Passing a non-const trait function item value to a const fn is no longer allowed in a constant context

[yvt]

Code

I tried this code:

const _: () = core::mem::forget(Box::<u32>::default);       // ERROR
const _: () = core::mem::forget(|| Box::<u32>::default());  // ok

(Playground)

I expected to see this happen: Successful compilation

Instead, this happened:

error[E0277]: the trait bound `Box<u32>: Default` is not satisfied
 --> src/lib.rs:1:15
  |
1 | const _: () = core::mem::forget(Box::<u32>::default);
  |               ^^^^^^^^^^^^^^^^^ the trait `~const Default` is not implemented for `Box<u32>`
  |
note: the trait `Default` is implemented for `Box<u32>`, but that implementation is not `const`
 --> src/lib.rs:1:15
  |
1 | const _: () = core::mem::forget(Box::<u32>::default);
  |               ^^^^^^^^^^^^^^^^^

Version it worked on

It most recently worked on: 1.65.0

Version with regression

rustc --version --verbose:

rustc 1.66.0-beta.1 (e080cc5a6 2022-11-01)
binary: rustc
commit-hash: e080cc5a659fb760c0bc561b722a790dad35b5e1
commit-date: 2022-11-01
host: aarch64-apple-darwin
release: 1.66.0-beta.1
LLVM version: 15.0.2

@rustbot modify labels: +regression-from-stable-to-beta -regression-untriaged

[jruderman]

This became an error due to #100982 (@fee1-dead, @oli-obk).

Bisect info

searched nightlies: from nightly-2022-09-18 to nightly-2022-11-07
regressed nightly: nightly-2022-09-23
searched commit range: 9062b78...e7119a0
regressed commit: 7a8636c

bisected with cargo-bisect-rustc v0.6.4

Host triple: x86_64-apple-darwin

I used cargo bisect-rustc --regress error on the following file

const _: () = core::mem::forget(Box::<u32>::default); 
fn main(){}

[inquisitivecrystal]

Assigning priority as discussed by the Prioritization Working Group.

[fee1-dead]

awaiting beta backport

[yvt]

Can this be closed now that beta backport (#104447) is complete?