Fix typescript side effects

[yuri-karadzhov]

Q	A
Fixed Issues?	`Fixes #8634
Patch: Bug Fix?	Yes
Major: Breaking Change?	No
Minor: New Feature?	No
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?	No
License	MIT

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/9496/

[danez]

Thank you very much for this, could you please add a test?

If you need help with the tests feel free to join our slack chat and ask there, but basically all the tests for the transforms have a file with the input code (input.mjs) and a file with the expected output (output.mjs). To enable certain plugins you can also create a file called options.json. For example look at this test: https://github.com/babel/babel/tree/master/packages/babel-plugin-transform-typescript/test/fixtures/imports/elide-react-no-2

[yuri-karadzhov]

Sure will do that this week. Thanks for detailed explanation.

[yuri-karadzhov]

Strange, it works in application, but not in test. I will investigate.

[danez]

The underlying problem was that babel-traverse was not visiting decorators which are added to params. This resulted in the identifier from the decorators never being counted as usage of a declaration (in this case the named imports). I changed the PR to reflect this. Now the test works.

The only 3 cases I could come up are identifiers, assignments and objectpatterns:

function boo (@dec() a, @dec() b = 1, @dec() { foo }) {}

rest params throw when annotated.

[yuri-karadzhov]

Any updates on this PR?

[pixelmeister]

Any ETA when this will be released? Are there nightly builds of Babel available that I could use in the interim?

[nicolo-ribaudo]

Usually we release a new version every ~2 weeks