Fix 'Missing class properties transform' error when parsing class properties with Typescript syntax

[pterolex]

Fixes issue in https://babeljs.io/repl/#?babili=false&browsers=&build=&builtIns=false&code_lz=MYGwhgzhAEBiD29oG8BQ1oCMwCcBc0EALjgJYB2A5qgL5A&debug=false&forceAllTransforms=false&shippedProposals=false&circleciRepo=&evaluate=false&fileSize=false&lineWrap=false&presets=es2015%2Ctypescript&prettier=false&targets=&version=7.0.0-beta.33&envVersion=7.0.0-beta.36

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/8353/

[loganfsmyth]

The way to fix this in line with the Flow strip plugin would be for the Typescript plugin to remove the class properties in the Class visitor. That's how we handle this edge case for Flowtype:

babel/packages/babel-plugin-transform-flow-strip-types/src/index.js

Line 75 in 981bff0

// We do this here instead of in a `ClassProperty` visitor because the class transform

so all the logic in

babel/packages/babel-plugin-transform-typescript/src/index.js

Line 158 in 981bff0

ClassProperty(path) {

should also be run for all properties inside

babel/packages/babel-plugin-transform-typescript/src/index.js

Line 186 in 981bff0

Class({ node }) {

[pterolex]

@loganfsmyth Thanks, I've changed the implementation as you suggested.

Now, there's is another issue: the babel-plugin-proposal-class-properties tests broke.
For example, according to the test, the following code

class C {
    x: T;
    y = 0;
    constructor(T) {}
}

should be transpiled to

class C {
  constructor(T) {
    this.x = void 0;
    this.y = 0;
  }

}

So, the x class property is initialized with undefined, but my change removes the x entirely.

What should be the correct behavior in this case?

P.S. The CI process has hung, so these particular tests are not shown

[pterolex]

TypeScript compiler also removes the unused type declarations inside a class:

https://www.typescriptlang.org/play/#src=class%20C%20%7B%0D%0A%20%20%20%20x%3A%20T%3B%0D%0A%20%20%20%20y%20%3D%200%3B%0D%0A%20%20%20%20constructor(T)%20%7B%7D%0D%0A%7D

[hzoo]

Thanks for the PR!