Removed Type-Defect label.
Added Type-Enhancement, Area-UI, Triaged labels.

I had the same thought when looking up http://dev.w3.org/html5/spec/the-input-element.html#the-input-element. A bunch of DOM properties on <input> are only valid for certain “type”s. Subtypes would be a cleaner way to model that.

I don’t know if it's technically feasible to fix this. The "type" can be mutated after the fact (could/should we prevent that?) and I'm not sure we could create the right type without intercepting all DOM calls that can return Elements (a big no-no), unless we have the capability to use ".type" as part of the type information in addition to the prototype (dunno that we've ever tried that before).

Here's a strawman solution using interfaces instead of subtypes. It's not as good but it's more feasible?

    class InputElement extends Element implements TextElement, CheckboxElement, ... {
     // same as it is now
    }

    abstract class TextElement implements Element {
     // only text stuff
    }

    abstract class CheckboxElement implements Element {
     // only checkbox stuff
    }

Still it has problems like "is CheckboxElement" would always return true, you'd have to test against .type == "checkbox".

I'm not sure it's worth it but wanted to kick off the discussion with some ideas.

cc @sethladd.

Issue #6673 has been merged into this issue.

Removed Area-UI label.
Added Area-HTML label.

Added this to the M3 milestone.

I think what John proposes works fairly well- it's definitely 'loose' as any input element could pretend to be any of these subtypes, but I think it really clarifies the API.

Nit on naming- I prefer if all of the types are *InputElement. It adds a bit for Checkbox and Button, but I think it's clearer for more of the types and avoids conflicts (with ButtonElement):
    ButtonInputElement
    CheckboxInputElement
    ColorInputElement
    DateInputElement
    DateTimeInputElement
    EmailInputElement
    FileUploadInputElement
    HiddenInputElement
    ImageButtonInputElement
    LocalDateTimeInputElement
    MonthInputElement
    NumberInputElement
    PasswordInputElement
    RadioButtonInputElement
    RangeInputElement
    ResetButtonInputElement
    SearchInputElement
    SubmitButtonInputElement
    TelephoneInputElement
    TextInputElement
    TimeInputElement
    UrlInputElement
    WeekInputElement

Set owner to @blois.
Added Accepted label.

Added Fixed label.

Awesome!