Revert "Rollup merge of rust-lang#127107 - mu001999-contrib:dead/enha…

…nce-2, r=pnkfelix"

This reverts commit 31fe962, reversing
changes made to f203078.

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.
     ///