Get the source code of a code block as a static string.

Example

```rust fn main() { let (k, src) = shower::source!(|| { for i in 0..5 { println!("{}", i); } "{abc}" });

// print the source code of the program
println!("{}", src);

println!("running program:");
let k = k();

println!("program returned={}", k);

} ```

Output

shower::source!(|| { for i in 0..5 { println!("{}", i); } "{abc}" }) running program: 0 1 2 3 4 program returned={abc}