permit negative impls for non-auto traits

src/test/ui/error-codes/E0192.rs

@@ -1,12 +0,0 @@
-#![feature(optin_builtin_traits)]
-
-trait Trait {
-    type Bar;
-}
-
-struct Foo;
-
-impl !Trait for Foo { } //~ ERROR E0192
-
-fn main() {
-}

src/test/ui/error-codes/E0192.stderr

@@ -1,11 +0,0 @@
-error[E0192]: invalid negative impl
-  --> $DIR/E0192.rs:9:6
-   |
-LL | impl !Trait for Foo { }
-   |      ^^^^^^
-   |
-   = note: negative impls are only allowed for auto traits, like `Send` and `Sync`
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0192`.

src/test/ui/specialization/defaultimpl/validation.rs

@@ -8,8 +8,9 @@ default impl S {} //~ ERROR inherent impls cannot be `default`
 
 default unsafe impl Send for S {} //~ ERROR impls of auto traits cannot be default
 default impl !Send for Z {} //~ ERROR impls of auto traits cannot be default
+                            //~^ ERROR negative impls cannot be default impls
 
 trait Tr {}
-default impl !Tr for S {} //~ ERROR invalid negative impl
+default impl !Tr for S {} //~ ERROR negative impls cannot be default impls
 
 fn main() {}

src/test/ui/specialization/defaultimpl/validation.stderr

@@ -24,14 +24,18 @@ LL | default impl !Send for Z {}
    | |
    | default because of this
 
-error[E0192]: invalid negative impl
-  --> $DIR/validation.rs:13:14
+error[E0750]: negative impls cannot be default impls
+  --> $DIR/validation.rs:10:14
+   |
+LL | default impl !Send for Z {}
+   | ^^^^^^^      ^
+
+error[E0750]: negative impls cannot be default impls
+  --> $DIR/validation.rs:14:14
    |
 LL | default impl !Tr for S {}
-   |              ^^^
-   |
-   = note: negative impls are only allowed for auto traits, like `Send` and `Sync`
+   | ^^^^^^^      ^
 
-error: aborting due to 4 previous errors
+error: aborting due to 5 previous errors
 
-For more information about this error, try `rustc --explain E0192`.
+For more information about this error, try `rustc --explain E0750`.

src/test/ui/syntax-trait-polarity.rs

@@ -12,7 +12,6 @@ trait TestTrait {}
 unsafe impl !Send for TestType {}
 //~^ ERROR negative impls cannot be unsafe
 impl !TestTrait for TestType {}
-//~^ ERROR invalid negative impl
 
 struct TestType2<T>(T);
 
@@ -22,6 +21,5 @@ impl<T> !TestType2<T> {}
 unsafe impl<T> !Send for TestType2<T> {}
 //~^ ERROR negative impls cannot be unsafe
 impl<T> !TestTrait for TestType2<T> {}
-//~^ ERROR invalid negative impl
 
 fn main() {}

src/test/ui/syntax-trait-polarity.stderr

@@ -16,7 +16,7 @@ LL | unsafe impl !Send for TestType {}
    | unsafe because of this
 
 error: inherent impls cannot be negative
-  --> $DIR/syntax-trait-polarity.rs:19:10
+  --> $DIR/syntax-trait-polarity.rs:18:10
    |
 LL | impl<T> !TestType2<T> {}
    |         -^^^^^^^^^^^^ inherent impl for this type
@@ -24,7 +24,7 @@ LL | impl<T> !TestType2<T> {}
    |         negative because of this
 
 error[E0198]: negative impls cannot be unsafe
-  --> $DIR/syntax-trait-polarity.rs:22:16
+  --> $DIR/syntax-trait-polarity.rs:21:16
    |
 LL | unsafe impl<T> !Send for TestType2<T> {}
    | ------         -^^^^
@@ -32,23 +32,6 @@ LL | unsafe impl<T> !Send for TestType2<T> {}
    | |              negative because of this
    | unsafe because of this
 
-error[E0192]: invalid negative impl
-  --> $DIR/syntax-trait-polarity.rs:14:6
-   |
-LL | impl !TestTrait for TestType {}
-   |      ^^^^^^^^^^
-   |
-   = note: negative impls are only allowed for auto traits, like `Send` and `Sync`
+error: aborting due to 4 previous errors
 
-error[E0192]: invalid negative impl
-  --> $DIR/syntax-trait-polarity.rs:24:9
-   |
-LL | impl<T> !TestTrait for TestType2<T> {}
-   |         ^^^^^^^^^^
-   |
-   = note: negative impls are only allowed for auto traits, like `Send` and `Sync`
-
-error: aborting due to 6 previous errors
-
-Some errors have detailed explanations: E0192, E0198.
-For more information about an error, try `rustc --explain E0192`.
+For more information about this error, try `rustc --explain E0198`.

