Build fails with rustc 1.27 on linux

[ya55en]

Cannot build slag on Linux (ubuntu 18.04 x86_64) with rustc 1.27.1:

Downloaded slag-master.zip, then unzip, cd slag-master && cargo build --release:

user@my-machine:~/slag-master$ cargo build --release
 Downloading docopt v0.6.86
 Downloading log v0.4.3
 .
 .
 Downloading winapi v0.2.8
   Compiling winapi v0.2.8
   Compiling libc v0.2.42
   Compiling thread_local v0.2.7
   .
   .
   Compiling regex v0.1.80
   Compiling syntex_syntax v0.7.0 (file:///home/user/slag-master/old_syntex)
error: no rules expected the token `flags`
  --> old_syntex/src/parse/parser.rs:89:5
   |
89 |     flags Restrictions: u8 {
   |     ^^^^^

error: aborting due to previous error

error: Could not compile `syntex_syntax`.
warning: build failed, waiting for other jobs to finish...
error: build failed

Verbose version info:

user@my-machine:~/slag-master$ rustc --version --verbose
rustc 1.27.1 (5f2b325f6 2018-07-07)
binary: rustc
commit-hash: 5f2b325f64ed6caa7179f3e04913db437656ec7e
commit-date: 2018-07-07
host: x86_64-unknown-linux-gnu
release: 1.27.1
LLVM version: 6.0