Add tests

Author: compiler-errors

tests/ui/traits/object/coherence-with-implied-auto-traits.rs

@@ -0,0 +1,9 @@
+trait Foo: Send {}
+
+trait Bar {}
+
+impl Bar for dyn Foo {}
+impl Bar for dyn Foo + Send {}
+//~^ ERROR conflicting implementations of trait `Bar` for type `(dyn Foo + 'static)`
+
+fn main() {}

tests/ui/traits/object/coherence-with-implied-auto-traits.stderr

@@ -0,0 +1,11 @@
+error[E0119]: conflicting implementations of trait `Bar` for type `(dyn Foo + 'static)`
+  --> $DIR/coherence-with-implied-auto-traits.rs:6:1
+   |
+LL | impl Bar for dyn Foo {}
+   | -------------------- first implementation here
+LL | impl Bar for dyn Foo + Send {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn Foo + 'static)`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0119`.

tests/ui/traits/object/upcasting-with-implied-auto-traits.rs

@@ -0,0 +1,13 @@
+// check-pass
+// revisions: current next
+//[next] compile-flags: -Znext-solver
+
+trait Target {}
+trait Source: Send + Target {}
+
+fn upcast(x: &dyn Source) -> &(dyn Target + Send) { x }
+
+fn same(x: &dyn Source) -> &(dyn Source + Send) { x }
+// ^ This isn't upcasting, just passing dyn through unchanged.
+
+fn main() {}