See the last paragraph of zarzavat's comment :) They wouldn't be added today, and they aren't widely used any more (they have non-codegen alternatives now). In

See the last paragraph of zarzavat's comment :) They wouldn't be added today, and they aren't widely used any more (they have non-codegen alternatives now). In other words, breaking changes in semantics shouldn't be a worry any more, since the TS team has consciously decided to attempt to avoid them a few years ago.