> not sure if Rust has return type inference of not
Rust has return type inference for function invocations, but not for function signatures. This is a conscious decision to force all functions to provide an explicit contract rather than having any global type inference. And really, I wouldn't want function return types to be completely inferred in Rust given its last-semicolon rule.
However, there is an RFC that would allow for "abstract return types", which would let a function state that its return type implements a certain trait and allow the programmer to omit the concrete type. This is somewhat essential for the new closure design, and also greatly benefits functions that return iterators (but it might not be relevant to your question at all, I haven't had my tea yet...).
However, there is an RFC that would allow for "abstract return types", which would let a function state that its return type implements a certain trait and allow the programmer to omit the concrete type. This is somewhat essential for the new closure design, and also greatly benefits functions that return iterators (but it might not be relevant to your question at all, I haven't had my tea yet...).
https://github.com/rust-lang/rfcs/pull/105/files
Never officially, but that doesn't mean an Emscripten backend isn't possible https://github.com/rust-lang/rust/issues/2235 :)