Rollup merge of rust-lang#84212 - CDirkx:void, r=m-ou-se

Replace `Void` in `sys` with never type

This PR replaces several occurrences in `sys` of the type `enum Void {}` with the Rust never type (`!`).
The name `Void` is unfortunate because in other languages (C etc.) it refers to a unit type, not an uninhabited type.

Note that the previous stabilization of the never type was reverted, however all uses here are implementation details and not publicly visible.

Author: m-ou-se

std/src/sys/hermit/fs.rs

@@ -9,7 +9,7 @@ use crate::sys::hermit::abi;
 use crate::sys::hermit::abi::{O_APPEND, O_CREAT, O_EXCL, O_RDONLY, O_RDWR, O_TRUNC, O_WRONLY};
 use crate::sys::hermit::fd::FileDesc;
 use crate::sys::time::SystemTime;
-use crate::sys::{unsupported, Void};
+use crate::sys::unsupported;
 use crate::sys_common::os_str_bytes::OsStrExt;
 
 pub use crate::sys_common::fs::copy;
@@ -22,11 +22,11 @@ fn cstr(path: &Path) -> io::Result<CString> {
 #[derive(Debug)]
 pub struct File(FileDesc);
 
-pub struct FileAttr(Void);
+pub struct FileAttr(!);
 
-pub struct ReadDir(Void);
+pub struct ReadDir(!);
 
-pub struct DirEntry(Void);
+pub struct DirEntry(!);
 
 #[derive(Clone, Debug)]
 pub struct OpenOptions {
@@ -41,146 +41,146 @@ pub struct OpenOptions {
     mode: i32,
 }
 
-pub struct FilePermissions(Void);
+pub struct FilePermissions(!);
 
-pub struct FileType(Void);
+pub struct FileType(!);
 
 #[derive(Debug)]
 pub struct DirBuilder {}
 
 impl FileAttr {
     pub fn size(&self) -> u64 {
-        match self.0 {}
+        self.0
     }
 
     pub fn perm(&self) -> FilePermissions {
-        match self.0 {}
+        self.0
     }
 
     pub fn file_type(&self) -> FileType {
-        match self.0 {}
+        self.0
     }
 
     pub fn modified(&self) -> io::Result<SystemTime> {
-        match self.0 {}
+        self.0
     }
 
     pub fn accessed(&self) -> io::Result<SystemTime> {
-        match self.0 {}
+        self.0
     }
 
     pub fn created(&self) -> io::Result<SystemTime> {
-        match self.0 {}
+        self.0
     }
 }
 
 impl Clone for FileAttr {
     fn clone(&self) -> FileAttr {
-        match self.0 {}
+        self.0
     }
 }
 
 impl FilePermissions {
     pub fn readonly(&self) -> bool {
-        match self.0 {}
+        self.0
     }
 
     pub fn set_readonly(&mut self, _readonly: bool) {
-        match self.0 {}
+        self.0
     }
 }
 
 impl Clone for FilePermissions {
     fn clone(&self) -> FilePermissions {
-        match self.0 {}
+        self.0
     }
 }
 
 impl PartialEq for FilePermissions {
     fn eq(&self, _other: &FilePermissions) -> bool {
-        match self.0 {}
+        self.0
     }
 }
 
 impl Eq for FilePermissions {}
 
 impl fmt::Debug for FilePermissions {
     fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self.0 {}
+        self.0
     }
 }
 
 impl FileType {
     pub fn is_dir(&self) -> bool {
-        match self.0 {}
+        self.0
     }
 
     pub fn is_file(&self) -> bool {
-        match self.0 {}
+        self.0
     }
 
     pub fn is_symlink(&self) -> bool {
-        match self.0 {}
+        self.0
     }
 }
 
 impl Clone for FileType {
     fn clone(&self) -> FileType {
-        match self.0 {}
+        self.0
     }
 }
 
 impl Copy for FileType {}
 
 impl PartialEq for FileType {
     fn eq(&self, _other: &FileType) -> bool {
-        match self.0 {}
+        self.0
     }
 }
 
