Allow keywords to be used in type annotations

[danez]

Q	A
Fixed Issues?
Patch: Bug Fix?	y
Major: Breaking Change?	n
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

This allows keywords to be used as type annotations like

function foo(a:function, b: switch) {}

Flow does also not error in this cases.

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/9614/

[jedwards1211]

@danez it does error in recent versions, even though the parser (questionably) accepts it:

$ flow
Error ┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈ test.js:3:29

Cannot resolve name switch.

     1│ // @flow
     2│
     3│ function foo(a:function, b: switch) {}
     4│

It doesn't allow switch in a TypeAlias anyway so I think supporting keyword type annotations is debatable:

$ flow
Error ┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈ test.js:3:6

Unexpected token switch

     1│ // @flow
     2│
     3│ type switch = number
     4│ function foo(a:function, b: switch) {}
     5│

[nicolo-ribaudo]

import type { s as switch, f as function } from "module";

function foo(a:function, b: switch) {}

Perfectly valid code 😛

[jedwards1211]

Just imagine if JS didn't have any reserved words 😄, like Fortran

import { as as default } from "module"

class class {
  async async() {
    function const() { }
    const function = let('foo') = () => { function(function) {...} }
    function().function(function)
    let switch = 'blah', case = 'blah', break = 'argh!'
    let await = () => ...
    await = await await()
    switch (switch) {
      case case: return break
      case default: return await
      default: return case
    }
  }
}