From 3562ec74cae80cfccda7d388c186609254437426 Mon Sep 17 00:00:00 2001
From: Oli Scherer <git-spam-no-reply9815368754983@oli-obk.de>
Date: Wed, 10 Jul 2024 07:54:17 +0000
Subject: [PATCH] Make `visit_clobber`'s impl safe
---
compiler/rustc_ast/src/mut_visit.rs | 17 +++--------------
1 file changed, 3 insertions(+), 14 deletions(-)
diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs
index cbf21317f1a77..1c1163551db5f 100644
--- a/compiler/rustc_ast/src/mut_visit.rs
+++ b/compiler/rustc_ast/src/mut_visit.rs
@@ -20,7 +20,7 @@ use rustc_span::symbol::Ident;
use rustc_span::Span;
use smallvec::{smallvec, Array, SmallVec};
use std::ops::DerefMut;
-use std::{panic, ptr};
+use std::panic;
use thin_vec::ThinVec;
pub trait ExpectOne<A: Array> {
@@ -318,19 +318,8 @@ pub trait MutVisitor: Sized {
//
// No `noop_` prefix because there isn't a corresponding method in `MutVisitor`.
pub fn visit_clobber<T: DummyAstNode>(t: &mut T, f: impl FnOnce(T) -> T) {
- unsafe {
- // Safe because `t` is used in a read-only fashion by `read()` before
- // being overwritten by `write()`.
- let old_t = ptr::read(t);
- let new_t =
- panic::catch_unwind(panic::AssertUnwindSafe(|| f(old_t))).unwrap_or_else(|err| {
- // Set `t` to some valid but possible meaningless value,
- // and pass the fatal error further.
- ptr::write(t, T::dummy());
- panic::resume_unwind(err);
- });
- ptr::write(t, new_t);
- }
+ let old_t = std::mem::replace(t, T::dummy());
+ *t = f(old_t);
}
// No `noop_` prefix because there isn't a corresponding method in `MutVisitor`.