chore: Fix CI's use of clippy

.travis.yml

@@ -18,10 +18,10 @@ matrix:
     install:
     script:
     - cargo check --tests --all-features
-  - env: CLIPPY_VERSION="0.0.209"
-    rust: nightly-2018-06-19
+  - env: CLIPPY
+    rust: nightly-2018-07-17
     install:
-      - travis_wait cargo install clippy --version $CLIPPY_VERSION || echo "clippy already installed"
+      - rustup component add clippy-preview
     script:
       - cargo clippy --all-features -- -D clippy
 

src/cargo.rs

@@ -131,7 +131,7 @@ pub fn main_binary_path() -> Result<path::PathBuf, CargoError> {
     let cargo = escargot::Cargo::new().build().current_release();
     let bins: Vec<_> = cargo
         .exec()
-        .map_err(|e| CargoError::with_cause(e))?
+        .map_err(CargoError::with_cause)?
         .filter_map(|m| extract_filenames(&m, "bin"))
         .collect();
     if bins.is_empty() {
@@ -150,7 +150,7 @@ pub fn cargo_bin_path<S: AsRef<ffi::OsStr>>(name: S) -> Result<path::PathBuf, Ca
     let cargo = escargot::Cargo::new().build().bin(name).current_release();
     let bins: Vec<_> = cargo
         .exec()
-        .map_err(|e| CargoError::with_cause(e))?
+        .map_err(CargoError::with_cause)?
         .filter_map(|m| extract_filenames(&m, "bin"))
         .collect();
     assert_eq!(bins.len(), 1);
@@ -165,7 +165,7 @@ pub fn cargo_example_path<S: AsRef<ffi::OsStr>>(name: S) -> Result<path::PathBuf
         .current_release();
     let bins: Vec<_> = cargo
         .exec()
-        .map_err(|e| CargoError::with_cause(e))?
+        .map_err(CargoError::with_cause)?
         .filter_map(|m| extract_filenames(&m, "example"))
         .collect();
     assert_eq!(bins.len(), 1);

src/errors.rs

@@ -106,7 +106,7 @@ impl Error for OutputError {
     }
 
     fn cause(&self) -> Option<&Error> {
-        if let &OutputCause::Unexpected(ref err) = &self.cause {
+        if let OutputCause::Unexpected(ref err) = self.cause {
             Some(err.as_ref())
         } else {
             None