From a2479523c58c1a4f0053e18d5fbd2d3aeb4a929a Mon Sep 17 00:00:00 2001 From: David Tolnay Date: Wed, 18 Jan 2023 22:43:05 -0800 Subject: [PATCH] Disallow impl autotrait for trait object --- compiler/rustc_data_structures/src/sync.rs | 4 +- .../src/coherence/orphan.rs | 121 ++++++++++++------ ...ce-impl-trait-for-marker-trait-negative.rs | 23 ++-- ...mpl-trait-for-marker-trait-negative.stderr | 42 +++++- ...ce-impl-trait-for-marker-trait-positive.rs | 23 ++-- ...mpl-trait-for-marker-trait-positive.stderr | 42 +++++- 6 files changed, 188 insertions(+), 67 deletions(-) diff --git a/compiler/rustc_data_structures/src/sync.rs b/compiler/rustc_data_structures/src/sync.rs index ed5341c40ef08..ad71dcdf9d953 100644 --- a/compiler/rustc_data_structures/src/sync.rs +++ b/compiler/rustc_data_structures/src/sync.rs @@ -31,8 +31,8 @@ cfg_if! { pub auto trait Send {} pub auto trait Sync {} - impl Send for T {} - impl Sync for T {} + impl Send for T {} + impl Sync for T {} #[macro_export] macro_rules! rustc_erase_owner { diff --git a/compiler/rustc_hir_analysis/src/coherence/orphan.rs b/compiler/rustc_hir_analysis/src/coherence/orphan.rs index 0d070f3d118e0..f06612059b84c 100644 --- a/compiler/rustc_hir_analysis/src/coherence/orphan.rs +++ b/compiler/rustc_hir_analysis/src/coherence/orphan.rs @@ -86,7 +86,7 @@ fn do_orphan_check_impl<'tcx>( // struct B { } // impl Foo for A { } // impl Foo for B { } - // impl !Send for (A, B) { } + // impl !Foo for (A, B) { } // ``` // // This final impl is legal according to the orphan @@ -99,50 +99,93 @@ fn do_orphan_check_impl<'tcx>( tcx.trait_is_auto(trait_def_id) ); - if tcx.trait_is_auto(trait_def_id) && !trait_def_id.is_local() { + if tcx.trait_is_auto(trait_def_id) { let self_ty = trait_ref.self_ty(); - let opt_self_def_id = match *self_ty.kind() { - ty::Adt(self_def, _) => Some(self_def.did()), - ty::Foreign(did) => Some(did), - _ => None, - }; + let self_ty_kind = self_ty.kind(); - let msg = match opt_self_def_id { - // We only want to permit nominal types, but not *all* nominal types. - // They must be local to the current crate, so that people - // can't do `unsafe impl Send for Rc` or - // `impl !Send for Box`. - Some(self_def_id) => { - if self_def_id.is_local() { - None - } else { - Some(( - format!( - "cross-crate traits with a default impl, like `{}`, \ - can only be implemented for a struct/enum type \ - defined in the current crate", - tcx.def_path_str(trait_def_id) - ), - "can't implement cross-crate trait for type in another crate", - )) + if trait_def_id.is_local() { + // If the auto-trait is local, almost anything goes. + // + // impl MyAuto for Rc {} // okay + // impl !MyAuto for *const T {} // okay + // impl MyAuto for T {} // okay + // + // But there is one important exception: implementing for a trait + // object is not allowed. + // + // impl MyAuto for dyn Trait {} // NOT OKAY + // impl MyAuto for T {} // NOT OKAY + // + let problematic_kind = match self_ty_kind { + ty::Dynamic(..) => Some("trait object"), + ty::Param(..) if !self_ty.is_sized(tcx, tcx.param_env(def_id)) => { + Some("generic type") } + _ => None, + }; + + if let Some(problematic_kind) = problematic_kind { + let msg = format!( + "traits with a default impl, like `{trait}`, \ + cannot be implemented for {problematic_kind} `{self_ty}`", + trait = tcx.def_path_str(trait_def_id), + ); + let label = format!( + "a trait object implements `{trait}` if and only if `{trait}` \ + is one of the trait object's trait bounds", + trait = tcx.def_path_str(trait_def_id), + ); + let reported = struct_span_err!(tcx.sess, sp, E0321, "{}", msg).note(label).emit(); + return Err(reported); } - _ => Some(( - format!