Use const Box::default in P::<[T]>::new

rust-lang · Apr 11, 2022 · 2d5eda8 · 2d5eda8
1 parent a2902eb
commit 2d5eda8
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Showing 2 changed files with 3 additions and 8 deletions.
diff --git a/compiler/rustc_ast/src/lib.rs b/compiler/rustc_ast/src/lib.rs
@@ -9,6 +9,8 @@
     test(attr(deny(warnings)))
 )]
 #![feature(box_patterns)]
+#![feature(const_default_impls)]
+#![feature(const_trait_impl)]
 #![feature(crate_visibility_modifier)]
 #![feature(if_let_guard)]
 #![feature(label_break_value)]

diff --git a/compiler/rustc_ast/src/ptr.rs b/compiler/rustc_ast/src/ptr.rs
@@ -128,14 +128,7 @@ impl<S: Encoder, T: Encodable<S>> Encodable<S> for P<T> {
 
 impl<T> P<[T]> {
     pub const fn new() -> P<[T]> {
-        // HACK(eddyb) bypass the lack of a `const fn` to create an empty `Box<[T]>`
-        // (as trait methods, `default` in this case, can't be `const fn` yet).
-        P {
-            ptr: unsafe {
-                use std::ptr::NonNull;
-                std::mem::transmute(NonNull::<[T; 0]>::dangling() as NonNull<[T]>)
-            },
-        }
+        P { ptr: Box::default() }
     }
 
     #[inline(never)]