RFC-2027: Add tests for new legal syntax and wf/coherence

Author: bovinebuddha

src/test/ui/coherence/coherence-unsafe-trait-object-impl.rs

@@ -0,0 +1,18 @@
+// Check that unsafe trait object do not implement themselves
+// automatically
+
+#![feature(object_safe_for_dispatch)]
+
+trait Trait: Sized {
+    fn call(&self);
+}
+
+fn takes_t<S: Trait>(s: S) {
+    s.call();
+}
+
+fn takes_t_obj(t: &dyn Trait) {
+    takes_t(t); //~ ERROR E0277
+}
+
+fn main() {}

src/test/ui/coherence/coherence-unsafe-trait-object-impl.stderr

@@ -0,0 +1,15 @@
+error[E0277]: the trait bound `&dyn Trait: Trait` is not satisfied
+  --> $DIR/coherence-unsafe-trait-object-impl.rs:15:5
+   |
+LL |     takes_t(t); //~ ERROR E0277
+   |     ^^^^^^^ the trait `Trait` is not implemented for `&dyn Trait`
+   |
+note: required by `takes_t`
+  --> $DIR/coherence-unsafe-trait-object-impl.rs:10:1
+   |
+LL | fn takes_t<S: Trait>(s: S) {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.

src/test/ui/rfc-2027-object-safe-for-dispatch/downcast-unsafe-trait-objects.rs

@@ -0,0 +1,23 @@
+// Check that we if we get ahold of an object unsafe trait
+// object with auto traits and lifetimes, we can downcast it
+//
+// compile-pass
+
+#![feature(object_safe_for_dispatch)]
+
+trait Trait: Sized {}
+
+fn downcast_auto(t: &(dyn Trait + Send)) -> &dyn Trait {
+    t
+}
+
+fn downcast_lifetime<'a, 'b, 't>(t: &'a (dyn Trait + 't))
+                                 -> &'b (dyn Trait + 't)
+where
+    'a: 'b,
+    't: 'a + 'b,
+{
+    t
+}
+
+fn main() {}

src/test/ui/rfc-2027-object-safe-for-dispatch/manual-self-impl-for-unsafe-obj.rs

@@ -0,0 +1,69 @@
+// Check that we can manually implement an object
+// unsafe trait for its trait object
+//
+// run-pass
+
+#![feature(object_safe_for_dispatch)]
+
+trait Bad {
+    fn stat() -> char {
+        'A'
+    }
+    fn virt(&self) -> char {
+        'B'
+    }
+    fn indirect(&self) -> char {
+        Self::stat()
+    }
+}
+
+trait Good {
+    fn good_virt(&self) -> char {
+        panic!()
+    }
+    fn good_indirect(&self) -> char {
+        panic!()
+    }
+}
+
+impl<'a> Bad for dyn Bad + 'a {
+    fn stat() -> char {
+        'C'
+    }
+    fn virt(&self) -> char {
+        'D'
+    }
+}
+
+struct Struct {}
+
+impl Bad for Struct {}
+
+impl Good for Struct {}
+
+fn main() {
+    let s = Struct {};
+
+    let mut res = String::new();
+
+    // Directly call static
+    res.push(Struct::stat()); // "A"
+    res.push(<dyn Bad>::stat()); // "AC"
+
+    let good: &dyn Good = &s;
+
+    // These look similar enough...
+    let bad = unsafe { std::mem::transmute::<&dyn Good, &dyn Bad>(good) };
+
+    // Call virtual
+    res.push(s.virt()); // "ACB"
+    res.push(bad.virt()); // "ACBD"
+
+    // Indirectly call static
+    res.push(s.indirect()); // "ACBDA"
+    res.push(bad.indirect()); // "ACBDAC"
+
+    if &res != "ACBDAC" {
+        panic!();
+    }
+}

src/test/ui/rfc-2027-object-safe-for-dispatch/static-dispatch-unsafe-object.rs

@@ -0,0 +1,37 @@
+// Check that we can statically dispatch methods for object
+// unsafe trait objects, directly and indirectly
+//
+// compile-pass
+
+#![feature(object_safe_for_dispatch)]
+
+trait Statics {
+    fn plain() {}
+    fn generic<T>() {}
+}
+
+trait Trait: Sized {}
+
+impl<'a> Statics for dyn Trait + 'a {}
+
+fn static_poly<T: Statics + ?Sized>() {
+    T::plain();
+    T::generic::<usize>();
+}
+
+fn inferred_poly<T: Statics + ?Sized>(t: &T) {
+    static_poly::<T>();
+    T::plain();
+    T::generic::<usize>();
+}
+
+fn call(t: &dyn Trait) {
+    static_poly::<dyn Trait>();
+    inferred_poly(t);
+}
+
+fn main() {
+    static_poly::<dyn Trait>();
+    <dyn Trait>::plain();
+    <dyn Trait>::generic::<usize>()
+}

src/test/ui/wf/wf-convert-unsafe-trait-obj-box.rs

@@ -0,0 +1,18 @@
+// Check that we do not allow casts or coercions
+// to object unsafe trait objects inside a Box
+
+#![feature(object_safe_for_dispatch)]
+
+trait Trait: Sized {}
+
+struct S;
+
+impl Trait for S {}
+
+fn takes_box(t: Box<dyn Trait>) {}
+
+fn main() {
+    Box::new(S) as Box<dyn Trait>; //~ ERROR E0038
+    let t_box: Box<dyn Trait> = Box::new(S); //~ ERROR E0038
+    takes_box(Box::new(S)); //~ ERROR E0038
+}

