clippy 0.0.198

A bunch of helpful lints to avoid common pitfalls in Rust
rustc 1.27.0-nightly (acd3871ba 2018-05-10)
binary: rustc
commit-hash: acd3871ba17316419c644e17547887787628ec2f
commit-date: 2018-05-10
host: x86_64-unknown-linux-gnu
release: 1.27.0-nightly
LLVM version: 6.0