Warn when JSDoc type cast misses parentheses

Search Terms

jsdoc. type cast

Suggestion

JSDoc type cast currently requires parentheses for technical reasons (#18212), but it does not warn when they don't exist.

Use Cases

// This doesn't work, the JSDoc comment is silently ignored
// A warning message will help.
const img = /** @type {HTMLImageElement} */ document.getElementById('#cat')
img.src = 'cat.gif'

Examples

const img = /** @type {HTMLImageElement} */ document.getElementById('#cat')
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            ^ Warning: The JSDoc type cast misses parentheses and is being ignored
img.src = 'cat.gif'

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

Start with the JSDoc type-cast handling described in the issue and the referenced issue #18212, then locate the related diagnostic and regression tests. The change is complete when a missing-parentheses cast produces the shown warning without changing JavaScript output, while parenthesized casts retain their current behavior.