diff --git a/src/backtrack.rs b/src/backtrack.rs
index 6100c17..a3d25d6 100644
--- a/src/backtrack.rs
+++ b/src/backtrack.rs
@@ -16,10 +16,10 @@
 // the bitset has to be zeroed on each execution, which becomes quite expensive
 // on large bitsets.
 
-use exec::ProgramCache;
-use input::{Input, InputAt};
-use prog::{InstPtr, Program};
-use re_trait::Slot;
+use crate::exec::ProgramCache;
+use crate::input::{Input, InputAt};
+use crate::prog::{InstPtr, Program};
+use crate::re_trait::Slot;
 
 type Bits = u32;
 
@@ -196,7 +196,7 @@
     }
 
     fn step(&mut self, mut ip: InstPtr, mut at: InputAt) -> bool {
-        use prog::Inst::*;
+        use crate::prog::Inst::*;
         loop {
             // This loop is an optimization to avoid constantly pushing/popping
             // from the stack. Namely, if we're pushing a job only to run it
diff --git a/src/compile.rs b/src/compile.rs
index 9ffd347..9a2ed5e 100644
--- a/src/compile.rs
+++ b/src/compile.rs
@@ -4,16 +4,16 @@
 use std::result;
 use std::sync::Arc;
 
-use syntax::hir::{self, Hir};
-use syntax::is_word_byte;
-use syntax::utf8::{Utf8Range, Utf8Sequence, Utf8Sequences};
+use regex_syntax::hir::{self, Hir};
+use regex_syntax::is_word_byte;
+use regex_syntax::utf8::{Utf8Range, Utf8Sequence, Utf8Sequences};
 
-use prog::{
+use crate::prog::{
     EmptyLook, Inst, InstBytes, InstChar, InstEmptyLook, InstPtr, InstRanges,
     InstSave, InstSplit, Program,
 };
 
-use Error;
+use crate::Error;
 
 type Result = result::Result<Patch, Error>;
 type ResultOrEmpty = result::Result<Option<Patch>, Error>;
@@ -38,6 +38,7 @@
     suffix_cache: SuffixCache,
     utf8_seqs: Option<Utf8Sequences>,
     byte_classes: ByteClassSet,
+    extra_inst_bytes: usize,
 }
 
 impl Compiler {
@@ -54,6 +55,7 @@
             suffix_cache: SuffixCache::new(1000),
             utf8_seqs: Some(Utf8Sequences::new('\x00', '\x00')),
             byte_classes: ByteClassSet::new(),
+            extra_inst_bytes: 0,
         }
     }
 
@@ -253,8 +255,8 @@
     /// Ok(None) is returned when an expression is compiled to no
     /// instruction, and so no patch.entry value makes sense.
     fn c(&mut self, expr: &Hir) -> ResultOrEmpty {
-        use prog;
-        use syntax::hir::HirKind::*;
+        use crate::prog;
+        use regex_syntax::hir::HirKind::*;
 
         self.check_size()?;
         match *expr.kind() {
@@ -316,6 +318,13 @@
                 }
                 self.compiled.has_unicode_word_boundary = true;
                 self.byte_classes.set_word_boundary();
+                // We also make sure that all ASCII bytes are in a different
+                // class from non-ASCII bytes. Otherwise, it's possible for
+                // ASCII bytes to get lumped into the same class as non-ASCII
+                // bytes. This in turn may cause the lazy DFA to falsely start
+                // when it sees an ASCII byte that maps to a byte class with
+                // non-ASCII bytes. This ensures that never happens.
+                self.byte_classes.set_range(0, 0x7F);
                 self.c_empty_look(prog::EmptyLook::WordBoundary)
             }
             WordBoundary(hir::WordBoundary::UnicodeNegate) => {
@@ -328,6 +337,8 @@
                 }
                 self.compiled.has_unicode_word_boundary = true;
                 self.byte_classes.set_word_boundary();
+                // See comments above for why we set the ASCII range here.
+                self.byte_classes.set_range(0, 0x7F);
                 self.c_empty_look(prog::EmptyLook::NotWordBoundary)
             }
             WordBoundary(hir::WordBoundary::Ascii) => {
@@ -420,6 +431,8 @@
     }
 
     fn c_class(&mut self, ranges: &[hir::ClassUnicodeRange]) -> ResultOrEmpty {
+        use std::mem::size_of;
+
         assert!(!ranges.is_empty());
         if self.compiled.uses_bytes() {
             Ok(Some(CompileClass { c: self, ranges: ranges }.compile()?))
@@ -429,6 +442,8 @@
             let hole = if ranges.len() == 1 && ranges[0].0 == ranges[0].1 {
                 self.push_hole(InstHole::Char { c: ranges[0].0 })
             } else {
+                self.extra_inst_bytes +=
+                    ranges.len() * (size_of::<char>() * 2);
                 self.push_hole(InstHole::Ranges { ranges: ranges })
             };
             Ok(Some(Patch { hole: hole, entry: self.insts.len() - 1 }))
@@ -548,7 +563,7 @@
     }
 
     fn c_repeat(&mut self, rep: &hir::Repetition) -> ResultOrEmpty {
-        use syntax::hir::RepetitionKind::*;
+        use regex_syntax::hir::RepetitionKind::*;
         match rep.kind {
             ZeroOrOne => self.c_repeat_zero_or_one(&rep.hir, rep.greedy),
             ZeroOrMore => self.c_repeat_zero_or_more(&rep.hir, rep.greedy),
@@ -795,7 +810,9 @@
     fn check_size(&self) -> result::Result<(), Error> {
         use std::mem::size_of;
 
-        if self.insts.len() * size_of::<Inst>() > self.size_limit {
+        let size =
+            self.extra_inst_bytes + (self.insts.len() * size_of::<Inst>());
+        if size > self.size_limit {
             Err(Error::CompiledTooBig(self.size_limit))
         } else {
             Ok(())
@@ -927,9 +944,10 @@
                 Inst::EmptyLook(InstEmptyLook { goto: goto, look: look })
             }
             InstHole::Char { c } => Inst::Char(InstChar { goto: goto, c: c }),
-            InstHole::Ranges { ref ranges } => {
-                Inst::Ranges(InstRanges { goto: goto, ranges: ranges.clone() })
-            }
+            InstHole::Ranges { ref ranges } => Inst::Ranges(InstRanges {
+                goto: goto,
+                ranges: ranges.clone().into_boxed_slice(),
+            }),
             InstHole::Bytes { start, end } => {
                 Inst::Bytes(InstBytes { goto: goto, start: start, end: end })
             }
diff --git a/src/dfa.rs b/src/dfa.rs
index 9ac0c2c..4b60f4d 100644
--- a/src/dfa.rs
+++ b/src/dfa.rs
@@ -42,9 +42,9 @@
 use std::mem;
 use std::sync::Arc;
 
-use exec::ProgramCache;
-use prog::{Inst, Program};
-use sparse::SparseSet;
+use crate::exec::ProgramCache;
+use crate::prog::{Inst, Program};
+use crate::sparse::SparseSet;
 
 /// Return true if and only if the given program can be executed by a DFA.
 ///
@@ -55,7 +55,7 @@
 /// This function will also return false if the given program has any Unicode
 /// instructions (Char or Ranges) since the DFA operates on bytes only.
 pub fn can_exec(insts: &Program) -> bool {
-    use prog::Inst::*;
+    use crate::prog::Inst::*;
     // If for some reason we manage to allocate a regex program with more
     // than i32::MAX instructions, then we can't execute the DFA because we
     // use 32 bit instruction pointer deltas for memory savings.
@@ -306,7 +306,7 @@
         StateFlags(self.data[0])
     }
 
-    fn inst_ptrs(&self) -> InstPtrs {
+    fn inst_ptrs(&self) -> InstPtrs<'_> {
         InstPtrs { base: 0, data: &self.data[1..] }
     }
 }
@@ -894,7 +894,7 @@
         mut si: StatePtr,
         b: Byte,
     ) -> Option<StatePtr> {
-        use prog::Inst::*;
+        use crate::prog::Inst::*;
 
         // Initialize a queue with the current DFA state's NFA states.
         qcur.clear();
@@ -1056,8 +1056,8 @@
         q: &mut SparseSet,
         flags: EmptyFlags,
     ) {
-        use prog::EmptyLook::*;
-        use prog::Inst::*;
+        use crate::prog::EmptyLook::*;
+        use crate::prog::Inst::*;
 
         // We need to traverse the NFA to follow epsilon transitions, so avoid
         // recursion with an explicit stack.
@@ -1190,7 +1190,7 @@
         q: &SparseSet,
         state_flags: &mut StateFlags,
     ) -> Option<State> {
-        use prog::Inst::*;
+        use crate::prog::Inst::*;
 
         // We need to build up enough information to recognize pre-built states
         // in the DFA. Generally speaking, this includes every instruction
@@ -1754,7 +1754,7 @@
 }
 
 impl fmt::Debug for State {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let ips: Vec<usize> = self.inst_ptrs().collect();
         f.debug_struct("State")
             .field("flags", &self.flags())
@@ -1764,7 +1764,7 @@
 }
 
 impl fmt::Debug for Transitions {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let mut fmtd = f.debug_map();
         for si in 0..self.num_states() {
             let s = si * self.num_byte_classes;
@@ -1778,7 +1778,7 @@
 struct TransitionsRow<'a>(&'a [StatePtr]);
 
 impl<'a> fmt::Debug for TransitionsRow<'a> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let mut fmtd = f.debug_map();
         for (b, si) in self.0.iter().enumerate() {
             match *si {
@@ -1796,7 +1796,7 @@
 }
 
 impl fmt::Debug for StateFlags {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("StateFlags")
             .field("is_match", &self.is_match())
             .field("is_word", &self.is_word())
@@ -1889,7 +1889,6 @@
 
 #[cfg(test)]
 mod tests {
-    extern crate rand;
 
     use super::{
         push_inst_ptr, read_vari32, read_varu32, write_vari32, write_varu32,
diff --git a/src/error.rs b/src/error.rs
index 1c32c85..3e0ec75 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -31,7 +31,7 @@
 }
 
 impl fmt::Display for Error {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
             Error::Syntax(ref err) => err.fmt(f),
             Error::CompiledTooBig(limit) => write!(
@@ -49,7 +49,7 @@
 // but the `Syntax` variant is already storing a `String` anyway, so we might
 // as well format it nicely.
 impl fmt::Debug for Error {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match *self {
             Error::Syntax(ref err) => {
                 let hr: String = repeat('~').take(79).collect();
diff --git a/src/exec.rs b/src/exec.rs
index 3d5a52b..d5fad1c 100644
--- a/src/exec.rs
+++ b/src/exec.rs
@@ -5,26 +5,26 @@
 
 #[cfg(feature = "perf-literal")]
 use aho_corasick::{AhoCorasick, AhoCorasickBuilder, MatchKind};
-use syntax::hir::literal::Literals;
-use syntax::hir::Hir;
-use syntax::ParserBuilder;
+use regex_syntax::hir::literal::Literals;
+use regex_syntax::hir::Hir;
+use regex_syntax::ParserBuilder;
 
