[Bug] Unused variable error happens when it used

[borispovod]

🐛 Bug

I'm trying to compile module contains while loop and variable defined before loop. Each iteration i change variable value. Yet i'm getting error and it seems a compiler bug.

To reproduce

module 0x1::Bug {
    public fun loop_over() {
        let i = 0;
        let something = 604800;
        let my_counter = 0;

        while (i < 100) {
            my_counter = something * i;

            if (my_counter > 100) {
                // do something
            };

            i = i + 1;
        }
    }
}

I got an error during compilation:

warning[W09003]: unused assignment
  ┌─ ./sources/Bug.move:5:13
  │
5 │         let my_counter = 0;
  │             ^^^^^^^^^^ Unused assignment or binding for local 'my_counter'. Consider removing, replacing with '_', or prefixing with '_' (e.g., '_my_counter')

Expected Behavior

I understand i can do let my_counter = something * i; in the start of each loop iteration instead of define counter before loop, yet i think my initial example should compile or show some explained error/warning.

Additional Context

I'm using Aptos CLI 0.1.2.

[tnowacki]

A bad error message, but it is finding something! The initial value is not used, so you could have let my_counter;

[borispovod]

Hi @tnowacki ,

Yeah, right, but still i think error message should be fixed, the rustc showing me something like:

warning: value assigned to `my_counter` is never read

IMHO, much more clear