I'm finding F# to be even closer because it has HM type inference, discriminated unions (note they are not as layout-efficient as Rust's, it is better in F# 9 t

I'm finding F# to be even closer because it has HM type inference, discriminated unions (note they are not as layout-efficient as Rust's, it is better in F# 9 though), is fully expression oriented and overall a quite terse language (Rust isn't really terse but can be made so in some cases). It's worse at dealing with ref structs so C# is better for some low-level tasks. But it has other niceties like IL-level function and lambda inlining.