build fails

[gwpl]

   stable-x86_64-unknown-linux-gnu unchanged - rustc 1.51.0 (2fd73fabe 2021-03-23)
  nightly-x86_64-unknown-linux-gnu unchanged - rustc 1.53.0-nightly (b0c818c5e 2021-04-16)

cargo clean && cargo build
   Compiling autocfg v1.0.1
   Compiling through v0.1.0
   Compiling bonzai v0.2.1
error[E0557]: feature has been removed
 --> /home/gw/.cargo/registry/src/github.com-1ecc6299db9ec823/bonzai-0.2.1/src/lib.rs:2:12
  |
2 | #![feature(optin_builtin_traits)]
  |            ^^^^^^^^^^^^^^^^^^^^ feature has been removed
  |
  = note: renamed to `auto_traits`

   Compiling smallqueue v0.1.0
error[E0554]: `#![feature]` may not be used on the stable release channel
 --> /home/gw/.cargo/registry/src/github.com-1ecc6299db9ec823/bonzai-0.2.1/src/lib.rs:1:1
  |
1 | #![feature(fixed_size_array)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0554]: `#![feature]` may not be used on the stable release channel
 --> /home/gw/.cargo/registry/src/github.com-1ecc6299db9ec823/bonzai-0.2.1/src/lib.rs:2:1
  |
2 | #![feature(optin_builtin_traits)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0658]: negative trait bounds are not yet fully implemented; use marker types for now
   --> /home/gw/.cargo/registry/src/github.com-1ecc6299db9ec823/bonzai-0.2.1/src/lib.rs:611:44
    |
611 | impl<'tree, T, C: FixedSizeArray<ChildId>> !Send for TreeOperation<'tree, T, C> {}
    |                                            ^^^^^
    |
    = note: see issue #68318 <https://github.com/rust-lang/rust/issues/68318> for more information

error[E0658]: negative trait bounds are not yet fully implemented; use marker types for now
   --> /home/gw/.cargo/registry/src/github.com-1ecc6299db9ec823/bonzai-0.2.1/src/lib.rs:612:44
    |
612 | impl<'tree, T, C: FixedSizeArray<ChildId>> !Sync for TreeOperation<'tree, T, C> {}
    |                                            ^^^^^
    |
    = note: see issue #68318 <https://github.com/rust-lang/rust/issues/68318> for more information

error[E0658]: negative trait bounds are not yet fully implemented; use marker types for now
   --> /home/gw/.cargo/registry/src/github.com-1ecc6299db9ec823/bonzai-0.2.1/src/lib.rs:737:58
    |
737 | impl<'op, 'node, 't: 'op, T, C: FixedSizeArray<ChildId>> !Send for NodeWriteGuard<'op, 'node, 't, T, C> {}
    |                                                          ^^^^^
    |
    = note: see issue #68318 <https://github.com/rust-lang/rust/issues/68318> for more information

error[E0658]: negative trait bounds are not yet fully implemented; use marker types for now
   --> /home/gw/.cargo/registry/src/github.com-1ecc6299db9ec823/bonzai-0.2.1/src/lib.rs:738:58
    |
738 | impl<'op, 'node, 't: 'op, T, C: FixedSizeArray<ChildId>> !Sync for NodeWriteGuard<'op, 'node, 't, T, C> {}
    |                                                          ^^^^^
    |
    = note: see issue #68318 <https://github.com/rust-lang/rust/issues/68318> for more information

error[E0658]: negative trait bounds are not yet fully implemented; use marker types for now
    --> /home/gw/.cargo/registry/src/github.com-1ecc6299db9ec823/bonzai-0.2.1/src/lib.rs:1135:58
     |
1135 | impl<'op, 'node, 't: 'op, T, C: FixedSizeArray<ChildId>> !Send for ChildWriteGuard<'op, 'node, 't, T, C> {}
     |                                                          ^^^^^
     |
     = note: see issue #68318 <https://github.com/rust-lang/rust/issues/68318> for more information

error[E0658]: negative trait bounds are not yet fully implemented; use marker types for now
    --> /home/gw/.cargo/registry/src/github.com-1ecc6299db9ec823/bonzai-0.2.1/src/lib.rs:1136:58
     |
1136 | impl<'op, 'node, 't: 'op, T, C: FixedSizeArray<ChildId>> !Sync for ChildWriteGuard<'op, 'node, 't, T, C> {}
     |                                                          ^^^^^
     |
     = note: see issue #68318 <https://github.com/rust-lang/rust/issues/68318> for more information

error: aborting due to 9 previous errors

Some errors have detailed explanations: E0554, E0557, E0658.
For more information about an error, try `rustc --explain E0554`.
error: could not compile `bonzai`

To learn more, run the command again with --verbose.
warning: build failed, waiting for other jobs to finish...
error: build failed

