Refactors which in TS would generate a type annotation should generate jsdoc in JS

[weswigham]

TypeScript Version: 3.1.0-dev.201xxxxx

Search Terms:

Code

// In TS
function x(): 42 {
  return /*extract to inner function*/42;
}
// In JS
// @ts-check
/**
 * @returns {42}
 */
function x() {
    return /*extract to inner function*/42;
}

Expected behavior:
Under ts-check, a refactoring should apply appropriate jsdocs to allow js to typecheck after a refactoring if it typechecked before it.

Actual behavior:

Playground Link:

Related Issues:

[RyanCavanaugh]

Is this only observable for literals and tuples?

[weswigham]

Anywhere a contextual type is required for the expression to be given the correct type. Although this also applied to anything that makes a new declaration without an initializer, like some forms in the async refactor PR.