Private type aliases result in a warning

I have code which looks roughly like this:

type FooBar = foo::Foo<bar::Bar>;

#[unsafe(no_mangle)]
pub unsafe extern "C" fn foo_bar(arg: &Arg) {
    // use `FooBar` inside functions
}

Running cbindgen results in the following warning:

WARN: Cannot find a mangling for generic path GenericPath { ... }. This usually means that a type referenced by this generic was incompatible or not found.

It's possible to work around it by adding /// cbindgen:ignore to the type alias, but I think cbindgen should just ignore such private type aliases automatically.

Reproduce the warning with the private FooBar alias and the cbindgen:ignore workaround shown in the issue. Trace how cbindgen handles private type aliases and generic paths; done means private aliases are ignored automatically without emitting the mangling warning.