Reduce symbol instantiations in lib.d.ts

[mhegazy]

A few changes:

• avoid using this types and instead add the overloads to every derived interface
• use Mapped types instead of listing event names/tag names explicitly in overloads

//cc: @zhengbli

Build diagnostics building dom.genenrated.d.ts before the change:

Files:            2
Lines:        18814
Nodes:       102909
Identifiers:  35546
Symbols:      95889
Types:        12369
Memory used: 94151K
I/O read:     0.00s
I/O write:    0.00s
Parse time:   0.36s
Bind time:    0.18s
Check time:   1.13s
Emit time:    0.02s
Total time:   1.68s

After the change:

Files:            2
Lines:        17559
Nodes:        69571
Identifiers:  23524
Symbols:      18183
Types:         4095
Memory used: 52984K
I/O read:     0.01s
I/O write:    0.00s
Parse time:   0.32s
Bind time:    0.15s
Check time:   0.50s
Emit time:    0.02s
Total time:   0.98s

[rictic]

This is so cool! It looks like this will be great news for custom elements. e.g. experimenting with the nightly build and some of the example code in microsoft/TypeScript#12311 it seems like this typechecks:

class MySlider extends HTMLElement {
  slide() {}
}
customElements.define('my-slider', MySlider);
interface HTMLKind {
  'my-slider': MySlider;
}

document.createElement('my-slider').slide()

So awesome!

[zhengbli]

So this returns the interface itself instead of the handlers it has?

[mhegazy]

yes. i could make it the interface name. but seemed the same

[zhengbli]

Then the name of the variable should be changed to implementedInterface and other places, otherwise it can be confusing later

[zhengbli]

It looks like ElementTagNameMap interface is always the same as HTMLElementTagNameMap? Then make is an alias instead

[mhegazy]

no they are different. not sure why though. i wanted to ask you about that.

[zhengbli]

Aha now I remember, the EmitHTMLElementTagNameMap only prints tag elements that either extends or implements the HTMLElement type.

[zhengbli]

We can do

type ElementListTagNameMap = { [K in ElementTagNameMap]: NodeListOf<ElementTagNameMap[K]> }

and avoid the loop

[mhegazy]

That is what i had earlier, then changed it. the issue is that NodeListOf has a constraint that T extends Node. we can not verify this constraint on ElementTagNameMap[K] unless i add a string indexer. adding the indexer makes the language service experience of the signature help much worse. so this is a work around for that.

[zhengbli]

remove this

[mhegazy]

done.

[zhengbli]

The addEventListener in the addedTypes.json file need to be changed as well, and other than that looks good to me. Thanks!