Roll to pickup pool changes

packages/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.
 
 import 'core_matchers.dart';
 import 'interfaces.dart';
 
-typedef bool _Predicate(value);
+typedef bool _Predicate<T>(T value);
 
 /// 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
@@ skipping 12 matching lines @@
 }
 
 /// 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 _Predicate) {
+  } else if (x is _Predicate<Object>) {
+    // x is already a predicate that can handle anything
     return predicate(x);
+  } else if (x is _Predicate<Null>) {
+    // x is a unary predicate, but expects a specific type
+    // so wrap it.
+    return predicate((a) => (x as dynamic)(a));
   } 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');
 }