diff --git a/.github/workflows/test-package.yml b/.github/workflows/test-package.yml
index 2030e2e..cbb5213 100644
--- a/.github/workflows/test-package.yml
+++ b/.github/workflows/test-package.yml
@@ -47,7 +47,7 @@ jobs:
       matrix:
         # Add macos-latest and/or windows-latest if relevant for this package.
         os: [ubuntu-latest, windows-latest]
-        sdk: [2.19.0, dev]
+        sdk: [3.0, dev]
     steps:
       - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11
       - uses: dart-lang/setup-dart@b64355ae6ca0b5d484f0106a033dd1388965d06d
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 70e7747..071dad0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 1.0.1-wip
+
+- Require Dart 3.0
+
 ## 1.0.0
 
 - Rev to `1.0.0` (note however that there are no API changes from `0.17.x`).
diff --git a/analysis_options.yaml b/analysis_options.yaml
index eb67f88..25e2df4 100644
--- a/analysis_options.yaml
+++ b/analysis_options.yaml
@@ -5,3 +5,9 @@ analyzer:
     strict-casts: true
     strict-inference: true
     strict-raw-types: true
+  errors:
+    comment_references: ignore #too many false positives
+
+linter:
+  rules:
+    - prefer_expression_function_bodies
diff --git a/example/main.dart b/example/main.dart
index 7aad004..88dc748 100644
--- a/example/main.dart
+++ b/example/main.dart
@@ -84,9 +84,8 @@ StyleSheet parseCss(
   String cssInput, {
   List<css.Message>? errors,
   css.PreprocessorOptions? opts,
-}) {
-  return css.parse(cssInput, errors: errors, options: opts ?? _default);
-}
+}) =>
+    css.parse(cssInput, errors: errors, options: opts ?? _default);
 
 /// Pretty printer for CSS.
 String prettyPrint(StyleSheet ss) =>
diff --git a/lib/parser.dart b/lib/parser.dart
index 15dd764..e978069 100644
--- a/lib/parser.dart
+++ b/lib/parser.dart
@@ -38,7 +38,7 @@ class ParserState extends TokenizerState {
 
 void _createMessages({List<Message>? errors, PreprocessorOptions? options}) {
   errors ??= [];
-  options ??= PreprocessorOptions(useColors: false, inputFile: 'memory');
+  options ??= const PreprocessorOptions(useColors: false, inputFile: 'memory');
 
   messages = Messages(options: options, printHandler: errors.add);
 }
@@ -258,9 +258,7 @@ class _Parser {
   ///////////////////////////////////////////////////////////////////
   // Basic support methods
   ///////////////////////////////////////////////////////////////////
-  int _peek() {
-    return _peekToken.kind;
-  }
+  int _peek() => _peekToken.kind;
 
   Token _next({bool unicodeRange = false}) {
     final next = _previousToken = _peekToken;
@@ -268,14 +266,10 @@ class _Parser {
     return next;
   }
 
-  bool _peekKind(int kind) {
-    return _peekToken.kind == kind;
-  }
+  bool _peekKind(int kind) => _peekToken.kind == kind;
 
   // Is the next token a legal identifier?  This includes pseudo-keywords.
-  bool _peekIdentifier() {
-    return TokenKind.isIdentifier(_peekToken.kind);
-  }
+  bool _peekIdentifier() => TokenKind.isIdentifier(_peekToken.kind);
 
   /// Marks the parser/tokenizer look ahead to support Less nested selectors.
   ParserState get _mark => ParserState(_peekToken, _previousToken, tokenizer);
@@ -792,9 +786,8 @@ class _Parser {
       }
 
