Auto merge of #56549 - pietroalbini:rollup, r=pietroalbini

Rollup of 15 pull requests

Successful merges:

 - #51753 (Document `From` implementations)
 - #55563 (Improve no result found sentence in doc search)
 - #55987 (Add Weak.ptr_eq)
 - #56119 (Utilize `?` instead of `return None`.)
 - #56372 (Refer to the second borrow as the "second borrow" in E0501.rs)
 - #56388 (More MIR borrow check cleanup)
 - #56424 (Mention raw-ident syntax)
 - #56452 (Remove redundant clones)
 - #56456 (Handle existential types in dead code analysis)
 - #56466 (data_structures: remove tuple_slice)
 - #56476 (Fix invalid line number match)
 - #56497 (cleanup: remove static lifetimes from consts in libstd)
 - #56498 (Fix line numbers display)
 - #56523 (Added a bare-bones eslint config (removing jslint))
 - #56538 (Use inner iterator may_have_side_effect for Cloned)

Failed merges:

r? @ghost

17 files changed, 194 insertions, 177 deletions

diff --git a/src/libstd/env.rs b/src/libstd/env.rs
index 9066c0b7694..d14efa2e3c7 100644
--- a/src/libstd/env.rs
+++ b/src/libstd/env.rs
@@ -828,7 +828,7 @@ pub mod consts {
     /// - s390x
     /// - sparc64
     #[stable(feature = "env", since = "1.0.0")]
-    pub const ARCH: &'static str = super::arch::ARCH;
+    pub const ARCH: &str = super::arch::ARCH;
 
     /// The family of the operating system. Example value is `unix`.
     ///
@@ -837,7 +837,7 @@ pub mod consts {
     /// - unix
     /// - windows
     #[stable(feature = "env", since = "1.0.0")]
-    pub const FAMILY: &'static str = os::FAMILY;
+    pub const FAMILY: &str = os::FAMILY;
 
     /// A string describing the specific operating system in use.
     /// Example value is `linux`.
@@ -856,7 +856,7 @@ pub mod consts {
     /// - android
     /// - windows
     #[stable(feature = "env", since = "1.0.0")]
-    pub const OS: &'static str = os::OS;
+    pub const OS: &str = os::OS;
 
     /// Specifies the filename prefix used for shared libraries on this
     /// platform. Example value is `lib`.
@@ -866,7 +866,7 @@ pub mod consts {
     /// - lib
     /// - `""` (an empty string)
     #[stable(feature = "env", since = "1.0.0")]
-    pub const DLL_PREFIX: &'static str = os::DLL_PREFIX;
+    pub const DLL_PREFIX: &str = os::DLL_PREFIX;
 
     /// Specifies the filename suffix used for shared libraries on this
     /// platform. Example value is `.so`.
@@ -877,7 +877,7 @@ pub mod consts {
     /// - .dylib
     /// - .dll
     #[stable(feature = "env", since = "1.0.0")]
-    pub const DLL_SUFFIX: &'static str = os::DLL_SUFFIX;
+    pub const DLL_SUFFIX: &str = os::DLL_SUFFIX;
 
     /// Specifies the file extension used for shared libraries on this
     /// platform that goes after the dot. Example value is `so`.
@@ -888,7 +888,7 @@ pub mod consts {
     /// - dylib
     /// - dll
     #[stable(feature = "env", since = "1.0.0")]
-    pub const DLL_EXTENSION: &'static str = os::DLL_EXTENSION;
+    pub const DLL_EXTENSION: &str = os::DLL_EXTENSION;
 
     /// Specifies the filename suffix used for executable binaries on this
     /// platform. Example value is `.exe`.
@@ -900,7 +900,7 @@ pub mod consts {
     /// - .pexe
     /// - `""` (an empty string)
     #[stable(feature = "env", since = "1.0.0")]
-    pub const EXE_SUFFIX: &'static str = os::EXE_SUFFIX;
+    pub const EXE_SUFFIX: &str = os::EXE_SUFFIX;
 
