Rollup merge of #134363 - estebank:derive-default, r=SparrowLii

Use `#[derive(Default)]` instead of manual `impl` when possible

While working on #134175 I noticed a few manual `Default` `impl`s that could be `derive`d instead. These likely predate the existence of the `#[default]` attribute for `enum`s.

2 files changed, 3 insertions, 14 deletions

diff --git a/library/std/src/panicking.rs b/library/std/src/panicking.rs
index dca5ccca0c4..e7ce5bc6140 100644
--- a/library/std/src/panicking.rs
+++ b/library/std/src/panicking.rs
@@ -81,7 +81,9 @@ extern "C" fn __rust_foreign_exception() -> ! {
     rtabort!("Rust cannot catch foreign exceptions");
 }
 
+#[derive(Default)]
 enum Hook {
+    #[default]
     Default,
     Custom(Box<dyn Fn(&PanicHookInfo<'_>) + 'static + Sync + Send>),
 }
@@ -96,13 +98,6 @@ impl Hook {
     }
 }
 
-impl Default for Hook {
-    #[inline]
-    fn default() -> Hook {
-        Hook::Default
-    }
-}
-
 static HOOK: RwLock<Hook> = RwLock::new(Hook::Default);
 
 /// Registers a custom panic hook, replacing the previously registered hook.
diff --git a/library/std/src/sys_common/process.rs b/library/std/src/sys_common/process.rs
index 5333ee146f7..9f61d69d858 100644
--- a/library/std/src/sys_common/process.rs
+++ b/library/std/src/sys_common/process.rs
@@ -8,19 +8,13 @@ use crate::sys::process::{EnvKey, ExitStatus, Process, StdioPipes};
 use crate::{env, fmt, io};
 
 // Stores a set of changes to an environment
-#[derive(Clone)]
+#[derive(Clone, Default)]
 pub struct CommandEnv {
     clear: bool,
     saw_path: bool,
     vars: BTreeMap<EnvKey, Option<OsString>>,
 }
 
-impl Default for CommandEnv {
-    fn default() -> Self {
-        CommandEnv { clear: false, saw_path: false, vars: Default::default() }
-    }
-}
-
 impl fmt::Debug for CommandEnv {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let mut debug_command_env = f.debug_struct("CommandEnv");