src/test/ui/traits/negative-impls/auxiliary/foreign_trait.rs

@@ -0,0 +1,6 @@
+#![feature(optin_builtin_traits)]
+
+pub trait ForeignTrait { }
+
+impl ForeignTrait for u32 { }
+impl !ForeignTrait for String {}

src/test/ui/traits/negative-impls/negated-auto-traits-error.stderr

@@ -1,5 +1,5 @@
 error[E0277]: `dummy::TestType` cannot be sent between threads safely
-  --> $DIR/traits-negative-impls.rs:23:11
+  --> $DIR/negated-auto-traits-error.rs:23:11
    |
 LL | struct Outer<T: Send>(T);
    | ------------------------- required by `Outer`
@@ -10,7 +10,7 @@ LL |     Outer(TestType);
    = help: the trait `std::marker::Send` is not implemented for `dummy::TestType`
 
 error[E0277]: `dummy::TestType` cannot be sent between threads safely
-  --> $DIR/traits-negative-impls.rs:23:5
+  --> $DIR/negated-auto-traits-error.rs:23:5
    |
 LL | struct Outer<T: Send>(T);
    | ------------------------- required by `Outer`
@@ -21,7 +21,7 @@ LL |     Outer(TestType);
    = help: the trait `std::marker::Send` is not implemented for `dummy::TestType`
 
 error[E0277]: `dummy1b::TestType` cannot be sent between threads safely
-  --> $DIR/traits-negative-impls.rs:32:13
+  --> $DIR/negated-auto-traits-error.rs:32:13
    |
 LL | fn is_send<T: Send>(_: T) {}
    |    -------    ---- required by this bound in `is_send`
@@ -32,7 +32,7 @@ LL |     is_send(TestType);
    = help: the trait `std::marker::Send` is not implemented for `dummy1b::TestType`
 
 error[E0277]: `dummy1c::TestType` cannot be sent between threads safely
-  --> $DIR/traits-negative-impls.rs:40:13
+  --> $DIR/negated-auto-traits-error.rs:40:13
    |
 LL | fn is_send<T: Send>(_: T) {}
    |    -------    ---- required by this bound in `is_send`
@@ -44,7 +44,7 @@ LL |     is_send((8, TestType));
    = note: required because it appears within the type `({integer}, dummy1c::TestType)`
 
 error[E0277]: `dummy2::TestType` cannot be sent between threads safely
-  --> $DIR/traits-negative-impls.rs:48:13
+  --> $DIR/negated-auto-traits-error.rs:48:13
    |
 LL | fn is_send<T: Send>(_: T) {}
    |    -------    ---- required by this bound in `is_send`
@@ -60,7 +60,7 @@ LL |     is_send(Box::new(TestType));
    = note: required because it appears within the type `std::boxed::Box<dummy2::TestType>`
 
 error[E0277]: `dummy3::TestType` cannot be sent between threads safely
-  --> $DIR/traits-negative-impls.rs:56:13
+  --> $DIR/negated-auto-traits-error.rs:56:13
    |
 LL | fn is_send<T: Send>(_: T) {}
    |    -------    ---- required by this bound in `is_send`
@@ -74,7 +74,7 @@ LL |     is_send(Box::new(Outer2(TestType)));
    = note: required because it appears within the type `std::boxed::Box<Outer2<dummy3::TestType>>`
 
 error[E0277]: `main::TestType` cannot be sent between threads safely
-  --> $DIR/traits-negative-impls.rs:66:13
+  --> $DIR/negated-auto-traits-error.rs:66:13
    |
 LL | fn is_sync<T: Sync>(_: T) {}
    |    -------    ---- required by this bound in `is_sync`

src/test/ui/traits/negative-impls/negative-default-impls.rs

@@ -0,0 +1,10 @@
+#![feature(optin_builtin_traits)]
+#![feature(specialization)]
+
+trait MyTrait {
+    type Foo;
+}
+
+default impl !MyTrait for u32 {} //~ ERROR negative impls cannot be default impls
+
+fn main() {}

src/test/ui/traits/negative-impls/negative-default-impls.stderr

@@ -0,0 +1,9 @@
+error[E0750]: negative impls cannot be default impls
+  --> $DIR/negative-default-impls.rs:8:14
+   |
+LL | default impl !MyTrait for u32 {}
+   | ^^^^^^^      ^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0750`.