     /// Specifies the file extension, if any, used for executable binaries
     /// on this platform. Example value is `exe`.
@@ -910,72 +910,72 @@ pub mod consts {
     /// - exe
     /// - `""` (an empty string)
     #[stable(feature = "env", since = "1.0.0")]
-    pub const EXE_EXTENSION: &'static str = os::EXE_EXTENSION;
+    pub const EXE_EXTENSION: &str = os::EXE_EXTENSION;
 }
 
 #[cfg(target_arch = "x86")]
 mod arch {
-    pub const ARCH: &'static str = "x86";
+    pub const ARCH: &str = "x86";
 }
 
 #[cfg(target_arch = "x86_64")]
 mod arch {
-    pub const ARCH: &'static str = "x86_64";
+    pub const ARCH: &str = "x86_64";
 }
 
 #[cfg(target_arch = "arm")]
 mod arch {
-    pub const ARCH: &'static str = "arm";
+    pub const ARCH: &str = "arm";
 }
 
 #[cfg(target_arch = "aarch64")]
 mod arch {
-    pub const ARCH: &'static str = "aarch64";
+    pub const ARCH: &str = "aarch64";
 }
 
 #[cfg(target_arch = "mips")]
 mod arch {
-    pub const ARCH: &'static str = "mips";
+    pub const ARCH: &str = "mips";
 }
 
 #[cfg(target_arch = "mips64")]
 mod arch {
-    pub const ARCH: &'static str = "mips64";
+    pub const ARCH: &str = "mips64";
 }
 
 #[cfg(target_arch = "powerpc")]
 mod arch {
-    pub const ARCH: &'static str = "powerpc";
+    pub const ARCH: &str = "powerpc";
 }
 
 #[cfg(target_arch = "powerpc64")]
 mod arch {
-    pub const ARCH: &'static str = "powerpc64";
+    pub const ARCH: &str = "powerpc64";
 }
 
 #[cfg(target_arch = "s390x")]
 mod arch {
-    pub const ARCH: &'static str = "s390x";
+    pub const ARCH: &str = "s390x";
 }
 
 #[cfg(target_arch = "sparc64")]
 mod arch {
-    pub const ARCH: &'static str = "sparc64";
+    pub const ARCH: &str = "sparc64";
 }
 
 #[cfg(target_arch = "le32")]
 mod arch {
-    pub const ARCH: &'static str = "le32";
+    pub const ARCH: &str = "le32";
 }
 
 #[cfg(target_arch = "asmjs")]
 mod arch {
-    pub const ARCH: &'static str = "asmjs";
+    pub const ARCH: &str = "asmjs";
 }
 
 #[cfg(target_arch = "wasm32")]
 mod arch {
-    pub const ARCH: &'static str = "wasm32";
+    pub const ARCH: &str = "wasm32";
 }
 
 #[cfg(test)]
diff --git a/src/libstd/ffi/c_str.rs b/src/libstd/ffi/c_str.rs
index 66718b95408..7c7f83967e0 100644
--- a/src/libstd/ffi/c_str.rs
+++ b/src/libstd/ffi/c_str.rs
@@ -671,7 +671,7 @@ impl fmt::Debug for CStr {
 #[stable(feature = "cstr_default", since = "1.10.0")]
 impl<'a> Default for &'a CStr {
     fn default() -> &'a CStr {
-        const SLICE: &'static [c_char] = &[0];
+        const SLICE: &[c_char] = &[0];
         unsafe { CStr::from_ptr(SLICE.as_ptr()) }
     }
 }
@@ -1475,7 +1475,7 @@ mod tests {
 
