Consecutive function declaration problems in JS files

Bug Report

🔎 Search Terms

function declaration, method declaration, consecutive, comma

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about jsdoc problems
  Tested with typescript@4.4.0-dev.20210602

⏯ Playground Link

Playground

💻 Code

/**
 * @param {number} num
 * @returns {number}
 */
const numb = (num) => num,
      /**
       * @param {string} str
       * @returns {string}
       */
      str = (str) => str

console.log(numb(2), str(4))

🙁 Actual behavior

Because of the consecutive declaration the real error is not catched. This only happens in js files

🙂 Expected behavior

Method declaration style shouldn't matter in js files either, so the error should be: ""Argument of type 'number' is not assignable to parameter of type 'string'."

Run the linked Playground reproduction with the supplied JavaScript code and confirm that the consecutive comma-separated declarations suppress the intended argument-type diagnostic. Find the JavaScript type-checking path and add a regression test for the example; done when it reports that number is not assignable to string, matching the expected behavior.