Possibly failing to detect template parameter T

Input C/C++ Header

Header file itself can be found here. It's C++ 17 and uses templating.

namespace seal
{
    template<typename T, typename = std::enable_if_t<std::is_integral<T>::value>>
    class IntArray
    {
    public:
        using size_type = std::size_t;

The definition seems pretty exotic so I suppose that something in it is unsupported.

Bindgen Invocation

 // Generate the bindings
    let bindings = bindgen::Builder::default()
        .generate_inline_functions(true)
        .derive_default(true)
        .header("./seal/src/seal/seal.h")
        .clang_arg("-I./seal/src/")
        .clang_arg("-std=c++17")
        .clang_arg("-x")
        .clang_arg("c++")
        .opaque_type("std::.*")
        .whitelist_type("seal::.*")
        .whitelist_function("seal::.*")
        .generate()
        .expect("Unable to generate bindings");

Actual Results

The bindings.rs file has an undefined T value in IntArray:

#[repr(C)]
#[derive(Debug)]
pub struct seal_IntArray {
    pub pool_: seal_MemoryPoolHandle,
    pub capacity_: seal_IntArray_size_type,
    pub size_: seal_IntArray_size_type,
    pub data_: seal_util_Pointer<T>,
}

Which causes the expected compilation error:

error[E0412]: cannot find type `T` in this scope
    --> src/./bindings.rs:6218:34
     |
6218 |     pub data_: seal_util_Pointer<T>,
     |                                  ^ not found in this scope

For reference, here is the relevant header file.

Expected Results

I would expect the generated code to compile.

For now, I have found that simply replacing T by u64 (since it's the only type they used as T in their code) works, but ideally I wouldn't have to edit the bindings by hand.

Possibly related: #1464
Also see issue: #1490

Start by reproducing the bindgen invocation against the linked seal/intarray.h header and inspecting the generated bindings.rs around seal_IntArray. Compare the C++ template declaration with the emitted Rust field using T; done means the generated bindings compile without manually replacing T, with coverage for this template case.