     #[test]
     fn cstr_const_constructor() {
-        const CSTR: &'static CStr = unsafe {
+        const CSTR: &CStr = unsafe {
             CStr::from_bytes_with_nul_unchecked(b"Hello, world!\0")
         };
 
diff --git a/src/libstd/keyword_docs.rs b/src/libstd/keyword_docs.rs
index 13cf3133dcd..c1eaf29bb44 100644
--- a/src/libstd/keyword_docs.rs
+++ b/src/libstd/keyword_docs.rs
@@ -65,7 +65,7 @@ mod as_keyword { }
 /// look like this:
 ///
 /// ```rust
-/// const WORDS: &'static str = "hello rust!";
+/// const WORDS: &str = "hello rust!";
 /// ```
 ///
 /// Thanks to static lifetime elision, you usually don't have to explicitly use 'static:
diff --git a/src/libstd/path.rs b/src/libstd/path.rs
index a153456370c..9fad40c5649 100644
--- a/src/libstd/path.rs
+++ b/src/libstd/path.rs
@@ -1397,6 +1397,9 @@ impl<'a> From<&'a Path> for Box<Path> {
 
 #[stable(feature = "path_buf_from_box", since = "1.18.0")]
 impl From<Box<Path>> for PathBuf {
+    /// Converts a `Box<Path>` into a `PathBuf`
+    ///
+    /// This conversion does not allocate or copy memory.
     fn from(boxed: Box<Path>) -> PathBuf {
         boxed.into_path_buf()
     }
@@ -1404,6 +1407,10 @@ impl From<Box<Path>> for PathBuf {
 
 #[stable(feature = "box_from_path_buf", since = "1.20.0")]
 impl From<PathBuf> for Box<Path> {
+    /// Converts a `PathBuf` into a `Box<Path>`
+    ///
+    /// This conversion currently should not allocate memory,
+    /// but this behavior is not guaranteed on all platforms or in all future versions.
     fn from(p: PathBuf) -> Box<Path> {
         p.into_boxed_path()
     }
@@ -1426,6 +1433,9 @@ impl<'a, T: ?Sized + AsRef<OsStr>> From<&'a T> for PathBuf {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl From<OsString> for PathBuf {
+    /// Converts a `OsString` into a `PathBuf`
+    ///
+    /// This conversion does not allocate or copy memory.
     fn from(s: OsString) -> PathBuf {
         PathBuf { inner: s }
     }
@@ -1433,6 +1443,9 @@ impl From<OsString> for PathBuf {
 
 #[stable(feature = "from_path_buf_for_os_string", since = "1.14.0")]
 impl From<PathBuf> for OsString {
+    /// Converts a `PathBuf` into a `OsString`
+    ///
+    /// This conversion does not allocate or copy memory.
     fn from(path_buf : PathBuf) -> OsString {
         path_buf.inner
     }
@@ -1440,6 +1453,9 @@ impl From<PathBuf> for OsString {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl From<String> for PathBuf {
+    /// Converts a `String` into a `PathBuf`
+    ///
+    /// This conversion does not allocate or copy memory.
     fn from(s: String) -> PathBuf {
         PathBuf::from(OsString::from(s))
     }
@@ -1536,6 +1552,7 @@ impl<'a> From<Cow<'a, Path>> for PathBuf {
 
 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
 impl From<PathBuf> for Arc<Path> {
+    /// Converts a Path into a Rc by copying the Path data into a new Rc buffer.
     #[inline]
     fn from(s: PathBuf) -> Arc<Path> {
         let arc: Arc<OsStr> = Arc::from(s.into_os_string());
@@ -1545,6 +1562,7 @@ impl From<PathBuf> for Arc<Path> {
 
 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
 impl<'a> From<&'a Path> for Arc<Path> {
+    /// Converts a Path into a Rc by copying the Path data into a new Rc buffer.
     #[inline]
     fn from(s: &Path) -> Arc<Path> {
         let arc: Arc<OsStr> = Arc::from(s.as_os_str());
@@ -1554,6 +1572,7 @@ impl<'a> From<&'a Path> for Arc<Path> {
 
