440: Implement type inference for boolean operators r=flodiebold a=marcusklaas
Tried implementing the easiest part of https://github.com/rust-analyzer/rust-analyzer/issues/390. Hope this is somewhat close to what the intent of the issue was. Found it surprisingly easy to find my way around the repository - it's well organized!
Very grateful for any pointers.
Co-authored-by: Marcus Klaas de Vries <mail@marcusklaas.nl>
This will really become necessary when we implement generics, but even now, it
allows us to reason 'backwards' to infer types of expressions that we didn't
understand for some reason.
We use ena, the union-find implementation extracted from rustc, to keep track of
type variables.
