib/linter.js:959:19)

Example repo:
https://github.com/ismail-syed/typescript-eslint-parser-example

[j-f1]

I think they’re checking the body of the function expressions, but that’s undefined, so they throw.

[ismail-syed]

Thanks for the suggestion @j-f1. Taking a stab at fixing these failures in eslint/eslint

[JamesHenry]

Thanks a lot for working on this @ismail-syed!

Unfortunately, it seems that modifying the core rules is not going to be a sustainable way forward.

This is arguably not technically an issue with the parser, but rather how it integrates with the wider ESLint ecosystem. However, I am definitely happy to keep this open here to track.

I am going to think about the best way forward with this and also chat with the TypeScript team about it.

[j-f1]

How about FunctionOverloadDeclaration and MethodOverloadDeclaration?

[ismail-syed]

Thanks for the update, @JamesHenry! Interested to hear what's decided for moving forward.

[ismail-syed]

Doing a check here for node.body and breaking if it's undefined fixes the small issue I have logged above. Would this be an appropriate temporary fix for this?

[JamesHenry]

This was finally fixed by #412. I added the source above as an integration test.