       var declGroup = processDeclarations(checkBrace: false);
-      if (declGroup.declarations.any((decl) {
-        return decl is Declaration && decl is! IncludeMixinAtDeclaration;
-      })) {
+      if (declGroup.declarations.any((decl) =>
+          decl is Declaration && decl is! IncludeMixinAtDeclaration)) {
         var newDecls = <Declaration>[];
         for (var include in productions) {
           // If declGroup has items that are declarations then we assume
@@ -2038,40 +2031,31 @@ class _Parser {
   DartStyleExpression? processOneNumber(Expressions exprs, int part) {
     var value = marginValue(exprs.expressions[0]);
     if (value != null) {
-      switch (part) {
-        case _marginPartLeft:
-          return MarginExpression(exprs.span, left: value);
-        case _marginPartTop:
-          return MarginExpression(exprs.span, top: value);
-        case _marginPartRight:
-          return MarginExpression(exprs.span, right: value);
-        case _marginPartBottom:
-          return MarginExpression(exprs.span, bottom: value);
-        case _borderPartLeft:
-        case _borderPartLeftWidth:
-          return BorderExpression(exprs.span, left: value);
-        case _borderPartTop:
-        case _borderPartTopWidth:
-          return BorderExpression(exprs.span, top: value);
-        case _borderPartRight:
-        case _borderPartRightWidth:
-          return BorderExpression(exprs.span, right: value);
-        case _borderPartBottom:
-        case _borderPartBottomWidth:
-          return BorderExpression(exprs.span, bottom: value);
-        case _heightPart:
-          return HeightExpression(exprs.span, value);
-        case _widthPart:
-          return WidthExpression(exprs.span, value);
-        case _paddingPartLeft:
-          return PaddingExpression(exprs.span, left: value);
-        case _paddingPartTop:
-          return PaddingExpression(exprs.span, top: value);
-        case _paddingPartRight:
-          return PaddingExpression(exprs.span, right: value);
-        case _paddingPartBottom:
-          return PaddingExpression(exprs.span, bottom: value);
-      }
+      return switch (part) {
+        _marginPartLeft => MarginExpression(exprs.span, left: value),
+        _marginPartTop => MarginExpression(exprs.span, top: value),
+        _marginPartRight => MarginExpression(exprs.span, right: value),
+        _marginPartBottom => MarginExpression(exprs.span, bottom: value),
+        _borderPartLeft ||
+        _borderPartLeftWidth =>
+          BorderExpression(exprs.span, left: value),
+        _borderPartTop ||
+        _borderPartTopWidth =>
+          BorderExpression(exprs.span, top: value),
+        _borderPartRight ||
+        _borderPartRightWidth =>
+          BorderExpression(exprs.span, right: value),
+        _borderPartBottom ||
+        _borderPartBottomWidth =>
+          BorderExpression(exprs.span, bottom: value),
+        _heightPart => HeightExpression(exprs.span, value),
+        _widthPart => WidthExpression(exprs.span, value),
+        _paddingPartLeft => PaddingExpression(exprs.span, left: value),
+        _paddingPartTop => PaddingExpression(exprs.span, top: value),
+        _paddingPartRight => PaddingExpression(exprs.span, right: value),
+        _paddingPartBottom => PaddingExpression(exprs.span, bottom: value),
+        _ => null
+      };
     }
     return null;
   }
diff --git a/lib/src/messages.dart b/lib/src/messages.dart
index cf97c22..fb1516c 100644
--- a/lib/src/messages.dart
+++ b/lib/src/messages.dart
@@ -86,7 +86,7 @@ class Messages {
   final List<Message> messages = <Message>[];
 
   Messages({PreprocessorOptions? options, this.printHandler = print})
-      : options = options ?? PreprocessorOptions();
+      : options = options ?? const PreprocessorOptions();
 
   /// Report a compile-time CSS error.
   void error(String message, SourceSpan? span) {
diff --git a/lib/src/property.dart b/lib/src/property.dart
index f884566..ec6b854 100644
--- a/lib/src/property.dart
+++ b/lib/src/property.dart
@@ -504,14 +504,12 @@ class Rgba implements _StyleProperty, ColorBase {
 
   factory Rgba.fromColor(Color color) => color.rgba;
 