-use backtrack;
-use compile::Compiler;
+use crate::backtrack;
+use crate::compile::Compiler;
 #[cfg(feature = "perf-dfa")]
-use dfa;
-use error::Error;
-use input::{ByteInput, CharInput};
-use literal::LiteralSearcher;
-use pikevm;
-use pool::{Pool, PoolGuard};
-use prog::Program;
-use re_builder::RegexOptions;
-use re_bytes;
-use re_set;
-use re_trait::{Locations, RegularExpression, Slot};
-use re_unicode;
-use utf8::next_utf8;
+use crate::dfa;
+use crate::error::Error;
+use crate::input::{ByteInput, CharInput};
+use crate::literal::LiteralSearcher;
+use crate::pikevm;
+use crate::pool::{Pool, PoolGuard};
+use crate::prog::Program;
+use crate::re_builder::RegexOptions;
+use crate::re_bytes;
+use crate::re_set;
+use crate::re_trait::{Locations, RegularExpression, Slot};
+use crate::re_unicode;
+use crate::utf8::next_utf8;
 
 /// `Exec` manages the execution of a regular expression.
 ///
@@ -140,7 +140,7 @@
     ///
     /// Note that when compiling 2 or more regular expressions, capture groups
     /// are completely unsupported. (This means both `find` and `captures`
-    /// wont work.)
+    /// won't work.)
     pub fn new_many<I, S>(res: I) -> Self
     where
         S: AsRef<str>,
@@ -373,9 +373,6 @@
             AhoCorasickBuilder::new()
                 .match_kind(MatchKind::LeftmostFirst)
                 .auto_configure(&lits)
-                // We always want this to reduce size, regardless
-                // of what auto-configure does.
-                .byte_classes(true)
                 .build_with_size::<u32, _, _>(&lits)
                 // This should never happen because we'd long exceed the
                 // compilation limit for regexes first.
@@ -739,7 +736,7 @@
         text: &[u8],
         start: usize,
     ) -> dfa::Result<(usize, usize)> {
-        use dfa::Result::*;
+        use crate::dfa::Result::*;
         let end = match dfa::Fsm::forward(
             &self.ro.dfa,
             self.cache.value(),
@@ -779,7 +776,7 @@
         text: &[u8],
         start: usize,
     ) -> dfa::Result<(usize, usize)> {
-        use dfa::Result::*;
+        use crate::dfa::Result::*;
         match dfa::Fsm::reverse(
             &self.ro.dfa_reverse,
             self.cache.value(),
@@ -835,7 +832,7 @@
         text: &[u8],
         original_start: usize,
     ) -> Option<dfa::Result<(usize, usize)>> {
-        use dfa::Result::*;
+        use crate::dfa::Result::*;
 
         let lcs = self.ro.suffixes.lcs();
         debug_assert!(lcs.len() >= 1);
@@ -880,7 +877,7 @@
         text: &[u8],
         start: usize,
     ) -> dfa::Result<(usize, usize)> {
-        use dfa::Result::*;
+        use crate::dfa::Result::*;
 
         let match_start = match self.exec_dfa_reverse_suffix(text, start) {
             None => return self.find_dfa_forward(text, start),
@@ -1263,7 +1260,7 @@
 impl Exec {
     /// Get a searcher that isn't Sync.
     #[cfg_attr(feature = "perf-inline", inline(always))]
-    pub fn searcher(&self) -> ExecNoSync {
+    pub fn searcher(&self) -> ExecNoSync<'_> {
         ExecNoSync {
             ro: &self.ro, // a clone is too expensive here! (and not needed)
             cache: self.pool.get(),
@@ -1272,7 +1269,7 @@
 
     /// Get a searcher that isn't Sync and can match on &str.
     #[cfg_attr(feature = "perf-inline", inline(always))]
-    pub fn searcher_str(&self) -> ExecNoSyncStr {
+    pub fn searcher_str(&self) -> ExecNoSyncStr<'_> {
         ExecNoSyncStr(self.searcher())
     }
 
@@ -1550,7 +1547,7 @@
 /// literals, and if so, returns them. Otherwise, this returns None.
 #[cfg(feature = "perf-literal")]
 fn alternation_literals(expr: &Hir) -> Option<Vec<Vec<u8>>> {
-    use syntax::hir::{HirKind, Literal};
+    use regex_syntax::hir::{HirKind, Literal};
 
     // This is pretty hacky, but basically, if `is_alternation_literal` is
     // true, then we can make several assumptions about the structure of our
@@ -1602,7 +1599,7 @@
 mod test {
     #[test]
     fn uppercut_s_backtracking_bytes_default_bytes_mismatch() {
-        use internal::ExecBuilder;
+        use crate::internal::ExecBuilder;
 
         let backtrack_bytes_re = ExecBuilder::new("^S")
             .bounded_backtracking()
@@ -1630,7 +1627,7 @@
 
     #[test]
     fn unicode_lit_star_backtracking_utf8bytes_default_utf8bytes_mismatch() {
-        use internal::ExecBuilder;
+        use crate::internal::ExecBuilder;
 
         let backtrack_bytes_re = ExecBuilder::new(r"^(?u:\*)")
             .bounded_backtracking()
diff --git a/src/expand.rs b/src/expand.rs
index 70dbf91..fd9c2d0 100644
--- a/src/expand.rs
+++ b/src/expand.rs
@@ -1,12 +1,12 @@
 use std::str;
 
-use find_byte::find_byte;
+use crate::find_byte::find_byte;
 
-use re_bytes;
-use re_unicode;
+use crate::re_bytes;
+use crate::re_unicode;
 
 pub fn expand_str(
-    caps: &re_unicode::Captures,
+    caps: &re_unicode::Captures<'_>,
     mut replacement: &str,
     dst: &mut String,
 ) {
@@ -48,7 +48,7 @@
 }
 
 pub fn expand_bytes(
-    caps: &re_bytes::Captures,
+    caps: &re_bytes::Captures<'_>,
     mut replacement: &[u8],
     dst: &mut Vec<u8>,
 ) {
@@ -125,7 +125,7 @@
 /// starting at the beginning of `replacement`.
 ///
 /// If no such valid reference could be found, None is returned.
-fn find_cap_ref(replacement: &[u8]) -> Option<CaptureRef> {
+fn find_cap_ref(replacement: &[u8]) -> Option<CaptureRef<'_>> {
     let mut i = 0;
     let rep: &[u8] = replacement.as_ref();
     if rep.len() <= 1 || rep[0] != b'$' {
@@ -157,7 +157,7 @@
     })
 }
 
-fn find_cap_ref_braced(rep: &[u8], mut i: usize) -> Option<CaptureRef> {
+fn find_cap_ref_braced(rep: &[u8], mut i: usize) -> Option<CaptureRef<'_>> {
     let start = i;
     while rep.get(i).map_or(false, |&b| b != b'}') {
         i += 1;
diff --git a/src/input.rs b/src/input.rs
index 3afa2d0..5d50ee3 100644
--- a/src/input.rs
+++ b/src/input.rs
@@ -4,11 +4,9 @@
 use std::ops;
 use std::u32;
 
-use syntax;
-
-use literal::LiteralSearcher;
-use prog::InstEmptyLook;
-use utf8::{decode_last_utf8, decode_utf8};
+use crate::literal::LiteralSearcher;
+use crate::prog::InstEmptyLook;
+use crate::utf8::{decode_last_utf8, decode_utf8};
 
 /// Represents a location in the input.
 #[derive(Clone, Copy, Debug)]
@@ -175,7 +173,7 @@
     }
 
     fn is_empty_match(&self, at: InputAt, empty: &InstEmptyLook) -> bool {
-        use prog::EmptyLook::*;
+        use crate::prog::EmptyLook::*;
         match empty.look {
             StartLine => {
                 let c = self.previous_char(at);
@@ -268,7 +266,7 @@
     }
 
     fn is_empty_match(&self, at: InputAt, empty: &InstEmptyLook) -> bool {
-        use prog::EmptyLook::*;
+        use crate::prog::EmptyLook::*;
         match empty.look {
             StartLine => {
                 let c = self.previous_char(at);
@@ -348,7 +346,7 @@
 pub struct Char(u32);
 
 impl fmt::Debug for Char {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match char::from_u32(self.0) {
             None => write!(f, "Empty"),
             Some(c) => write!(f, "{:?}", c),
@@ -379,7 +377,7 @@
         // available. However, our compiler ensures that if a Unicode word
         // boundary is used, then the data must also be available. If it isn't,
         // then the compiler returns an error.
-        char::from_u32(self.0).map_or(false, syntax::is_word_character)
+        char::from_u32(self.0).map_or(false, regex_syntax::is_word_character)
     }
 
     /// Returns true iff the byte is a word byte.
@@ -387,7 +385,7 @@
     /// If the byte is absent, then false is returned.
     pub fn is_word_byte(self) -> bool {
         match char::from_u32(self.0) {
-            Some(c) if c <= '\u{7F}' => syntax::is_word_byte(c as u8),
+            Some(c) if c <= '\u{7F}' => regex_syntax::is_word_byte(c as u8),
             None | Some(_) => false,
         }
     }
diff --git a/src/lib.rs b/src/lib.rs
index 357ac0d..7f2dec8 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -22,12 +22,6 @@
 regex = "1"
 ```
 
-If you're using Rust 2015, then you'll also need to add it to your crate root:
-
-```rust
-extern crate regex;
-```
-
 # Example: find a date
 
 General use of regular expressions in this package involves compiling an
@@ -68,9 +62,7 @@
 For example:
 
 ```rust
-#[macro_use] extern crate lazy_static;
-extern crate regex;
-
+use lazy_static::lazy_static;
 use regex::Regex;
 
 fn some_helper_function(text: &str) -> bool {
@@ -94,7 +86,7 @@
 them by their component pieces:
 
 ```rust
-# extern crate regex; use regex::Regex;
+# use regex::Regex;
 # fn main() {
 let re = Regex::new(r"(\d{4})-(\d{2})-(\d{2})").unwrap();
 let text = "2012-03-14, 2013-01-01 and 2014-07-05";
@@ -119,7 +111,7 @@
 in our replacement text:
 
 ```rust
-# extern crate regex; use regex::Regex;
+# use regex::Regex;
 # fn main() {
 let re = Regex::new(r"(?P<y>\d{4})-(?P<m>\d{2})-(?P<d>\d{2})").unwrap();
 let before = "2012-03-14, 2013-01-01 and 2014-07-05";
@@ -136,7 +128,7 @@
 enable insignificant whitespace mode, which also lets you write comments:
 
 ```rust
-# extern crate regex; use regex::Regex;
+# use regex::Regex;
 # fn main() {
 let re = Regex::new(r"(?x)
   (?P<y>\d{4}) # the year
@@ -217,7 +209,7 @@
 in your expression:
 
 ```rust
-# extern crate regex; use regex::Regex;
+# use regex::Regex;
 # fn main() {
 let re = Regex::new(r"(?i)Δ+").unwrap();
 let mat = re.find("ΔδΔ").unwrap();
@@ -244,7 +236,7 @@
 match a sequence of numerals, Greek or Cherokee letters:
 
 ```rust
-# extern crate regex; use regex::Regex;
+# use regex::Regex;
 # fn main() {
 let re = Regex::new(r"[\pN\p{Greek}\p{Cherokee}]+").unwrap();
 let mat = re.find("abcΔᎠβⅠᏴγδⅡxyz").unwrap();
@@ -391,7 +383,7 @@
 case-insensitively for the first part but case-sensitively for the second part:
 
