From e3800a1a04f338ce69bd403f230a019cebc54ece Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Wed, 9 Aug 2023 00:31:26 +0000
Subject: [PATCH 1/2] Allow dropping dyn principal
---
.../rustc_codegen_cranelift/src/unsize.rs | 4 +-
compiler/rustc_codegen_ssa/src/base.rs | 5 +-
.../src/solve/trait_goals.rs | 3 +-
.../src/traits/select/candidate_assembly.rs | 2 +-
.../src/traits/select/confirmation.rs | 4 ++
.../impl-trait/unsized_coercion5.next.stderr | 14 -----
.../impl-trait/unsized_coercion5.old.stderr | 18 +-----
tests/ui/impl-trait/unsized_coercion5.rs | 2 +-
tests/ui/traits/dyn-drop-principal.rs | 62 +++++++++++++++++++
tests/ui/traits/dyn-drop-principal.run.stdout | 4 ++
10 files changed, 83 insertions(+), 35 deletions(-)
delete mode 100644 tests/ui/impl-trait/unsized_coercion5.next.stderr
create mode 100644 tests/ui/traits/dyn-drop-principal.rs
create mode 100644 tests/ui/traits/dyn-drop-principal.run.stdout
diff --git a/compiler/rustc_codegen_cranelift/src/unsize.rs b/compiler/rustc_codegen_cranelift/src/unsize.rs
index 5c297ebfadbfd..336934354e11b 100644
--- a/compiler/rustc_codegen_cranelift/src/unsize.rs
+++ b/compiler/rustc_codegen_cranelift/src/unsize.rs
@@ -34,7 +34,9 @@ pub(crate) fn unsized_info<'tcx>(
{
let old_info =
old_info.expect("unsized_info: missing old info for trait upcasting coercion");
- if data_a.principal_def_id() == data_b.principal_def_id() {
+ let b_principal_def_id = data_b.principal_def_id();
+ if data_a.principal_def_id() == b_principal_def_id || b_principal_def_id.is_none() {
+ // A NOP cast that doesn't actually change anything, should be allowed even with invalid vtables.
debug_assert!(
validate_trivial_unsize(fx.tcx, data_a, data_b),
"NOP unsize vtable changed principal trait ref: {data_a} -> {data_b}"
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index d91c0f0790d9d..f3d9a7d37e6cc 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -147,7 +147,7 @@ pub fn validate_trivial_unsize<'tcx>(
infcx.leak_check(universe, None).is_ok()
})
}
- (None, None) => true,
+ (_, None) => true,
_ => false,
}
}
@@ -175,7 +175,8 @@ fn unsized_info<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
{
let old_info =
old_info.expect("unsized_info: missing old info for trait upcasting coercion");
- if data_a.principal_def_id() == data_b.principal_def_id() {
+ let b_principal_def_id = data_b.principal_def_id();
+ if data_a.principal_def_id() == b_principal_def_id || b_principal_def_id.is_none() {
// Codegen takes advantage of the additional assumption, where if the
// principal trait def id of what's being casted doesn't change,
// then we don't need to adjust the vtable at all. This
diff --git a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
index 5828b2ecf34d5..2cbed0bceb2d9 100644
--- a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
@@ -785,7 +785,8 @@ where
let mut responses = vec![];
// If the principal def ids match (or are both none), then we're not doing
// trait upcasting. We're just removing auto traits (or shortening the lifetime).
- if a_data.principal_def_id() == b_data.principal_def_id() {
+ let b_principal_def_id = b_data.principal_def_id();
+ if a_data.principal_def_id() == b_principal_def_id || b_principal_def_id.is_none() {
responses.extend(self.consider_builtin_upcast_to_principal(
goal,
CandidateSource::BuiltinImpl(BuiltinImplSource::Misc),
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index 52048ca79f92f..aa313a526c1db 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -1018,7 +1018,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// #2 (region bounds).
let principal_def_id_a = a_data.principal_def_id();
let principal_def_id_b = b_data.principal_def_id();
- if principal_def_id_a == principal_def_id_b {
+ if principal_def_id_a == principal_def_id_b || principal_def_id_b.is_none() {
// We may upcast to auto traits that are either explicitly listed in
// the object type's bounds, or implied by the principal trait ref's
// supertraits.