( - "cross-crate traits with a default impl, like `{}`, can \ + } else { + // If the auto-trait is not local, it must only be getting + // implemented for a nominal type, and specifically one local to the + // current crate. + // + // impl Sync for MyStruct {} // okay + // + // impl Sync for Rc {} // NOT OKAY + // + let opt_self_def_id = match *self_ty_kind { + ty::Adt(self_def, _) => Some(self_def.did()), + ty::Foreign(did) => Some(did), + _ => None, + }; + + let msg = match opt_self_def_id { + Some(self_def_id) => { + if self_def_id.is_local() { + None + } else { + Some(( + format!( + "cross-crate traits with a default impl, like `{}`, \ + can only be implemented for a struct/enum type \ + defined in the current crate", + tcx.def_path_str(trait_def_id) + ), + "can't implement cross-crate trait for type in another crate", + )) + } + } + None => Some(( + format!( + "cross-crate traits with a default impl, like `{}`, can \ only be implemented for a struct/enum type, not `{}`", - tcx.def_path_str(trait_def_id), - self_ty - ), - "can't implement cross-crate trait with a default impl for \ - non-struct/enum type", - )), - }; + tcx.def_path_str(trait_def_id), + self_ty + ), + "can't implement cross-crate trait with a default impl for \ + non-struct/enum type", + )), + }; - if let Some((msg, label)) = msg { - let reported = - struct_span_err!(tcx.sess, sp, E0321, "{}", msg).span_label(sp, label).emit(); - return Err(reported); + if let Some((msg, label)) = msg { + let reported = + struct_span_err!(tcx.sess, sp, E0321, "{}", msg).span_label(sp, label).emit(); + return Err(reported); + } } } diff --git a/tests/ui/coherence/coherence-impl-trait-for-marker-trait-negative.rs b/tests/ui/coherence/coherence-impl-trait-for-marker-trait-negative.rs index 50d9a480ad1e5..98f1558b7ffe1 100644 --- a/tests/ui/coherence/coherence-impl-trait-for-marker-trait-negative.rs +++ b/tests/ui/coherence/coherence-impl-trait-for-marker-trait-negative.rs @@ -12,19 +12,26 @@ auto trait Marker2 {} trait Object: Marker1 {} // A supertrait marker is illegal... -impl !Marker1 for dyn Object + Marker2 { } //~ ERROR E0371 +impl !Marker1 for dyn Object + Marker2 {} //~ ERROR E0371 + //~^ ERROR 0321 // ...and also a direct component. -impl !Marker2 for dyn Object + Marker2 { } //~ ERROR E0371 - -// But implementing a marker if it is not present is OK. -impl !Marker2 for dyn Object {} // OK +impl !Marker2 for dyn Object + Marker2 {} //~ ERROR E0371 + //~^ ERROR 0321 // A non-principal trait-object type is orphan even in its crate. impl !Send for dyn Marker2 {} //~ ERROR E0117 -// And impl'ing a remote marker for a local trait object is forbidden -// by one of these special orphan-like rules. +// Implementing a marker for a local trait object is forbidden by a special +// orphan-like rule. +impl !Marker2 for dyn Object {} //~ ERROR E0321 impl !Send for dyn Object {} //~ ERROR E0321 impl !Send for dyn Object + Marker2 {} //~ ERROR E0321 -fn main() { } +// Blanket impl that applies to dyn Object is equally problematic. +auto trait Marker3 {} +impl !Marker3 for T {} //~ ERROR E0321 + +auto trait Marker4 {} +impl !Marker4 for T {} // okay + +fn main() {} diff --git a/tests/ui/coherence/coherence-impl-trait-for-marker-trait-negative.stderr b/tests/ui/coherence/coherence-impl-trait-for-marker-trait-negative.stderr index c364c707ff9ea..ea38afc40ce80 100644 --- a/tests/ui/coherence/coherence-impl-trait-for-marker-trait-negative.stderr +++ b/tests/ui/coherence/coherence-impl-trait-for-marker-trait-negative.stderr @@ -1,17 +1,41 @@ error[E0371]: the object type `(dyn Object + Marker2 + 'static)` automatically implements the trait `Marker1` --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:15:1 | -LL | impl !Marker1 for dyn Object + Marker2 { } +LL | impl !Marker1 for dyn Object + Marker2 {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `(dyn Object + Marker2 + 'static)` automatically implements trait `Marker1` +error[E0321]: traits with a default impl, like `Marker1`, cannot be implemented for trait object `(dyn Object + Marker2 + 'static)` + --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:15:1 + | +LL | impl !Marker1 for dyn Object + Marker2 {} + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: a trait object implements `Marker1` if and only if `Marker1` is one of the trait object's trait bounds + error[E0371]: the object type `(dyn Object + Marker2 + 'static)` automatically implements the trait `Marker2` - --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:17:1 + --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:18:1 | -LL | impl !Marker2 for dyn Object + Marker2 { } +LL | impl !Marker2 for dyn Object + Marker2 {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `(dyn Object + Marker2 + 'static)` automatically implements trait `Marker2` +error[E0321]: traits with a default impl, like `Marker2`, cannot be implemented for trait object `(dyn Object + Marker2 + 'static)` + --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:18:1 + | +LL | impl !Marker2 for dyn Object + Marker2 {} + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: a trait object implements `Marker2` if and only if `Marker2` is one of the trait object's trait bounds + +error[E0321]: traits with a default impl, like `Marker2`, cannot be implemented for trait object `(dyn Object + 'static)` + --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:26:1 + | +LL | impl !Marker2 for dyn Object {} + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: a trait object implements `Marker2` if and only if `Marker2` is one of the trait object's trait bounds + error[E0117]: only traits defined in the current crate can be implemented for arbitrary types - --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:23:1 + --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:22:1 | LL | impl !Send for dyn Marker2 {} | ^^^^^^^^^^^^^^^----------- @@ -33,7 +57,15 @@ error[E0321]: cross-crate traits with a default impl, like `Send`, can only be i LL | impl !Send for dyn Object + Marker2 {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't implement cross-crate trait with a default impl for non-struct/enum type -error: aborting due to 5 previous errors +error[E0321]: traits with a default impl, like `Marker3`, cannot be implemented for generic type `T` + --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:32:1 + | +LL | impl !Marker3 for T {} + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: a trait object implements `Marker3` if and only if `Marker3` is one of the trait object's trait bounds + +error: aborting due to 9 previous errors Some errors have detailed explanations: E0117, E0321, E0371. For more information about an error, try `rustc --explain E0117`. diff --git a/tests/ui/coherence/coherence-impl-trait-for-marker-trait-positive.rs b/tests/ui/coherence/coherence-impl-trait-for-marker-trait-positive.rs index faac6d983f31e..db2e2b4509a2a 100644 --- a/tests/ui/coherence/coherence-impl-trait-for-marker-trait-positive.rs +++ b/tests/ui/coherence/coherence-impl-trait-for-marker-trait-positive.rs @@ -12,19 +12,26 @@ auto trait Marker2 {} trait Object: Marker1 {} // A supertrait marker is illegal... -impl Marker1 for dyn Object + Marker2 { } //~ ERROR E0371 +impl Marker1 for dyn Object + Marker2 {} //~ ERROR E0371 + //~^ ERROR E0321 // ...and also a direct component. -impl Marker2 for dyn Object + Marker2 { } //~ ERROR E0371 - -// But implementing a marker if it is not present is OK. -impl Marker2 for dyn Object {} // OK +impl Marker2 for dyn Object + Marker2 {} //~ ERROR E0371 + //~^ ERROR E0321 // A non-principal trait-object type is orphan even in its crate. unsafe impl Send for dyn Marker2 {} //~ ERROR E0117 -// And impl'ing a remote marker for a local trait object is forbidden -// by one of these special orphan-like rules. +// Implementing a marker for a local trait object is forbidden by a special +// orphan-like rule. +impl Marker2 for dyn Object {} //~ ERROR E0321 unsafe impl Send for dyn