user0/rust
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Auto merge of #152738 - workingjubilee:revert-unsound-ice-patch, r=mati865

Browse source 
Revert "Fix an ICE in the vtable iteration for a trait reference"

The ICE fix appears to be unsound, causing a miscompilation involving `dyn Trait` and `async {}` which induces segfaults in safe Rust code. As the patch only hid an ICE, it does not seem worth the risk.

This addresses the problem in rust-lang/rust#152735 but it may still merit team discussion even if this PR is merged.

This reverts commit 8afd63610b, reversing changes made to 19122c03c7.
This commit is contained in:
bors 2026-02-17 09:36:10 +00:00
commit 3f6250a7bb
8 changed files with 35 additions and 88 deletions
Download patch file Download diff file Expand all files Collapse all files

8
compiler/rustc_trait_selection/src/traits/vtable.rs
View file

@ -12,7 +12,7 @@ use rustc_span::DUMMY_SP;
use smallvec::{SmallVec, smallvec};
use tracing::debug;
use crate::traits::is_vtable_safe_method;
use crate::traits::{impossible_predicates, is_vtable_safe_method};
#[derive(Clone, Debug)]
pub enum VtblSegment<'tcx> {
@ -276,7 +276,11 @@ fn vtable_entries<'tcx>(
// do not hold for this particular set of type parameters.
// Note that this method could then never be called, so we
// do not want to try and codegen it, in that case (see #23435).
if tcx.instantiate_and_check_impossible_predicates((def_id, args)) {
let predicates = tcx.predicates_of(def_id).instantiate_own(tcx, args);
if impossible_predicates(
tcx,
predicates.map(|(predicate, _)| predicate).collect(),
) {
debug!("vtable_entries: predicates do not hold");
return VtblEntry::Vacant;
}