2 files changed, 76 insertions, 0 deletions
diff --git a/src/test/ui/issues/issue-78372.rs b/src/test/ui/issues/issue-78372.rs
new file mode 100644
index 00000000000..77a8c92c81c
--- /dev/null
+++ b/src/test/ui/issues/issue-78372.rs
@@ -0,0 +1,14 @@
+use std::ops::DispatchFromDyn; //~ ERROR use of unstable library feature 'dispatch_from_dyn'
+struct Smaht<T, MISC>(PhantomData); //~ ERROR cannot find type `PhantomData` in this scope
+impl<T> DispatchFromDyn<Smaht<U, MISC>> for T {} //~ ERROR cannot find type `U` in this scope
+//~^ ERROR cannot find type `MISC` in this scope
+//~| ERROR use of unstable library feature 'dispatch_from_dyn'
+//~| ERROR the trait `DispatchFromDyn` may only be implemented for a coercion between structures
+//~| ERROR type parameter `T` must be covered by another type when it appears before the first
+trait Foo: X<u32> {}
+trait X<T> {
+    fn foo(self: Smaht<Self, T>);
+}
+trait Marker {}
+impl Marker for dyn Foo {}
+fn main() {}
diff --git a/src/test/ui/issues/issue-78372.stderr b/src/test/ui/issues/issue-78372.stderr
new file mode 100644
index 00000000000..9267e838cea
--- /dev/null
+++ b/src/test/ui/issues/issue-78372.stderr
@@ -0,0 +1,62 @@
+error[E0412]: cannot find type `PhantomData` in this scope
+  --> $DIR/issue-78372.rs:2:23
+   |
+LL | struct Smaht<T, MISC>(PhantomData);
+   |                       ^^^^^^^^^^^ not found in this scope
+   |
+help: consider importing this struct
+   |
+LL | use std::marker::PhantomData;
+   |
+
+error[E0412]: cannot find type `U` in this scope
+  --> $DIR/issue-78372.rs:3:31
+   |
+LL | impl<T> DispatchFromDyn<Smaht<U, MISC>> for T {}
+   |      -                        ^ help: a type parameter with a similar name exists: `T`
+   |      |
+   |      similarly named type parameter `T` defined here
+
+error[E0412]: cannot find type `MISC` in this scope
+  --> $DIR/issue-78372.rs:3:34
+   |
+LL | impl<T> DispatchFromDyn<Smaht<U, MISC>> for T {}
+   |       -                          ^^^^ not found in this scope
+   |       |
+   |       help: you might be missing a type parameter: `, MISC`
+
+error[E0658]: use of unstable library feature 'dispatch_from_dyn'
+  --> $DIR/issue-78372.rs:1:5
+   |
+LL | use std::ops::DispatchFromDyn;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(dispatch_from_dyn)]` to the crate attributes to enable
+
+error[E0658]: use of unstable library feature 'dispatch_from_dyn'
+  --> $DIR/issue-78372.rs:3:9
+   |
+LL | impl<T> DispatchFromDyn<Smaht<U, MISC>> for T {}
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(dispatch_from_dyn)]` to the crate attributes to enable
+
+error[E0378]: the trait `DispatchFromDyn` may only be implemented for a coercion between structures
+  --> $DIR/issue-78372.rs:3:1
+   |
+LL | impl<T> DispatchFromDyn<Smaht<U, MISC>> for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0210]: type parameter `T` must be covered by another type when it appears before the first local type (`Smaht<[type error], [type error]>`)
+  --> $DIR/issue-78372.rs:3:6
+   |
+LL | impl<T> DispatchFromDyn<Smaht<U, MISC>> for T {}
+   |      ^ type parameter `T` must be covered by another type when it appears before the first local type (`Smaht<[type error], [type error]>`)
+   |
+   = note: implementing a foreign trait is only possible if at least one of the types for which it is implemented is local, and no uncovered type parameters appear before that first local type
+   = note: in this case, 'before' refers to the following order: `impl<..> ForeignTrait<T1, ..., Tn> for T0`, where `T0` is the first and `Tn` is the last
+
+error: aborting due to 7 previous errors
+
+Some errors have detailed explanations: E0210, E0378, E0412, E0658.
+For more information about an error, try `rustc --explain E0210`.