-  factory Rgba.fromArgbValue(num value) {
-    return Rgba(
-      (value.toInt() & 0xff000000) >> 0x18, // a
-      (value.toInt() & 0xff0000) >> 0x10, // r
-      (value.toInt() & 0xff00) >> 8, // g
-      value.toInt() & 0xff,
-    ); // b
-  }
+  factory Rgba.fromArgbValue(num value) => Rgba(
+        (value.toInt() & 0xff000000) >> 0x18, // a
+        (value.toInt() & 0xff0000) >> 0x10, // r
+        (value.toInt() & 0xff00) >> 8, // g
+        value.toInt() & 0xff,
+      ); // b
 
   factory Rgba.fromHsla(Hsla hsla) {
     // Convert to Rgba.
@@ -752,10 +750,9 @@ class PointXY implements _StyleProperty {
   const PointXY(this.x, this.y);
 
   @override
-  String? get cssExpression {
-    // TODO(terry): TBD
-    return null;
-  }
+  String? get cssExpression =>
+      // TODO(terry): TBD
+      null;
 }
 
 // TODO(terry): Implement style and color.
@@ -779,14 +776,12 @@ class Border implements _StyleProperty {
   int get height => top! + bottom!;
 
   @override
-  String get cssExpression {
-    return (top == left && bottom == right && top == right)
-        ? '${left}px'
-        : "${top != null ? '$top' : '0'}px "
-            "${right != null ? '$right' : '0'}px "
-            "${bottom != null ? '$bottom' : '0'}px "
-            "${left != null ? '$left' : '0'}px";
-  }
+  String get cssExpression => (top == left && bottom == right && top == right)
+      ? '${left}px'
+      : "${top != null ? '$top' : '0'}px "
+          "${right != null ? '$right' : '0'}px "
+          "${bottom != null ? '$bottom' : '0'}px "
+          "${left != null ? '$left' : '0'}px";
 }
 
 /// Font style constants.
@@ -1069,10 +1064,9 @@ class Font implements _StyleProperty {
   }
 
   @override
-  int get hashCode {
-    // TODO(jimhug): Lot's of potential collisions here. List of fonts, etc.
-    return size!.toInt() % family![0].hashCode;
-  }
+  int get hashCode =>
+      // TODO(jimhug): Lot's of potential collisions here. List of fonts, etc.
+      size!.toInt() % family![0].hashCode;
 
   @override
   bool operator ==(Object other) {
diff --git a/lib/src/token_kind.dart b/lib/src/token_kind.dart
index b654379..3f50402 100644
--- a/lib/src/token_kind.dart
+++ b/lib/src/token_kind.dart
@@ -507,24 +507,20 @@ class TokenKind {
   }
 
   /// Return the token that matches the unit ident found.
-  static int matchUnits(String text, int offset, int length) {
-    return matchList(_UNITS, 'unit', text, offset, length);
-  }
+  static int matchUnits(String text, int offset, int length) =>
+      matchList(_UNITS, 'unit', text, offset, length);
 
   /// Return the token that matches the directive name found.
-  static int matchDirectives(String text, int offset, int length) {
-    return matchList(_DIRECTIVES, 'type', text, offset, length);
-  }
+  static int matchDirectives(String text, int offset, int length) =>
+      matchList(_DIRECTIVES, 'type', text, offset, length);
 
   /// Return the token that matches the margin directive name found.
-  static int matchMarginDirectives(String text, int offset, int length) {
-    return matchList(MARGIN_DIRECTIVES, 'type', text, offset, length);
-  }
+  static int matchMarginDirectives(String text, int offset, int length) =>
+      matchList(MARGIN_DIRECTIVES, 'type', text, offset, length);
 
   /// Return the token that matches the media operator found.
-  static int matchMediaOperator(String text, int offset, int length) {
-    return matchList(MEDIA_OPERATORS, 'type', text, offset, length);
-  }
+  static int matchMediaOperator(String text, int offset, int length) =>
+      matchList(MEDIA_OPERATORS, 'type', text, offset, length);
 
   static String? idToValue(Iterable<Object?> identList, int tokenId) {
     for (var entry in identList) {
@@ -564,9 +560,7 @@ class TokenKind {
   }
 