 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
 impl From<PathBuf> for Rc<Path> {
+    /// Converts a Path into a Rc by copying the Path data into a new Rc buffer.
     #[inline]
     fn from(s: PathBuf) -> Rc<Path> {
         let rc: Rc<OsStr> = Rc::from(s.into_os_string());
@@ -1563,6 +1582,7 @@ impl From<PathBuf> for Rc<Path> {
 
 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
 impl<'a> From<&'a Path> for Rc<Path> {
+    /// Converts a Path into a Rc by copying the Path data into a new Rc buffer.
     #[inline]
     fn from(s: &Path) -> Rc<Path> {
         let rc: Rc<OsStr> = Rc::from(s.as_os_str());
diff --git a/src/libstd/sys/cloudabi/shims/env.rs b/src/libstd/sys/cloudabi/shims/env.rs
index 31777aa94bc..c7691e3b2df 100644
--- a/src/libstd/sys/cloudabi/shims/env.rs
+++ b/src/libstd/sys/cloudabi/shims/env.rs
@@ -9,11 +9,11 @@
 // except according to those terms.
 
 pub mod os {
-    pub const FAMILY: &'static str = "cloudabi";
-    pub const OS: &'static str = "cloudabi";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".so";
-    pub const DLL_EXTENSION: &'static str = "so";
-    pub const EXE_SUFFIX: &'static str = "";
-    pub const EXE_EXTENSION: &'static str = "";
+    pub const FAMILY: &str = "cloudabi";
+    pub const OS: &str = "cloudabi";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
 }
diff --git a/src/libstd/sys/redox/env.rs b/src/libstd/sys/redox/env.rs
index 669b7520df8..75e35046fb7 100644
--- a/src/libstd/sys/redox/env.rs
+++ b/src/libstd/sys/redox/env.rs
@@ -9,11 +9,11 @@
 // except according to those terms.
 
 pub mod os {
-    pub const FAMILY: &'static str = "redox";
-    pub const OS: &'static str = "redox";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".so";
-    pub const DLL_EXTENSION: &'static str = "so";
-    pub const EXE_SUFFIX: &'static str = "";
-    pub const EXE_EXTENSION: &'static str = "";
+    pub const FAMILY: &str = "redox";
+    pub const OS: &str = "redox";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
 }
diff --git a/src/libstd/sys/redox/path.rs b/src/libstd/sys/redox/path.rs
index e6a267dd5d9..b1a4ed30404 100644
--- a/src/libstd/sys/redox/path.rs
+++ b/src/libstd/sys/redox/path.rs
@@ -35,5 +35,5 @@ pub fn parse_prefix(path: &OsStr) -> Option<Prefix> {
     }
 }
 
-pub const MAIN_SEP_STR: &'static str = "/";
+pub const MAIN_SEP_STR: &str = "/";
 pub const MAIN_SEP: char = '/';
diff --git a/src/libstd/sys/redox/process.rs b/src/libstd/sys/redox/process.rs
index 4370c1e0502..8f6d83c544a 100644
--- a/src/libstd/sys/redox/process.rs
+++ b/src/libstd/sys/redox/process.rs
@@ -143,7 +143,7 @@ impl Command {
 
     pub fn spawn(&mut self, default: Stdio, needs_stdin: bool)
                  -> io::Result<(Process, StdioPipes)> {
-         const CLOEXEC_MSG_FOOTER: &'static [u8] = b"NOEX";
+         const CLOEXEC_MSG_FOOTER: &[u8] = b"NOEX";
 
          if self.saw_nul {
              return Err(io::Error::new(ErrorKind::InvalidInput,
diff --git a/src/libstd/sys/unix/env.rs b/src/libstd/sys/unix/env.rs
index ad116c57f55..1b6838f0295 100644
--- a/src/libstd/sys/unix/env.rs
+++ b/src/libstd/sys/unix/env.rs
@@ -10,176 +10,176 @@
 