src/test/ui/wf/wf-convert-unsafe-trait-obj-box.stderr

@@ -0,0 +1,30 @@
+error[E0038]: the trait `Trait` cannot be made into an object
+  --> $DIR/wf-convert-unsafe-trait-obj-box.rs:16:33
+   |
+LL |     let t_box: Box<dyn Trait> = Box::new(S); //~ ERROR E0038
+   |                                 ^^^^^^^^^^^ the trait `Trait` cannot be made into an object
+   |
+   = note: the trait cannot require that `Self : Sized`
+   = note: required when trying to coerce from type `std::boxed::Box<S>` to type 'std::boxed::Box<dyn Trait>`
+
+error[E0038]: the trait `Trait` cannot be made into an object
+  --> $DIR/wf-convert-unsafe-trait-obj-box.rs:17:15
+   |
+LL |     takes_box(Box::new(S)); //~ ERROR E0038
+   |               ^^^^^^^^^^^ the trait `Trait` cannot be made into an object
+   |
+   = note: the trait cannot require that `Self : Sized`
+   = note: required when trying to coerce from type `std::boxed::Box<S>` to type 'std::boxed::Box<(dyn Trait + 'static)>`
+
+error[E0038]: the trait `Trait` cannot be made into an object
+  --> $DIR/wf-convert-unsafe-trait-obj-box.rs:15:20
+   |
+LL |     Box::new(S) as Box<dyn Trait>; //~ ERROR E0038
+   |                    ^^^^^^^^^^^^^^ the trait `Trait` cannot be made into an object
+   |
+   = note: the trait cannot require that `Self : Sized`
+   = note: required by cast to type 'std::boxed::Box<dyn Trait>'
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0038`.

src/test/ui/wf/wf-convert-unsafe-trait-obj.rs

@@ -0,0 +1,18 @@
+// Check that we do not allow casts or coercions
+// to object unsafe trait objects by ref
+
+#![feature(object_safe_for_dispatch)]
+
+trait Trait: Sized {}
+
+struct S;
+
+impl Trait for S {}
+
+fn takes_trait(t: &dyn Trait) {}
+
+fn main() {
+    &S as &dyn Trait; //~ ERROR E0038
+    let t: &dyn Trait = &S; //~ ERROR E0038
+    takes_trait(&S); //~ ERROR E0038
+}

src/test/ui/wf/wf-convert-unsafe-trait-obj.stderr

@@ -0,0 +1,30 @@
+error[E0038]: the trait `Trait` cannot be made into an object
+  --> $DIR/wf-convert-unsafe-trait-obj.rs:16:25
+   |
+LL |     let t: &dyn Trait = &S; //~ ERROR E0038
+   |                         ^^ the trait `Trait` cannot be made into an object
+   |
+   = note: the trait cannot require that `Self : Sized`
+   = note: required when trying to coerce from type `&S` to type '&dyn Trait`
+
+error[E0038]: the trait `Trait` cannot be made into an object
+  --> $DIR/wf-convert-unsafe-trait-obj.rs:17:17
+   |
+LL |     takes_trait(&S); //~ ERROR E0038
+   |                 ^^ the trait `Trait` cannot be made into an object
+   |
+   = note: the trait cannot require that `Self : Sized`
+   = note: required when trying to coerce from type `&S` to type '&dyn Trait`
+
+error[E0038]: the trait `Trait` cannot be made into an object
+  --> $DIR/wf-convert-unsafe-trait-obj.rs:15:11
+   |
+LL |     &S as &dyn Trait; //~ ERROR E0038
+   |           ^^^^^^^^^^ the trait `Trait` cannot be made into an object
+   |
+   = note: the trait cannot require that `Self : Sized`
+   = note: required by cast to type '&dyn Trait'
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0038`.

src/test/ui/wf/wf-unsafe-trait-obj-match.rs

@@ -0,0 +1,29 @@
+// Check that we do not allow coercions to object
+// unsafe trait objects in match arms
+
+#![feature(object_safe_for_dispatch)]
+
+trait Trait: Sized {}
+
+struct S;
+
+impl Trait for S {}
+
+struct R;
+
+impl Trait for R {}
+
+fn opt() -> Option<()> {
+    Some(())
+}
+
+fn main() {
+    match opt() { //~ ERROR E0308
+        Some(()) => &S,
+        None => &R,
+    }
+    let t: &dyn Trait = match opt() { //~ ERROR E0308
+        Some(()) => &S,
+        None => &R,
+    };
+}

src/test/ui/wf/wf-unsafe-trait-obj-match.stderr

@@ -0,0 +1,27 @@
+error[E0308]: match arms have incompatible types
+  --> $DIR/wf-unsafe-trait-obj-match.rs:23:17
+   |
+LL | /     match opt() { //~ ERROR E0308
+LL | |         Some(()) => &S,
+   | |                     -- this is found to be of type `&S`
+LL | |         None => &R,
+   | |                 ^^ expected struct `S`, found struct `R`
+LL | |     }
+   | |_____- `match` arms have incompatible types
+   |
+   = note: expected type `&S`
+              found type `&R`
+
+error[E0038]: the trait `Trait` cannot be made into an object
+  --> $DIR/wf-unsafe-trait-obj-match.rs:26:21
+   |
+LL |         Some(()) => &S,
+   |                     ^^ the trait `Trait` cannot be made into an object
+   |
+   = note: the trait cannot require that `Self : Sized`
+   = note: required when trying to coerce from type `&S` to type '&dyn Trait`
+
+error: aborting due to 2 previous errors
+
+Some errors occurred: E0038, E0308.
+For more information about an error, try `rustc --explain E0038`.