Use derive(Default) in rustfmt

Author: estebank

src/tools/rustfmt/src/config/options.rs

@@ -155,9 +155,11 @@ pub enum ReportTactic {
 
 /// What Rustfmt should emit. Mostly corresponds to the `--emit` command line
 /// option.
+#[derive(Default)]
 #[config_type]
 pub enum EmitMode {
     /// Emits to files.
+    #[default]
     Files,
     /// Writes the output to stdout.
     Stdout,
@@ -310,12 +312,6 @@ impl ::std::str::FromStr for WidthHeuristics {
     }
 }
 
-impl Default for EmitMode {
-    fn default() -> EmitMode {
-        EmitMode::Files
-    }
-}
-
 /// A set of directories, files and modules that rustfmt should ignore.
 #[derive(Default, Clone, Debug, PartialEq)]
 pub struct IgnoreList {
@@ -425,10 +421,12 @@ pub trait CliOptions {
 }
 
 /// The edition of the syntax and semantics of code (RFC 2052).
+#[derive(Default)]
 #[config_type]
 pub enum Edition {
     #[value = "2015"]
     #[doc_hint = "2015"]
+    #[default]
     /// Edition 2015.
     Edition2015,
     #[value = "2018"]
@@ -445,12 +443,6 @@ pub enum Edition {
     Edition2024,
 }
 
-impl Default for Edition {
-    fn default() -> Edition {
-        Edition::Edition2015
-    }
-}
-
 impl From<Edition> for rustc_span::edition::Edition {
     fn from(edition: Edition) -> Self {
         match edition {