Lint: no-inferrable-types for a declared type

[rodolphocastro]

Hello!

Currently when running deno lint --unstable I get some issues with no-inferrable-types on fields that I'm actually declaring the type and then assigning a value.

For instance the following snippet causes the output from deno lint:

export function createString(
  prefix: string = "",
  params: GeneratorParameters = defaultParameters,
): string {
  if (!validateGeneratorParameters(params)) {
    throw new Error(`The parameters ${params} aren't valid`);
  }

  const suffix = generateRandomNumber(params).toString();
  return prefix !== "" ? prefix + suffix : suffix;
}

(no-inferrable-types) inferrable types are not allowed
  prefix: string = "",
  ^^^^^^^^^^^^^^^^^^^
    at E:\Src\dixture\src\_simpleGenerator.ts:45:2

Even tho the lint option is flagged as unstable I was unable to find this reported elsewhere so hopefully this is just a duplicate and this is a know issue 😅

You can find the failing snippet on this GitHub repository, just nevermind the no-explicit-any (as those are intended by me right now 😅)

[solson]

This is actually working as intended according to eslint's definition of no-inferrable-types. Under "The following are invalid" they include this example:

function fn(a: number = 5, b: boolean = true) {}

So the idea of this lint is that even types in signatures should be removed when they are trivially inferrable from a literal value. There is an ignoreParameters option that makes it work how you expect, but I don't think deno lint allows configuration currently.

[solson]

Also, in case it is unclear, note that the parameter does still end up with the expected type (hence why the lint considers declaring it redundant):

[rodolphocastro]

Thanks for the clarification @solson !

That makes sense haha. If only I hadn't included Deno as a hardcoded search term I might've ended up on eslint's docs 😅.

Update: lol, this is now on the first page of google for deno + inferrable-types so I guess there's something good about my poor googling skills leading to this issue hahaha 🥳