Rust has type inference similar to Haskell: type information can flow "backwards". It is very different to Go and C++ where types of locals are 'inferred' from their initialiser, and nothing else.

E.g.

  fn main() {
      let mut v;

      if true {
          v = vec![];
          v.push("foo");
      }
  }

is a valid Rust program: the compiler can infer that `v` must have type `Vec<&str>` based on how it is used. I don't think it's possible to syntactically write a Go program at all similar to this (a variable has to be either initialised or have a type), and the C++ equivalent (using `auto v;`) is rejected, as `auto` variables need an initialiser.