Add regression test for issue #144888

tests/ui/traits/unhandled-crate-mod-issue-144888.rs

@@ -0,0 +1,30 @@
+// Regression test for <https://github.com/rust-lang/rust/issues/144888>.
+// This used to ICE with `unhandled node Crate(Mod)`.
+
+#![crate_type = "lib"]
+
+struct ActuallySuper;
+
+trait Super<Q> {
+    type Assoc;
+}
+
+trait Dyn {}
+impl<T, U> Dyn for dyn Foo<T, U> + '_ {}
+//~^ ERROR the trait `Foo` is not dyn compatible
+
+trait Foo<T, U>: Super<ActuallySuper, Assoc = T>
+where
+    <Self as Mirror>::Assoc: Super,
+    //~^ ERROR missing generics for trait `Super`
+{
+    fn transmute(&self, t: T) -> <Self as Super>::Assoc;
+    //~^ ERROR missing generics for trait `Super`
+}
+
+trait Mirror {
+    type Assoc: ?Sized;
+}
+
+impl<T: Super<ActuallySuper, Assoc = T>> Mirror for T {}
+//~^ ERROR not all trait items implemented

tests/ui/traits/unhandled-crate-mod-issue-144888.stderr

@@ -0,0 +1,62 @@
+error[E0107]: missing generics for trait `Super`
+  --> $DIR/unhandled-crate-mod-issue-144888.rs:18:30
+   |
+LL |     <Self as Mirror>::Assoc: Super,
+   |                              ^^^^^ expected 1 generic argument
+   |
+note: trait defined here, with 1 generic parameter: `Q`
+  --> $DIR/unhandled-crate-mod-issue-144888.rs:8:7
+   |
+LL | trait Super<Q> {
+   |       ^^^^^ -
+help: add missing generic argument
+   |
+LL |     <Self as Mirror>::Assoc: Super<Q>,
+   |                                   +++
+
+error[E0107]: missing generics for trait `Super`
+  --> $DIR/unhandled-crate-mod-issue-144888.rs:21:43
+   |
+LL |     fn transmute(&self, t: T) -> <Self as Super>::Assoc;
+   |                                           ^^^^^ expected 1 generic argument
+   |
+note: trait defined here, with 1 generic parameter: `Q`
+  --> $DIR/unhandled-crate-mod-issue-144888.rs:8:7
+   |
+LL | trait Super<Q> {
+   |       ^^^^^ -
+help: add missing generic argument
+   |
+LL |     fn transmute(&self, t: T) -> <Self as Super<Q>>::Assoc;
+   |                                                +++
+
+error[E0038]: the trait `Foo` is not dyn compatible
+  --> $DIR/unhandled-crate-mod-issue-144888.rs:13:20
+   |
+LL | impl<T, U> Dyn for dyn Foo<T, U> + '_ {}
+   |                    ^^^^^^^^^^^^^^^^^^ `Foo` is not dyn compatible
+   |
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#dyn-compatibility>
+  --> $DIR/unhandled-crate-mod-issue-144888.rs:21:34
+   |
+LL | trait Foo<T, U>: Super<ActuallySuper, Assoc = T>
+   |       --- this trait is not dyn compatible...
+...
+LL |     fn transmute(&self, t: T) -> <Self as Super>::Assoc;
+   |                                  ^^^^^^^^^^^^^^^^^^^^^^ ...because method `transmute` references the `Self` type in its return type
+   = help: consider moving `transmute` to another trait
+
+error[E0046]: not all trait items implemented, missing: `Assoc`
+  --> $DIR/unhandled-crate-mod-issue-144888.rs:29:1
+   |
+LL |     type Assoc: ?Sized;
+   |     ------------------ `Assoc` from trait
+...
+LL | impl<T: Super<ActuallySuper, Assoc = T>> Mirror for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `Assoc` in implementation
+
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0038, E0046, E0107.
+For more information about an error, try `rustc --explain E0038`.