Object {} //~ ERROR E0321 unsafe impl Send for dyn Object + Marker2 {} //~ ERROR E0321 -fn main() { } +// Blanket impl that applies to dyn Object is equally problematic. +auto trait Marker3 {} +impl Marker3 for T {} //~ ERROR E0321 + +auto trait Marker4 {} +impl Marker4 for T {} // okay + +fn main() {} diff --git a/tests/ui/coherence/coherence-impl-trait-for-marker-trait-positive.stderr b/tests/ui/coherence/coherence-impl-trait-for-marker-trait-positive.stderr index b80429794f92c..2a8713bc32794 100644 --- a/tests/ui/coherence/coherence-impl-trait-for-marker-trait-positive.stderr +++ b/tests/ui/coherence/coherence-impl-trait-for-marker-trait-positive.stderr @@ -1,17 +1,41 @@ error[E0371]: the object type `(dyn Object + Marker2 + 'static)` automatically implements the trait `Marker1` --> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:15:1 | -LL | impl Marker1 for dyn Object + Marker2 { } +LL | impl Marker1 for dyn Object + Marker2 {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `(dyn Object + Marker2 + 'static)` automatically implements trait `Marker1` +error[E0321]: traits with a default impl, like `Marker1`, cannot be implemented for trait object `(dyn Object + Marker2 + 'static)` + --> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:15:1 + | +LL | impl Marker1 for dyn Object + Marker2 {} + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: a trait object implements `Marker1` if and only if `Marker1` is one of the trait object's trait bounds + error[E0371]: the object type `(dyn Object + Marker2 + 'static)` automatically implements the trait `Marker2` - --> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:17:1 + --> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:18:1 | -LL | impl Marker2 for dyn Object + Marker2 { } +LL | impl Marker2 for dyn Object + Marker2 {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `(dyn Object + Marker2 + 'static)` automatically implements trait `Marker2` +error[E0321]: traits with a default impl, like `Marker2`, cannot be implemented for trait object `(dyn Object + Marker2 + 'static)` + --> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:18:1 + | +LL | impl Marker2 for dyn Object + Marker2 {} + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: a trait object implements `Marker2` if and only if `Marker2` is one of the trait object's trait bounds + +error[E0321]: traits with a default impl, like `Marker2`, cannot be implemented for trait object `(dyn Object + 'static)` + --> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:26:1 + | +LL | impl Marker2 for dyn Object {} + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: a trait object implements `Marker2` if and only if `Marker2` is one of the trait object's trait bounds + error[E0117]: only traits defined in the current crate can be implemented for arbitrary types - --> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:23:1 + --> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:22:1 | LL | unsafe impl Send for dyn Marker2 {} | ^^^^^^^^^^^^^^^^^^^^^----------- @@ -33,7 +57,15 @@ error[E0321]: cross-crate traits with a default impl, like `Send`, can only be i LL | unsafe impl Send for dyn Object + Marker2 {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't implement cross-crate trait with a default impl for non-struct/enum type -error: aborting due to 5 previous errors +error[E0321]: traits with a default impl, like `Marker3`, cannot be implemented for generic type `T` + --> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:32:1 + | +LL | impl Marker3 for T {} + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: a trait object implements `Marker3` if and only if `Marker3` is one of the trait object's trait bounds + +error: aborting due to 9 previous errors Some errors have detailed explanations: E0117, E0321, E0371. For more information about an error, try `rustc --explain E0117`.