Migrate manual extern types to extern_ty!

Use the macro to replace repeated handwritten uninhabited enums. In
order to keep the same traits, `extern_ty!` now implements `Clone` and
`Copy` in addition to the existing `Debug`, which affects existing uses
of `extern_ty!`. We don't need these traits since they can never be used
on uninhabited types, but there is no harm in adding them for now and
dropping later on.

(backport <#4759>)
(cherry picked from commit 147b462)

Author: tgross35

src/fuchsia/mod.rs

@@ -78,32 +78,10 @@ pub type fsblkcnt_t = c_ulonglong;
 pub type fsfilcnt_t = c_ulonglong;
 pub type rlim_t = c_ulonglong;
 
-// FIXME(fuchsia): why are these uninhabited types? that seems... wrong?
-// Presumably these should be `()` or an `extern type` (when that stabilizes).
-#[derive(Debug)]
-pub enum timezone {}
-impl Copy for timezone {}
-impl Clone for timezone {
-    fn clone(&self) -> timezone {
-        *self
-    }
-}
-#[derive(Debug)]
-pub enum DIR {}
-impl Copy for DIR {}
-impl Clone for DIR {
-    fn clone(&self) -> DIR {
-        *self
-    }
-}
-
-#[derive(Debug)]
-pub enum fpos64_t {} // FIXME(fuchsia): fill this out with a struct
-impl Copy for fpos64_t {}
-impl Clone for fpos64_t {
-    fn clone(&self) -> fpos64_t {
-        *self
-    }
+extern_ty! {
+    pub enum timezone {}
+    pub enum DIR {}
+    pub enum fpos64_t {} // FIXME(fuchsia): fill this out with a struct
 }
 
 // PUB_STRUCT
@@ -3421,21 +3399,9 @@ fn __MHDR_END(mhdr: *const msghdr) -> *mut c_uchar {
 #[link(name = "fdio")]
 extern "C" {}
 
-#[derive(Debug)]
-pub enum FILE {}
-impl Copy for FILE {}
-impl Clone for FILE {
-    fn clone(&self) -> FILE {
-        *self
-    }
-}
-#[derive(Debug)]
-pub enum fpos_t {} // FIXME(fuchsia): fill this out with a struct
-impl Copy for fpos_t {}
-impl Clone for fpos_t {
-    fn clone(&self) -> fpos_t {
-        *self
-    }
+extern_ty! {
+    pub enum FILE {}
+    pub enum fpos_t {} // FIXME(fuchsia): fill this out with a struct
 }
 
 extern "C" {

src/macros.rs

@@ -203,8 +203,9 @@ macro_rules! s_no_extra_traits {
     );
 }
 
-/// Create an uninhabited type that can't be constructed. It implements `Debug` but no
-/// other traits.
+/// Create an uninhabited type that can't be constructed. It implements `Debug`, `Clone`,
+/// and `Copy`, but these aren't meaningful for extern types so they should eventually
+/// be removed.
 ///
 /// Really what we want here is something that also can't be named without indirection (in
 /// ADTs or function signatures), but this doesn't exist.
@@ -214,9 +215,13 @@ macro_rules! extern_ty {
         pub enum $i:ident {}
     )*) => ($(
         $(#[$attr])*
-        #[allow(missing_copy_implementations)]
-        // FIXME(1.0): the type is uninhabited so this trait is unreachable.
-        #[::core::prelude::v1::derive(::core::fmt::Debug)]
+        // FIXME(1.0): the type is uninhabited so these traits are unreachable and could be
+        // removed.
+        #[::core::prelude::v1::derive(
+            ::core::clone::Clone,
+            ::core::marker::Copy,
+            ::core::fmt::Debug,
+        )]
         pub enum $i { }
     )*);
 }

src/solid/mod.rs

@@ -395,21 +395,9 @@ pub const SIGUSR1: c_int = 30;
 pub const SIGUSR2: c_int = 31;
 pub const SIGPWR: c_int = 32;
 
-#[derive(Debug)]
-pub enum FILE {}
-impl Copy for FILE {}
-impl Clone for FILE {
-    fn clone(&self) -> FILE {
-        *self
-    }
-}
-#[derive(Debug)]
-pub enum fpos_t {}
-impl Copy for fpos_t {}
-impl Clone for fpos_t {
-    fn clone(&self) -> fpos_t {
-        *self
-    }
+extern_ty! {
+    pub enum FILE {}
+    pub enum fpos_t {}
 }
 
 extern "C" {

src/unix/bsd/apple/mod.rs

@@ -179,13 +179,8 @@ deprecated_mach! {
     pub type mach_timebase_info_data_t = mach_timebase_info;
 }
 
