Testing instantiation with argument of a type that we didn't generate bindings for

[fitzgen]

Input C/C++ Header

namespace JS {
template <typename a> class Rooted { a b; };
class AutoValueVector : Rooted<int> {
  using Vec = int;
  using c = Rooted<Vec>;
};
}

Bindgen Invocation

Some complicated thing from SM bindings. Will see what more minimal flags required are and report back.

Actual Results

/* automatically generated by rust-bindgen */

#![feature(const_fn)]
pub use self::root::*;
unsafe impl Sync for JSClass {}
unsafe impl Sync for JSFunctionSpec {}
unsafe impl Sync for JSNativeWrapper {}
unsafe impl Sync for JSPropertySpec {}
unsafe impl Sync for JSTypedMethodJitInfo {}

#[allow(non_snake_case, non_camel_case_types, non_upper_case_globals)]
pub mod root {
    #[allow(unused_imports)]
    use self::super::root;
    pub mod JS {
        #[allow(unused_imports)]
        use self::super::super::root;
        #[repr(C)]
        #[derive(Debug, Copy, Clone)]
        pub struct Rooted<a> {
            pub b: a,
            pub _phantom_0: ::std::marker::PhantomData<::std::cell::UnsafeCell<a>>,
        }
    }
    #[test]
    fn __bindgen_test_layout_Rooted_instantiation_1() {
        assert_eq!(::std::mem::size_of::<root::JS::Rooted<::std::os::raw::c_int>>()
                   , 4usize , concat ! (
                   "Size of template specialization: " , stringify ! (
                   root::JS::Rooted<::std::os::raw::c_int> ) ));
        assert_eq!(::std::mem::align_of::<root::JS::Rooted<::std::os::raw::c_int>>()
                   , 4usize , concat ! (
                   "Alignment of template specialization: " , stringify ! (
                   root::JS::Rooted<::std::os::raw::c_int> ) ));
    }
    #[test]
    fn __bindgen_test_layout_Rooted_instantiation_2() {
        assert_eq!(::std::mem::size_of::<root::JS::Rooted<root::JS::AutoValueVector_Vec>>()
                   , 4usize , concat ! (
                   "Size of template specialization: " , stringify ! (
                   root::JS::Rooted<root::JS::AutoValueVector_Vec> ) ));
        assert_eq!(::std::mem::align_of::<root::JS::Rooted<root::JS::AutoValueVector_Vec>>()
                   , 4usize , concat ! (
                   "Alignment of template specialization: " , stringify ! (
                   root::JS::Rooted<root::JS::AutoValueVector_Vec> ) ));
    }
}

And then this fails to compile because we don't emit any definition for AutoValueVector_Vec:

error[E0412]: cannot find type `AutoValueVector_Vec` in module `root::JS`
  --> js.rs:42:70
   |
42 |         assert_eq!(::std::mem::align_of::<root::JS::Rooted<root::JS::AutoValueVector_Vec>>()
   |                                                                      ^^^^^^^^^^^^^^^^^^^ not found in `root::JS`

Expected Results

We probably should just avoid emitting tests of any instantiation involving non-whitelisted things.

[fitzgen]

It seems that --enable-cxx-namespaces --whitelist-type JS::Rooted is enough to trigger this.

[fitzgen]

Slightly more reduced test case:

// bindgen-flags: --enable-cxx-namespaces --whitelist-type Rooted

template <typename T>
class Rooted {
    T member;
};

class AutoValueVector : Rooted<int> {
    using IntAlias = int;
    using RootedIntAlias = Rooted<IntAlias>;
};

[fitzgen]

We probably should just avoid emitting tests of any instantiation involving non-whitelisted things.

Alternatively, we should consider the argument type whitelisted, and should emit bindings for it. I think that this is what is supposed to be happening, but we are collapsing a type alias away (or maybe libclang is doing this before giving it to us...).

[fitzgen]

Ok, here's what's going on: the alias is whitelisted, but because its parent is a struct, and not a module, and its parent struct is not whitelisted, we don't ever add it as a child of a module in BindgenContext::add_item and therefore don't ever generate a definition for it in the codegen phase.