add regression test for RUST-143222

Author: lolbinarycat

tests/rustdoc/reexport/auxiliary/wrap-unnamable-type.rs

@@ -0,0 +1,12 @@
+pub trait Assoc {
+    type Ty;
+}
+
+pub struct Foo(<Foo as crate::Assoc>::Ty);
+
+const _: () = {
+    impl crate::Assoc for Foo {
+        type Ty = Bar;
+    }
+    pub struct Bar;
+};

tests/rustdoc/reexport/wrapped-unnamble-type-143222.rs

@@ -0,0 +1,12 @@
+//@ compile-flags: -Z normalize-docs --document-private-items -Zunstable-options --show-type-layout
+//@ aux-build:wrap-unnamable-type.rs
+//@ build-aux-docs
+
+#![crate_name = "foo"]
+
+extern crate wrap_unnamable_type as helper;
+//extern crate helper;
+//@ has 'foo/struct.Foo.html'
+//@ !hasraw - '_/struct.Bar.html'
+#[doc(inline)]
+pub use helper::Foo;