cbindgen panics during generation #2

[pjenvey]

A little similar to #65 but different, I'm seeing an assertion error when running cbindgen --lang C over the https://github.com/mozilla-services/autopush/tree/master/autopush_rs codebase. It doesn't occur under C++:

thread 'main' panicked at 'assertion failed: self.generic_params.len() > 0 &&
    self.generic_params.len() == generic_values.len()', /home/pjenvey/.cargo/registry/src/github.com-1ecc6299db9ec823/cbindgen-0.4.3/src/bindgen/ir/typedef.rs:134:8
stack backtrace:
   0: std::sys::imp::backtrace::tracing::imp::unwind_backtrace
             at /checkout/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::_print
             at /checkout/src/libstd/sys_common/backtrace.rs:68
   2: std::panicking::default_hook::{{closure}}
             at /checkout/src/libstd/sys_common/backtrace.rs:57
             at /checkout/src/libstd/panicking.rs:381
   3: std::panicking::default_hook
             at /checkout/src/libstd/panicking.rs:397
   4: std::panicking::rust_panic_with_hook
             at /checkout/src/libstd/panicking.rs:577
   5: std::panicking::begin_panic
             at /checkout/src/libstd/panicking.rs:538
   6: <cbindgen::bindgen::ir::typedef::Typedef as cbindgen::bindgen::ir::item::Item>::instantiate_monomorph
             at /home/pjenvey/.cargo/registry/src/github.com-1ecc6299db9ec823/cbindgen-0.4.3/src/bindgen/ir/typedef.rs:134
   7: cbindgen::bindgen::ir::ty::Type::add_monomorphs
             at /home/pjenvey/.cargo/registry/src/github.com-1ecc6299db9ec823/cbindgen-0.4.3/src/bindgen/ir/ty.rs:428
   8: cbindgen::bindgen::ir::typedef::Typedef::add_monomorphs
             at /home/pjenvey/.cargo/registry/src/github.com-1ecc6299db9ec823/cbindgen-0.4.3/src/bindgen/ir/typedef.rs:89
   9: cbindgen::bindgen::library::Library::instantiate_monomorphs::{{closure}}
             at /home/pjenvey/.cargo/registry/src/github.com-1ecc6299db9ec823/cbindgen-0.4.3/src/bindgen/library.rs:290
  10: <cbindgen::bindgen::ir::item::ItemMap<T>>::for_all_items
             at /home/pjenvey/.cargo/registry/src/github.com-1ecc6299db9ec823/cbindgen-0.4.3/src/bindgen/ir/item.rs:175
  11: cbindgen::bindgen::library::Library::instantiate_monomorphs
             at /home/pjenvey/.cargo/registry/src/github.com-1ecc6299db9ec823/cbindgen-0.4.3/src/bindgen/library.rs:289
  12: cbindgen::bindgen::library::Library::generate
             at /home/pjenvey/.cargo/registry/src/github.com-1ecc6299db9ec823/cbindgen-0.4.3/src/bindgen/library.rs:62
  13: cbindgen::bindgen::builder::Builder::generate
             at /home/pjenvey/.cargo/registry/src/github.com-1ecc6299db9ec823/cbindgen-0.4.3/src/bindgen/builder.rs:279
  14: cbindgen::generate_with_config
             at /home/pjenvey/.cargo/registry/src/github.com-1ecc6299db9ec823/cbindgen-0.4.3/src/lib.rs:33
  15: build_script_build::main
             at ./build.rs:16
  16: __rust_maybe_catch_panic
             at /checkout/src/libpanic_unwind/lib.rs:101
  17: std::rt::lang_start
             at /checkout/src/libstd/panicking.rs:459
             at /checkout/src/libstd/panic.rs:365
             at /checkout/src/libstd/rt.rs:58
  18: main
  19: __libc_start_main
  20: _start

I've narrowed it down somewhat to an addition to one of the integration tests, it's blowing up on the Sender type alias:

diff --git a/tests/rust/typedef.rs b/tests/rust/typedef.rs
index bf7ceb8..91eee76 100644
--- a/tests/rust/typedef.rs
+++ b/tests/rust/typedef.rs
@@ -9,3 +9,24 @@ type IntFoo<T> = Foo<i32, T>;
 #[no_mangle]
 pub extern "C" fn root(a: IntFoo<i32>)
 { }
+
+use std::sync::mpsc;
+use std::sync::Mutex;
+#[repr(C)]
+pub struct AutopushQueue {
+    rx: Mutex<Option<Sender>>,
+}
+trait FnBox: Send {
+    fn call(self: Box<Self>, input: &str);
+}
+pub struct PythonCall {
+    input: String,
+    output: Box<FnBox>,
+}
+pub type Sender = mpsc::Sender<Option<PythonCall>>;
+#[no_mangle]
+pub extern "C" fn autopush_queue_free(queue: *mut AutopushQueue) {
+    unsafe {
+        Box::from_raw(queue);
+    }
+}

['cargo', 'run', '--', '--lang', 'c', 'tests/rust/typedef.rs', '-o', 'tests/expectations/typedef.c']
    Finished dev [unoptimized + debuginfo] target(s) in 0.0 secs
     Running `target/debug/cbindgen --lang c tests/rust/typedef.rs -o tests/expectations/typedef.c`
thread 'main' panicked at 'assertion failed: self.generic_params.len() > 0 &&
    self.generic_params.len() == generic_values.len()', src/bindgen/ir/typedef.rs:137:9
note: Run with `RUST_BACKTRACE=1` for a backtrace.

[eqrion]

Okay, the problem here is that cbindgen doesn't understand rust paths well. So the mpsc in pub type Sender = mpsc::Sender<..> is ignored causing cbindgen to try and instantiate a generic type for the Sender typedef but it doesn't have any parameters.

The issue to fix the root cause is #7. A workaround would be to rename the type alias to something other than Sender. Running locally I can confirm that resolves this.

[eqrion]

I'm going to close this as a duplicate of #7.