 ```rust
-# extern crate regex; use regex::Regex;
+# use regex::Regex;
 # fn main() {
 let re = Regex::new(r"(?i)a+(?-i)b+").unwrap();
 let cap = re.captures("AaAaAbbBBBb").unwrap();
@@ -425,7 +417,7 @@
 word boundary:
 
 ```rust
-# extern crate regex; use regex::Regex;
+# use regex::Regex;
 # fn main() {
 let re = Regex::new(r"(?-u:\b).+(?-u:\b)").unwrap();
 let cap = re.captures("$$abc$$").unwrap();
@@ -614,38 +606,30 @@
 */
 
 #![deny(missing_docs)]
-#![cfg_attr(test, deny(warnings))]
 #![cfg_attr(feature = "pattern", feature(pattern))]
 #![warn(missing_debug_implementations)]
 
 #[cfg(not(feature = "std"))]
 compile_error!("`std` feature is currently required to build this crate");
 
-#[cfg(feature = "perf-literal")]
-extern crate aho_corasick;
-// #[cfg(doctest)]
-// extern crate doc_comment;
-#[cfg(feature = "perf-literal")]
-extern crate memchr;
-#[cfg(test)]
-#[cfg_attr(feature = "perf-literal", macro_use)]
-extern crate quickcheck;
-extern crate regex_syntax as syntax;
-
+// To check README's example
+// TODO: Re-enable this once the MSRV is 1.43 or greater.
+// See: https://github.com/rust-lang/regex/issues/684
+// See: https://github.com/rust-lang/regex/issues/685
 // #[cfg(doctest)]
 // doc_comment::doctest!("../README.md");
 
 #[cfg(feature = "std")]
-pub use error::Error;
+pub use crate::error::Error;
 #[cfg(feature = "std")]
-pub use re_builder::set_unicode::*;
+pub use crate::re_builder::set_unicode::*;
 #[cfg(feature = "std")]
-pub use re_builder::unicode::*;
+pub use crate::re_builder::unicode::*;
 #[cfg(feature = "std")]
-pub use re_set::unicode::*;
+pub use crate::re_set::unicode::*;
 #[cfg(feature = "std")]
 #[cfg(feature = "std")]
-pub use re_unicode::{
+pub use crate::re_unicode::{
     escape, CaptureLocations, CaptureMatches, CaptureNames, Captures,
     Locations, Match, Matches, NoExpand, Regex, Replacer, ReplacerRef, Split,
     SplitN, SubCaptureMatches,
@@ -740,10 +724,10 @@
 */
 #[cfg(feature = "std")]
 pub mod bytes {
-    pub use re_builder::bytes::*;
-    pub use re_builder::set_bytes::*;
-    pub use re_bytes::*;
-    pub use re_set::bytes::*;
+    pub use crate::re_builder::bytes::*;
+    pub use crate::re_builder::set_bytes::*;
+    pub use crate::re_bytes::*;
+    pub use crate::re_set::bytes::*;
 }
 
 mod backtrack;
@@ -754,8 +738,6 @@
 mod exec;
 mod expand;
 mod find_byte;
-#[cfg(feature = "perf-literal")]
-mod freqs;
 mod input;
 mod literal;
 #[cfg(feature = "pattern")]
@@ -777,9 +759,9 @@
 #[doc(hidden)]
 #[cfg(feature = "std")]
 pub mod internal {
-    pub use compile::Compiler;
-    pub use exec::{Exec, ExecBuilder};
-    pub use input::{Char, CharInput, Input, InputAt};
-    pub use literal::LiteralSearcher;
-    pub use prog::{EmptyLook, Inst, InstRanges, Program};
+    pub use crate::compile::Compiler;
+    pub use crate::exec::{Exec, ExecBuilder};
+    pub use crate::input::{Char, CharInput, Input, InputAt};
+    pub use crate::literal::LiteralSearcher;
+    pub use crate::prog::{EmptyLook, Inst, InstRanges, Program};
 }
diff --git a/src/literal/imp.rs b/src/literal/imp.rs
index e4d04ed..82f050a 100644
--- a/src/literal/imp.rs
+++ b/src/literal/imp.rs
@@ -1,11 +1,8 @@
-use std::cmp;
 use std::mem;
 
 use aho_corasick::{self, packed, AhoCorasick, AhoCorasickBuilder};
-use memchr::{memchr, memchr2, memchr3};
-use syntax::hir::literal::{Literal, Literals};
-
-use freqs::BYTE_FREQUENCIES;
+use memchr::{memchr, memchr2, memchr3, memmem};
+use regex_syntax::hir::literal::{Literal, Literals};
 
 /// A prefix extracted from a compiled regular expression.
 ///
@@ -15,8 +12,8 @@
 #[derive(Clone, Debug)]
 pub struct LiteralSearcher {
     complete: bool,
-    lcp: FreqyPacked,
-    lcs: FreqyPacked,
+    lcp: Memmem,
+    lcs: Memmem,
     matcher: Matcher,
 }
 
@@ -26,10 +23,8 @@
     Empty,
     /// A set of four or more single byte literals.
     Bytes(SingleByteSet),
-    /// A single substring, find using memchr and frequency analysis.
-    FreqyPacked(FreqyPacked),
-    /// A single substring, find using Boyer-Moore.
-    BoyerMoore(BoyerMooreSearch),
+    /// A single substring, using vector accelerated routines when available.
+    Memmem(Memmem),
     /// An Aho-Corasick automaton.
     AC { ac: AhoCorasick<u32>, lits: Vec<Literal> },
     /// A packed multiple substring searcher, using SIMD.
@@ -63,8 +58,8 @@
         let complete = lits.all_complete();
         LiteralSearcher {
             complete: complete,
-            lcp: FreqyPacked::new(lits.longest_common_prefix().to_vec()),
-            lcs: FreqyPacked::new(lits.longest_common_suffix().to_vec()),
+            lcp: Memmem::new(lits.longest_common_prefix()),
+            lcs: Memmem::new(lits.longest_common_suffix()),
             matcher: matcher,
         }
     }
@@ -86,8 +81,7 @@
         match self.matcher {
             Empty => Some((0, 0)),
             Bytes(ref sset) => sset.find(haystack).map(|i| (i, i + 1)),
-            FreqyPacked(ref s) => s.find(haystack).map(|i| (i, i + s.len())),
-            BoyerMoore(ref s) => s.find(haystack).map(|i| (i, i + s.len())),
+            Memmem(ref s) => s.find(haystack).map(|i| (i, i + s.len())),
             AC { ref ac, .. } => {
                 ac.find(haystack).map(|m| (m.start(), m.end()))
             }
@@ -124,24 +118,23 @@
     }
 
     /// Returns an iterator over all literals to be matched.
-    pub fn iter(&self) -> LiteralIter {
+    pub fn iter(&self) -> LiteralIter<'_> {
         match self.matcher {
             Matcher::Empty => LiteralIter::Empty,
             Matcher::Bytes(ref sset) => LiteralIter::Bytes(&sset.dense),
-            Matcher::FreqyPacked(ref s) => LiteralIter::Single(&s.pat),
-            Matcher::BoyerMoore(ref s) => LiteralIter::Single(&s.pattern),
+            Matcher::Memmem(ref s) => LiteralIter::Single(&s.finder.needle()),
             Matcher::AC { ref lits, .. } => LiteralIter::AC(lits),
             Matcher::Packed { ref lits, .. } => LiteralIter::Packed(lits),
         }
     }
 
     /// Returns a matcher for the longest common prefix of this matcher.
-    pub fn lcp(&self) -> &FreqyPacked {
+    pub fn lcp(&self) -> &Memmem {
         &self.lcp
     }
 
     /// Returns a matcher for the longest common suffix of this matcher.
-    pub fn lcs(&self) -> &FreqyPacked {
+    pub fn lcs(&self) -> &Memmem {
         &self.lcs
     }
 
@@ -156,8 +149,7 @@
         match self.matcher {
             Empty => 0,
             Bytes(ref sset) => sset.dense.len(),
-            FreqyPacked(_) => 1,
-            BoyerMoore(_) => 1,
+            Memmem(_) => 1,
             AC { ref ac, .. } => ac.pattern_count(),
             Packed { ref lits, .. } => lits.len(),
         }
@@ -169,8 +161,7 @@
         match self.matcher {
             Empty => 0,
             Bytes(ref sset) => sset.approximate_size(),
-            FreqyPacked(ref single) => single.approximate_size(),
-            BoyerMoore(ref single) => single.approximate_size(),
+            Memmem(ref single) => single.approximate_size(),
             AC { ref ac, .. } => ac.heap_bytes(),
             Packed { ref s, .. } => s.heap_bytes(),
         }
@@ -205,12 +196,7 @@
             return Matcher::Bytes(sset);
         }
         if lits.literals().len() == 1 {
-            let lit = lits.literals()[0].to_vec();
-            if BoyerMooreSearch::should_use(lit.as_slice()) {
-                return Matcher::BoyerMoore(BoyerMooreSearch::new(lit));
-            } else {
-                return Matcher::FreqyPacked(FreqyPacked::new(lit));
-            }
+            return Matcher::Memmem(Memmem::new(&lits.literals()[0]));
         }
 
         let pats = lits.literals().to_owned();
@@ -367,116 +353,27 @@
     }
 }
 
-/// Provides an implementation of fast subtring search using frequency
-/// analysis.
+/// A simple wrapper around the memchr crate's memmem implementation.
 ///
-/// memchr is so fast that we do everything we can to keep the loop in memchr
-/// for as long as possible. The easiest way to do this is to intelligently
-/// pick the byte to send to memchr. The best byte is the byte that occurs
-/// least frequently in the haystack. Since doing frequency analysis on the
-/// haystack is far too expensive, we compute a set of fixed frequencies up
-/// front and hard code them in src/freqs.rs. Frequency analysis is done via
-/// scripts/frequencies.py.
+/// The API this exposes mirrors the API of previous substring searchers that
+/// this supplanted.
 #[derive(Clone, Debug)]
-pub struct FreqyPacked {
-    /// The pattern.
-    pat: Vec<u8>,
-    /// The number of Unicode characters in the pattern. This is useful for
-    /// determining the effective length of a pattern when deciding which
-    /// optimizations to perform. A trailing incomplete UTF-8 sequence counts
-    /// as one character.
+pub struct Memmem {
+    finder: memmem::Finder<'static>,
     char_len: usize,
-    /// The rarest byte in the pattern, according to pre-computed frequency
-    /// analysis.
-    rare1: u8,
-    /// The offset of the rarest byte in `pat`.
-    rare1i: usize,
-    /// The second rarest byte in the pattern, according to pre-computed
-    /// frequency analysis. (This may be equivalent to the rarest byte.)
-    ///
-    /// The second rarest byte is used as a type of guard for quickly detecting
-    /// a mismatch after memchr locates an instance of the rarest byte. This
-    /// is a hedge against pathological cases where the pre-computed frequency
-    /// analysis may be off. (But of course, does not prevent *all*
-    /// pathological cases.)
-    rare2: u8,
-    /// The offset of the second rarest byte in `pat`.
-    rare2i: usize,
 }
 
-impl FreqyPacked {
-    fn new(pat: Vec<u8>) -> FreqyPacked {
-        if pat.is_empty() {
-            return FreqyPacked::empty();
-        }
-
-        // Find the rarest two bytes. Try to make them distinct (but it's not
-        // required).
-        let mut rare1 = pat[0];
-        let mut rare2 = pat[0];
-        for b in pat[1..].iter().cloned() {
-            if freq_rank(b) < freq_rank(rare1) {
-                rare1 = b;
-            }
-        }
-        for &b in &pat {
-            if rare1 == rare2 {
-                rare2 = b
-            } else if b != rare1 && freq_rank(b) < freq_rank(rare2) {
-                rare2 = b;
-            }
-        }
-
-        // And find the offsets of their last occurrences.
-        let rare1i = pat.iter().rposition(|&b| b == rare1).unwrap();
-        let rare2i = pat.iter().rposition(|&b| b == rare2).unwrap();
-
-        let char_len = char_len_lossy(&pat);
-        FreqyPacked {
-            pat: pat,
-            char_len: char_len,
-            rare1: rare1,
-            rare1i: rare1i,
-            rare2: rare2,
-            rare2i: rare2i,
-        }
-    }
-
-    fn empty() -> FreqyPacked {
-        FreqyPacked {
-            pat: vec![],
-            char_len: 0,
-            rare1: 0,
-            rare1i: 0,
