Inlining const React children

[kerams]

Inlining const React children

[MangelMaxime]

While looking at this issue, I learned for the first time about [<ParamList>] attribute.

According to the changelog and the Fable.Core doc comment, it seems to only exist for Fable.React...

Changelog

## 3.0.0-nagareyama-alpha-003 - 2020-09-14

* Fix: Add names with $reflection suffix to root scope
* Fix deriving from imported JS classes
* Keep support for ParamList attribute until removed from Fable.React

Fable.Core

/// Used to spread the last argument. Mainly intended for `React.createElement` binding, not for general use.
[<AttributeUsage(AttributeTargets.Parameter)>]
type ParamListAttribute() =
    inherit Attribute()

type ParamSeqAttribute = ParamListAttribute

Looking thought the code and after an empiric test,
I am unsure what the effect of [<ParamList>] attributes is, looking through the code it seems to be of the same effect as when we use [<ParamArray>].

IHMO If that's confirmed it would be nice, to remove it in a future major version of Fable.

With that said, while testing what happen if we remove that attribute I discovered that the code should still be working without but it would not save the few extra bytes that you mentioned which is probably not what we want.

// With [<ParamList>]
export function f() {
    const children_4 = [react.createElement("div", {}), react.createElement("span", {})];
    return react.createElement("div", {}, ...children_4);
}

// Without [<ParamList>]
export function f() {
    const children_4 = [react.createElement("div", {}, []), react.createElement("span", {}, [])];
    return react.createElement("div", {}, children_4);
}

// With [<ParamArray>]
export function f() {
    const children_4 = [react.createElement("div", {}), react.createElement("span", {})];
    return react.createElement("div", {}, ...children_4);
}

Regarding the creation of the intermediate variable children_4, I am unsure how Fable decide to create it. What I mean by that is why Fable create a intermediate variable for children and not for the properties object {} in the exemple Without [<ParamList>].