From 2d73597b93d27b94e1b534d84352f51629418380 Mon Sep 17 00:00:00 2001
From: Oli Scherer <git-spam-no-reply9815368754983@oli-obk.de>
Date: Thu, 8 Feb 2024 17:51:32 +0000
Subject: [PATCH] Bail out of drop elaboration when encountering error types

---
 .../src/move_paths/builder.rs                 |  5 ++++-
 tests/ui/drop/drop_elaboration_with_errors.rs | 20 +++++++++++++++++++
 .../drop/drop_elaboration_with_errors.stderr  | 14 +++++++++++++
 3 files changed, 38 insertions(+), 1 deletion(-)
 create mode 100644 tests/ui/drop/drop_elaboration_with_errors.rs
 create mode 100644 tests/ui/drop/drop_elaboration_with_errors.stderr

diff --git a/compiler/rustc_mir_dataflow/src/move_paths/builder.rs b/compiler/rustc_mir_dataflow/src/move_paths/builder.rs
index 30dd915521c..8c2690574e5 100644
--- a/compiler/rustc_mir_dataflow/src/move_paths/builder.rs
+++ b/compiler/rustc_mir_dataflow/src/move_paths/builder.rs
@@ -1,7 +1,7 @@
 use rustc_index::IndexVec;
 use rustc_middle::mir::tcx::{PlaceTy, RvalueInitializationState};
 use rustc_middle::mir::*;
-use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
 use smallvec::{smallvec, SmallVec};
 
 use std::mem;
@@ -132,6 +132,9 @@ fn move_path_for(&mut self, place: Place<'tcx>) -> MovePathResult {
             let body = self.builder.body;
             let tcx = self.builder.tcx;
             let place_ty = place_ref.ty(body, tcx).ty;
+            if place_ty.references_error() {
+                return MovePathResult::Error;
+            }
             match elem {
                 ProjectionElem::Deref => match place_ty.kind() {
                     ty::Ref(..) | ty::RawPtr(..) => {
diff --git a/tests/ui/drop/drop_elaboration_with_errors.rs b/tests/ui/drop/drop_elaboration_with_errors.rs
new file mode 100644
index 00000000000..77862762e87
--- /dev/null
+++ b/tests/ui/drop/drop_elaboration_with_errors.rs
@@ -0,0 +1,20 @@
+// can't use build-fail, because this also fails check-fail, but
+// the ICE from #120787 only reproduces on build-fail.
+// compile-flags: --emit=mir
+
+#![feature(type_alias_impl_trait)]
+
+struct Foo {
+    field: String,
+}
+
+type Tait = impl Sized;
+
+fn ice_cold(beverage: Tait) {
+    let Foo { field } = beverage;
+    _ = field;
+}
+
+fn main() {
+    Ok(()) //~ ERROR mismatched types
+}
diff --git a/tests/ui/drop/drop_elaboration_with_errors.stderr b/tests/ui/drop/drop_elaboration_with_errors.stderr
new file mode 100644
index 00000000000..bec229631e1
--- /dev/null
+++ b/tests/ui/drop/drop_elaboration_with_errors.stderr
@@ -0,0 +1,14 @@
+error[E0308]: mismatched types
+  --> $DIR/drop_elaboration_with_errors.rs:19:5
+   |
+LL | fn main() {
+   |          - expected `()` because of default return type
+LL |     Ok(())
+   |     ^^^^^^ expected `()`, found `Result<(), _>`
+   |
+   = note: expected unit type `()`
+                   found enum `Result<(), _>`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.