Fix nightly CI

[ngoldbaum]

I'm pretty sure rustc is wrong and these structs are properly marked as pub?

[ngoldbaum]

You can trigger the error locally doing

RUSTFLAGS="-D warnings" cargo test --no-default-features --features "multiple-pymethods abi3 full nightly"

With the latest nightly rustc:

error: struct `PyByteArrayObject` is never constructed
  --> pyo3-ffi/src/bytearrayobject.rs:21:16
   |
21 | opaque_struct!(PyByteArrayObject);
   |                ^^^^^^^^^^^^^^^^^
   |
   = note: `-D dead-code` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(dead_code)]`
   = note: this error originates in the macro `opaque_struct` (in Nightly builds, run with -Z macro-backtrace for more info)

error: struct `PyDictObject` is never constructed
   --> pyo3-ffi/src/dictobject.rs:114:16
    |
114 | opaque_struct!(PyDictObject);
    |                ^^^^^^^^^^^^
    |
    = note: this error originates in the macro `opaque_struct` (in Nightly builds, run with -Z macro-backtrace for more info)

error: struct `PyFloatObject` is never constructed
 --> pyo3-ffi/src/floatobject.rs:7:16
  |
7 | opaque_struct!(PyFloatObject);
  |                ^^^^^^^^^^^^^
  |
  = note: this error originates in the macro `opaque_struct` (in Nightly builds, run with -Z macro-backtrace for more info)

error: struct `PyWeakReference` is never constructed
 --> pyo3-ffi/src/weakrefobject.rs:7:16
  |
7 | opaque_struct!(PyWeakReference);
  |                ^^^^^^^^^^^^^^^
  |
  = note: this error originates in the macro `opaque_struct` (in Nightly builds, run with -Z macro-backtrace for more info)

[ngoldbaum]

Seems to be fixed in the july 31 nightly, closing

[ngoldbaum]

Actually, I confused myself by having an older nightly installed on my local setup, the nightly failure is still there. Maybe I'm wrong and the new dead code analysis is correct and a code change needed somewhere?

[davidhewitt]

I will try to reach out on the rust zulip. For what it's worth, nightly is set to continue on error so shouldn't block merges (and I typically prefer not to pin so that we can see if any PyO3 stuff might be affecting users on currently nightly)