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index cc5c7532b5053..0ba3b4e6e5518 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -1153,6 +1153,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// We already checked the compatibility of auto traits within `assemble_candidates_for_unsizing`.
let iter = data_a
.principal()
+ .filter(|_| {
+ // optionally drop the principal, if we're unsizing to no principal
+ data_b.principal().is_some()
+ })
.map(|b| b.map_bound(ty::ExistentialPredicate::Trait))
.into_iter()
.chain(
diff --git a/tests/ui/impl-trait/unsized_coercion5.next.stderr b/tests/ui/impl-trait/unsized_coercion5.next.stderr
deleted file mode 100644
index 5644ac7ab04bc..0000000000000
--- a/tests/ui/impl-trait/unsized_coercion5.next.stderr
+++ /dev/null
@@ -1,14 +0,0 @@
-error[E0308]: mismatched types
- --> $DIR/unsized_coercion5.rs:16:32
- |
-LL | let y: Box<dyn Send> = x as Box<dyn Trait + Send>;
- | ------------- ^^^^^^^^^^^^^^^^^^^^^^^^^^ expected trait `Send`, found trait `Trait + Send`
- | |
- | expected due to this
- |
- = note: expected struct `Box<dyn Send>`
- found struct `Box<dyn Trait + Send>`
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/impl-trait/unsized_coercion5.old.stderr b/tests/ui/impl-trait/unsized_coercion5.old.stderr
index 06ad54b1f1d8b..e56c026b037c6 100644
--- a/tests/ui/impl-trait/unsized_coercion5.old.stderr
+++ b/tests/ui/impl-trait/unsized_coercion5.old.stderr
@@ -1,16 +1,5 @@
-error[E0308]: mismatched types
- --> $DIR/unsized_coercion5.rs:16:32
- |
-LL | let y: Box<dyn Send> = x as Box<dyn Trait + Send>;
- | ------------- ^^^^^^^^^^^^^^^^^^^^^^^^^^ expected trait `Send`, found trait `Trait + Send`
- | |
- | expected due to this
- |
- = note: expected struct `Box<dyn Send>`
- found struct `Box<dyn Trait + Send>`
-
error[E0277]: the size for values of type `impl Trait + ?Sized` cannot be known at compilation time
- --> $DIR/unsized_coercion5.rs:16:32
+ --> $DIR/unsized_coercion5.rs:17:32
|
LL | let y: Box<dyn Send> = x as Box<dyn Trait + Send>;
| ^ doesn't have a size known at compile-time
@@ -18,7 +7,6 @@ LL | let y: Box<dyn Send> = x as Box<dyn Trait + Send>;
= help: the trait `Sized` is not implemented for `impl Trait + ?Sized`
= note: required for the cast from `Box<impl Trait + ?Sized>` to `Box<dyn Trait + Send>`
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
-Some errors have detailed explanations: E0277, E0308.
-For more information about an error, try `rustc --explain E0277`.
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/impl-trait/unsized_coercion5.rs b/tests/ui/impl-trait/unsized_coercion5.rs
index 85d313caa1355..81f8a6afe9ac1 100644
--- a/tests/ui/impl-trait/unsized_coercion5.rs
+++ b/tests/ui/impl-trait/unsized_coercion5.rs
@@ -3,6 +3,7 @@
//@ revisions: next old
//@[next] compile-flags: -Znext-solver
+//@[next] check-pass
#![feature(trait_upcasting)]
@@ -15,7 +16,6 @@ fn hello() -> Box<impl Trait + ?Sized> {
let x = hello();
let y: Box<dyn Send> = x as Box<dyn Trait + Send>;
//[old]~^ ERROR: the size for values of type `impl Trait + ?Sized` cannot be know
- //~^^ ERROR: mismatched types