   /// Return RGB value as [int] from a color entry in _EXTENDED_COLOR_NAMES.
-  static int colorValue(Map<String, Object> entry) {
-    return entry['value'] as int;
-  }
+  static int colorValue(Map<String, Object> entry) => entry['value'] as int;
 
   static String? hexToColorName(Object hexValue) {
     for (final entry in _EXTENDED_COLOR_NAMES) {
@@ -604,82 +598,44 @@ class TokenKind {
     return invertResult.toString();
   }
 
-  static String kindToString(int kind) {
-    switch (kind) {
-      case TokenKind.UNUSED:
-        return 'ERROR';
-      case TokenKind.END_OF_FILE:
-        return 'end of file';
-      case TokenKind.LPAREN:
-        return '(';
-      case TokenKind.RPAREN:
-        return ')';
-      case TokenKind.LBRACK:
-        return '[';
-      case TokenKind.RBRACK:
-        return ']';
-      case TokenKind.LBRACE:
-        return '{';
-      case TokenKind.RBRACE:
-        return '}';
-      case TokenKind.DOT:
-        return '.';
-      case TokenKind.SEMICOLON:
-        return ';';
-      case TokenKind.AT:
-        return '@';
-      case TokenKind.HASH:
-        return '#';
-      case TokenKind.PLUS:
-        return '+';
-      case TokenKind.GREATER:
-        return '>';
-      case TokenKind.TILDE:
-        return '~';
-      case TokenKind.ASTERISK:
-        return '*';
-      case TokenKind.NAMESPACE:
-        return '|';
-      case TokenKind.COLON:
-        return ':';
-      case TokenKind.PRIVATE_NAME:
-        return '_';
-      case TokenKind.COMMA:
-        return ',';
-      case TokenKind.SPACE:
-        return ' ';
-      case TokenKind.TAB:
-        return '\t';
-      case TokenKind.NEWLINE:
-        return '\n';
-      case TokenKind.RETURN:
-        return '\r';
-      case TokenKind.PERCENT:
-        return '%';
-      case TokenKind.SINGLE_QUOTE:
-        return "'";
-      case TokenKind.DOUBLE_QUOTE:
-        return '"';
-      case TokenKind.SLASH:
-        return '/';
-      case TokenKind.EQUALS:
-        return '=';
-      case TokenKind.CARET:
-        return '^';
-      case TokenKind.DOLLAR:
-        return '\$';
-      case TokenKind.LESS:
-        return '<';
-      case TokenKind.BANG:
-        return '!';
-      case TokenKind.MINUS:
-        return '-';
-      case TokenKind.BACKSLASH:
-        return '\\';
-      default:
-        throw StateError('Unknown TOKEN');
-    }
-  }
+  static String kindToString(int kind) => switch (kind) {
+        TokenKind.UNUSED => 'ERROR',
+        TokenKind.END_OF_FILE => 'end of file',
+        TokenKind.LPAREN => '(',
+        TokenKind.RPAREN => ')',
+        TokenKind.LBRACK => '[',
+        TokenKind.RBRACK => ']',
+        TokenKind.LBRACE => '{',
+        TokenKind.RBRACE => '}',
+        TokenKind.DOT => '.',
+        TokenKind.SEMICOLON => ';',
+        TokenKind.AT => '@',
+        TokenKind.HASH => '#',
+        TokenKind.PLUS => '+',
+        TokenKind.GREATER => '>',
+        TokenKind.TILDE => '~',
+        TokenKind.ASTERISK => '*',
+        TokenKind.NAMESPACE => '|',
+        TokenKind.COLON => ':',
+        TokenKind.PRIVATE_NAME => '_',
+        TokenKind.COMMA => ',',
+        TokenKind.SPACE => ' ',
+        TokenKind.TAB => '\t',
+        TokenKind.NEWLINE => '\n',
+        TokenKind.RETURN => '\r',
+        TokenKind.PERCENT => '%',
+        TokenKind.SINGLE_QUOTE => "'",
+        TokenKind.DOUBLE_QUOTE => '"',
+        TokenKind.SLASH => '/',
+        TokenKind.EQUALS => '=',
+        TokenKind.CARET => '^',
+        TokenKind.DOLLAR => '\$',
+        TokenKind.LESS => '<',
+        TokenKind.BANG => '!',
+        TokenKind.MINUS => '-',
+        TokenKind.BACKSLASH => '\\',
+        _ => throw StateError('Unknown TOKEN')
+      };
 
   static bool isKindIdentifier(int kind) {
     switch (kind) {
@@ -724,9 +680,7 @@ class TokenKind {
     }
   }
 
