Search Terms

[read types and write types], [read type]

Suggestion

Many DOM APIs have setters that coerce values to strings. Using these APIs in perfectly valid ways will result in type warnings:

const input = document.createElement('input');
input.type = 'range';
input.max = 42; // Type '42' is not assignable to type 'string'.

These APIs could be more accurately described if getters and setters could have different types, like:

interface HTMLInputElement extends HTMLElement {
    /**
     * Defines the maximum acceptable value for an input element with type="number".When used with the min and step attributes, lets you control the range and increment (such as only even numbers) that the user can enter into an input field.
     */
    get max(): string;
    set max(v: any);
}

Related Issues

#590
#814

Use Cases

Use DOM APIs :)

Also see: runem/lit-analyzer#43

Examples

Shown above

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.