They want to build up the language compiler itself to better support machine learning. That requires a language with enough type information to support sophisticated analysis. It should be built on LLVM. It needs an existing ecosystem of tools and libraries. And having a better performing language than Python is likely a win.
Swift fits the requirements. As Chris Lattner is driving this, no one could ask that he choose something else.
But Rust also would have been a plausible choice. As the Rust team is very interested in applying the language to exciting new use-cases, it's a bit of a loss for it to miss out on collaboration here. Perhaps this could inspire similar work on the Rust side; many of the concepts would likely transfer straightforwardly.
Swift fits the requirements. As Chris Lattner is driving this, no one could ask that he choose something else.
But Rust also would have been a plausible choice. As the Rust team is very interested in applying the language to exciting new use-cases, it's a bit of a loss for it to miss out on collaboration here. Perhaps this could inspire similar work on the Rust side; many of the concepts would likely transfer straightforwardly.