Bug: Can't compile with the implement feature

[robmikh]

Which crate is this about?

windows

Crate version

v0.34.0

Summary

Using the implement feature causes several compiler errors.

Toolchain version/configuration

Default host: x86_64-pc-windows-msvc
rustup home:  C:\...\.rustup

installed toolchains
--------------------

stable-x86_64-pc-windows-msvc
beta-x86_64-pc-windows-msvc
nightly-x86_64-pc-windows-msvc

installed targets for active toolchain
--------------------------------------

aarch64-pc-windows-msvc
wasm32-unknown-unknown
wasm32-wasi
x86_64-pc-windows-msvc

active toolchain
----------------

stable-x86_64-pc-windows-msvc (default)
rustc 1.59.0 (9d1b2106e 2022-02-23)

Reproducible example

fn main() {
    println!("Hello, world!");
}

Crate manifest

[dependencies.windows]
version = "0.34.0"
features = [
    "alloc",
    "implement",
    "Win32_System_WinRT",
]

Expected behavior

No compiler errors.

Actual behavior

There are 90 errors, but they're all variations on these:

error[E0658]: trait bounds other than `Sized` on const fn parameters are unstable
   --> C:\...\.cargo\registry\src\github.com-1ecc6299db9ec823\windows-0.34.0\src\Windows\Win32\System\WinRT\impl.rs:939:63
    |
939 |     pub const fn new<Identity: ::windows::core::IUnknownImpl, Impl: IWeakReferenceSource_Impl, const OFFSET: isize>() -> IWeakReferenceSo...
    |                                                               ^^^^
    |
    = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information

error[E0658]: function pointer casts are not allowed in constant functions
   --> C:\...\.cargo\registry\src\github.com-1ecc6299db9ec823\windows-0.34.0\src\Windows\Win32\System\WinRT\impl.rs:951:98
    |
951 | ...:new::<Identity, OFFSET>(), GetWeakReference: GetWeakReference::<Identity, Impl, OFFSET> }
    |                                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information

Additional comments

No response

[robmikh]

Ah, I missed that implement now requires nightly. I had been using build in a previous version of the create.

[kennykerr]

Sorry about the confusion. I have pinned #1523 to make this more discoverable. Won't be long now. 😉