That's excellent. I didn't realized Rust to Wasm can be squeezed to such small size. Great work.

I wonder what the wasm-backend people are doing that the embedded-backend people aren’t — I’d have thought embedded was even more particular about small size, but I just started playing with rust-esp32 and found that “hello world” is 15MB (to be fair it’s only 4MB with debug info stripped)...

I don't think he mentions it, and I doubt it's relevant in your Hello World example, but if you have a lot of generic code, it's useful to extract the non-generic parts into a separate non-generic function. For example:

  fn foo>(s: T) -> String {
      bar(s.as_ref())
  }
  
  fn bar(s: &str) -> String {
      // A whole bunch of other stuff
      s.to_string()
  }