x is not generic panic

[ankane]

Hi, thanks again for this project!

I wanted to report an x is not generic panic. This may be related to #770.

thread 'main' panicked at 'Dataset is not generic', src/bindgen/ir/generic_path.rs:83:9
stack backtrace:
   0: _rust_begin_unwind
   1: core::panicking::panic_fmt
   2: cbindgen::bindgen::ir::generic_path::GenericParams::call
   3: <cbindgen::bindgen::ir::typedef::Typedef as cbindgen::bindgen::ir::item::Item>::instantiate_monomorph
   4: cbindgen::bindgen::ir::ty::Type::add_monomorphs
   5: cbindgen::bindgen::library::Library::generate
   6: cbindgen::bindgen::builder::Builder::generate
   7: cbindgen::main

To reproduce, create two libs:

cargo new lib1 --lib
cargo new lib2 --lib

In lib1/src/lib.rs, add:

pub struct Dataset<T> {
    data: Vec<T>,
}

impl<T> Dataset<T> {
    pub fn new() -> Self {
        Self {
            data: Vec::new()
        }
    }
}

In lib2/Cargo.toml, add under [dependencies]:

lib1 = { path = "../lib1" }

In lib2/src/lib.rs, add:

pub type Dataset = lib1::Dataset<u32>;

#[no_mangle]
pub unsafe extern "C" fn hello() -> *mut Dataset {
    Box::into_raw(Box::new(Dataset::new()))
}

And in lib2, run:

cbindgen --lang c

A few notes:

• There's no panic with C++
• There's no panic when the code is in the same package
• It's happening with the latest version (0.24.3)

[ankane]

My bad, I think this may be a duplicate of #286.

[ankane]

For future readers, one way around this is to use an additional struct instead of a type alias.

pub struct Dataset(lib1::Dataset<u32>);

#[no_mangle]
pub unsafe extern "C" fn hello() -> *mut Dataset {
    Box::into_raw(Box::new(Dataset(lib1::Dataset::new())))
}