[al2o3cr]

"If only there was a way to deprecate a language, with the same meaning as deprecating an API method"

One way that usually works is to release a newer version and stop updating the old one after five years. Oh wait...

[derefr]

It's the "using it in strict mode is an error" part that's important. Compilers can automatically refuse to compile deprecated-but-not-broken code. What can automatically refuse to let you start a new project in a deprecated-but-not-broken language?