From 8d2c12e5540d801a48eae396eac6aa350ce8c1b1 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Fri, 26 Jul 2024 13:18:29 -0400
Subject: [PATCH] Don't ICE when encountering error regions when confirming
 object method candidate

---
 compiler/rustc_hir_typeck/src/method/confirm.rs    | 14 +++++++++++++-
 tests/crashes/122914.rs                            | 11 -----------
 .../dont-ice-on-object-lookup-w-error-region.rs    | 11 +++++++++++
 ...dont-ice-on-object-lookup-w-error-region.stderr | 11 +++++++++++
 4 files changed, 35 insertions(+), 12 deletions(-)
 delete mode 100644 tests/crashes/122914.rs
 create mode 100644 tests/ui/methods/dont-ice-on-object-lookup-w-error-region.rs
 create mode 100644 tests/ui/methods/dont-ice-on-object-lookup-w-error-region.stderr

diff --git a/compiler/rustc_hir_typeck/src/method/confirm.rs b/compiler/rustc_hir_typeck/src/method/confirm.rs
index e70431a68ff..be3de812a96 100644
--- a/compiler/rustc_hir_typeck/src/method/confirm.rs
+++ b/compiler/rustc_hir_typeck/src/method/confirm.rs
@@ -16,7 +16,8 @@ use rustc_middle::ty::adjustment::{Adjust, Adjustment, PointerCoercion};
 use rustc_middle::ty::adjustment::{AllowTwoPhase, AutoBorrow, AutoBorrowMutability};
 use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::{
-    self, GenericArgs, GenericArgsRef, GenericParamDefKind, Ty, TyCtxt, UserArgs, UserType,
+    self, GenericArgs, GenericArgsRef, GenericParamDefKind, Ty, TyCtxt, TypeVisitableExt, UserArgs,
+    UserType,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_span::{Span, DUMMY_SP};
@@ -268,6 +269,17 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
 
             probe::ObjectPick => {
                 let trait_def_id = pick.item.container_id(self.tcx);
+
+                // This shouldn't happen for non-region error kinds, but may occur
+                // when we have error regions. Specifically, since we canonicalize
+                // during method steps, we may successfully deref when we assemble
+                // the pick, but fail to deref when we try to extract the object
+                // type from the pick during confirmation. This is fine, we're basically
+                // already doomed by this point.
+                if self_ty.references_error() {
+                    return ty::GenericArgs::extend_with_error(self.tcx, trait_def_id, &[]);
+                }
+
                 self.extract_existential_trait_ref(self_ty, |this, object_ty, principal| {
                     // The object data has no entry for the Self
                     // Type. For the purposes of this method call, we
diff --git a/tests/crashes/122914.rs b/tests/crashes/122914.rs
deleted file mode 100644
index 63a84bc8099..00000000000
--- a/tests/crashes/122914.rs
+++ /dev/null
@@ -1,11 +0,0 @@
-//@ known-bug: #122914
-use std::future::Future;
-use std::pin::Pin;
-
-impl<'a, F> Poll {
-    fn project<'_>(self: Pin<&'pin mut Future>) -> Projection<'pin, 'a, F> {
-        me.local_set.with(|| {
-            let _ = self.poll(cx);
-        })
-    }
-}
diff --git a/tests/ui/methods/dont-ice-on-object-lookup-w-error-region.rs b/tests/ui/methods/dont-ice-on-object-lookup-w-error-region.rs
new file mode 100644
index 00000000000..0a6d196364f
--- /dev/null
+++ b/tests/ui/methods/dont-ice-on-object-lookup-w-error-region.rs
@@ -0,0 +1,11 @@
+// Fix for issue: #122914
+
+use std::future::Future;
+use std::pin::Pin;
+
+fn project(x: Pin<&'missing mut dyn Future<Output = ()>>) {
+    //~^ ERROR use of undeclared lifetime name `'missing`
+    let _ = x.poll(todo!());
+}
+
+fn main() {}
diff --git a/tests/ui/methods/dont-ice-on-object-lookup-w-error-region.stderr b/tests/ui/methods/dont-ice-on-object-lookup-w-error-region.stderr
new file mode 100644
index 00000000000..2c33941be43
--- /dev/null
+++ b/tests/ui/methods/dont-ice-on-object-lookup-w-error-region.stderr
@@ -0,0 +1,11 @@
+error[E0261]: use of undeclared lifetime name `'missing`
+  --> $DIR/dont-ice-on-object-lookup-w-error-region.rs:6:20
+   |
+LL | fn project(x: Pin<&'missing mut dyn Future<Output = ()>>) {
+   |           -        ^^^^^^^^ undeclared lifetime
+   |           |
+   |           help: consider introducing lifetime `'missing` here: `<'missing>`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0261`.