From c89ee081dd33eead1b4d0c3d287f96f3a664553b Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Wed, 15 Jan 2025 04:15:48 +0000
Subject: [PATCH] Make sure we actually use the right trivial lifetime substs
 when eagerly monomorphizing drop for structs

---
 compiler/rustc_monomorphize/src/collector.rs  | 22 +++++++++++++++----
 compiler/rustc_type_ir/src/binder.rs          |  2 +-
 .../item-collection/drop-glue-eager.rs        | 13 +++++++++++
 3 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs
index 0f3943cfe6a1a..bb603df112942 100644
--- a/compiler/rustc_monomorphize/src/collector.rs
+++ b/compiler/rustc_monomorphize/src/collector.rs
@@ -1410,19 +1410,33 @@ impl<'v> RootCollector<'_, 'v> {
                     && !self.tcx.generics_of(id.owner_id).requires_monomorphization(self.tcx)
                 {
                     debug!("RootCollector: ADT drop-glue for `{id:?}`",);
+                    let id_args =
+                        ty::GenericArgs::for_item(self.tcx, id.owner_id.to_def_id(), |param, _| {
+                            match param.kind {
+                                GenericParamDefKind::Lifetime => {
+                                    self.tcx.lifetimes.re_erased.into()
+                                }
+                                GenericParamDefKind::Type { .. }
+                                | GenericParamDefKind::Const { .. } => {
+                                    unreachable!(
+                                        "`own_requires_monomorphization` check means that \
+                                we should have no type/const params"
+                                    )
+                                }
+                            }
+                        });
 
                     // This type is impossible to instantiate, so we should not try to
                     // generate a `drop_in_place` instance for it.
                     if self.tcx.instantiate_and_check_impossible_predicates((
                         id.owner_id.to_def_id(),
-                        ty::List::empty(),
+                        id_args,
                     )) {
                         return;
                     }
 
-                    let ty = self.tcx.erase_regions(
-                        self.tcx.type_of(id.owner_id.to_def_id()).instantiate_identity(),
-                    );
+                    let ty =
+                        self.tcx.type_of(id.owner_id.to_def_id()).instantiate(self.tcx, id_args);
                     assert!(!ty.has_non_region_param());
                     visit_drop_use(self.tcx, ty, true, DUMMY_SP, self.output);
                 }
diff --git a/compiler/rustc_type_ir/src/binder.rs b/compiler/rustc_type_ir/src/binder.rs
index cb59bc608c203..0d0092ea1aa08 100644
--- a/compiler/rustc_type_ir/src/binder.rs
+++ b/compiler/rustc_type_ir/src/binder.rs
@@ -804,7 +804,7 @@ impl<'a, I: Interner> ArgFolder<'a, I> {
     #[inline(never)]
     fn region_param_out_of_range(&self, ebr: I::EarlyParamRegion, r: I::Region) -> ! {
         panic!(
-            "const parameter `{:?}` ({:?}/{}) out of range when instantiating args={:?}",
+            "region parameter `{:?}` ({:?}/{}) out of range when instantiating args={:?}",
             ebr,
             r,
             ebr.index(),
diff --git a/tests/codegen-units/item-collection/drop-glue-eager.rs b/tests/codegen-units/item-collection/drop-glue-eager.rs
index 77470767ee1a3..c81074de49040 100644
--- a/tests/codegen-units/item-collection/drop-glue-eager.rs
+++ b/tests/codegen-units/item-collection/drop-glue-eager.rs
@@ -41,3 +41,16 @@ impl<'a> Drop for StructWithDropAndLt<'a> {
 struct StructWithDropAndLt<'a> {
     x: &'a i32,
 }
+
+// Make sure we don't ICE when checking impossible predicates for the struct.
+// Regression test for <https://github.com/rust-lang/rust/issues/135515>.
+//~ MONO_ITEM fn std::ptr::drop_in_place::<StructWithLtAndPredicate<'_>> - shim(Some(StructWithLtAndPredicate<'_>))
+struct StructWithLtAndPredicate<'a: 'a> {
+    x: &'a i32,
+}
+
+// We should be able to monomorphize drops for struct with lifetimes.
+impl<'a> Drop for StructWithLtAndPredicate<'a> {
+    //~ MONO_ITEM fn <StructWithLtAndPredicate<'_> as std::ops::Drop>::drop
+    fn drop(&mut self) {}
+}