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Properly normalize types in bck when checking pointer casts

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This commit is contained in:
Maybe Lapkin 2024-07-04 17:53:37 +02:00
parent 9ef533e8de
commit a1f20f17c8
3 changed files with 47 additions and 2 deletions
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7
compiler/rustc_borrowck/src/type_check/mod.rs
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@ -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).

27
tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.rs Normal file
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@ -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();
}

15
tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.stderr Normal file
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@ -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