`generic_const_exprs` causes code to fail compilation even if the feature is not used

I tried this code:

#![allow(incomplete_features)]
#![feature(generic_const_exprs)]
fn main() {
    println!("Hello, world!");
    let a = foo::<1>();
    println!("{}", a.0);
}
const fn foo<const A: usize>() -> (usize, usize) {
    const { assert!(A > 0); }
    (0, 0)
}

And it fails with:

error: overly complex generic constant
 --> src/main.rs:9:11
  |
9 |     const { assert!(A > 0); }
  |           ^^^^^^^^^^^^^^^^^^^ blocks are not supported in generic constants
  |
  = help: consider moving this anonymous constant into a `const` function
  = note: this operation may be supported in the future

error: could not compile `testconst` (bin "testconst") due to 1 previous error

However if the feature(generic_const_exprs) is removed it works fine:

fn main() {
    println!("Hello, world!");
    let a = foo::<1>();
    println!("{}", a.0);
}
const fn foo<const A: usize>() -> (usize, usize) {
    const { assert!(A > 0); }
    (0, 0)
}

Output from cargo run

Hello, world!
0

Meta

rustc --version --verbose:

rustc 1.95.0-nightly (838709580 2026-02-17)
binary: rustc
commit-hash: 8387095803f21a256a9a772ac1f9b41ed4d5aa0a
commit-date: 2026-02-17
host: aarch64-apple-darwin
release: 1.95.0-nightly
LLVM version: 22.1.0

error: overly complex generic constant
 --> src/main.rs:9:11
  |
9 |     const { assert!(A > 0); }
  |           ^^^^^^^^^^^^^^^^^^^ blocks are not supported in generic constants
  |
  = help: consider moving this anonymous constant into a `const` function
  = note: this operation may be supported in the future

error: could not compile `testconst` (bin "testconst") due to 1 previous error

Reproduce the failure from the example in src/main.rs with cargo run using the listed nightly rustc. Trace handling of the const block with generic_const_exprs enabled; done means the example compiles and prints Hello, world! and 0 with the feature enabled, without breaking the no-feature case.