How do I print the type of a variable in Rust?

Question

I have the following:

let mut my_number = 32.90;

How do I print the type of my_number?

Using type and

Answer 1

There's a @ChrisMorgan answer to get approximate type ("float") in stable rust and there's a @ShubhamJain answer to get precise type ("f64") through unstable function in nightly rust.

Now here's a way one can get precise type (ie decide between f32 and f64) in stable rust:

fn main() {
    let a = 5.;
    let _: () = unsafe { std::mem::transmute(a) };
}

results in

error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
 --> main.rs:3:27
  |
3 |     let _: () = unsafe { std::mem::transmute(a) };
  |                           ^^^^^^^^^^^^^^^^^^^
  |
  = note: source type: `f64` (64 bits)
  = note: target type: `()` (0 bits)

Update

The turbofish variation

fn main() {
    let a = 5.;
    unsafe { std::mem::transmute::<_, ()>(a) }
}

is slightly shorter but somewhat less readable.