Incorrect derive partial eq/Hash for struct contains incomplete array field

[photoszzt]

Input C/C++ Header

struct test {
     int a;
     char data[0];
 };

Bindgen Invocation

$ bindgen --with-derive-partialeq --with-derive-hash test.h > test.rs

Actual Results

error[E0277]: the trait bound `__IncompleteArrayField<i8>: std::hash::Hash` is not satisfied
  --> test.rs:40:5
   |
40 |     pub data: __IncompleteArrayField<::std::os::raw::c_char>,
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::hash::Hash` is not implemented for `__IncompleteArrayField<i8>`
   |
   = note: required by `std::hash::Hash::hash`

error[E0369]: binary operation `==` cannot be applied to type `__IncompleteArrayField<i8>`
  --> test.rs:40:5
   |
40 |     pub data: __IncompleteArrayField<::std::os::raw::c_char>,
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: an implementation of `std::cmp::PartialEq` might be missing for `__IncompleteArrayField<i8>`

error[E0369]: binary operation `!=` cannot be applied to type `__IncompleteArrayField<i8>`
  --> test.rs:40:5
   |
40 |     pub data: __IncompleteArrayField<::std::os::raw::c_char>,
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: an implementation of `std::cmp::PartialEq` might be missing for `__IncompleteArrayField<i8>`

#[repr(C)]
 #[derive(Default)]
 pub struct __IncompleteArrayField<T>(::std::marker::PhantomData<T>);
 impl <T> __IncompleteArrayField<T> {
     #[inline]
     pub fn new() -> Self {
         __IncompleteArrayField(::std::marker::PhantomData)
     }
     #[inline]
     pub unsafe fn as_ptr(&self) -> *const T { ::std::mem::transmute(self) }
     #[inline]
     pub unsafe fn as_mut_ptr(&mut self) -> *mut T {
         ::std::mem::transmute(self)
     }
     #[inline]
     pub unsafe fn as_slice(&self, len: usize) -> &[T] {
         ::std::slice::from_raw_parts(self.as_ptr(), len)
     }
     #[inline]
     pub unsafe fn as_mut_slice(&mut self, len: usize) -> &mut [T] {
         ::std::slice::from_raw_parts_mut(self.as_mut_ptr(), len)
     }
 }
 impl <T> ::std::fmt::Debug for __IncompleteArrayField<T> {
     fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
         fmt.write_str("__IncompleteArrayField")
     }
 }
 impl <T> ::std::clone::Clone for __IncompleteArrayField<T> {
     #[inline]
     fn clone(&self) -> Self { Self::new() }
 }
 impl <T> ::std::marker::Copy for __IncompleteArrayField<T> { }
 #[repr(C)]
 #[derive(Debug, Hash, PartialEq)]
 pub struct test {
     pub a: ::std::os::raw::c_int,
     pub data: __IncompleteArrayField<::std::os::raw::c_char>,
 }

Expected Results

Either implement Hash and PartialEq for IncompleteArrayField or don't derive Hash and PartialEq for the struct.

[emilio]

Either implement Hash and PartialEq for IncompleteArrayField or don't derive Hash and PartialEq for the struct.

Yeah, I don't think there's a good way of deriving PartialEq for these, the array field may have a different meaning depending on how the user uses it...

[fitzgen]

I thought we were already treating incomplete and zero-sized arrays as not-derive-able, but I guess not...

Thanks for the bug report @photoszzt :)

[photoszzt]

@fitzgen I think the fixed version hasn't published. The version that has this problem is 0.30 which is what I get from crates.io. I try the master version, it doesn't have the problem for partial eq but fails for hash.

[photoszzt]

@highfive assign me.

[highfive]

Hey @photoszzt! Thanks for your interest in working on this issue. It's now assigned to you!