-  static bool isIdentifier(int kind) {
-    return kind == IDENTIFIER;
-  }
+  static bool isIdentifier(int kind) => kind == IDENTIFIER;
 }
 
 // Note: these names should match TokenKind names
diff --git a/lib/src/tokenizer.dart b/lib/src/tokenizer.dart
index 15f5ad0..d090106 100644
--- a/lib/src/tokenizer.dart
+++ b/lib/src/tokenizer.dart
@@ -234,24 +234,20 @@ class Tokenizer extends TokenizerBase {
     }
   }
 
-  bool varDef(int ch) {
-    return ch == 'v'.codeUnitAt(0) &&
-        _maybeEatChar('a'.codeUnitAt(0)) &&
-        _maybeEatChar('r'.codeUnitAt(0)) &&
-        _maybeEatChar('-'.codeUnitAt(0));
-  }
-
-  bool varUsage(int ch) {
-    return ch == 'v'.codeUnitAt(0) &&
-        _maybeEatChar('a'.codeUnitAt(0)) &&
-        _maybeEatChar('r'.codeUnitAt(0)) &&
-        (_peekChar() == '-'.codeUnitAt(0));
-  }
+  bool varDef(int ch) =>
+      ch == 'v'.codeUnitAt(0) &&
+      _maybeEatChar('a'.codeUnitAt(0)) &&
+      _maybeEatChar('r'.codeUnitAt(0)) &&
+      _maybeEatChar('-'.codeUnitAt(0));
+
+  bool varUsage(int ch) =>
+      ch == 'v'.codeUnitAt(0) &&
+      _maybeEatChar('a'.codeUnitAt(0)) &&
+      _maybeEatChar('r'.codeUnitAt(0)) &&
+      (_peekChar() == '-'.codeUnitAt(0));
 
   @override
-  Token _errorToken([String? message]) {
-    return _finishToken(TokenKind.ERROR);
-  }
+  Token _errorToken([String? message]) => _finishToken(TokenKind.ERROR);
 
   @override
   int getIdentifierKind() {
@@ -444,39 +440,32 @@ class Tokenizer extends TokenizerBase {
 
 /// Static helper methods.
 class TokenizerHelpers {
-  static bool isIdentifierStart(int c) {
-    return isIdentifierStartExpr(c) || c == 45 /*-*/;
-  }
+  static bool isIdentifierStart(int c) =>
+      isIdentifierStartExpr(c) || c == 45 /*-*/;
 
-  static bool isDigit(int c) {
-    return c >= 48 /*0*/ && c <= 57 /*9*/;
-  }
+  static bool isDigit(int c) => c >= 48 /*0*/ && c <= 57 /*9*/;
 
-  static bool isHexDigit(int c) {
-    return isDigit(c) ||
-        (c >= 97 /*a*/ && c <= 102 /*f*/) ||
-        (c >= 65 /*A*/ && c <= 70 /*F*/);
-  }
+  static bool isHexDigit(int c) =>
+      isDigit(c) ||
+      (c >= 97 /*a*/ && c <= 102 /*f*/) ||
+      (c >= 65 /*A*/ && c <= 70 /*F*/);
 
-  static bool isIdentifierPart(int c) {
-    return isIdentifierPartExpr(c) || c == 45 /*-*/;
-  }
+  static bool isIdentifierPart(int c) =>
+      isIdentifierPartExpr(c) || c == 45 /*-*/;
 