src/test/ui/traits/negative-impls/negative-specializes-positive-item.rs

@@ -0,0 +1,13 @@
+#![feature(specialization)]
+#![feature(optin_builtin_traits)]
+
+// Negative impl for u32 cannot "specialize" the base impl.
+trait MyTrait {
+    fn foo();
+}
+impl<T> MyTrait for T {
+    default fn foo() { }
+}
+impl !MyTrait for u32 { } //~ ERROR conflicting implementations
+
+fn main() { }

src/test/ui/traits/negative-impls/negative-specializes-positive-item.stderr

@@ -0,0 +1,12 @@
+error[E0119]: conflicting implementations of trait `MyTrait` for type `u32`:
+  --> $DIR/negative-specializes-positive-item.rs:11:1
+   |
+LL | impl<T> MyTrait for T {
+   | --------------------- first implementation here
+...
+LL | impl !MyTrait for u32 { }
+   | ^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `u32`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0119`.

src/test/ui/traits/negative-impls/negative-specializes-positive.rs

@@ -0,0 +1,14 @@
+#![feature(specialization)]
+#![feature(optin_builtin_traits)]
+
+// Negative impl for u32 cannot "specialize" the base impl.
+trait MyTrait { }
+impl<T> MyTrait for T { }
+impl !MyTrait for u32 { } //~ ERROR conflicting implementations
+
+// The second impl specializes the first, no error.
+trait MyTrait2 { }
+impl<T> MyTrait2 for T { }
+impl MyTrait2 for u32 { }
+
+fn main() { }

src/test/ui/traits/negative-impls/negative-specializes-positive.stderr

@@ -0,0 +1,11 @@
+error[E0119]: conflicting implementations of trait `MyTrait` for type `u32`:
+  --> $DIR/negative-specializes-positive.rs:7:1
+   |
+LL | impl<T> MyTrait for T { }
+   | --------------------- first implementation here
+LL | impl !MyTrait for u32 { }
+   | ^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `u32`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0119`.

src/test/ui/traits/negative-impls/no-items.rs

@@ -0,0 +1,11 @@
+#![feature(optin_builtin_traits)]
+
+trait MyTrait {
+    type Foo;
+}
+
+impl !MyTrait for u32 {
+    type Foo = i32; //~ ERROR negative impls cannot have any items
+}
+
+fn main() {}

src/test/ui/traits/negative-impls/no-items.stderr

@@ -0,0 +1,9 @@
+error[E0749]: negative impls cannot have any items
+  --> $DIR/no-items.rs:8:5
+   |
+LL |     type Foo = i32;
+   |     ^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0749`.

src/test/ui/traits/negative-impls/pin-unsound-issue-66544-clone.rs

@@ -0,0 +1,26 @@
+use std::cell::Cell;
+use std::marker::PhantomPinned;
+use std::pin::Pin;
+
+struct MyType<'a>(Cell<Option<&'a mut MyType<'a>>>, PhantomPinned);
+
+impl<'a> Clone for &'a mut MyType<'a> { //~ ERROR conflicting implementations
+    fn clone(&self) -> &'a mut MyType<'a> {
+        self.0.replace(None).unwrap()
+    }
+}
+
+
+fn main() {
+    let mut unpinned = MyType(Cell::new(None), PhantomPinned);
+    let bad_addr = &unpinned as *const MyType<'_> as usize;
+    let mut p = Box::pin(MyType(Cell::new(Some(&mut unpinned)), PhantomPinned));
+
+    // p_mut1 is okay: it does not point to the bad_addr
+    let p_mut1: Pin<&mut MyType<'_>> = p.as_mut();
+    assert_ne!(bad_addr, &*p_mut1 as *const _ as usize);
+
+    // but p_mut2 does point to bad_addr! this is unsound
+    let p_mut2: Pin<&mut MyType<'_>> = p_mut1.clone();
+    assert_eq!(bad_addr, &*p_mut2 as *const _ as usize);
+}

src/test/ui/traits/negative-impls/pin-unsound-issue-66544-clone.stderr

@@ -0,0 +1,13 @@
+error[E0119]: conflicting implementations of trait `std::clone::Clone` for type `&mut MyType<'_>`:
+  --> $DIR/pin-unsound-issue-66544-clone.rs:7:1
+   |
+LL | impl<'a> Clone for &'a mut MyType<'a> {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: conflicting implementation in crate `core`:
+           - impl<T> std::clone::Clone for &mut T
+             where T: ?Sized;
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0119`.

