Allow using stable os::fd::raw items through unstable os::wasi module

This fixes a regression from stable to nightly.

Closes #99502.

library/std/src/os/fd/raw.rs

@@ -14,6 +14,7 @@ use crate::os::wasi::io::OwnedFd;
 use crate::sys_common::{AsInner, IntoInner};
 
 /// Raw file descriptors.
+#[cfg_attr(not(bootstrap), rustc_allowed_through_unstable_modules)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub type RawFd = raw::c_int;
 
@@ -22,6 +23,7 @@ pub type RawFd = raw::c_int;
 /// This is only available on unix and WASI platforms and must be imported in
 /// order to call the method. Windows platforms have a corresponding
 /// `AsRawHandle` and `AsRawSocket` set of traits.
+#[cfg_attr(not(bootstrap), rustc_allowed_through_unstable_modules)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait AsRawFd {
  /// Extracts the raw file descriptor.
@@ -57,6 +59,7 @@ pub trait AsRawFd {
 
 /// A trait to express the ability to construct an object from a raw file
 /// descriptor.
+#[cfg_attr(not(bootstrap), rustc_allowed_through_unstable_modules)]
 #[stable(feature = "from_raw_os", since = "1.1.0")]
 pub trait FromRawFd {
  /// Constructs a new instance of `Self` from the given raw file
@@ -100,6 +103,7 @@ pub trait FromRawFd {
 
 /// A trait to express the ability to consume an object and acquire ownership of
 /// its raw file descriptor.
+#[cfg_attr(not(bootstrap), rustc_allowed_through_unstable_modules)]
 #[stable(feature = "into_raw_os", since = "1.4.0")]
 pub trait IntoRawFd {
  /// Consumes this object, returning the raw underlying file descriptor.

library/std/src/os/wasi/io/raw.rs

@@ -2,4 +2,19 @@
 
 #![unstable(feature = "wasi_ext", issue = "71213")]
 
+// NOTE: despite the fact that this module is unstable,
+// stable Rust had the capability to access the stable
+// re-exported items from os::fd::raw through this
+// unstable module.
+// In PR #95956 the stability checker was changed to check
+// all path segments of an item rather than just the last,
+// which caused the aforementioned stable usage to regress
+// (see issue #99502).
+// As a result, the items in os::fd::raw were given the
+// rustc_allowed_through_unstable_modules attribute.
+// No regression tests were added to ensure this property,
+// as CI is not configured to test wasm32-wasi.
+// If this module is stabilized,
+// you may want to remove those attributes
+// (assuming no other unstable modules need them).
 pub use crate::os::fd::raw::*;