Auto merge of #85746 - m-ou-se:io-error-other, r=joshtriplett

Redefine `ErrorKind::Other` and stop using it in std.

This implements the idea I shared yesterday in the libs meeting when we were discussing how to handle adding new `ErrorKind`s to the standard library: This redefines `Other` to be for *user defined errors only*, and changes all uses of `Other` in the standard library to a `#[doc(hidden)]` and permanently `#[unstable]` `ErrorKind` that users can not match on. This ensures that adding `ErrorKind`s at a later point in time is not a breaking change, since the user couldn't match on these errors anyway. This way, we use the `#[non_exhaustive]` property of the enum in a more effective way.

Open questions:
- How do we check this change doesn't cause too much breakage? Will a crate run help and be enough?
- How do we ensure we don't accidentally start using `Other` again in the standard library? We don't have a `pub(not crate)` or `#[deprecated(in this crate only)]`.

cc https://github.com/rust-lang/rust/pull/79965

cc `@rust-lang/libs` `@ijackson`

r? `@dtolnay`

2 files changed, 5 insertions, 4 deletions

diff --git a/library/std/src/sys/wasi/fs.rs b/library/std/src/sys/wasi/fs.rs
index 45e38f68b8c..8ffa1c88d88 100644
--- a/library/std/src/sys/wasi/fs.rs
+++ b/library/std/src/sys/wasi/fs.rs
@@ -648,7 +648,7 @@ fn open_parent(p: &Path) -> io::Result<(ManuallyDrop<WasiFd>, PathBuf)> {
                      through which {:?} could be opened",
                     p
                 );
-                return Err(io::Error::new(io::ErrorKind::Other, msg));
+                return Err(io::Error::new(io::ErrorKind::Uncategorized, msg));
             }
             let relative = CStr::from_ptr(relative_path).to_bytes().to_vec();
 
@@ -670,7 +670,8 @@ fn open_parent(p: &Path) -> io::Result<(ManuallyDrop<WasiFd>, PathBuf)> {
 }
 
 pub fn osstr2str(f: &OsStr) -> io::Result<&str> {
-    f.to_str().ok_or_else(|| io::Error::new_const(io::ErrorKind::Other, &"input must be utf-8"))
+    f.to_str()
+        .ok_or_else(|| io::Error::new_const(io::ErrorKind::Uncategorized, &"input must be utf-8"))
 }
 
 pub fn copy(from: &Path, to: &Path) -> io::Result<u64> {
diff --git a/library/std/src/sys/wasi/mod.rs b/library/std/src/sys/wasi/mod.rs
index 45a829c0cd2..4af99bfa464 100644
--- a/library/std/src/sys/wasi/mod.rs
+++ b/library/std/src/sys/wasi/mod.rs
@@ -58,7 +58,7 @@ pub use common::*;
 pub fn decode_error_kind(errno: i32) -> std_io::ErrorKind {
     use std_io::ErrorKind::*;
     if errno > u16::MAX as i32 || errno < 0 {
-        return Other;
+        return Uncategorized;
     }
     match errno as u16 {
         wasi::ERRNO_CONNREFUSED => ConnectionRefused,
@@ -77,7 +77,7 @@ pub fn decode_error_kind(errno: i32) -> std_io::ErrorKind {
         wasi::ERRNO_AGAIN => WouldBlock,
         wasi::ERRNO_NOSYS => Unsupported,
         wasi::ERRNO_NOMEM => OutOfMemory,
-        _ => Other,
+        _ => Uncategorized,
     }
 }