syntax: remove 'std::error::Error::description' impls

This method was deprecated a while ago, but we kept it around because it
wasn't worth a breaking release to remove them.

This also simplifies some imports.

regex-syntax/src/ast/mod.rs

@@ -3,7 +3,6 @@ Defines an abstract syntax for regular expressions.
 */
 
 use std::cmp::Ordering;
-use std::error;
 use std::fmt;
 
 pub use crate::ast::visitor::{visit, Visitor};
@@ -178,46 +177,7 @@ pub enum ErrorKind {
     __Nonexhaustive,
 }
 
-impl error::Error for Error {
-    // TODO: Remove this method entirely on the next breaking semver release.
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        use self::ErrorKind::*;
-        match self.kind {
-            CaptureLimitExceeded => "capture group limit exceeded",
-            ClassEscapeInvalid => "invalid escape sequence in character class",
-            ClassRangeInvalid => "invalid character class range",
-            ClassRangeLiteral => "invalid range boundary, must be a literal",
-            ClassUnclosed => "unclosed character class",
-            DecimalEmpty => "empty decimal literal",
-            DecimalInvalid => "invalid decimal literal",
-            EscapeHexEmpty => "empty hexadecimal literal",
-            EscapeHexInvalid => "invalid hexadecimal literal",
-            EscapeHexInvalidDigit => "invalid hexadecimal digit",
-            EscapeUnexpectedEof => "unexpected eof (escape sequence)",
-            EscapeUnrecognized => "unrecognized escape sequence",
-            FlagDanglingNegation => "dangling flag negation operator",
-            FlagDuplicate { .. } => "duplicate flag",
-            FlagRepeatedNegation { .. } => "repeated negation",
-            FlagUnexpectedEof => "unexpected eof (flag)",
-            FlagUnrecognized => "unrecognized flag",
-            GroupNameDuplicate { .. } => "duplicate capture group name",
-            GroupNameEmpty => "empty capture group name",
-            GroupNameInvalid => "invalid capture group name",
-            GroupNameUnexpectedEof => "unclosed capture group name",
-            GroupUnclosed => "unclosed group",
-            GroupUnopened => "unopened group",
-            NestLimitExceeded(_) => "nest limit exceeded",
-            RepetitionCountInvalid => "invalid repetition count range",
-            RepetitionCountUnclosed => "unclosed counted repetition",
-            RepetitionMissing => "repetition operator missing expression",
-            UnicodeClassInvalid => "invalid Unicode character class",
-            UnsupportedBackreference => "backreferences are not supported",
-            UnsupportedLookAround => "look-around is not supported",
-            _ => unreachable!(),
-        }
-    }
-}
+impl std::error::Error for Error {}
 
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

regex-syntax/src/error.rs

@@ -1,5 +1,4 @@
 use std::cmp;
-use std::error;
 use std::fmt;
 use std::result;
 
@@ -39,17 +38,7 @@ impl From<hir::Error> for Error {
     }
 }
 
-impl error::Error for Error {
-    // TODO: Remove this method entirely on the next breaking semver release.
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        match *self {
-            Error::Parse(ref x) => x.description(),
-            Error::Translate(ref x) => x.description(),
-            _ => unreachable!(),
-        }
-    }
-}
+impl std::error::Error for Error {}
 
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

regex-syntax/src/hir/mod.rs

@@ -3,7 +3,6 @@ Defines a high-level intermediate representation for regular expressions.
 */
 use std::char;
 use std::cmp;
-use std::error;
 use std::fmt;
 use std::result;
 use std::u8;
@@ -97,12 +96,19 @@ pub enum ErrorKind {
 // Simplify repetitions (get rid of ZeroOrOne, OneOrMore etc)
 // Get rid of deprecated things
 
-impl ErrorKind {
-    // TODO: Remove this method entirely on the next breaking semver release.
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
+impl std::error::Error for Error {}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        crate::error::Formatter::from(self).fmt(f)
+    }
+}
+
+impl fmt::Display for ErrorKind {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         use self::ErrorKind::*;
-        match *self {
+
+        let msg = match *self {
             UnicodeNotAllowed => "Unicode not allowed here",
             InvalidUtf8 => "pattern can match invalid UTF-8",
             UnicodePropertyNotFound => "Unicode property not found",
@@ -117,29 +123,8 @@ impl ErrorKind {
             }
             EmptyClassNotAllowed => "empty character classes are not allowed",
             __Nonexhaustive => unreachable!(),
-        }
-    }
-}
-
-impl error::Error for Error {
-    // TODO: Remove this method entirely on the next breaking semver release.
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        self.kind.description()
-    }
-}
-
-impl fmt::Display for Error {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        crate::error::Formatter::from(self).fmt(f)
-    }
-}
-
-impl fmt::Display for ErrorKind {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        // TODO: Remove this on the next breaking semver release.
-        #[allow(deprecated)]
-        f.write_str(self.description())
+        };
+        f.write_str(msg)
     }
 }