   /// Pseudo function expressions identifiers can't have a minus sign.
-  static bool isIdentifierStartExpr(int c) {
-    return (c >= 97 /*a*/ && c <= 122 /*z*/) ||
-        (c >= 65 /*A*/ && c <= 90 /*Z*/) ||
-        // Note: Unicode 10646 chars U+00A0 or higher are allowed, see:
-        // http://www.w3.org/TR/CSS21/syndata.html#value-def-identifier
-        // http://www.w3.org/TR/CSS21/syndata.html#characters
-        // Also, escaped character should be allowed.
-        c == 95 /*_*/ ||
-        c >= 0xA0 ||
-        c == 92 /*\*/;
-  }
+  static bool isIdentifierStartExpr(int c) =>
+      (c >= 97 /*a*/ && c <= 122 /*z*/) ||
+      (c >= 65 /*A*/ && c <= 90 /*Z*/) ||
+      // Note: Unicode 10646 chars U+00A0 or higher are allowed, see:
+      // http://www.w3.org/TR/CSS21/syndata.html#value-def-identifier
+      // http://www.w3.org/TR/CSS21/syndata.html#characters
+      // Also, escaped character should be allowed.
+      c == 95 /*_*/ ||
+      c >= 0xA0 ||
+      c == 92 /*\*/;
 
   /// Pseudo function expressions identifiers can't have a minus sign.
-  static bool isIdentifierPartExpr(int c) {
-    return isIdentifierStartExpr(c) || isDigit(c);
-  }
+  static bool isIdentifierPartExpr(int c) =>
+      isIdentifierStartExpr(c) || isDigit(c);
 }
diff --git a/lib/src/tokenizer_base.dart b/lib/src/tokenizer_base.dart
index bb44fee..bcac7be 100644
--- a/lib/src/tokenizer_base.dart
+++ b/lib/src/tokenizer_base.dart
@@ -107,14 +107,10 @@ abstract class TokenizerBase {
     return false;
   }
 
-  Token _finishToken(int kind) {
-    return Token(kind, _file.span(_startIndex, _index));
-  }
+  Token _finishToken(int kind) => Token(kind, _file.span(_startIndex, _index));
 
-  Token _errorToken([String? message]) {
-    return ErrorToken(
-        TokenKind.ERROR, _file.span(_startIndex, _index), message);
-  }
+  Token _errorToken([String? message]) =>
+      ErrorToken(TokenKind.ERROR, _file.span(_startIndex, _index), message);
 
   Token finishWhitespace() {
     _index--;
diff --git a/lib/src/tree.dart b/lib/src/tree.dart
index 3c7df97..94655cf 100644
--- a/lib/src/tree.dart
+++ b/lib/src/tree.dart
@@ -22,12 +22,11 @@ class Identifier extends TreeNode {
   dynamic visit(VisitorBase visitor) => visitor.visitIdentifier(this);
 
   @override
-  String toString() {
-    // Try to use the identifier's original lexeme to preserve any escape codes
-    // as authored. The name, which may include escaped values, may no longer be
-    // a valid identifier.
-    return span?.text ?? name;
-  }
+  String toString() =>
+      // Try to use the identifier's original lexeme to preserve any escape
+      // codes as authored. The name, which may include escaped values, may no
+      // longer be a valid identifier.
+      span?.text ?? name;
 }
 
 class Wildcard extends TreeNode {
@@ -147,20 +146,13 @@ class SimpleSelectorSequence extends TreeNode {
   bool get isCombinatorDescendant =>
       combinator == TokenKind.COMBINATOR_DESCENDANT;
 
-  String get _combinatorToString {
-    switch (combinator) {
-      case TokenKind.COMBINATOR_DESCENDANT:
-        return ' ';
-      case TokenKind.COMBINATOR_GREATER:
-        return ' > ';
-      case TokenKind.COMBINATOR_PLUS:
-        return ' + ';
-      case TokenKind.COMBINATOR_TILDE:
-        return ' ~ ';
-      default:
-        return '';
-    }
-  }
+  String get _combinatorToString => switch (combinator) {
+        TokenKind.COMBINATOR_DESCENDANT => ' ',
+        TokenKind.COMBINATOR_GREATER => ' > ',
+        TokenKind.COMBINATOR_PLUS => ' + ',
+        TokenKind.COMBINATOR_TILDE => ' ~ ',
+        _ => ''
+      };
 
