error[E0435]: attempt to use a non-constant value in a constant
  --> $DIR/issue-91560.rs:10:19
   |
LL |     let mut length: usize = 2;
   |     -------------- help: consider using `const` instead of `let`: `const length`
LL |
LL |     let arr = [0; length];
   |                   ^^^^^^ non-constant value

error[E0435]: attempt to use a non-constant value in a constant
  --> $DIR/issue-91560.rs:17:19
   |
LL |     let   length: usize = 2;
   |     ------------ help: consider using `const` instead of `let`: `const length`
LL |
LL |     let arr = [0; length];
   |                   ^^^^^^ non-constant value

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0435`.