review comments

compiler/rustc_ast_pretty/src/pprust/state/fixup.rs

@@ -1,8 +1,8 @@
 use rustc_ast::Expr;
 use rustc_ast::util::{classify, parser};
 
-// The default amount of fixing is minimal fixing. Fixups should be turned on
-// in a targeted fashion where needed.
+// The default amount of fixing is minimal fixing, so all fixups are set to `false` by `Default`.
+// Fixups should be turned on in a targeted fashion where needed.
 #[derive(Copy, Clone, Debug, Default)]
 pub(crate) struct FixupContext {
     /// Print expression such that it can be parsed back as a statement

library/core/src/default.rs

@@ -161,6 +161,7 @@ macro_rules! default_impl {
 default_impl! { (), (), "Returns the default value of `()`" }
 default_impl! { bool, false, "Returns the default value of `false`" }
 default_impl! { char, '\x00', "Returns the default value of `\\x00`" }
+default_impl! { AsciiChar, AsciiChar::Null, "Returns the default value of `Null`" }
 
 default_impl! { usize, 0, "Returns the default value of `0`" }
 default_impl! { u8, 0, "Returns the default value of `0`" }

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

@@ -155,11 +155,9 @@ 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,
@@ -312,6 +310,12 @@ 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 {
@@ -421,12 +425,10 @@ 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"]
@@ -443,6 +445,12 @@ 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 {