-            rare2: 0,
-            rare2i: 0,
+impl Memmem {
+    fn new(pat: &[u8]) -> Memmem {
+        Memmem {
+            finder: memmem::Finder::new(pat).into_owned(),
+            char_len: char_len_lossy(pat),
         }
     }
 
     #[cfg_attr(feature = "perf-inline", inline(always))]
     pub fn find(&self, haystack: &[u8]) -> Option<usize> {
-        let pat = &*self.pat;
-        if haystack.len() < pat.len() || pat.is_empty() {
-            return None;
-        }
-        let mut i = self.rare1i;
-        while i < haystack.len() {
-            i += match memchr(self.rare1, &haystack[i..]) {
-                None => return None,
-                Some(i) => i,
-            };
-            let start = i - self.rare1i;
-            let end = start + pat.len();
-            if end > haystack.len() {
-                return None;
-            }
-            let aligned = &haystack[start..end];
-            if aligned[self.rare2i] == self.rare2 && aligned == &*self.pat {
-                return Some(start);
-            }
-            i += 1;
-        }
-        None
+        self.finder.find(haystack)
     }
 
     #[cfg_attr(feature = "perf-inline", inline(always))]
@@ -484,11 +381,11 @@
         if text.len() < self.len() {
             return false;
         }
-        text[text.len() - self.len()..] == *self.pat
+        &text[text.len() - self.len()..] == self.finder.needle()
     }
 
     pub fn len(&self) -> usize {
-        self.pat.len()
+        self.finder.needle().len()
     }
 
     pub fn char_len(&self) -> usize {
@@ -496,627 +393,10 @@
     }
 
     fn approximate_size(&self) -> usize {
-        self.pat.len() * mem::size_of::<u8>()
+        self.finder.needle().len() * mem::size_of::<u8>()
     }
 }
 
 fn char_len_lossy(bytes: &[u8]) -> usize {
     String::from_utf8_lossy(bytes).chars().count()
 }
-
-/// An implementation of Tuned Boyer-Moore as laid out by
-/// Andrew Hume and Daniel Sunday in "Fast String Searching".
-/// O(n) in the size of the input.
-///
-/// Fast string searching algorithms come in many variations,
-/// but they can generally be described in terms of three main
-/// components.
-///
-/// The skip loop is where the string searcher wants to spend
-/// as much time as possible. Exactly which character in the
-/// pattern the skip loop examines varies from algorithm to
-/// algorithm, but in the simplest case this loop repeated
-/// looks at the last character in the pattern and jumps
-/// forward in the input if it is not in the pattern.
-/// Robert Boyer and J Moore called this the "fast" loop in
-/// their original paper.
-///
-/// The match loop is responsible for actually examining the
-/// whole potentially matching substring. In order to fail
-/// faster, the match loop sometimes has a guard test attached.
-/// The guard test uses frequency analysis of the different
-/// characters in the pattern to choose the least frequency
-/// occurring character and use it to find match failures
-/// as quickly as possible.
-///
-/// The shift rule governs how the algorithm will shuffle its
-/// test window in the event of a failure during the match loop.
-/// Certain shift rules allow the worst-case run time of the
-/// algorithm to be shown to be O(n) in the size of the input
-/// rather than O(nm) in the size of the input and the size
-/// of the pattern (as naive Boyer-Moore is).
-///
-/// "Fast String Searching", in addition to presenting a tuned
-/// algorithm, provides a comprehensive taxonomy of the many
-/// different flavors of string searchers. Under that taxonomy
-/// TBM, the algorithm implemented here, uses an unrolled fast
-/// skip loop with memchr fallback, a forward match loop with guard,
-/// and the mini Sunday's delta shift rule. To unpack that you'll have to
-/// read the paper.
-#[derive(Clone, Debug)]
-pub struct BoyerMooreSearch {
-    /// The pattern we are going to look for in the haystack.
-    pattern: Vec<u8>,
-
-    /// The skip table for the skip loop.
-    ///
-    /// Maps the character at the end of the input
-    /// to a shift.
-    skip_table: Vec<usize>,
-
-    /// The guard character (least frequently occurring char).
-    guard: u8,
-    /// The reverse-index of the guard character in the pattern.
-    guard_reverse_idx: usize,
-
-    /// Daniel Sunday's mini generalized delta2 shift table.
-    ///
-    /// We use a skip loop, so we only have to provide a shift
-    /// for the skip char (last char). This is why it is a mini
-    /// shift rule.
-    md2_shift: usize,
-}
-
-impl BoyerMooreSearch {
-    /// Create a new string searcher, performing whatever
-    /// compilation steps are required.
-    fn new(pattern: Vec<u8>) -> Self {
-        debug_assert!(!pattern.is_empty());
-
-        let (g, gi) = Self::select_guard(pattern.as_slice());
-        let skip_table = Self::compile_skip_table(pattern.as_slice());
-        let md2_shift = Self::compile_md2_shift(pattern.as_slice());
-        BoyerMooreSearch {
-            pattern: pattern,
-            skip_table: skip_table,
-            guard: g,
-            guard_reverse_idx: gi,
-            md2_shift: md2_shift,
-        }
-    }
-
-    /// Find the pattern in `haystack`, returning the offset
-    /// of the start of the first occurrence of the pattern
-    /// in `haystack`.
-    #[inline]
-    fn find(&self, haystack: &[u8]) -> Option<usize> {
-        if haystack.len() < self.pattern.len() {
-            return None;
-        }
-
-        let mut window_end = self.pattern.len() - 1;
-
-        // Inspired by the grep source. It is a way
-        // to do correct loop unrolling without having to place
-        // a crashpad of terminating charicters at the end in
-        // the way described in the Fast String Searching paper.
-        const NUM_UNROLL: usize = 10;
-        // 1 for the initial position, and 1 for the md2 shift
-        let short_circut = (NUM_UNROLL + 2) * self.pattern.len();
-
-        if haystack.len() > short_circut {
-            // just 1 for the md2 shift
-            let backstop =
-                haystack.len() - ((NUM_UNROLL + 1) * self.pattern.len());
-            loop {
-                window_end =
-                    match self.skip_loop(haystack, window_end, backstop) {
-                        Some(i) => i,
-                        None => return None,
-                    };
-                if window_end >= backstop {
-                    break;
-                }
-
-                if self.check_match(haystack, window_end) {
-                    return Some(window_end - (self.pattern.len() - 1));
-                } else {
-                    let skip = self.skip_table[haystack[window_end] as usize];
-                    window_end +=
-                        if skip == 0 { self.md2_shift } else { skip };
-                    continue;
-                }
-            }
-        }
-
-        // now process the input after the backstop
-        while window_end < haystack.len() {
-            let mut skip = self.skip_table[haystack[window_end] as usize];
-            if skip == 0 {
-                if self.check_match(haystack, window_end) {
-                    return Some(window_end - (self.pattern.len() - 1));
-                } else {
-                    skip = self.md2_shift;
-                }
-            }
-            window_end += skip;
-        }
-
-        None
-    }
-
-    fn len(&self) -> usize {
-        return self.pattern.len();
-    }
-
-    /// The key heuristic behind which the BoyerMooreSearch lives.
-    ///
-    /// See `rust-lang/regex/issues/408`.
-    ///
-    /// Tuned Boyer-Moore is actually pretty slow! It turns out a handrolled
-    /// platform-specific memchr routine with a bit of frequency
-    /// analysis sprinkled on top actually wins most of the time.
-    /// However, there are a few cases where Tuned Boyer-Moore still
-    /// wins.
-    ///
-    /// If the haystack is random, frequency analysis doesn't help us,
-    /// so Boyer-Moore will win for sufficiently large needles.
-    /// Unfortunately, there is no obvious way to determine this
-    /// ahead of time.
-    ///
-    /// If the pattern itself consists of very common characters,
-    /// frequency analysis won't get us anywhere. The most extreme
-    /// example of this is a pattern like `eeeeeeeeeeeeeeee`. Fortunately,
-    /// this case is wholly determined by the pattern, so we can actually
-    /// implement the heuristic.
-    ///
-    /// A third case is if the pattern is sufficiently long. The idea
-    /// here is that once the pattern gets long enough the Tuned
-    /// Boyer-Moore skip loop will start making strides long enough
-    /// to beat the asm deep magic that is memchr.
-    fn should_use(pattern: &[u8]) -> bool {
-        // The minimum pattern length required to use TBM.
-        const MIN_LEN: usize = 9;
-        // The minimum frequency rank (lower is rarer) that every byte in the
-        // pattern must have in order to use TBM. That is, if the pattern
-        // contains _any_ byte with a lower rank, then TBM won't be used.
-        const MIN_CUTOFF: usize = 150;
-        // The maximum frequency rank for any byte.
-        const MAX_CUTOFF: usize = 255;
-        // The scaling factor used to determine the actual cutoff frequency
-        // to use (keeping in mind that the minimum frequency rank is bounded
-        // by MIN_CUTOFF). This scaling factor is an attempt to make TBM more
-        // likely to be used as the pattern grows longer. That is, longer
-        // patterns permit somewhat less frequent bytes than shorter patterns,
-        // under the assumption that TBM gets better as the pattern gets
-        // longer.
-        const LEN_CUTOFF_PROPORTION: usize = 4;
-
-        let scaled_rank = pattern.len().wrapping_mul(LEN_CUTOFF_PROPORTION);
-        let cutoff = cmp::max(
-            MIN_CUTOFF,
-            MAX_CUTOFF - cmp::min(MAX_CUTOFF, scaled_rank),
-        );
-        // The pattern must be long enough to be worthwhile. e.g., memchr will
-        // be faster on `e` because it is short even though e is quite common.
-        pattern.len() > MIN_LEN
-            // all the bytes must be more common than the cutoff.
-            && pattern.iter().all(|c| freq_rank(*c) >= cutoff)
-    }
-
-    /// Check to see if there is a match at the given position
-    #[inline]
-    fn check_match(&self, haystack: &[u8], window_end: usize) -> bool {
-        // guard test
-        if haystack[window_end - self.guard_reverse_idx] != self.guard {
-            return false;
-        }
-
-        // match loop
-        let window_start = window_end - (self.pattern.len() - 1);
-        for i in 0..self.pattern.len() {
-            if self.pattern[i] != haystack[window_start + i] {
-                return false;
-            }
-        }
-
-        true
-    }
-
-    /// Skip forward according to the shift table.
-    ///
-    /// Returns the offset of the next occurrence