-#[derive(Debug)]
-pub enum timezone {}
-impl Copy for timezone {}
-impl Clone for timezone {
-    fn clone(&self) -> timezone {
-        *self
-    }
+extern_ty! {
+    pub enum timezone {}
 }
 
 #[derive(Debug)]

src/unix/bsd/freebsdlike/dragonfly/mod.rs

@@ -45,13 +45,8 @@ pub type vm_map_entry_t = *mut vm_map_entry;
 
 pub type pmap = __c_anonymous_pmap;
 
-#[derive(Debug)]
-pub enum sem {}
-impl Copy for sem {}
-impl Clone for sem {
-    fn clone(&self) -> sem {
-        *self
-    }
+extern_ty! {
+    pub enum sem {}
 }
 
 e! {

src/unix/bsd/freebsdlike/mod.rs

@@ -59,13 +59,8 @@ cfg_if! {
 
 // link.h
 
-#[derive(Debug)]
-pub enum timezone {}
-impl Copy for timezone {}
-impl Clone for timezone {
-    fn clone(&self) -> timezone {
-        *self
-    }
+extern_ty! {
+    pub enum timezone {}
 }
 
 impl siginfo_t {

src/unix/bsd/netbsdlike/mod.rs

@@ -16,21 +16,9 @@ pub type id_t = u32;
 pub type sem_t = *mut sem;
 pub type key_t = c_long;
 
-#[derive(Debug)]
-pub enum timezone {}
-impl Copy for timezone {}
-impl Clone for timezone {
-    fn clone(&self) -> timezone {
-        *self
-    }
-}
-#[derive(Debug)]
-pub enum sem {}
-impl Copy for sem {}
-impl Clone for sem {
-    fn clone(&self) -> sem {
-        *self
-    }
+extern_ty! {
+    pub enum timezone {}
+    pub enum sem {}
 }
 
 s! {

src/unix/cygwin/mod.rs

@@ -28,13 +28,8 @@ pub type nlink_t = c_ushort;
 pub type suseconds_t = c_long;
 pub type useconds_t = c_ulong;
 
-#[derive(Debug)]
-pub enum timezone {}
-impl Copy for timezone {}
-impl Clone for timezone {
-    fn clone(&self) -> timezone {
-        *self
-    }
+extern_ty! {
+    pub enum timezone {}
 }
 
 pub type sigset_t = c_ulong;
@@ -75,13 +70,8 @@ pub type nfds_t = c_uint;
 
 pub type sem_t = *mut sem;
 
-#[derive(Debug)]
-pub enum sem {}
-impl Copy for sem {}
-impl Clone for sem {
-    fn clone(&self) -> sem {
-        *self
-    }
+extern_ty! {
+    pub enum sem {}
 }
 
 pub type tcflag_t = c_uint;

src/unix/haiku/mod.rs

@@ -80,13 +80,8 @@ pub type ACTION = c_int;
 pub type posix_spawnattr_t = *mut c_void;
 pub type posix_spawn_file_actions_t = *mut c_void;
 
-#[derive(Debug)]
-pub enum timezone {}
-impl Copy for timezone {}
-impl Clone for timezone {
-    fn clone(&self) -> timezone {
-        *self
-    }
+extern_ty! {
+    pub enum timezone {}
 }
 
 impl siginfo_t {

src/unix/hurd/mod.rs

@@ -225,22 +225,9 @@ pub type nl_item = c_int;
 
 pub type iconv_t = *mut c_void;
 
-#[derive(Debug)]
-pub enum fpos64_t {} // FIXME(hurd): fill this out with a struct
-impl Copy for fpos64_t {}
-impl Clone for fpos64_t {
-    fn clone(&self) -> fpos64_t {
-        *self
-    }
-}
-
-#[derive(Debug)]
-pub enum timezone {}
-impl Copy for timezone {}
-impl Clone for timezone {
-    fn clone(&self) -> timezone {
-        *self
-    }
+extern_ty! {
+    pub enum fpos64_t {} // FIXME(hurd): fill this out with a struct
+    pub enum timezone {}
 }
 
 // structs