rustc nightly fails with error: trait objects without an explicit dyn are deprecated

[ctaggart]

ctaggart@rustasia:~/rust-bindgen$ cargo build --release
warning: Pattern matching for Cargo's include/exclude fields has changed and file `csmith-fuzzing/README.md` is now included.
See <https://github.com/rust-lang/cargo/issues/4268> for more information.
   Compiling cc v1.0.25
   Compiling version_check v0.1.4
   Compiling cfg-if v0.1.5
   Compiling libc v0.2.43
   Compiling rustc-demangle v0.1.14
   Compiling proc-macro2 v0.4.19
   Compiling ucd-util v0.1.1
   Compiling regex v1.0.5
   Compiling glob v0.2.11
   Compiling utf8-ranges v1.0.1
   Compiling quick-error v1.2.2
   Compiling unicode-xid v0.1.0
   Compiling unicode-width v0.1.5
   Compiling bindgen v0.50.0 (/home/ctaggart/rust-bindgen)
   Compiling byteorder v1.2.7
   Compiling termcolor v1.0.4
   Compiling vec_map v0.8.1
   Compiling bitflags v1.0.4
   Compiling ansi_term v0.11.0
   Compiling strsim v0.7.0
   Compiling shlex v0.1.1
   Compiling peeking_take_while v0.1.2
   Compiling lazy_static v1.1.0
   Compiling memchr v2.1.0
   Compiling log v0.4.5
   Compiling atty v0.2.11
   Compiling regex-syntax v0.6.2
   Compiling backtrace-sys v0.1.28
   Compiling libloading v0.5.0
   Compiling humantime v1.1.1
   Compiling textwrap v0.10.0
   Compiling clang-sys v0.28.0
   Compiling fxhash v0.2.1
   Compiling clap v2.32.0
   Compiling quote v0.6.8
   Compiling thread_local v0.3.6
   Compiling aho-corasick v0.6.8
   Compiling nom v4.0.0
   Compiling backtrace v0.3.11
   Compiling cexpr v0.3.3
   Compiling failure v0.1.5
   Compiling which v2.0.1
   Compiling env_logger v0.6.0
error: trait objects without an explicit `dyn` are deprecated

error: Could not compile `bindgen`.

To learn more, run the command again with --verbose.
ctaggart@rustasia:~/rust-bindgen$ cargo +stable build --release
   Compiling bindgen v0.50.0 (/home/ctaggart/rust-bindgen)
    Finished release [optimized] target(s) in 43.50s

I have the latest nightly:

ctaggart@rustasia:~/rust-bindgen$ rustup show
Default host: x86_64-unknown-linux-gnu

installed toolchains
--------------------

stable-x86_64-unknown-linux-gnu
nightly-x86_64-unknown-linux-gnu (default)

active toolchain
----------------

nightly-x86_64-unknown-linux-gnu (default)
rustc 1.38.0-nightly (a7f28678b 2019-07-23)

on latest from master:

ctaggart@rustasia:~/rust-bindgen$ git log -1
commit a3d8cf75f85fda70d36f2c74d2ecd0b414a63736 (HEAD -> master, origin/master, origin/HEAD)
Author: Emilio Cobos Álvarez <[email protected]>
Date:   Wed Jul 24 11:11:17 2019 +0200

    Cleanup wchar_t layout computation to happen later. (#1596)

    This is a breaking cheange since WChar is exposed, but should be no behavior
    change otherwise.

[ctaggart]

Same error when I use cargo +beta build --release