enabling `generic_const_parameter_types` breaks `unsized_const_params`

I tried this code: Playground

#![feature(adt_const_params)]
#![feature(unsized_const_params)]
#![feature(generic_const_parameter_types)] // comment me out!
//
#![allow(incomplete_features)]

pub struct Foo<const S: &'static [()]>;

fn breaks() {
    let _: Foo<{ &[] }> = Foo;
}

I expected to see this happen: compiles fine.

Instead, this happened: doesn't compile.

Removing #![feature(generic_const_parameter_types)] (whose functionality is unused here afaict) makes this start compiling as expected.

Meta

rustc --version --verbose: (Playground)

1.99.0-nightly (2026-08-05 7608eb7b07eaf93f16d7)

Compiling playground v0.0.1 (/playground)
error: anonymous constants with lifetimes in their type are not yet supported
  --> src/lib.rs:10:16
   |
10 |     let _: Foo<{ &[] }> = Foo;
   |                ^^^^^^^

error: could not compile `playground` (lib) due to 1 previous error

Start by reproducing the Playground example with adt_const_params, unsized_const_params, and generic_const_parameter_types enabled, then compare it with the version where the last feature is removed. Trace the compiler path that emits "anonymous constants with lifetimes in their type are not yet supported" for Foo<{ &[] }>; done means the example compiles with all three features enabled.