I don't think constructors are the challenging part. It's about lexically scoped destruction. Certainly there are languages that have that and permit garbage co

I don't think constructors are the challenging part. It's about lexically scoped destruction. Certainly there are languages that have that and permit garbage collection, however those constructed values are necessarily second-class citizens and behave somewhat differently than ordinary values. There's probably some reasonable middle-ground, like constructors returning an owned reference that explicitly can be turned into an unowned reference, thus opting out of deterministic destruction.