type numbers to names in wgsl

Question

I have recently tried to save a arrayLength(&inArr) into i32 but I ended up getting this error.

   ┌─ gpu_test:24:9
   │
24 │         outArr[i] = arrLen;
   │         ^^^^^^^^^ naga::Expression [40]


    Entry point main at Compute is invalid
    Store of [41] into [40] doesn't have matching types

Im assuming this means I have an incorrect type but I haven't really found any information about naga::Expression [40] a side from a rust lib that didnt seem to have to do anything with it. Can anyone help me a bit and point me to the source where I can read about naga::Expression with a list of types and there numbers?