TypeScript 5.1, featuring easier implicit returns for undefined-returning functions and allowing unrelated types for getters and setters, has moved to a release candidate stage as of May 18. The release candidate (RC) changes the behavior for init hooks in decorators and emit behavior under isolatedModules.
The changes to the emit behavior under isolatedModules ensure that script files are not rewritten to modules. They also ensure that using the transpileModule API will not result in script files being interpreted as modules, as transpileModule assumes the usage of isolatedModules.