Add test for ambiguous associated item

The `#[pyclass]` macro implements `IntoPyObject` for the annotated enum.
When the enum has any of `Error`, `Output` or `Target` as members, this
clashes with the associated types of `IntoPyObject`.

This also happens when deriving `IntoPyObject` directly.

tests/test_compile_error.rs

@@ -67,4 +67,5 @@ fn test_compile_errors() {
     t.compile_fail("tests/ui/duplicate_pymodule_submodule.rs");
     #[cfg(all(not(Py_LIMITED_API), Py_3_11))]
     t.compile_fail("tests/ui/invalid_base_class.rs");
+    t.pass("tests/ui/ambiguous_associated_items.rs");
 }

tests/ui/ambiguous_associated_items.rs

@@ -0,0 +1,25 @@
+use pyo3::prelude::*;
+
+#[pyclass(eq)]
+#[derive(PartialEq)]
+pub enum SimpleItems {
+    Error,
+    Output,
+    Target,
+}
+
+#[pyclass]
+pub enum ComplexItems {
+    Error(PyObject),
+    Output(PyObject),
+    Target(PyObject),
+}
+
+#[derive(IntoPyObject)]
+enum DeriveItems {
+    Error(PyObject),
+    Output(PyObject),
+    Target(PyObject),
+}
+
+fn main() {}