Very nice. As you say, it doesn't just cast at the end, but actually uses the type through the whole calculation! To illustrate the difference:

Rust:

    fn main() {
      let a: f32 = 1e7 + 0.5 + 0.5;
      let b: f32 = 1e7f32 + 0.5f32 + 0.5f32;
      println!("{}", a==c); // true
    }

C:

    #include <stdio.h>
    int main() {
      float a = 1e7 + 0.5 + 0.5;
      float b = 1e7f + 0.5f + 0.5f;
      printf("%s\n", a==b ? "true" : "false"); // false
    }

That's awesome. I'm totally fine with an annoying suffix like f32 if I never actually need to use it. While f might be a nicer suffice than f32, no suffix is even better.