src/test/ui/traits/negative-impls/pin-unsound-issue-66544-derefmut.rs

@@ -0,0 +1,33 @@
+// Demonstrate that "rogue" `DerefMut` impls for `&T` are not allowed.
+//
+// https://github.com/rust-lang/rust/issues/66544
+
+use std::cell::Cell;
+use std::marker::PhantomPinned;
+use std::ops::DerefMut;
+use std::pin::Pin;
+
+struct MyType<'a>(Cell<Option<&'a mut MyType<'a>>>, PhantomPinned);
+
+impl<'a> DerefMut for &'a MyType<'a> { //~ ERROR conflicting implementations
+    fn deref_mut(&mut self) -> &mut MyType<'a> {
+        self.0.replace(None).unwrap()
+    }
+}
+
+
+fn main() {
+    let mut unpinned = MyType(Cell::new(None), PhantomPinned);
+    let bad_addr = &unpinned as *const MyType<'_> as usize;
+    let p = Box::pin(MyType(Cell::new(Some(&mut unpinned)), PhantomPinned));
+
+    // p_ref is okay: it does not point to the bad_addr
+    let mut p_ref: Pin<&MyType<'_>> = p.as_ref();
+    assert_ne!(bad_addr, &*p_ref as *const _ as usize);
+
+    // but p_mut does point to bad_addr! this is unsound
+    let p_mut: Pin<&mut MyType<'_>> = p_ref.as_mut();
+    assert_eq!(bad_addr, &*p_mut as *const _ as usize);
+
+    println!("oh no!");
+}

src/test/ui/traits/negative-impls/pin-unsound-issue-66544-derefmut.stderr

@@ -0,0 +1,13 @@
+error[E0119]: conflicting implementations of trait `std::ops::DerefMut` for type `&MyType<'_>`:
+  --> $DIR/pin-unsound-issue-66544-derefmut.rs:12:1
+   |
+LL | impl<'a> DerefMut for &'a MyType<'a> {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: conflicting implementation in crate `core`:
+           - impl<T> std::ops::DerefMut for &T
+             where T: ?Sized;
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0119`.

src/test/ui/traits/negative-impls/positive-specializes-negative.rs

@@ -0,0 +1,9 @@
+#![feature(specialization)]
+#![feature(optin_builtin_traits)]
+
+trait MyTrait { }
+
+impl<T> !MyTrait for T { }
+impl MyTrait for u32 { } //~ ERROR conflicting implementations
+
+fn main() { }

src/test/ui/traits/negative-impls/positive-specializes-negative.stderr

@@ -0,0 +1,11 @@
+error[E0119]: conflicting implementations of trait `MyTrait` for type `u32`:
+  --> $DIR/positive-specializes-negative.rs:7:1
+   |
+LL | impl<T> !MyTrait for T { }
+   | ---------------------- first implementation here
+LL | impl MyTrait for u32 { }
+   | ^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `u32`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0119`.

src/test/ui/traits/negative-impls/rely-on-negative-impl-in-coherence.rs

@@ -0,0 +1,21 @@
+#![feature(optin_builtin_traits)]
+
+// aux-build: foreign_trait.rs
+
+// Test that we cannot implement `LocalTrait` for `String`,
+// even though there is a `String: !ForeignTrait` impl.
+//
+// This may not be the behavior we want long term, but it's the
+// current semantics that we implemented so as to land `!Foo` impls
+// quickly. See internals thread:
+//
+// https://internals.rust-lang.org/t/foo/11587/
+
+extern crate foreign_trait;
+use foreign_trait::ForeignTrait;
+
+trait LocalTrait { }
+impl<T: ForeignTrait> LocalTrait for T { }
+impl LocalTrait for String { } //~ ERROR conflicting implementations
+
+fn main() { }

src/test/ui/traits/negative-impls/rely-on-negative-impl-in-coherence.stderr

@@ -0,0 +1,11 @@
+error[E0119]: conflicting implementations of trait `LocalTrait` for type `std::string::String`:
+  --> $DIR/rely-on-negative-impl-in-coherence.rs:19:1
+   |
+LL | impl<T: ForeignTrait> LocalTrait for T { }
+   | -------------------------------------- first implementation here
+LL | impl LocalTrait for String { }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `std::string::String`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0119`.

src/test/ui/traits/negative-impls/typeck-negative-impls-builtin.rs

@@ -1,12 +1,14 @@
+// run-pass
+
 #![feature(optin_builtin_traits)]
+#![allow(dead_code)]
 
 struct TestType;
 
 trait TestTrait {
-    fn dummy(&self) { }
+    fn dummy(&self) {}
 }
 
 impl !TestTrait for TestType {}
-//~^ ERROR invalid negative impl
 
 fn main() {}

src/test/ui/typeck/typeck-negative-impls-builtin.stderr

@@ -1,11 +0,0 @@
-error[E0192]: invalid negative impl
-  --> $DIR/typeck-negative-impls-builtin.rs:9:6
-   |
-LL | impl !TestTrait for TestType {}
-   |      ^^^^^^^^^^
-   |
-   = note: negative impls are only allowed for auto traits, like `Send` and `Sync`
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0192`.