With nightly it fails too:

cargo +nightly build
   Compiling bonzai v0.2.1
   Compiling num-traits v0.2.14
   Compiling num-integer v0.1.44
   Compiling num-bigint v0.2.6
   Compiling num-rational v0.2.4
   Compiling num-iter v0.1.42
   Compiling num-complex v0.2.4
error[E0557]: feature has been removed
 --> /home/gw/.cargo/registry/src/github.com-1ecc6299db9ec823/bonzai-0.2.1/src/lib.rs:2:12
  |
2 | #![feature(optin_builtin_traits)]
  |            ^^^^^^^^^^^^^^^^^^^^ feature has been removed
  |
  = note: renamed to `auto_traits`

error[E0432]: unresolved import `core::array::FixedSizeArray`
  --> /home/gw/.cargo/registry/src/github.com-1ecc6299db9ec823/bonzai-0.2.1/src/lib.rs:12:5
   |
12 | use core::array::FixedSizeArray;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ no `FixedSizeArray` in `array`

error[E0658]: negative trait bounds are not yet fully implemented; use marker types for now
   --> /home/gw/.cargo/registry/src/github.com-1ecc6299db9ec823/bonzai-0.2.1/src/lib.rs:611:44
    |
611 | impl<'tree, T, C: FixedSizeArray<ChildId>> !Send for TreeOperation<'tree, T, C> {}
    |                                            ^^^^^
    |
    = note: see issue #68318 <https://github.com/rust-lang/rust/issues/68318> for more information
    = help: add `#![feature(negative_impls)]` to the crate attributes to enable

error[E0658]: negative trait bounds are not yet fully implemented; use marker types for now
   --> /home/gw/.cargo/registry/src/github.com-1ecc6299db9ec823/bonzai-0.2.1/src/lib.rs:612:44
    |
612 | impl<'tree, T, C: FixedSizeArray<ChildId>> !Sync for TreeOperation<'tree, T, C> {}
    |                                            ^^^^^
    |
    = note: see issue #68318 <https://github.com/rust-lang/rust/issues/68318> for more information
    = help: add `#![feature(negative_impls)]` to the crate attributes to enable

error[E0658]: negative trait bounds are not yet fully implemented; use marker types for now
   --> /home/gw/.cargo/registry/src/github.com-1ecc6299db9ec823/bonzai-0.2.1/src/lib.rs:737:58
    |
737 | impl<'op, 'node, 't: 'op, T, C: FixedSizeArray<ChildId>> !Send for NodeWriteGuard<'op, 'node, 't, T, C> {}
    |                                                          ^^^^^
    |
    = note: see issue #68318 <https://github.com/rust-lang/rust/issues/68318> for more information
    = help: add `#![feature(negative_impls)]` to the crate attributes to enable

error[E0658]: negative trait bounds are not yet fully implemented; use marker types for now
   --> /home/gw/.cargo/registry/src/github.com-1ecc6299db9ec823/bonzai-0.2.1/src/lib.rs:738:58
    |
738 | impl<'op, 'node, 't: 'op, T, C: FixedSizeArray<ChildId>> !Sync for NodeWriteGuard<'op, 'node, 't, T, C> {}
    |                                                          ^^^^^
    |
    = note: see issue #68318 <https://github.com/rust-lang/rust/issues/68318> for more information
    = help: add `#![feature(negative_impls)]` to the crate attributes to enable

error[E0658]: negative trait bounds are not yet fully implemented; use marker types for now
    --> /home/gw/.cargo/registry/src/github.com-1ecc6299db9ec823/bonzai-0.2.1/src/lib.rs:1135:58
     |
1135 | impl<'op, 'node, 't: 'op, T, C: FixedSizeArray<ChildId>> !Send for ChildWriteGuard<'op, 'node, 't, T, C> {}
     |                                                          ^^^^^
     |
     = note: see issue #68318 <https://github.com/rust-lang/rust/issues/68318> for more information
     = help: add `#![feature(negative_impls)]` to the crate attributes to enable

error[E0658]: negative trait bounds are not yet fully implemented; use marker types for now
    --> /home/gw/.cargo/registry/src/github.com-1ecc6299db9ec823/bonzai-0.2.1/src/lib.rs:1136:58
     |
1136 | impl<'op, 'node, 't: 'op, T, C: FixedSizeArray<ChildId>> !Sync for ChildWriteGuard<'op, 'node, 't, T, C> {}
     |                                                          ^^^^^
     |
     = note: see issue #68318 <https://github.com/rust-lang/rust/issues/68318> for more information
     = help: add `#![feature(negative_impls)]` to the crate attributes to enable

error: aborting due to 8 previous errors

Some errors have detailed explanations: E0432, E0557, E0658.
For more information about an error, try `rustc --explain E0432`.
error: could not compile `bonzai`

To learn more, run the command again with --verbose.
warning: build failed, waiting for other jobs to finish...
error: build failed

[gwpl]

Suggestion: maybe include Cargo.lock to make build more reproducible?