 #[cfg(target_os = "linux")]
 pub mod os {
-    pub const FAMILY: &'static str = "unix";
-    pub const OS: &'static str = "linux";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".so";
-    pub const DLL_EXTENSION: &'static str = "so";
-    pub const EXE_SUFFIX: &'static str = "";
-    pub const EXE_EXTENSION: &'static str = "";
+    pub const FAMILY: &str = "unix";
+    pub const OS: &str = "linux";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
 }
 
 #[cfg(target_os = "macos")]
 pub mod os {
-    pub const FAMILY: &'static str = "unix";
-    pub const OS: &'static str = "macos";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".dylib";
-    pub const DLL_EXTENSION: &'static str = "dylib";
-    pub const EXE_SUFFIX: &'static str = "";
-    pub const EXE_EXTENSION: &'static str = "";
+    pub const FAMILY: &str = "unix";
+    pub const OS: &str = "macos";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".dylib";
+    pub const DLL_EXTENSION: &str = "dylib";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
 }
 
 #[cfg(target_os = "ios")]
 pub mod os {
-    pub const FAMILY: &'static str = "unix";
-    pub const OS: &'static str = "ios";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".dylib";
-    pub const DLL_EXTENSION: &'static str = "dylib";
-    pub const EXE_SUFFIX: &'static str = "";
-    pub const EXE_EXTENSION: &'static str = "";
+    pub const FAMILY: &str = "unix";
+    pub const OS: &str = "ios";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".dylib";
+    pub const DLL_EXTENSION: &str = "dylib";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
 }
 
 #[cfg(target_os = "freebsd")]
 pub mod os {
-    pub const FAMILY: &'static str = "unix";
-    pub const OS: &'static str = "freebsd";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".so";
-    pub const DLL_EXTENSION: &'static str = "so";
-    pub const EXE_SUFFIX: &'static str = "";
-    pub const EXE_EXTENSION: &'static str = "";
+    pub const FAMILY: &str = "unix";
+    pub const OS: &str = "freebsd";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
 }
 
 #[cfg(target_os = "dragonfly")]
 pub mod os {
-    pub const FAMILY: &'static str = "unix";
-    pub const OS: &'static str = "dragonfly";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".so";
-    pub const DLL_EXTENSION: &'static str = "so";
-    pub const EXE_SUFFIX: &'static str = "";
-    pub const EXE_EXTENSION: &'static str = "";
+    pub const FAMILY: &str = "unix";
+    pub const OS: &str = "dragonfly";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
 }
 
 #[cfg(target_os = "bitrig")]
 pub mod os {
-    pub const FAMILY: &'static str = "unix";
-    pub const OS: &'static str = "bitrig";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".so";
-    pub const DLL_EXTENSION: &'static str = "so";
-    pub const EXE_SUFFIX: &'static str = "";
-    pub const EXE_EXTENSION: &'static str = "";
+    pub const FAMILY: &str = "unix";
+    pub const OS: &str = "bitrig";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
 }
 
 #[cfg(target_os = "netbsd")]
 pub mod os {
-    pub const FAMILY: &'static str = "unix";
-    pub const OS: &'static str = "netbsd";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".so";
-    pub const DLL_EXTENSION: &'static str = "so";
-    pub const EXE_SUFFIX: &'static str = "";
-    pub const EXE_EXTENSION: &'static str = "";
+    pub const FAMILY: &str = "unix";
+    pub const OS: &str = "netbsd";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
 }
 
 #[cfg(target_os = "openbsd")]
 pub mod os {
-    pub const FAMILY: &'static str = "unix";
-    pub const OS: &'static str = "openbsd";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".so";
-    pub const DLL_EXTENSION: &'static str = "so";
-    pub const EXE_SUFFIX: &'static str = "";
-    pub const EXE_EXTENSION: &'static str = "";
+    pub const FAMILY: &str = "unix";
+    pub const OS: &str = "openbsd";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
 }
 