-    /// of the last char in the pattern, or the none
-    /// if it never reappears. If `skip_loop` hits the backstop
-    /// it will leave early.
-    #[inline]
-    fn skip_loop(
-        &self,
-        haystack: &[u8],
-        mut window_end: usize,
-        backstop: usize,
-    ) -> Option<usize> {
-        let window_end_snapshot = window_end;
-        let skip_of = |we: usize| -> usize {
-            // Unsafe might make this faster, but the benchmarks
-            // were hard to interpret.
-            self.skip_table[haystack[we] as usize]
-        };
-
-        loop {
-            let mut skip = skip_of(window_end);
-            window_end += skip;
-            skip = skip_of(window_end);
-            window_end += skip;
-            if skip != 0 {
-                skip = skip_of(window_end);
-                window_end += skip;
-                skip = skip_of(window_end);
-                window_end += skip;
-                skip = skip_of(window_end);
-                window_end += skip;
-                if skip != 0 {
-                    skip = skip_of(window_end);
-                    window_end += skip;
-                    skip = skip_of(window_end);
-                    window_end += skip;
-                    skip = skip_of(window_end);
-                    window_end += skip;
-                    if skip != 0 {
-                        skip = skip_of(window_end);
-                        window_end += skip;
-                        skip = skip_of(window_end);
-                        window_end += skip;
-
-                        // If ten iterations did not make at least 16 words
-                        // worth of progress, we just fall back on memchr.
-                        if window_end - window_end_snapshot
-                            > 16 * mem::size_of::<usize>()
-                        {
-                            // Returning a window_end >= backstop will
-                            // immediatly break us out of the inner loop in
-                            // `find`.
-                            if window_end >= backstop {
-                                return Some(window_end);
-                            }
-
-                            continue; // we made enough progress
-                        } else {
-                            // In case we are already there, and so that
-                            // we will catch the guard char.
-                            window_end = window_end
-                                .checked_sub(1 + self.guard_reverse_idx)
-                                .unwrap_or(0);
-
-                            match memchr(self.guard, &haystack[window_end..]) {
-                                None => return None,
-                                Some(g_idx) => {
-                                    return Some(
-                                        window_end
-                                            + g_idx
-                                            + self.guard_reverse_idx,
-                                    );
-                                }
-                            }
-                        }
-                    }
-                }
-            }
-
-            return Some(window_end);
-        }
-    }
-
-    /// Compute the ufast skip table.
-    fn compile_skip_table(pattern: &[u8]) -> Vec<usize> {
-        let mut tab = vec![pattern.len(); 256];
-
-        // For every char in the pattern, we write a skip
-        // that will line us up with the rightmost occurrence.
-        //
-        // N.B. the sentinel (0) is written by the last
-        // loop iteration.
-        for (i, c) in pattern.iter().enumerate() {
-            tab[*c as usize] = (pattern.len() - 1) - i;
-        }
-
-        tab
-    }
-
-    /// Select the guard character based off of the precomputed
-    /// frequency table.
-    fn select_guard(pattern: &[u8]) -> (u8, usize) {
-        let mut rarest = pattern[0];
-        let mut rarest_rev_idx = pattern.len() - 1;
-        for (i, c) in pattern.iter().enumerate() {
-            if freq_rank(*c) < freq_rank(rarest) {
-                rarest = *c;
-                rarest_rev_idx = (pattern.len() - 1) - i;
-            }
-        }
-
-        (rarest, rarest_rev_idx)
-    }
-
-    /// If there is another occurrence of the skip
-    /// char, shift to it, otherwise just shift to
-    /// the next window.
-    fn compile_md2_shift(pattern: &[u8]) -> usize {
-        let shiftc = *pattern.last().unwrap();
-
-        // For a pattern of length 1 we will never apply the
-        // shift rule, so we use a poison value on the principle
-        // that failing fast is a good thing.
-        if pattern.len() == 1 {
-            return 0xDEADBEAF;
-        }
-
-        let mut i = pattern.len() - 2;
-        while i > 0 {
-            if pattern[i] == shiftc {
-                return (pattern.len() - 1) - i;
-            }
-            i -= 1;
-        }
-
-        // The skip char never re-occurs in the pattern, so
-        // we can just shift the whole window length.
-        pattern.len() - 1
-    }
-
-    fn approximate_size(&self) -> usize {
-        (self.pattern.len() * mem::size_of::<u8>())
-            + (256 * mem::size_of::<usize>()) // skip table
-    }
-}
-
-fn freq_rank(b: u8) -> usize {
-    BYTE_FREQUENCIES[b as usize] as usize
-}
-
-#[cfg(test)]
-mod tests {
-    use super::{BoyerMooreSearch, FreqyPacked};
-
-    //
-    // Unit Tests
-    //
-
-    // The "hello, world" of string searching
-    #[test]
-    fn bm_find_subs() {
-        let searcher = BoyerMooreSearch::new(Vec::from(&b"pattern"[..]));
-        let haystack = b"I keep seeing patterns in this text";
-        assert_eq!(14, searcher.find(haystack).unwrap());
-    }
-
-    #[test]
-    fn bm_find_no_subs() {
-        let searcher = BoyerMooreSearch::new(Vec::from(&b"pattern"[..]));
-        let haystack = b"I keep seeing needles in this text";
-        assert_eq!(None, searcher.find(haystack));
-    }
-
-    //
-    // Regression Tests
-    //
-
-    #[test]
-    fn bm_skip_reset_bug() {
-        let haystack = vec![0, 0, 0, 0, 0, 1, 1, 0];
-        let needle = vec![0, 1, 1, 0];
-
-        let searcher = BoyerMooreSearch::new(needle);
-        let offset = searcher.find(haystack.as_slice()).unwrap();
-        assert_eq!(4, offset);
-    }
-
-    #[test]
-    fn bm_backstop_underflow_bug() {
-        let haystack = vec![0, 0];
-        let needle = vec![0, 0];
-
-        let searcher = BoyerMooreSearch::new(needle);
-        let offset = searcher.find(haystack.as_slice()).unwrap();
-        assert_eq!(0, offset);
-    }
-
-    #[test]
-    fn bm_naive_off_by_one_bug() {
-        let haystack = vec![91];
-        let needle = vec![91];
-
-        let naive_offset = naive_find(&needle, &haystack).unwrap();
-        assert_eq!(0, naive_offset);
-    }
-
-    #[test]
-    fn bm_memchr_fallback_indexing_bug() {
-        let mut haystack = vec![
-            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-            0, 0, 0, 0, 0, 87, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-            0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-        ];
-        let needle = vec![1, 1, 1, 1, 32, 32, 87];
-        let needle_start = haystack.len();
-        haystack.extend(needle.clone());
-
-        let searcher = BoyerMooreSearch::new(needle);
-        assert_eq!(needle_start, searcher.find(haystack.as_slice()).unwrap());
-    }
-
-    #[test]
-    fn bm_backstop_boundary() {
-        let haystack = b"\
-// aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
-e_data.clone_created(entity_id, entity_to_add.entity_id);
-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
-"
-        .to_vec();
-        let needle = b"clone_created".to_vec();
-
-        let searcher = BoyerMooreSearch::new(needle);
-        let result = searcher.find(&haystack);
-        assert_eq!(Some(43), result);
-    }
-
-    #[test]
-    fn bm_win_gnu_indexing_bug() {
-        let haystack_raw = vec![
-            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-        ];
-        let needle = vec![1, 1, 1, 1, 1, 1, 1];
-        let haystack = haystack_raw.as_slice();
-
-        BoyerMooreSearch::new(needle.clone()).find(haystack);
-    }
-
-    //
-    // QuickCheck Properties
-    //
-
-    use quickcheck::TestResult;
-
-    fn naive_find(needle: &[u8], haystack: &[u8]) -> Option<usize> {
-        assert!(needle.len() <= haystack.len());
-
-        for i in 0..(haystack.len() - (needle.len() - 1)) {
-            if haystack[i] == needle[0]
-                && &haystack[i..(i + needle.len())] == needle
-            {
-                return Some(i);
-            }
-        }
-
-        None
-    }
-
-    quickcheck! {
-        fn qc_bm_equals_nieve_find(pile1: Vec<u8>, pile2: Vec<u8>) -> TestResult {
-            if pile1.len() == 0 || pile2.len() == 0 {
-                return TestResult::discard();
-            }
-
-            let (needle, haystack) = if pile1.len() < pile2.len() {
-                (pile1, pile2.as_slice())
-            } else {
-                (pile2, pile1.as_slice())
-            };
-
-            let searcher = BoyerMooreSearch::new(needle.clone());
-            TestResult::from_bool(
-                searcher.find(haystack) == naive_find(&needle, haystack))
-        }
-
-        fn qc_bm_equals_single(pile1: Vec<u8>, pile2: Vec<u8>) -> TestResult {
-            if pile1.len() == 0 || pile2.len() == 0 {
-                return TestResult::discard();
-            }
-
-            let (needle, haystack) = if pile1.len() < pile2.len() {
-                (pile1, pile2.as_slice())
-            } else {
-                (pile2, pile1.as_slice())
-            };
-
-            let bm_searcher = BoyerMooreSearch::new(needle.clone());
-            let freqy_memchr = FreqyPacked::new(needle);
-            TestResult::from_bool(
-                bm_searcher.find(haystack) == freqy_memchr.find(haystack))
-        }
-
-        fn qc_bm_finds_trailing_needle(
-            haystack_pre: Vec<u8>,
-            needle: Vec<u8>
-        ) -> TestResult {
-            if needle.len() == 0 {
-                return TestResult::discard();
-            }
-
-            let mut haystack = haystack_pre.clone();
-            let searcher = BoyerMooreSearch::new(needle.clone());
-
-            if haystack.len() >= needle.len() &&
-                searcher.find(haystack.as_slice()).is_some() {
-                return TestResult::discard();
-            }
-
-            haystack.extend(needle.clone());
-
-            // What if the the tail of the haystack can start the
-            // needle?
-            let start = haystack_pre.len()
-                .checked_sub(needle.len())
-                .unwrap_or(0);
-            for i in 0..(needle.len() - 1) {
-                if searcher.find(&haystack[(i + start)..]).is_some() {
-                    return TestResult::discard();
