pkg/(unit)test: include a copy of old matcher

lib/src/matcher/util.dart

Index: lib/src/matcher/util.dart
diff --git a/lib/src/matcher/util.dart b/lib/src/matcher/util.dart
new file mode 100644
index 0000000000000000000000000000000000000000..87060097d04a736f66d22d00f6c9984c35784eeb
--- /dev/null
+++ b/lib/src/matcher/util.dart
@@ -0,0 +1,65 @@
+// 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 matcher.util;
+
+import 'core_matchers.dart';
+import 'interfaces.dart';
+
+/// A [Map] between whitespace characters and their escape sequences.
+const _escapeMap = const {
+  '\n': r'\n',
+  '\r': r'\r',
+  '\f': r'\f',
+  '\b': r'\b',
+  '\t': r'\t',
+  '\v': r'\v',
+  '\x7F': r'\x7F', // delete
+};
+
+/// A [RegExp] that matches whitespace characters that should be escaped.
+final _escapeRegExp = new RegExp(
+    "[\\x00-\\x07\\x0E-\\x1F${_escapeMap.keys.map(_getHexLiteral).join()}]");
+
+/// Useful utility for nesting match states.
+void addStateInfo(Map matchState, Map values) {
+  var innerState = new Map.from(matchState);
+  matchState.clear();
+  matchState['state'] = innerState;
+  matchState.addAll(values);
+}
+
+/// Takes an argument and returns an equivalent [Matcher].
+///
+/// If the argument is already a matcher this does nothing,
+/// else if the argument is a function, it generates a predicate
+/// function matcher, else it generates an equals matcher.
+Matcher wrapMatcher(x) {
+  if (x is Matcher) {
+    return x;
+  } else if (x is Function) {
+    return predicate(x);
+  } else {
+    return equals(x);
+  }
+}
+
+/// Returns [str] with all whitespace characters represented as their escape
+/// sequences.
+///
+/// Backslash characters are escaped as `\\`
+String escape(String str) {
+  str = str.replaceAll('\\', r'\\');
+  return str.replaceAllMapped(_escapeRegExp, (match) {
+    var mapped = _escapeMap[match[0]];
+    if (mapped != null) return mapped;
+    return _getHexLiteral(match[0]);
+  });
+}
+
+/// Given single-character string, return the hex-escaped equivalent.
+String _getHexLiteral(String input) {
+  int rune = input.runes.single;
+  return r'\x' + rune.toRadixString(16).toUpperCase().padLeft(2, '0');
+}