 impl Eq for FileType {}
 
 impl Hash for FileType {
     fn hash<H: Hasher>(&self, _h: &mut H) {
-        match self.0 {}
+        self.0
     }
 }
 
 impl fmt::Debug for FileType {
     fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self.0 {}
+        self.0
     }
 }
 
 impl fmt::Debug for ReadDir {
     fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self.0 {}
+        self.0
     }
 }
 
 impl Iterator for ReadDir {
     type Item = io::Result<DirEntry>;
 
     fn next(&mut self) -> Option<io::Result<DirEntry>> {
-        match self.0 {}
+        self.0
     }
 }
 
 impl DirEntry {
     pub fn path(&self) -> PathBuf {
-        match self.0 {}
+        self.0
     }
 
     pub fn file_name(&self) -> OsString {
-        match self.0 {}
+        self.0
     }
 
     pub fn metadata(&self) -> io::Result<FileAttr> {
-        match self.0 {}
+        self.0
     }
 
     pub fn file_type(&self) -> io::Result<FileType> {
-        match self.0 {}
+        self.0
     }
 }
 

std/src/sys/hermit/mod.rs

@@ -61,11 +61,6 @@ pub fn unsupported_err() -> crate::io::Error {
     )
 }
 
-// This enum is used as the storage for a bunch of types which can't actually
-// exist.
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
-pub enum Void {}
-
 pub unsafe fn strlen(start: *const c_char) -> usize {
     let mut str = start;
 

std/src/sys/hermit/net.rs

@@ -6,7 +6,7 @@ use crate::str;
 use crate::sync::Arc;
 use crate::sys::hermit::abi;
 use crate::sys::hermit::abi::IpAddress::{Ipv4, Ipv6};
-use crate::sys::{unsupported, Void};
+use crate::sys::unsupported;
 use crate::sys_common::AsInner;
 use crate::time::Duration;
 
@@ -411,18 +411,18 @@ impl fmt::Debug for UdpSocket {
     }
 }
 
-pub struct LookupHost(Void);
+pub struct LookupHost(!);
 
 impl LookupHost {
     pub fn port(&self) -> u16 {
-        match self.0 {}
+        self.0
     }
 }
 
 impl Iterator for LookupHost {
     type Item = SocketAddr;
     fn next(&mut self) -> Option<SocketAddr> {
-        match self.0 {}
+        self.0
     }
 }
 

std/src/sys/hermit/os.rs

@@ -9,7 +9,7 @@ use crate::path::{self, PathBuf};
 use crate::str;
 use crate::sync::Mutex;
 use crate::sys::hermit::abi;
-use crate::sys::{unsupported, Void};
+use crate::sys::unsupported;
 use crate::sys_common::os_str_bytes::*;
 use crate::vec;
 
@@ -29,7 +29,7 @@ pub fn chdir(_: &path::Path) -> io::Result<()> {
     unsupported()
 }
 
-pub struct SplitPaths<'a>(&'a Void);
+pub struct SplitPaths<'a>(!, PhantomData<&'a ()>);
 
 pub fn split_paths(_unparsed: &OsStr) -> SplitPaths<'_> {
     panic!("unsupported")
@@ -38,7 +38,7 @@ pub fn split_paths(_unparsed: &OsStr) -> SplitPaths<'_> {
 impl<'a> Iterator for SplitPaths<'a> {
     type Item = PathBuf;
     fn next(&mut self) -> Option<PathBuf> {
-        match *self.0 {}
+        self.0
     }
 }
 

std/src/sys/sgx/mod.rs

@@ -115,11 +115,6 @@ pub fn decode_error_kind(code: i32) -> ErrorKind {
     }
 }
 
-// This enum is used as the storage for a bunch of types which can't actually
-// exist.
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
-pub enum Void {}
-
 pub unsafe fn strlen(mut s: *const c_char) -> usize {
     let mut n = 0;
     while unsafe { *s } != 0 {