-                }
-            }
-
-            TestResult::from_bool(
-                searcher.find(haystack.as_slice())
-                        .map(|x| x == haystack_pre.len())
-                        .unwrap_or(false))
-        }
-
-        // qc_equals_* is only testing the negative case as @burntsushi
-        // pointed out in https://github.com/rust-lang/regex/issues/446.
-        // This quickcheck prop represents an effort to force testing of
-        // the positive case. qc_bm_finds_first and qc_bm_finds_trailing_needle
-        // already check some of the positive cases, but they don't cover
-        // cases where the needle is in the middle of haystack. This prop
-        // fills that hole.
-        fn qc_bm_finds_subslice(
-            haystack: Vec<u8>,
-            needle_start: usize,
-            needle_length: usize
-        ) -> TestResult {
-            if haystack.len() == 0 {
-                return TestResult::discard();
-            }
-
-            let needle_start = needle_start % haystack.len();
-            let needle_length = needle_length % (haystack.len() - needle_start);
-
-            if needle_length == 0 {
-                return TestResult::discard();
-            }
-
-            let needle = &haystack[needle_start..(needle_start + needle_length)];
-
-            let bm_searcher = BoyerMooreSearch::new(needle.to_vec());
-
-            let start = naive_find(&needle, &haystack);
-            match start {
-                None => TestResult::from_bool(false),
-                Some(nf_start) =>
-                    TestResult::from_bool(
-                        nf_start <= needle_start
-                            && bm_searcher.find(&haystack) == start
-                    )
-            }
-        }
-
-        fn qc_bm_finds_first(needle: Vec<u8>) -> TestResult {
-            if needle.len() == 0 {
-                return TestResult::discard();
-            }
-
-            let mut haystack = needle.clone();
-            let searcher = BoyerMooreSearch::new(needle.clone());
-            haystack.extend(needle);
-
-            TestResult::from_bool(
-                searcher.find(haystack.as_slice())
-                        .map(|x| x == 0)
-                        .unwrap_or(false))
-        }
-    }
-}
diff --git a/src/literal/mod.rs b/src/literal/mod.rs
index 783c63b..980f523 100644
--- a/src/literal/mod.rs
+++ b/src/literal/mod.rs
@@ -6,7 +6,7 @@
 #[allow(missing_docs)]
 #[cfg(not(feature = "perf-literal"))]
 mod imp {
-    use syntax::hir::literal::Literals;
+    use regex_syntax::hir::literal::Literals;
 
     #[derive(Clone, Debug)]
     pub struct LiteralSearcher(());
diff --git a/src/pattern.rs b/src/pattern.rs
index e942667..b4ffd8e 100644
--- a/src/pattern.rs
+++ b/src/pattern.rs
@@ -1,7 +1,8 @@
 use std::str::pattern::{Pattern, SearchStep, Searcher};
 
-use re_unicode::{Matches, Regex};
+use crate::re_unicode::{Matches, Regex};
 
+#[derive(Debug)]
 pub struct RegexSearcher<'r, 't> {
     haystack: &'t str,
     it: Matches<'r, 't>,
diff --git a/src/pikevm.rs b/src/pikevm.rs
index 299087d..9a14240 100644
--- a/src/pikevm.rs
+++ b/src/pikevm.rs
@@ -17,11 +17,11 @@
 
 use std::mem;
 
-use exec::ProgramCache;
-use input::{Input, InputAt};
-use prog::{InstPtr, Program};
-use re_trait::Slot;
-use sparse::SparseSet;
+use crate::exec::ProgramCache;
+use crate::input::{Input, InputAt};
+use crate::prog::{InstPtr, Program};
+use crate::re_trait::Slot;
+use crate::sparse::SparseSet;
 
 /// An NFA simulation matching engine.
 #[derive(Debug)]
@@ -231,7 +231,7 @@
         at: InputAt,
         at_next: InputAt,
     ) -> bool {
-        use prog::Inst::*;
+        use crate::prog::Inst::*;
         match self.prog[ip] {
             Match(match_slot) => {
                 if match_slot < matches.len() {
@@ -300,7 +300,7 @@
         // traverse the set of states. We only push to the stack when we
         // absolutely need recursion (restoring captures or following a
         // branch).
-        use prog::Inst::*;
+        use crate::prog::Inst::*;
         loop {
             // Don't visit states we've already added.
             if nlist.set.contains(ip) {
diff --git a/src/pool.rs b/src/pool.rs
index a506ee9..6a6f15b 100644
--- a/src/pool.rs
+++ b/src/pool.rs
@@ -154,7 +154,7 @@
 unsafe impl<T: Send> Sync for Pool<T> {}
 
 impl<T: ::std::fmt::Debug> ::std::fmt::Debug for Pool<T> {
-    fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+    fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
         f.debug_struct("Pool")
             .field("stack", &self.stack)
             .field("owner", &self.owner)
@@ -168,7 +168,7 @@
 /// The purpose of the guard is to use RAII to automatically put the value back
 /// in the pool once it's dropped.
 #[derive(Debug)]
-pub struct PoolGuard<'a, T: 'a + Send> {
+pub struct PoolGuard<'a, T: Send> {
     /// The pool that this guard is attached to.
     pool: &'a Pool<T>,
     /// This is None when the guard represents the special "owned" value. In
@@ -193,7 +193,7 @@
     /// the value to go back into the pool) and then calling get again is NOT
     /// guaranteed to return the same value received in the first get call.
     #[cfg_attr(feature = "perf-inline", inline(always))]
-    pub fn get(&self) -> PoolGuard<T> {
+    pub fn get(&self) -> PoolGuard<'_, T> {
         // Our fast path checks if the caller is the thread that "owns" this
         // pool. Or stated differently, whether it is the first thread that
         // tried to extract a value from the pool. If it is, then we can return
@@ -217,7 +217,7 @@
     ///
     /// If the pool has no owner, then this will set the owner.
     #[cold]
-    fn get_slow(&self, caller: usize, owner: usize) -> PoolGuard<T> {
+    fn get_slow(&self, caller: usize, owner: usize) -> PoolGuard<'_, T> {
         use std::sync::atomic::Ordering::Relaxed;
 
         if owner == 0 {
@@ -284,7 +284,7 @@
 
     #[test]
     fn oibits() {
-        use exec::ProgramCache;
+        use crate::exec::ProgramCache;
 
         fn has_oibits<T: Send + Sync + UnwindSafe + RefUnwindSafe>() {}
         has_oibits::<Pool<ProgramCache>>();
diff --git a/src/prog.rs b/src/prog.rs
index 74e5f2f..475a811 100644
--- a/src/prog.rs
+++ b/src/prog.rs
@@ -6,8 +6,8 @@
 use std::slice;
 use std::sync::Arc;
 
-use input::Char;
-use literal::LiteralSearcher;
+use crate::input::Char;
+use crate::literal::LiteralSearcher;
 
 /// `InstPtr` represents the index of an instruction in a regex program.
 pub type InstPtr = usize;
@@ -168,7 +168,7 @@
 }
 
 impl fmt::Debug for Program {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         use self::Inst::*;
 
         fn with_goto(cur: usize, goto: usize, fmtd: String) -> String {
@@ -259,8 +259,8 @@
 ///
 /// Other than the benefit of moving invariants into the type system, another
 /// benefit is the decreased size. If we remove the `Char` and `Ranges`
-/// instructions from the `Inst` enum, then its size shrinks from 40 bytes to
-/// 24 bytes. (This is because of the removal of a `Vec` in the `Ranges`
+/// instructions from the `Inst` enum, then its size shrinks from 32 bytes to
+/// 24 bytes. (This is because of the removal of a `Box<[]>` in the `Ranges`
 /// variant.) Given that byte based machines are typically much bigger than
 /// their Unicode analogues (because they can decode UTF-8 directly), this ends
 /// up being a pretty significant savings.
@@ -374,7 +374,7 @@
     /// succeeds.
     pub goto: InstPtr,
     /// The set of Unicode scalar value ranges to test.
-    pub ranges: Vec<(char, char)>,
+    pub ranges: Box<[(char, char)]>,
 }
 
 impl InstRanges {
@@ -432,3 +432,16 @@
         self.start <= byte && byte <= self.end
     }
 }
+
+#[cfg(test)]
+mod test {
+    #[test]
+    #[cfg(target_pointer_width = "64")]
+    fn test_size_of_inst() {
+        use std::mem::size_of;
+
+        use super::Inst;
+
+        assert_eq!(32, size_of::<Inst>());
+    }
+}
diff --git a/src/re_builder.rs b/src/re_builder.rs
index fc140f8..ee63836 100644
--- a/src/re_builder.rs
+++ b/src/re_builder.rs
@@ -37,10 +37,10 @@
     ($name:ident, $regex_mod:ident, $only_utf8:expr) => {
         pub mod $name {
             use super::RegexOptions;
-            use error::Error;
-            use exec::ExecBuilder;
+            use crate::error::Error;
+            use crate::exec::ExecBuilder;
 
-            use $regex_mod::Regex;
+            use crate::$regex_mod::Regex;
 
             /// A configurable builder for a regular expression.
             ///
@@ -235,10 +235,10 @@
     ($name:ident, $regex_mod:ident, $only_utf8:expr) => {
         pub mod $name {
             use super::RegexOptions;
-            use error::Error;
-            use exec::ExecBuilder;
+            use crate::error::Error;
+            use crate::exec::ExecBuilder;
 
-            use re_set::$regex_mod::RegexSet;
+            use crate::re_set::$regex_mod::RegexSet;
 
             /// A configurable builder for a set of regular expressions.
             ///
diff --git a/src/re_bytes.rs b/src/re_bytes.rs
index 204a70a..ae55d6d 100644
--- a/src/re_bytes.rs
+++ b/src/re_bytes.rs
@@ -6,13 +6,13 @@
 use std::str::FromStr;
 use std::sync::Arc;
 
-use find_byte::find_byte;
+use crate::find_byte::find_byte;
 
-use error::Error;
-use exec::{Exec, ExecNoSync};
-use expand::expand_bytes;
-use re_builder::bytes::RegexBuilder;
-use re_trait::{self, RegularExpression, SubCapturesPosIter};
+use crate::error::Error;
+use crate::exec::{Exec, ExecNoSync};
+use crate::expand::expand_bytes;
+use crate::re_builder::bytes::RegexBuilder;
+use crate::re_trait::{self, RegularExpression, SubCapturesPosIter};
 
 /// Match represents a single match of a regex in a haystack.
 ///
@@ -79,14 +79,14 @@
 
 impl fmt::Display for Regex {
     /// Shows the original regular expression.
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "{}", self.as_str())
     }
 }
 
 impl fmt::Debug for Regex {
     /// Shows the original regular expression.
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Display::fmt(self, f)
     }
 }
@@ -133,7 +133,7 @@
     /// bytes:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::bytes::Regex;
+    /// # use regex::bytes::Regex;
     /// # fn main() {
     /// let text = b"I categorically deny having triskaidekaphobia.";
     /// assert!(Regex::new(r"\b\w{13}\b").unwrap().is_match(text));
@@ -156,7 +156,7 @@
     /// ASCII word bytes:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::bytes::Regex;
+    /// # use regex::bytes::Regex;
     /// # fn main() {
     /// let text = b"I categorically deny having triskaidekaphobia.";
     /// let mat = Regex::new(r"\b\w{13}\b").unwrap().find(text).unwrap();
@@ -177,7 +177,7 @@
     /// word bytes:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::bytes::Regex;
+    /// # use regex::bytes::Regex;
     /// # fn main() {
     /// let text = b"Retroactively relinquishing remunerations is reprehensible.";
