From a1f20f17c86a7a0a51728be48afd121d5ae2df64 Mon Sep 17 00:00:00 2001
From: Maybe Lapkin <waffle.lapkin@gmail.com>
Date: Thu, 4 Jul 2024 17:53:37 +0200
Subject: [PATCH] Properly normalize types in bck when checking pointer casts
---
compiler/rustc_borrowck/src/type_check/mod.rs | 7 +++--
...to-trait-obj-different-regions-id-trait.rs | 27 +++++++++++++++++++
...rait-obj-different-regions-id-trait.stderr | 15 +++++++++++
3 files changed, 47 insertions(+), 2 deletions(-)
create mode 100644 tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.rs
create mode 100644 tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.stderr
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 81ce7418852..6fd49c8027b 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -2320,8 +2320,11 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
let cast_ty_to = CastTy::from_ty(*ty);
match (cast_ty_from, cast_ty_to) {
(Some(CastTy::Ptr(src)), Some(CastTy::Ptr(dst))) => {
- let src_tail = tcx.struct_tail_without_normalization(src.ty);
- let dst_tail = tcx.struct_tail_without_normalization(dst.ty);
+ let mut normalize = |t| self.normalize(t, location);
+ let src_tail =
+ tcx.struct_tail_with_normalize(src.ty, &mut normalize, || ());
+ let dst_tail =
+ tcx.struct_tail_with_normalize(dst.ty, &mut normalize, || ());
// This checks (lifetime part of) vtable validity for pointer casts,
// which is irrelevant when there are aren't principal traits on both sides (aka only auto traits).
diff --git a/tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.rs b/tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.rs
new file mode 100644
index 00000000000..cdd55e24392
--- /dev/null
+++ b/tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.rs
@@ -0,0 +1,27 @@
+//@ check-fail
+//
+// Make sure we can't trick the compiler by using a projection.
+
+trait Cat<'a> {}
+impl Cat<'_> for () {}
+
+trait Id {
+ type Id: ?Sized;
+}
+impl<T: ?Sized> Id for T {
+ type Id = T;
+}
+
+struct S<T: ?Sized> {
+ tail: <T as Id>::Id,
+}
+
+fn m<'a>() {
+ let unsend: *const dyn Cat<'a> = &();
+ let _send = unsend as *const S<dyn Cat<'static>>;
+ //~^ error: lifetime may not live long enough
+}
+
+fn main() {
+ m();
+}
diff --git a/tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.stderr b/tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.stderr
new file mode 100644
index 00000000000..d1d598e603f
--- /dev/null
+++ b/tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.stderr
@@ -0,0 +1,15 @@
+error: lifetime may not live long enough
+ --> $DIR/ptr-to-trait-obj-different-regions-id-trait.rs:21:17
+ |
+LL | fn m<'a>() {
+ | -- lifetime `'a` defined here
+LL | let unsend: *const dyn Cat<'a> = &();
+LL | let _send = unsend as *const S<dyn Cat<'static>>;
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
+ |
+ = note: requirement occurs because of the type `S<dyn Cat<'_>>`, which makes the generic argument `dyn Cat<'_>` invariant
+ = note: the struct `S<T>` is invariant over the parameter `T`
+ = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
+
+error: aborting due to 1 previous error
+