}
Box::new(1u32)
}
diff --git a/tests/ui/traits/dyn-drop-principal.rs b/tests/ui/traits/dyn-drop-principal.rs
new file mode 100644
index 0000000000000..eeff0550fcbe3
--- /dev/null
+++ b/tests/ui/traits/dyn-drop-principal.rs
@@ -0,0 +1,62 @@
+//@ run-pass
+//@ check-run-results
+
+use std::any::Any;
+
+const fn yeet_principal(x: Box<dyn Any + Send>) -> Box<dyn Send> {
+ x
+}
+
+trait Bar: Send + Sync {}
+
+impl<T: Send + Sync> Bar for T {}
+
+const fn yeet_principal_2(x: Box<dyn Bar>) -> Box<dyn Send> {
+ x
+}
+
+struct CallMe<F: FnOnce()>(Option<F>);
+
+impl<F: FnOnce()> CallMe<F> {
+ fn new(f: F) -> Self {
+ CallMe(Some(f))
+ }
+}
+
+impl<F: FnOnce()> Drop for CallMe<F> {
+ fn drop(&mut self) {
+ (self.0.take().unwrap())();
+ }
+}
+
+fn goodbye() {
+ println!("goodbye");
+}
+
+fn main() {
+ let x = Box::new(CallMe::new(goodbye)) as Box<dyn Any + Send>;
+ let y = yeet_principal(x);
+ println!("before");
+ drop(y);
+
+ let x = Box::new(CallMe::new(goodbye)) as Box<dyn Bar>;
+ let y = yeet_principal_2(x);
+ println!("before");
+ drop(y);
+}
+
+// Test that upcast works in `const`
+
+const fn yeet_principal_3(x: &(dyn Any + Send + Sync)) -> &(dyn Send + Sync) {
+ x
+}
+
+#[used]
+pub static FOO: &(dyn Send + Sync) = yeet_principal_3(&false);
+
+const fn yeet_principal_4(x: &dyn Bar) -> &(dyn Send + Sync) {
+ x
+}
+
+#[used]
+pub static BAR: &(dyn Send + Sync) = yeet_principal_4(&false);
diff --git a/tests/ui/traits/dyn-drop-principal.run.stdout b/tests/ui/traits/dyn-drop-principal.run.stdout
new file mode 100644
index 0000000000000..edd99a114a112
--- /dev/null
+++ b/tests/ui/traits/dyn-drop-principal.run.stdout
@@ -0,0 +1,4 @@
+before
+goodbye
+before
+goodbye
From c4bce0b8b13f2ae39bfd01e55bf98a556b2d703f Mon Sep 17 00:00:00 2001
From: Jules Bertholet <julesbertholet@quoi.xyz>
Date: Wed, 10 Jul 2024 13:00:36 -0400
Subject: [PATCH 2/2] Add more tests
---
src/tools/miri/tests/pass/dyn-upcast.rs | 51 +++++++++++++++++++
src/tools/miri/tests/pass/dyn-upcast.stdout | 4 ++
tests/ui/traits/dyn-drop-principal.rs | 8 ++-
tests/ui/traits/dyn-star-drop-principal.rs | 12 +++++
.../ui/traits/dyn-star-drop-principal.stderr | 11 ++++
5 files changed, 85 insertions(+), 1 deletion(-)
create mode 100644 src/tools/miri/tests/pass/dyn-upcast.stdout
create mode 100644 tests/ui/traits/dyn-star-drop-principal.rs
create mode 100644 tests/ui/traits/dyn-star-drop-principal.stderr
diff --git a/src/tools/miri/tests/pass/dyn-upcast.rs b/src/tools/miri/tests/pass/dyn-upcast.rs
index ff995f38196fa..306e9ab9c6715 100644
--- a/src/tools/miri/tests/pass/dyn-upcast.rs
+++ b/src/tools/miri/tests/pass/dyn-upcast.rs
@@ -9,6 +9,7 @@ fn main() {
struct_();
replace_vptr();
vtable_nop_cast();
+ drop_principal();
}
fn vtable_nop_cast() {
@@ -430,3 +431,53 @@ fn replace_vptr() {
let s = S(42);
invoke_outer(&s);
}
+
+fn drop_principal() {
+ use std::{alloc::Layout, any::Any};
+
+ const fn yeet_principal(x: Box<dyn Any + Send>) -> Box<dyn Send> {
+ x
+ }
+
+ trait Bar: Send + Sync {}
+
+ impl<T: Send + Sync> Bar for T {}
+
+ const fn yeet_principal_2(x: Box<dyn Bar>) -> Box<dyn Send> {
+ x
+ }
+