     /// for mat in Regex::new(r"\b\w{13}\b").unwrap().find_iter(text) {
@@ -205,7 +205,7 @@
     /// year separately.
     ///
     /// ```rust
-    /// # extern crate regex; use regex::bytes::Regex;
+    /// # use regex::bytes::Regex;
     /// # fn main() {
     /// let re = Regex::new(r"'([^']+)'\s+\((\d{4})\)").unwrap();
     /// let text = b"Not my favorite movie: 'Citizen Kane' (1941).";
@@ -227,7 +227,7 @@
     /// We can make this example a bit clearer by using *named* capture groups:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::bytes::Regex;
+    /// # use regex::bytes::Regex;
     /// # fn main() {
     /// let re = Regex::new(r"'(?P<title>[^']+)'\s+\((?P<year>\d{4})\)")
     ///                .unwrap();
@@ -271,7 +271,7 @@
     /// some text, where the movie is formatted like "'Title' (xxxx)":
     ///
     /// ```rust
-    /// # extern crate regex; use std::str; use regex::bytes::Regex;
+    /// # use std::str; use regex::bytes::Regex;
     /// # fn main() {
     /// let re = Regex::new(r"'(?P<title>[^']+)'\s+\((?P<year>\d{4})\)")
     ///                .unwrap();
@@ -305,7 +305,7 @@
     /// To split a string delimited by arbitrary amounts of spaces or tabs:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::bytes::Regex;
+    /// # use regex::bytes::Regex;
     /// # fn main() {
     /// let re = Regex::new(r"[ \t]+").unwrap();
     /// let fields: Vec<&[u8]> = re.split(b"a b \t  c\td    e").collect();
@@ -331,7 +331,7 @@
     /// Get the first two words in some text:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::bytes::Regex;
+    /// # use regex::bytes::Regex;
     /// # fn main() {
     /// let re = Regex::new(r"\W+").unwrap();
     /// let fields: Vec<&[u8]> = re.splitn(b"Hey! How are you?", 3).collect();
@@ -379,7 +379,7 @@
     /// In typical usage, this can just be a normal byte string:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::bytes::Regex;
+    /// # use regex::bytes::Regex;
     /// # fn main() {
     /// let re = Regex::new("[^01]+").unwrap();
     /// assert_eq!(re.replace(b"1078910", &b""[..]), &b"1010"[..]);
@@ -392,7 +392,7 @@
     /// group matches easily:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::bytes::Regex;
+    /// # use regex::bytes::Regex;
     /// # use regex::bytes::Captures; fn main() {
     /// let re = Regex::new(r"([^,\s]+),\s+(\S+)").unwrap();
     /// let result = re.replace(b"Springsteen, Bruce", |caps: &Captures| {
@@ -411,7 +411,7 @@
     /// with named capture groups:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::bytes::Regex;
+    /// # use regex::bytes::Regex;
     /// # fn main() {
     /// let re = Regex::new(r"(?P<last>[^,\s]+),\s+(?P<first>\S+)").unwrap();
     /// let result = re.replace(b"Springsteen, Bruce", &b"$first $last"[..]);
@@ -428,7 +428,7 @@
     /// underscore:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::bytes::Regex;
+    /// # use regex::bytes::Regex;
     /// # fn main() {
     /// let re = Regex::new(r"(?P<first>\w+)\s+(?P<second>\w+)").unwrap();
     /// let result = re.replace(b"deep fried", &b"${first}_$second"[..]);
@@ -445,7 +445,7 @@
     /// byte string with `NoExpand`:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::bytes::Regex;
+    /// # use regex::bytes::Regex;
     /// # fn main() {
     /// use regex::bytes::NoExpand;
     ///
@@ -546,7 +546,7 @@
     /// `a`.
     ///
     /// ```rust
-    /// # extern crate regex; use regex::bytes::Regex;
+    /// # use regex::bytes::Regex;
     /// # fn main() {
     /// let text = b"aaaaa";
     /// let pos = Regex::new(r"a+").unwrap().shortest_match(text);
@@ -658,7 +658,7 @@
     }
 
     /// Returns an iterator over the capture names.
-    pub fn capture_names(&self) -> CaptureNames {
+    pub fn capture_names(&self) -> CaptureNames<'_> {
         CaptureNames(self.0.capture_names().iter())
     }
 
@@ -990,15 +990,15 @@
 }
 
 impl<'t> fmt::Debug for Captures<'t> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("Captures").field(&CapturesDebug(self)).finish()
     }
 }
 
-struct CapturesDebug<'c, 't: 'c>(&'c Captures<'t>);
+struct CapturesDebug<'c, 't>(&'c Captures<'t>);
 
 impl<'c, 't> fmt::Debug for CapturesDebug<'c, 't> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fn escape_bytes(bytes: &[u8]) -> String {
             let mut s = String::new();
             for &b in bytes {
@@ -1084,7 +1084,7 @@
 /// The lifetime `'c` corresponds to the lifetime of the `Captures` value, and
 /// the lifetime `'t` corresponds to the originally matched text.
 #[derive(Clone, Debug)]
-pub struct SubCaptureMatches<'c, 't: 'c> {
+pub struct SubCaptureMatches<'c, 't> {
     caps: &'c Captures<'t>,
     it: SubCapturesPosIter<'c>,
 }
@@ -1116,7 +1116,7 @@
     ///
     /// For example, a no-op replacement would be
     /// `dst.extend(&caps[0])`.
-    fn replace_append(&mut self, caps: &Captures, dst: &mut Vec<u8>);
+    fn replace_append(&mut self, caps: &Captures<'_>, dst: &mut Vec<u8>);
 
     /// Return a fixed unchanging replacement byte string.
     ///
@@ -1159,10 +1159,10 @@
 ///
 /// Returned by [`Replacer::by_ref`](trait.Replacer.html#method.by_ref).
 #[derive(Debug)]
-pub struct ReplacerRef<'a, R: ?Sized + 'a>(&'a mut R);
+pub struct ReplacerRef<'a, R: ?Sized>(&'a mut R);
 
 impl<'a, R: Replacer + ?Sized + 'a> Replacer for ReplacerRef<'a, R> {
-    fn replace_append(&mut self, caps: &Captures, dst: &mut Vec<u8>) {
+    fn replace_append(&mut self, caps: &Captures<'_>, dst: &mut Vec<u8>) {
         self.0.replace_append(caps, dst)
     }
     fn no_expansion<'r>(&'r mut self) -> Option<Cow<'r, [u8]>> {
@@ -1171,56 +1171,56 @@
 }
 
 impl<'a> Replacer for &'a [u8] {
-    fn replace_append(&mut self, caps: &Captures, dst: &mut Vec<u8>) {
+    fn replace_append(&mut self, caps: &Captures<'_>, dst: &mut Vec<u8>) {
         caps.expand(*self, dst);
     }
 
-    fn no_expansion(&mut self) -> Option<Cow<[u8]>> {
+    fn no_expansion(&mut self) -> Option<Cow<'_, [u8]>> {
         no_expansion(self)
     }
 }
 
 impl<'a> Replacer for &'a Vec<u8> {
-    fn replace_append(&mut self, caps: &Captures, dst: &mut Vec<u8>) {
+    fn replace_append(&mut self, caps: &Captures<'_>, dst: &mut Vec<u8>) {
         caps.expand(*self, dst);
     }
 
-    fn no_expansion(&mut self) -> Option<Cow<[u8]>> {
+    fn no_expansion(&mut self) -> Option<Cow<'_, [u8]>> {
         no_expansion(self)
     }
 }
 
 impl Replacer for Vec<u8> {
-    fn replace_append(&mut self, caps: &Captures, dst: &mut Vec<u8>) {
+    fn replace_append(&mut self, caps: &Captures<'_>, dst: &mut Vec<u8>) {
         caps.expand(self, dst);
     }
 
-    fn no_expansion(&mut self) -> Option<Cow<[u8]>> {
+    fn no_expansion(&mut self) -> Option<Cow<'_, [u8]>> {
         no_expansion(self)
     }
 }
 
 impl<'a> Replacer for Cow<'a, [u8]> {
-    fn replace_append(&mut self, caps: &Captures, dst: &mut Vec<u8>) {
+    fn replace_append(&mut self, caps: &Captures<'_>, dst: &mut Vec<u8>) {
         caps.expand(self.as_ref(), dst);
     }
 
-    fn no_expansion(&mut self) -> Option<Cow<[u8]>> {
+    fn no_expansion(&mut self) -> Option<Cow<'_, [u8]>> {
         no_expansion(self)
     }
 }
 
 impl<'a> Replacer for &'a Cow<'a, [u8]> {
-    fn replace_append(&mut self, caps: &Captures, dst: &mut Vec<u8>) {
+    fn replace_append(&mut self, caps: &Captures<'_>, dst: &mut Vec<u8>) {
         caps.expand(self.as_ref(), dst);
     }
 
-    fn no_expansion(&mut self) -> Option<Cow<[u8]>> {
+    fn no_expansion(&mut self) -> Option<Cow<'_, [u8]>> {
         no_expansion(self)
     }
 }
 
-fn no_expansion<T: AsRef<[u8]>>(t: &T) -> Option<Cow<[u8]>> {
+fn no_expansion<T: AsRef<[u8]>>(t: &T) -> Option<Cow<'_, [u8]>> {
     let s = t.as_ref();
     match find_byte(b'$', s) {
         Some(_) => None,
@@ -1230,10 +1230,10 @@
 
 impl<F, T> Replacer for F
 where
-    F: FnMut(&Captures) -> T,
+    F: FnMut(&Captures<'_>) -> T,
     T: AsRef<[u8]>,
 {
-    fn replace_append(&mut self, caps: &Captures, dst: &mut Vec<u8>) {
+    fn replace_append(&mut self, caps: &Captures<'_>, dst: &mut Vec<u8>) {
         dst.extend_from_slice((*self)(caps).as_ref());
     }
 }
@@ -1250,11 +1250,11 @@
 pub struct NoExpand<'t>(pub &'t [u8]);
 
 impl<'t> Replacer for NoExpand<'t> {
-    fn replace_append(&mut self, _: &Captures, dst: &mut Vec<u8>) {
+    fn replace_append(&mut self, _: &Captures<'_>, dst: &mut Vec<u8>) {
         dst.extend_from_slice(self.0);
     }
 
-    fn no_expansion(&mut self) -> Option<Cow<[u8]>> {
+    fn no_expansion(&mut self) -> Option<Cow<'_, [u8]>> {
         Some(Cow::Borrowed(self.0))
     }
 }
diff --git a/src/re_set.rs b/src/re_set.rs
index 5cb47ad..73d5953 100644
--- a/src/re_set.rs
+++ b/src/re_set.rs
@@ -7,10 +7,10 @@
             use std::slice;
             use std::vec;
 
-            use error::Error;
-            use exec::Exec;
-            use re_builder::$builder_mod::RegexSetBuilder;
-            use re_trait::RegularExpression;
+            use crate::error::Error;
+            use crate::exec::Exec;
+            use crate::re_builder::$builder_mod::RegexSetBuilder;
+            use crate::re_trait::RegularExpression;
 
 /// Match multiple (possibly overlapping) regular expressions in a single scan.
 ///
@@ -292,7 +292,7 @@
     /// This will always produces matches in ascending order of index, where
     /// the index corresponds to the index of the regex that matched with
     /// respect to its position when initially building the set.
-    pub fn iter(&self) -> SetMatchesIter {
+    pub fn iter(&self) -> SetMatchesIter<'_> {
         SetMatchesIter((&*self.matches).into_iter().enumerate())
     }
 }
@@ -405,7 +405,7 @@
 }
 
 impl fmt::Debug for RegexSet {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "RegexSet({:?})", self.0.regex_strings())
     }
 }
diff --git a/src/re_trait.rs b/src/re_trait.rs
index ea6be9c..680aa54 100644
--- a/src/re_trait.rs
+++ b/src/re_trait.rs
@@ -30,7 +30,7 @@
     /// Creates an iterator of all the capture group positions in order of
     /// appearance in the regular expression. Positions are byte indices
     /// in terms of the original string matched.
-    pub fn iter(&self) -> SubCapturesPosIter {
+    pub fn iter(&self) -> SubCapturesPosIter<'_> {
         SubCapturesPosIter { idx: 0, locs: self }
     }
 
@@ -138,13 +138,13 @@
 
     /// Returns an iterator over all non-overlapping successive leftmost-first
     /// matches.
-    fn find_iter(self, text: &Self::Text) -> Matches<Self> {
+    fn find_iter(self, text: &Self::Text) -> Matches<'_, Self> {
         Matches { re: self, text: text, last_end: 0, last_match: None }
     }
 
     /// Returns an iterator over all non-overlapping successive leftmost-first
     /// matches with captures.
-    fn captures_iter(self, text: &Self::Text) -> CaptureMatches<Self> {
+    fn captures_iter(self, text: &Self::Text) -> CaptureMatches<'_, Self> {
         CaptureMatches(self.find_iter(text))
     }