 #[cfg(target_os = "android")]
 pub mod os {
-    pub const FAMILY: &'static str = "unix";
-    pub const OS: &'static str = "android";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".so";
-    pub const DLL_EXTENSION: &'static str = "so";
-    pub const EXE_SUFFIX: &'static str = "";
-    pub const EXE_EXTENSION: &'static str = "";
+    pub const FAMILY: &str = "unix";
+    pub const OS: &str = "android";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
 }
 
 #[cfg(target_os = "solaris")]
 pub mod os {
-    pub const FAMILY: &'static str = "unix";
-    pub const OS: &'static str = "solaris";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".so";
-    pub const DLL_EXTENSION: &'static str = "so";
-    pub const EXE_SUFFIX: &'static str = "";
-    pub const EXE_EXTENSION: &'static str = "";
+    pub const FAMILY: &str = "unix";
+    pub const OS: &str = "solaris";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
 }
 
 #[cfg(target_os = "haiku")]
 pub mod os {
-    pub const FAMILY: &'static str = "unix";
-    pub const OS: &'static str = "haiku";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".so";
-    pub const DLL_EXTENSION: &'static str = "so";
-    pub const EXE_SUFFIX: &'static str = "";
-    pub const EXE_EXTENSION: &'static str = "";
+    pub const FAMILY: &str = "unix";
+    pub const OS: &str = "haiku";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
 }
 
 #[cfg(all(target_os = "emscripten", target_arch = "asmjs"))]
 pub mod os {
-    pub const FAMILY: &'static str = "unix";
-    pub const OS: &'static str = "emscripten";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".so";
-    pub const DLL_EXTENSION: &'static str = "so";
-    pub const EXE_SUFFIX: &'static str = ".js";
-    pub const EXE_EXTENSION: &'static str = "js";
+    pub const FAMILY: &str = "unix";
+    pub const OS: &str = "emscripten";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = ".js";
+    pub const EXE_EXTENSION: &str = "js";
 }
 
 #[cfg(all(target_os = "emscripten", target_arch = "wasm32"))]
 pub mod os {
-    pub const FAMILY: &'static str = "unix";
-    pub const OS: &'static str = "emscripten";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".so";
-    pub const DLL_EXTENSION: &'static str = "so";
-    pub const EXE_SUFFIX: &'static str = ".js";
-    pub const EXE_EXTENSION: &'static str = "js";
+    pub const FAMILY: &str = "unix";
+    pub const OS: &str = "emscripten";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = ".js";
+    pub const EXE_EXTENSION: &str = "js";
 }
 
 #[cfg(target_os = "fuchsia")]
 pub mod os {
-    pub const FAMILY: &'static str = "unix";
-    pub const OS: &'static str = "fuchsia";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".so";
-    pub const DLL_EXTENSION: &'static str = "so";
-    pub const EXE_SUFFIX: &'static str = "";
-    pub const EXE_EXTENSION: &'static str = "";
+    pub const FAMILY: &str = "unix";
+    pub const OS: &str = "fuchsia";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
 }
 
 #[cfg(target_os = "l4re")]
 pub mod os {
-    pub const FAMILY: &'static str = "unix";
-    pub const OS: &'static str = "l4re";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".so";
-    pub const DLL_EXTENSION: &'static str = "so";
-    pub const EXE_SUFFIX: &'static str = "";
-    pub const EXE_EXTENSION: &'static str = "";
+    pub const FAMILY: &str = "unix";
+    pub const OS: &str = "l4re";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
 }
 
