Support default `autocomplete` values for input based on `type`

If I'm reading the autocomplete processing algorithm correctly, the "default" behavior (when the attribute is absent or empty) is to not have any default at all. There are suggested heuristics for password inputs (at the very end of that section), but little else.

I would expect that for <input> elements where the valid type attribute directly corresponds to a valid autocomplete token (aka, for type="email", "tel", "url"*), that the type would be used as the default autofill field name.

The main benefit would be to reduce verbosity:

<label>Email: <input type="email" autocomplete="email" name="email" /></label>

Could I skip typing "email" just once, please?

Since most browsers support heuristics for autocomplete, I suspect the resulting autofill behavior is already widely supported. It would be a matter of making it standard & exposed to the API.

* (But not for type="image", since that's just its own weird legacy thing.)

Start with the linked HTML Standard autocomplete processing algorithm and the section describing input types and autocomplete tokens. Identify which valid type values correspond to autocomplete tokens, and verify that image is excluded as noted. Done means the standard clearly defines the default behavior and its exposed API implications.