 }
diff --git a/src/re_unicode.rs b/src/re_unicode.rs
index 1b478cd..142c78f 100644
--- a/src/re_unicode.rs
+++ b/src/re_unicode.rs
@@ -6,21 +6,20 @@
 use std::str::FromStr;
 use std::sync::Arc;
 
-use find_byte::find_byte;
-use syntax;
+use crate::find_byte::find_byte;
 
-use error::Error;
-use exec::{Exec, ExecNoSyncStr};
-use expand::expand_str;
-use re_builder::unicode::RegexBuilder;
-use re_trait::{self, RegularExpression, SubCapturesPosIter};
+use crate::error::Error;
+use crate::exec::{Exec, ExecNoSyncStr};
+use crate::expand::expand_str;
+use crate::re_builder::unicode::RegexBuilder;
+use crate::re_trait::{self, RegularExpression, SubCapturesPosIter};
 
 /// Escapes all regular expression meta characters in `text`.
 ///
 /// The string returned may be safely used as a literal in a regular
 /// expression.
 pub fn escape(text: &str) -> String {
-    syntax::escape(text)
+    regex_syntax::escape(text)
 }
 
 /// Match represents a single match of a regex in a haystack.
@@ -138,14 +137,14 @@
 
 impl fmt::Display for Regex {
     /// Shows the original regular expression.
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "{}", self.as_str())
     }
 }
 
 impl fmt::Debug for Regex {
     /// Shows the original regular expression.
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Display::fmt(self, f)
     }
 }
@@ -189,7 +188,7 @@
     /// Unicode word characters:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::Regex;
+    /// # use regex::Regex;
     /// # fn main() {
     /// let text = "I categorically deny having triskaidekaphobia.";
     /// assert!(Regex::new(r"\b\w{13}\b").unwrap().is_match(text));
@@ -212,7 +211,7 @@
     /// Unicode word characters:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::Regex;
+    /// # use regex::Regex;
     /// # fn main() {
     /// let text = "I categorically deny having triskaidekaphobia.";
     /// let mat = Regex::new(r"\b\w{13}\b").unwrap().find(text).unwrap();
@@ -234,7 +233,7 @@
     /// word characters:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::Regex;
+    /// # use regex::Regex;
     /// # fn main() {
     /// let text = "Retroactively relinquishing remunerations is reprehensible.";
     /// for mat in Regex::new(r"\b\w{13}\b").unwrap().find_iter(text) {
@@ -262,7 +261,7 @@
     /// year separately.
     ///
     /// ```rust
-    /// # extern crate regex; use regex::Regex;
+    /// # use regex::Regex;
     /// # fn main() {
     /// let re = Regex::new(r"'([^']+)'\s+\((\d{4})\)").unwrap();
     /// let text = "Not my favorite movie: 'Citizen Kane' (1941).";
@@ -284,7 +283,7 @@
     /// We can make this example a bit clearer by using *named* capture groups:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::Regex;
+    /// # use regex::Regex;
     /// # fn main() {
     /// let re = Regex::new(r"'(?P<title>[^']+)'\s+\((?P<year>\d{4})\)")
     ///                .unwrap();
@@ -328,7 +327,7 @@
     /// some text, where the movie is formatted like "'Title' (xxxx)":
     ///
     /// ```rust
-    /// # extern crate regex; use regex::Regex;
+    /// # use regex::Regex;
     /// # fn main() {
     /// let re = Regex::new(r"'(?P<title>[^']+)'\s+\((?P<year>\d{4})\)")
     ///                .unwrap();
@@ -361,7 +360,7 @@
     /// To split a string delimited by arbitrary amounts of spaces or tabs:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::Regex;
+    /// # use regex::Regex;
     /// # fn main() {
     /// let re = Regex::new(r"[ \t]+").unwrap();
     /// let fields: Vec<&str> = re.split("a b \t  c\td    e").collect();
@@ -385,7 +384,7 @@
     /// Get the first two words in some text:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::Regex;
+    /// # use regex::Regex;
     /// # fn main() {
     /// let re = Regex::new(r"\W+").unwrap();
     /// let fields: Vec<&str> = re.splitn("Hey! How are you?", 3).collect();
@@ -432,7 +431,7 @@
     /// In typical usage, this can just be a normal string:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::Regex;
+    /// # use regex::Regex;
     /// # fn main() {
     /// let re = Regex::new("[^01]+").unwrap();
     /// assert_eq!(re.replace("1078910", ""), "1010");
@@ -445,7 +444,7 @@
     /// capturing group matches easily:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::Regex;
+    /// # use regex::Regex;
     /// # use regex::Captures; fn main() {
     /// let re = Regex::new(r"([^,\s]+),\s+(\S+)").unwrap();
     /// let result = re.replace("Springsteen, Bruce", |caps: &Captures| {
@@ -461,7 +460,7 @@
     /// with named capture groups:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::Regex;
+    /// # use regex::Regex;
     /// # fn main() {
     /// let re = Regex::new(r"(?P<last>[^,\s]+),\s+(?P<first>\S+)").unwrap();
     /// let result = re.replace("Springsteen, Bruce", "$first $last");
@@ -478,7 +477,7 @@
     /// underscore:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::Regex;
+    /// # use regex::Regex;
     /// # fn main() {
     /// let re = Regex::new(r"(?P<first>\w+)\s+(?P<second>\w+)").unwrap();
     /// let result = re.replace("deep fried", "${first}_$second");
@@ -495,7 +494,7 @@
     /// byte string with `NoExpand`:
     ///
     /// ```rust
-    /// # extern crate regex; use regex::Regex;
+    /// # use regex::Regex;
     /// # fn main() {
     /// use regex::NoExpand;
     ///
@@ -605,7 +604,7 @@
     /// `a`.
     ///
     /// ```rust
-    /// # extern crate regex; use regex::Regex;
+    /// # use regex::Regex;
     /// # fn main() {
     /// let text = "aaaaa";
     /// let pos = Regex::new(r"a+").unwrap().shortest_match(text);
@@ -717,7 +716,7 @@
     }
 
     /// Returns an iterator over the capture names.
-    pub fn capture_names(&self) -> CaptureNames {
+    pub fn capture_names(&self) -> CaptureNames<'_> {
         CaptureNames(self.0.capture_names().iter())
     }
 
@@ -1001,15 +1000,15 @@
 }
 
 impl<'t> fmt::Debug for Captures<'t> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("Captures").field(&CapturesDebug(self)).finish()
     }
 }
 
-struct CapturesDebug<'c, 't: 'c>(&'c Captures<'t>);
+struct CapturesDebug<'c, 't>(&'c Captures<'t>);
 
 impl<'c, 't> fmt::Debug for CapturesDebug<'c, 't> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // We'd like to show something nice here, even if it means an
         // allocation to build a reverse index.
         let slot_to_name: HashMap<&usize, &String> =
@@ -1080,7 +1079,7 @@
 /// The lifetime `'c` corresponds to the lifetime of the `Captures` value, and
 /// the lifetime `'t` corresponds to the originally matched text.
 #[derive(Clone, Debug)]
-pub struct SubCaptureMatches<'c, 't: 'c> {
+pub struct SubCaptureMatches<'c, 't> {
     caps: &'c Captures<'t>,
     it: SubCapturesPosIter<'c>,
 }
@@ -1158,7 +1157,7 @@
     ///
     /// For example, a no-op replacement would be
     /// `dst.push_str(caps.get(0).unwrap().as_str())`.
-    fn replace_append(&mut self, caps: &Captures, dst: &mut String);
+    fn replace_append(&mut self, caps: &Captures<'_>, dst: &mut String);
 
     /// Return a fixed unchanging replacement string.
     ///
@@ -1201,68 +1200,68 @@
 ///
 /// Returned by [`Replacer::by_ref`](trait.Replacer.html#method.by_ref).
 #[derive(Debug)]
-pub struct ReplacerRef<'a, R: ?Sized + 'a>(&'a mut R);
+pub struct ReplacerRef<'a, R: ?Sized>(&'a mut R);
 
 impl<'a, R: Replacer + ?Sized + 'a> Replacer for ReplacerRef<'a, R> {
-    fn replace_append(&mut self, caps: &Captures, dst: &mut String) {
+    fn replace_append(&mut self, caps: &Captures<'_>, dst: &mut String) {
         self.0.replace_append(caps, dst)
     }
-    fn no_expansion(&mut self) -> Option<Cow<str>> {
+    fn no_expansion(&mut self) -> Option<Cow<'_, str>> {
         self.0.no_expansion()
     }
 }
 
 impl<'a> Replacer for &'a str {
-    fn replace_append(&mut self, caps: &Captures, dst: &mut String) {
+    fn replace_append(&mut self, caps: &Captures<'_>, dst: &mut String) {
         caps.expand(*self, dst);
     }
 
-    fn no_expansion(&mut self) -> Option<Cow<str>> {
+    fn no_expansion(&mut self) -> Option<Cow<'_, str>> {
         no_expansion(self)
     }
 }
 
 impl<'a> Replacer for &'a String {
-    fn replace_append(&mut self, caps: &Captures, dst: &mut String) {
+    fn replace_append(&mut self, caps: &Captures<'_>, dst: &mut String) {
         self.as_str().replace_append(caps, dst)
     }
 
-    fn no_expansion(&mut self) -> Option<Cow<str>> {
+    fn no_expansion(&mut self) -> Option<Cow<'_, str>> {
         no_expansion(self)
     }
 }
 
 impl Replacer for String {
-    fn replace_append(&mut self, caps: &Captures, dst: &mut String) {
+    fn replace_append(&mut self, caps: &Captures<'_>, dst: &mut String) {
         self.as_str().replace_append(caps, dst)
     }
 
-    fn no_expansion(&mut self) -> Option<Cow<str>> {
+    fn no_expansion(&mut self) -> Option<Cow<'_, str>> {
         no_expansion(self)
     }
 }
 
 impl<'a> Replacer for Cow<'a, str> {
-    fn replace_append(&mut self, caps: &Captures, dst: &mut String) {
+    fn replace_append(&mut self, caps: &Captures<'_>, dst: &mut String) {
         self.as_ref().replace_append(caps, dst)
     }
 
-    fn no_expansion(&mut self) -> Option<Cow<str>> {
+    fn no_expansion(&mut self) -> Option<Cow<'_, str>> {
         no_expansion(self)
     }
 }
 
 impl<'a> Replacer for &'a Cow<'a, str> {
-    fn replace_append(&mut self, caps: &Captures, dst: &mut String) {
+    fn replace_append(&mut self, caps: &Captures<'_>, dst: &mut String) {
         self.as_ref().replace_append(caps, dst)
     }
 
-    fn no_expansion(&mut self) -> Option<Cow<str>> {
+    fn no_expansion(&mut self) -> Option<Cow<'_, str>> {
         no_expansion(self)
     }
 }
 
-fn no_expansion<T: AsRef<str>>(t: &T) -> Option<Cow<str>> {
+fn no_expansion<T: AsRef<str>>(t: &T) -> Option<Cow<'_, str>> {
     let s = t.as_ref();
     match find_byte(b'$', s.as_bytes()) {
         Some(_) => None,
@@ -1272,10 +1271,10 @@
 
 impl<F, T> Replacer for F
 where
-    F: FnMut(&Captures) -> T,
+    F: FnMut(&Captures<'_>) -> T,
     T: AsRef<str>,
 {
-    fn replace_append(&mut self, caps: &Captures, dst: &mut String) {
+    fn replace_append(&mut self, caps: &Captures<'_>, dst: &mut String) {
         dst.push_str((*self)(caps).as_ref());
     }
 }
@@ -1292,11 +1291,11 @@
 pub struct NoExpand<'t>(pub &'t str);
 
 impl<'t> Replacer for NoExpand<'t> {
-    fn replace_append(&mut self, _: &Captures, dst: &mut String) {
+    fn replace_append(&mut self, _: &Captures<'_>, dst: &mut String) {
         dst.push_str(self.0);
     }
 
-    fn no_expansion(&mut self) -> Option<Cow<str>> {
+    fn no_expansion(&mut self) -> Option<Cow<'_, str>> {
         Some(Cow::Borrowed(self.0))
     }
 }
diff --git a/src/sparse.rs b/src/sparse.rs
index 421d6b6..98b7266 100644
--- a/src/sparse.rs
+++ b/src/sparse.rs
@@ -62,7 +62,7 @@
 }
 
 impl fmt::Debug for SparseSet {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "SparseSet({:?})", self.dense)
     }
 }