If you control both the compiler and the scheduler these optimizations become somewhat easier and without any syntax changes, no? Like removing naive synchronization on channel operations and having scheduler to deal with them, tracking states, amortizing synchronization, etc.
Some become easier, yes. But I don't think it's that easy to tell how many threads access a channel. We have runtime race-checkers precisely because we don't know how to check that at compile time. Whether the specific case of channels in Go is easier, I don't know. You can in Rust because the language makes you specify which threads owns what and two threads can't own the same thing at the same time (as I understand it anyway.)