   @override
   SimpleSelectorSequence clone() =>
@@ -243,44 +235,27 @@ class AttributeSelector extends SimpleSelector {
 
   int get operatorKind => _op;
 
-  String? matchOperator() {
-    switch (_op) {
-      case TokenKind.EQUALS:
-        return '=';
-      case TokenKind.INCLUDES:
-        return '~=';
-      case TokenKind.DASH_MATCH:
-        return '|=';
-      case TokenKind.PREFIX_MATCH:
-        return '^=';
-      case TokenKind.SUFFIX_MATCH:
-        return '\$=';
-      case TokenKind.SUBSTRING_MATCH:
-        return '*=';
-      case TokenKind.NO_MATCH:
-        return '';
-    }
-    return null;
-  }
+  String? matchOperator() => switch (_op) {
+        TokenKind.EQUALS => '=',
+        TokenKind.INCLUDES => '~=',
+        TokenKind.DASH_MATCH => '|=',
+        TokenKind.PREFIX_MATCH => '^=',
+        TokenKind.SUFFIX_MATCH => '\$=',
+        TokenKind.SUBSTRING_MATCH => '*=',
+        TokenKind.NO_MATCH => '',
+        _ => null
+      };
 
   // Return the TokenKind for operator used by visitAttributeSelector.
-  String? matchOperatorAsTokenString() {
-    switch (_op) {
-      case TokenKind.EQUALS:
-        return 'EQUALS';
-      case TokenKind.INCLUDES:
-        return 'INCLUDES';
-      case TokenKind.DASH_MATCH:
-        return 'DASH_MATCH';
-      case TokenKind.PREFIX_MATCH:
-        return 'PREFIX_MATCH';
-      case TokenKind.SUFFIX_MATCH:
-        return 'SUFFIX_MATCH';
-      case TokenKind.SUBSTRING_MATCH:
-        return 'SUBSTRING_MATCH';
-    }
-    return null;
-  }
+  String? matchOperatorAsTokenString() => switch (_op) {
+        TokenKind.EQUALS => 'EQUALS',
+        TokenKind.INCLUDES => 'INCLUDES',
+        TokenKind.DASH_MATCH => 'DASH_MATCH',
+        TokenKind.PREFIX_MATCH => 'PREFIX_MATCH',
+        TokenKind.SUFFIX_MATCH => 'SUFFIX_MATCH',
+        TokenKind.SUBSTRING_MATCH => 'SUBSTRING_MATCH',
+        _ => null
+      };
 
   String valueToString() {
     if (value != null) {
@@ -406,9 +381,8 @@ class SelectorExpression extends TreeNode {
   SourceSpan get span => super.span!;
 
   @override
-  SelectorExpression clone() {
-    return SelectorExpression(expressions.map((e) => e.clone()).toList(), span);
-  }
+  SelectorExpression clone() =>
+      SelectorExpression(expressions.map((e) => e.clone()).toList(), span);
 
   @override
   dynamic visit(VisitorBase visitor) => visitor.visitSelectorExpression(this);
@@ -824,20 +798,15 @@ class KeyFrameDirective extends Directive {
     _blocks.add(block);
   }
 
-  String? get keyFrameName {
-    switch (_keyframeName) {
-      case TokenKind.DIRECTIVE_KEYFRAMES:
-      case TokenKind.DIRECTIVE_MS_KEYFRAMES:
-        return '@keyframes';
-      case TokenKind.DIRECTIVE_WEB_KIT_KEYFRAMES:
-        return '@-webkit-keyframes';
-      case TokenKind.DIRECTIVE_MOZ_KEYFRAMES:
-        return '@-moz-keyframes';
-      case TokenKind.DIRECTIVE_O_KEYFRAMES:
-        return '@-o-keyframes';
-    }
-    return null;
-  }
+  String? get keyFrameName => switch (_keyframeName) {
+        TokenKind.DIRECTIVE_KEYFRAMES ||
+        TokenKind.DIRECTIVE_MS_KEYFRAMES =>
+          '@keyframes',
+        TokenKind.DIRECTIVE_WEB_KIT_KEYFRAMES => '@-webkit-keyframes',
+        TokenKind.DIRECTIVE_MOZ_KEYFRAMES => '@-moz-keyframes',
+        TokenKind.DIRECTIVE_O_KEYFRAMES => '@-o-keyframes',
+        _ => null
+      };
 
