Rewrite the pkg/yaml parser.

pkg/yaml/lib/src/token.dart

Index: pkg/yaml/lib/src/token.dart
diff --git a/pkg/yaml/lib/src/token.dart b/pkg/yaml/lib/src/token.dart
new file mode 100644
index 0000000000000000000000000000000000000000..20ae547c65dfba7238781d861ac100e3ff3201d7
--- /dev/null
+++ b/pkg/yaml/lib/src/token.dart
@@ -0,0 +1,148 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// 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.
+
+library yaml.token;
+
+import 'package:source_span/source_span.dart';
+
+import 'style.dart';
+
+/// A token emitted by a [Scanner].
+class Token {
+  /// The token type.
+  final TokenType type;
+
+  /// The span associated with the token.
+  final FileSpan span;
+
+  Token(this.type, this.span);
+
+  String toString() => type.toString();
+}
+
+/// A token representing a `%YAML` directive.
+class VersionDirectiveToken implements Token {
+  get type => TokenType.VERSION_DIRECTIVE;
+  final FileSpan span;
+
+  /// The declared major version of the document.
+  final int major;
+
+  /// The declared minor version of the document.
+  final int minor;
+
+  VersionDirectiveToken(this.span, this.major, this.minor);
+
+  String toString() => "VERSION_DIRECTIVE $major.$minor";
+}
+
+/// A token representing a `%TAG` directive.
+class TagDirectiveToken implements Token {
+  get type => TokenType.TAG_DIRECTIVE;
+  final FileSpan span;
+
+  /// The tag handle used in the document.
+  final String handle;
+
+  /// The tag prefix that the handle maps to.
+  final String prefix;
+
+  TagDirectiveToken(this.span, this.handle, this.prefix);
+
+  String toString() => "TAG_DIRECTIVE $handle $prefix";
+}
+
+/// A token representing an anchor (`&foo`).
+class AnchorToken implements Token {
+  get type => TokenType.ANCHOR;
+  final FileSpan span;
+
+  /// The name of the anchor.
+  final String name;
+
+  AnchorToken(this.span, this.name);
+
+  String toString() => "ANCHOR $name";
+}
+
+/// A token representing an alias (`*foo`).
+class AliasToken implements Token {
+  get type => TokenType.ALIAS;
+  final FileSpan span;
+
+  /// The name of the anchor.
+  final String name;
+
+  AliasToken(this.span, this.name);
+
+  String toString() => "ALIAS $name";
+}
+
+/// A token representing a tag (`!foo`).
+class TagToken implements Token {
+  get type => TokenType.TAG;
+  final FileSpan span;
+
+  /// The tag handle.
+  final String handle;
+
+  /// The tag suffix, or `null`.
+  final String suffix;
+
+  TagToken(this.span, this.handle, this.suffix);
+
+  String toString() => "TAG $handle $suffix";
+}
+
+/// A tkoen representing a scalar value.
+class ScalarToken implements Token {
+  get type => TokenType.SCALAR;
+  final FileSpan span;
+
+  /// The contents of the scalar.
+  final String value;
+
+  /// The style of the scalar in the original source.
+  final ScalarStyle style;
+
+  ScalarToken(this.span, this.value, this.style);
+
+  String toString() => "SCALAR $style \"$value\"";
+}
+
+/// An enum of types of [Token] object.
+class TokenType {
+  static const STREAM_START = const TokenType._("STREAM_START");
+  static const STREAM_END = const TokenType._("STREAM_END");
+
+  static const VERSION_DIRECTIVE = const TokenType._("VERSION_DIRECTIVE");
+  static const TAG_DIRECTIVE = const TokenType._("TAG_DIRECTIVE");
+  static const DOCUMENT_START = const TokenType._("DOCUMENT_START");
+  static const DOCUMENT_END = const TokenType._("DOCUMENT_END");
+
+  static const BLOCK_SEQUENCE_START = const TokenType._("BLOCK_SEQUENCE_START");
+  static const BLOCK_MAPPING_START = const TokenType._("BLOCK_MAPPING_START");
+  static const BLOCK_END = const TokenType._("BLOCK_END");
+
+  static const FLOW_SEQUENCE_START = const TokenType._("FLOW_SEQUENCE_START");
+  static const FLOW_SEQUENCE_END = const TokenType._("FLOW_SEQUENCE_END");
+  static const FLOW_MAPPING_START = const TokenType._("FLOW_MAPPING_START");
+  static const FLOW_MAPPING_END = const TokenType._("FLOW_MAPPING_END");
+
+  static const BLOCK_ENTRY = const TokenType._("BLOCK_ENTRY");
+  static const FLOW_ENTRY = const TokenType._("FLOW_ENTRY");
+  static const KEY = const TokenType._("KEY");
+  static const VALUE = const TokenType._("VALUE");
+
+  static const ALIAS = const TokenType._("ALIAS");
+  static const ANCHOR = const TokenType._("ANCHOR");
+  static const TAG = const TokenType._("TAG");
+  static const SCALAR = const TokenType._("SCALAR");
+
+  final String name;
+
+  const TokenType._(this.name);
+
+  String toString() => name;
+}