Detect unused structs which derived Default

mu001999 · mu001999 · commit 5d08a54141c1 · 2024-06-25T23:29:44.000+08:00
diff --git a/alloc/src/sync/tests.rs b/alloc/src/sync/tests.rs
@@ -396,7 +396,7 @@ fn show_arc() {
 
 // Make sure deriving works with Arc<T>
 #[derive(Eq, Ord, PartialEq, PartialOrd, Clone, Debug, Default)]
-struct Foo {
+struct _Foo {
     inner: Arc<i32>,
 }
 
diff --git a/core/src/default.rs b/core/src/default.rs
@@ -103,6 +103,7 @@ use crate::ascii::Char as AsciiChar;
 /// ```
 #[cfg_attr(not(test), rustc_diagnostic_item = "Default")]
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(bootstrap), rustc_trivial_field_reads)]
 pub trait Default: Sized {
     /// Returns the "default value" for a type.
     ///

Original file line number	Diff line number	Diff line change
`@@ -396,7 +396,7 @@ fn show_arc() {`
`396`	`396`
`397`	`397`	`// Make sure deriving works with Arc<T>`
`398`	`398`	`#[derive(Eq, Ord, PartialEq, PartialOrd, Clone, Debug, Default)]`
`399`		`-struct Foo {`
	`399`	`+struct _Foo {`
`400`	`400`	`inner: Arc<i32>,`
`401`	`401`	`}`
`402`	`402`