Rollup merge of #128239 - compiler-errors:error-on-object-cand-confirm, r=oli-obk

Don't ICE when encountering error regions when confirming object method candidate

See the inline comment for an explanation.

Fixes #122914

compiler/rustc_hir_typeck/src/method/confirm.rs

@@ -16,7 +16,8 @@ use rustc_middle::ty::adjustment::{
 };
 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};
@@ -269,6 +270,17 @@ 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

tests/crashes/122914.rs

@@ -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);
-        })
-    }
-}

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() {}

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`.