error[E0308]: mismatched types
  --> $DIR/issue-39974.rs:5:19
   |
LL |     f: [[f64; 2]; LENGTH],
   |                   ^^^^^^ expected `usize`, found `f64`

error[E0308]: mismatched types
  --> $DIR/issue-39974.rs:1:21
   |
LL | const LENGTH: f64 = 2;
   |                     ^
   |                     |
   |                     expected `f64`, found integer
   |                     help: use a float literal: `2.0`

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0308`.