pkg/matcher: refactored code around data-structure vs execution-based matchers

pkg/matcher/lib/src/util.dart

+// 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';
+
+/// 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);
+  }
+}