 #[cfg(target_os = "hermit")]
 pub mod os {
-    pub const FAMILY: &'static str = "unix";
-    pub const OS: &'static str = "hermit";
-    pub const DLL_PREFIX: &'static str = "lib";
-    pub const DLL_SUFFIX: &'static str = ".so";
-    pub const DLL_EXTENSION: &'static str = "so";
-    pub const EXE_SUFFIX: &'static str = "";
-    pub const EXE_EXTENSION: &'static str = "";
+    pub const FAMILY: &str = "unix";
+    pub const OS: &str = "hermit";
+    pub const DLL_PREFIX: &str = "lib";
+    pub const DLL_SUFFIX: &str = ".so";
+    pub const DLL_EXTENSION: &str = "so";
+    pub const EXE_SUFFIX: &str = "";
+    pub const EXE_EXTENSION: &str = "";
 }
diff --git a/src/libstd/sys/unix/path.rs b/src/libstd/sys/unix/path.rs
index bf9af7a4353..834b4b448dc 100644
--- a/src/libstd/sys/unix/path.rs
+++ b/src/libstd/sys/unix/path.rs
@@ -25,5 +25,5 @@ pub fn parse_prefix(_: &OsStr) -> Option<Prefix> {
     None
 }
 
-pub const MAIN_SEP_STR: &'static str = "/";
+pub const MAIN_SEP_STR: &str = "/";
 pub const MAIN_SEP: char = '/';
diff --git a/src/libstd/sys/unix/process/process_unix.rs b/src/libstd/sys/unix/process/process_unix.rs
index bfbf12f34ee..3248f424460 100644
--- a/src/libstd/sys/unix/process/process_unix.rs
+++ b/src/libstd/sys/unix/process/process_unix.rs
@@ -22,7 +22,7 @@ use sys;
 impl Command {
     pub fn spawn(&mut self, default: Stdio, needs_stdin: bool)
                  -> io::Result<(Process, StdioPipes)> {
-        const CLOEXEC_MSG_FOOTER: &'static [u8] = b"NOEX";
+        const CLOEXEC_MSG_FOOTER: &[u8] = b"NOEX";
 
         let envp = self.capture_env();
 
diff --git a/src/libstd/sys/wasm/env.rs b/src/libstd/sys/wasm/env.rs
index 1422042bd02..09235a944ee 100644
--- a/src/libstd/sys/wasm/env.rs
+++ b/src/libstd/sys/wasm/env.rs
@@ -9,11 +9,11 @@
 // except according to those terms.
 
 pub mod os {
-    pub const FAMILY: &'static str = "";
-    pub const OS: &'static str = "";
-    pub const DLL_PREFIX: &'static str = "";
-    pub const DLL_SUFFIX: &'static str = ".wasm";
-    pub const DLL_EXTENSION: &'static str = "wasm";
-    pub const EXE_SUFFIX: &'static str = ".wasm";
-    pub const EXE_EXTENSION: &'static str = "wasm";
+    pub const FAMILY: &str = "";
+    pub const OS: &str = "";
+    pub const DLL_PREFIX: &str = "";
+    pub const DLL_SUFFIX: &str = ".wasm";
+    pub const DLL_EXTENSION: &str = "wasm";
+    pub const EXE_SUFFIX: &str = ".wasm";
+    pub const EXE_EXTENSION: &str = "wasm";
 }
diff --git a/src/libstd/sys/wasm/path.rs b/src/libstd/sys/wasm/path.rs
index 395b8c1e40e..fcc9d617a87 100644
--- a/src/libstd/sys/wasm/path.rs
+++ b/src/libstd/sys/wasm/path.rs
@@ -25,5 +25,5 @@ pub fn parse_prefix(_: &OsStr) -> Option<Prefix> {
     None
 }
 
-pub const MAIN_SEP_STR: &'static str = "/";
+pub const MAIN_SEP_STR: &str = "/";
 pub const MAIN_SEP: char = '/';
diff --git a/src/libstd/sys/windows/env.rs b/src/libstd/sys/windows/env.rs
index e6d74895774..4523df04f24 100644
--- a/src/libstd/sys/windows/env.rs
+++ b/src/libstd/sys/windows/env.rs
@@ -9,11 +9,11 @@
 // except according to those terms.
 
