1 files changed, 6 insertions, 0 deletions
diff --git a/compiler/rustc_ast/src/ast_traits.rs b/compiler/rustc_ast/src/ast_traits.rs
index 21de7ff7719..797ab297319 100644
--- a/compiler/rustc_ast/src/ast_traits.rs
+++ b/compiler/rustc_ast/src/ast_traits.rs
@@ -304,6 +304,7 @@ impl HasAttrs for Stmt {
 }
 
 /// A newtype around an AST node that implements the traits above if the node implements them.
+#[repr(transparent)]
 pub struct AstNodeWrapper<Wrapped, Tag> {
     pub wrapped: Wrapped,
     pub tag: PhantomData<Tag>,
@@ -313,6 +314,11 @@ impl<Wrapped, Tag> AstNodeWrapper<Wrapped, Tag> {
     pub fn new(wrapped: Wrapped, _tag: Tag) -> AstNodeWrapper<Wrapped, Tag> {
         AstNodeWrapper { wrapped, tag: Default::default() }
     }
+
+    pub fn from_mut(wrapped: &mut Wrapped, _tag: Tag) -> &mut AstNodeWrapper<Wrapped, Tag> {
+        // SAFETY: `AstNodeWrapper` is `repr(transparent)` w.r.t `Wrapped`
+        unsafe { &mut *<*mut Wrapped>::cast(wrapped) }
+    }
 }
 
 impl<Wrapped: HasNodeId, Tag> HasNodeId for AstNodeWrapper<Wrapped, Tag> {