   @override
   KeyFrameDirective clone() {
@@ -1611,9 +1580,8 @@ class FontExpression extends DartStyleExpression {
   }
 
   /// Merge the two FontExpression and return the result.
-  factory FontExpression.merge(FontExpression x, FontExpression y) {
-    return FontExpression._merge(x, y, y.span);
-  }
+  factory FontExpression.merge(FontExpression x, FontExpression y) =>
+      FontExpression._merge(x, y, y.span);
 
   FontExpression._merge(FontExpression x, FontExpression y, SourceSpan? span)
       : font = Font.merge(x.font, y.font)!,
@@ -1676,9 +1644,8 @@ class MarginExpression extends BoxExpression {
   }
 
   /// Merge the two MarginExpressions and return the result.
-  factory MarginExpression.merge(MarginExpression x, MarginExpression y) {
-    return MarginExpression._merge(x, y, y.span);
-  }
+  factory MarginExpression.merge(MarginExpression x, MarginExpression y) =>
+      MarginExpression._merge(x, y, y.span);
 
   MarginExpression._merge(
       MarginExpression x, MarginExpression y, SourceSpan? span)
@@ -1712,9 +1679,8 @@ class BorderExpression extends BoxExpression {
   }
 
   /// Merge the two BorderExpression and return the result.
-  factory BorderExpression.merge(BorderExpression x, BorderExpression y) {
-    return BorderExpression._merge(x, y, y.span);
-  }
+  factory BorderExpression.merge(BorderExpression x, BorderExpression y) =>
+      BorderExpression._merge(x, y, y.span);
 
   BorderExpression._merge(
       BorderExpression x, BorderExpression y, SourceSpan? span)
@@ -1793,9 +1759,8 @@ class PaddingExpression extends BoxExpression {
   }
 
   /// Merge the two PaddingExpression and return the result.
-  factory PaddingExpression.merge(PaddingExpression x, PaddingExpression y) {
-    return PaddingExpression._merge(x, y, y.span);
-  }
+  factory PaddingExpression.merge(PaddingExpression x, PaddingExpression y) =>
+      PaddingExpression._merge(x, y, y.span);
 
   PaddingExpression._merge(
       PaddingExpression x, PaddingExpression y, SourceSpan? span)
diff --git a/lib/src/validate.dart b/lib/src/validate.dart
index b99a898..608c093 100644
--- a/lib/src/validate.dart
+++ b/lib/src/validate.dart
@@ -2,9 +2,10 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:csslib/visitor.dart';
 import 'package:source_span/source_span.dart';
 
+import '../visitor.dart';
+
 /// Can be thrown on any Css runtime problem includes source location.
 class CssSelectorException extends SourceSpanException {
   CssSelectorException(super.message, [super.span]);
diff --git a/pubspec.yaml b/pubspec.yaml
index e0eab9a..7a1cb94 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: csslib
-version: 1.0.0
+version: 1.0.1-wip
 description: A library for parsing and analyzing CSS (Cascading Style Sheets).
 repository: https://github.com/dart-lang/csslib
 
@@ -7,13 +7,13 @@ topics:
   - css
 
 environment:
-  sdk: '>=2.19.0 <4.0.0'
+  sdk: ^3.0.0
 
 dependencies:
   source_span: ^1.8.0
 
 dev_dependencies:
-  dart_flutter_team_lints: ^1.0.0
+  dart_flutter_team_lints: ^2.0.0
   path: ^1.8.0
   term_glyph: ^1.2.0
   test: ^1.16.0