+ struct CallMe<F: FnOnce()>(Option<F>);
+
+ impl<F: FnOnce()> CallMe<F> {
+ fn new(f: F) -> Self {
+ CallMe(Some(f))
+ }
+ }
+
+ impl<F: FnOnce()> Drop for CallMe<F> {
+ fn drop(&mut self) {
+ (self.0.take().unwrap())();
+ }
+ }
+
+ fn goodbye() {
+ println!("goodbye");
+ }
+
+ let x = Box::new(CallMe::new(goodbye)) as Box<dyn Any + Send>;
+ let x_layout = Layout::for_value(&*x);
+ let y = yeet_principal(x);
+ let y_layout = Layout::for_value(&*y);
+ assert_eq!(x_layout, y_layout);
+ println!("before");
+ drop(y);
+
+ let x = Box::new(CallMe::new(goodbye)) as Box<dyn Bar>;
+ let x_layout = Layout::for_value(&*x);
+ let y = yeet_principal_2(x);
+ let y_layout = Layout::for_value(&*y);
+ assert_eq!(x_layout, y_layout);
+ println!("before");
+ drop(y);
+}
diff --git a/src/tools/miri/tests/pass/dyn-upcast.stdout b/src/tools/miri/tests/pass/dyn-upcast.stdout
new file mode 100644
index 0000000000000..edd99a114a112
--- /dev/null
+++ b/src/tools/miri/tests/pass/dyn-upcast.stdout
@@ -0,0 +1,4 @@
+before
+goodbye
+before
+goodbye
diff --git a/tests/ui/traits/dyn-drop-principal.rs b/tests/ui/traits/dyn-drop-principal.rs
index eeff0550fcbe3..c233127e43d2d 100644
--- a/tests/ui/traits/dyn-drop-principal.rs
+++ b/tests/ui/traits/dyn-drop-principal.rs
@@ -1,7 +1,7 @@
//@ run-pass
//@ check-run-results
-use std::any::Any;
+use std::{alloc::Layout, any::Any};
const fn yeet_principal(x: Box<dyn Any + Send>) -> Box<dyn Send> {
x
@@ -35,12 +35,18 @@ fn goodbye() {
fn main() {
let x = Box::new(CallMe::new(goodbye)) as Box<dyn Any + Send>;
+ let x_layout = Layout::for_value(&*x);
let y = yeet_principal(x);
+ let y_layout = Layout::for_value(&*y);
+ assert_eq!(x_layout, y_layout);
println!("before");
drop(y);
let x = Box::new(CallMe::new(goodbye)) as Box<dyn Bar>;
+ let x_layout = Layout::for_value(&*x);
let y = yeet_principal_2(x);
+ let y_layout = Layout::for_value(&*y);
+ assert_eq!(x_layout, y_layout);
println!("before");
drop(y);
}
diff --git a/tests/ui/traits/dyn-star-drop-principal.rs b/tests/ui/traits/dyn-star-drop-principal.rs
new file mode 100644
index 0000000000000..1ad99070339ad
--- /dev/null
+++ b/tests/ui/traits/dyn-star-drop-principal.rs
@@ -0,0 +1,12 @@
+#![feature(dyn_star)]
+#![allow(incomplete_features)]
+
+trait Trait {}
+impl Trait for usize {}
+
+fn main() {
+ // We allow &dyn Trait + Send -> &dyn Send (i.e. dropping principal),
+ // but we don't (currently?) allow the same for dyn*
+ let x: dyn* Trait + Send = 1usize;
+ x as dyn* Send; //~ error: `dyn* Trait + Send` needs to have the same ABI as a pointer
+}
diff --git a/tests/ui/traits/dyn-star-drop-principal.stderr b/tests/ui/traits/dyn-star-drop-principal.stderr
new file mode 100644
index 0000000000000..721ae7e191ef0
--- /dev/null
+++ b/tests/ui/traits/dyn-star-drop-principal.stderr
@@ -0,0 +1,11 @@
+error[E0277]: `dyn* Trait + Send` needs to have the same ABI as a pointer
+ --> $DIR/dyn-star-drop-principal.rs:11:5
+ |
+LL | x as dyn* Send;
+ | ^ `dyn* Trait + Send` needs to be a pointer-like type
+ |
+ = help: the trait `PointerLike` is not implemented for `dyn* Trait + Send`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.