 pub mod os {
-    pub const FAMILY: &'static str = "windows";
-    pub const OS: &'static str = "windows";
-    pub const DLL_PREFIX: &'static str = "";
-    pub const DLL_SUFFIX: &'static str = ".dll";
-    pub const DLL_EXTENSION: &'static str = "dll";
-    pub const EXE_SUFFIX: &'static str = ".exe";
-    pub const EXE_EXTENSION: &'static str = "exe";
+    pub const FAMILY: &str = "windows";
+    pub const OS: &str = "windows";
+    pub const DLL_PREFIX: &str = "";
+    pub const DLL_SUFFIX: &str = ".dll";
+    pub const DLL_EXTENSION: &str = "dll";
+    pub const EXE_SUFFIX: &str = ".exe";
+    pub const EXE_EXTENSION: &str = "exe";
 }
diff --git a/src/libstd/sys/windows/os.rs b/src/libstd/sys/windows/os.rs
index 29ea82c2053..4d7b7236c59 100644
--- a/src/libstd/sys/windows/os.rs
+++ b/src/libstd/sys/windows/os.rs
@@ -48,8 +48,8 @@ pub fn error_string(mut errnum: i32) -> String {
         // `[MS-ERREF]`: https://msdn.microsoft.com/en-us/library/cc231198.aspx
         if (errnum & c::FACILITY_NT_BIT as i32) != 0 {
             // format according to https://support.microsoft.com/en-us/help/259693
-            const NTDLL_DLL: &'static [u16] = &['N' as _, 'T' as _, 'D' as _, 'L' as _, 'L' as _,
-                                                '.' as _, 'D' as _, 'L' as _, 'L' as _, 0];
+            const NTDLL_DLL: &[u16] = &['N' as _, 'T' as _, 'D' as _, 'L' as _, 'L' as _,
+                                        '.' as _, 'D' as _, 'L' as _, 'L' as _, 0];
             module = c::GetModuleHandleW(NTDLL_DLL.as_ptr());
 
             if module != ptr::null_mut() {
diff --git a/src/libstd/sys/windows/path.rs b/src/libstd/sys/windows/path.rs
index 98d62a0c953..385ea8e0531 100644
--- a/src/libstd/sys/windows/path.rs
+++ b/src/libstd/sys/windows/path.rs
@@ -91,10 +91,7 @@ pub fn parse_prefix<'a>(path: &'a OsStr) -> Option<Prefix> {
     }
 
     fn parse_two_comps(mut path: &[u8], f: fn(u8) -> bool) -> Option<(&[u8], &[u8])> {
-        let first = match path.iter().position(|x| f(*x)) {
-            None => return None,
-            Some(x) => &path[..x],
-        };
+        let first = &path[..path.iter().position(|x| f(*x))?];
         path = &path[(first.len() + 1)..];
         let idx = path.iter().position(|x| f(*x));
         let second = &path[..idx.unwrap_or(path.len())];
@@ -102,5 +99,5 @@ pub fn parse_prefix<'a>(path: &'a OsStr) -> Option<Prefix> {
     }
 }
 
-pub const MAIN_SEP_STR: &'static str = "\\";
+pub const MAIN_SEP_STR: &str = "\\";
 pub const MAIN_SEP: char = '\\';
diff --git a/src/libstd/sys_common/wtf8.rs b/src/libstd/sys_common/wtf8.rs
index 19ce932aa12..3530b7af9ad 100644
--- a/src/libstd/sys_common/wtf8.rs
+++ b/src/libstd/sys_common/wtf8.rs
@@ -40,7 +40,7 @@ use str;
 use sync::Arc;
 use sys_common::AsInner;
 
-const UTF8_REPLACEMENT_CHARACTER: &'static str = "\u{FFFD}";
+const UTF8_REPLACEMENT_CHARACTER: &str = "\u{FFFD}";
 
 /// A Unicode code point: from U+0000 to U+10FFFF.
 ///