Enabling feature(generic_const_exprs) being ignored by "cargo build"

Question

I have the following code in src/algebra.rs:

#![feature(const_generics, generic_const_exprs)]
// Algebra module.

struct Polynomial<const Order: usize> {
    coefficients: [f64; Order + 1] // f(x) = sum_i=0^Order coefficients[i] * x^i
}

which is imported in src/lib.rs:

pub mod algebra;

When I run cargo +nightly build, I still get the error:

error: generic parameters may not be used in const operations
 --> src\algebra.rs:5:25
  |
5 |     coefficients: [f64; Order + 1] // f(x) = sum_i=0^Order coefficients[i] * x^i
  |                         ^^^^^ cannot perform const operation using `Order`
  |
  = help: const parameters may only be used as standalone arguments, i.e. `Order`
  = help: use `#![feature(const_generics)]` and `#![feature(const_evaluatable_checked)]` to allow generic const expressions

error: aborting due to previous error

error: could not compile `optimisation`

To learn more, run the command again with --verbose.

I'm confused, because https://blog.rust-lang.org/inside-rust/2021/09/06/Splitting-const-generics.html says that #![feature(generic_const_exprs)] is enough to enable const generic expressions? What am I doing wrong?

I am using 1.52.0 version of Rust.