add test for issue 36007

Author: Rageking8

src/test/ui/coercion/issue-36007.rs

@@ -0,0 +1,20 @@
+// check-pass
+#![feature(coerce_unsized, unsize)]
+
+use std::marker::Unsize;
+use std::ops::CoerceUnsized;
+
+struct Foo<T: ?Sized>(Box<T>);
+
+impl<T> CoerceUnsized<Foo<dyn Baz>> for Foo<T> where T: Unsize<dyn Baz> {}
+
+struct Bar;
+
+trait Baz {}
+
+impl Baz for Bar {}
+
+fn main() {
+    let foo = Foo(Box::new(Bar));
+    let foobar: Foo<Bar> = foo;
+}