Fix analyzer hints in pkg/collection.

pkg/collection/lib/src/unmodifiable_wrappers.dart

 // Copyright (c) 2013, 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.
 
 /**
  * Wrappers that prevent a List, Set, or Map object from being modified.
  *
  * The [Set] and [Map] wrappers allow reading from the wrapped collection,
  * but prohibit writing.
  *
@@ skipping 35 matching lines @@
    * operations that change the length of the list are disallowed.
    */
   void set length(int newLength) => _throw();
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the length of the list are disallowed.
    */
   bool add(E value) {
     _throw();
+    throw 'unreachable';

[Lasse Reichstein Nielsen, 2014/05/29 21:55:06]

Maybe change _throw to return dynamic and write this as:
  return _throw();
where the return type isn't void.

I think I prefer that to an unreachable line that looks like it throws a string.

[nweiz, 2014/05/30 00:49:41]

Done.

   }
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the length of the list are disallowed.
    */
   void addAll(Iterable<E> iterable) => _throw();
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the length of the list are disallowed.
    */
   void insert(int index, E element) => _throw();
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the length of the list are disallowed.
    */
   void insertAll(int index, Iterable<E> iterable) => _throw();
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the length of the list are disallowed.
    */
-  bool remove(Object value) { _throw(); }
+  bool remove(Object value) {
+    _throw();
+    throw 'unreachable';
+  }
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the length of the list are disallowed.
    */
-  E removeAt(int index) { _throw(); }
+  E removeAt(int index) {
+    _throw();
+    throw 'unreachable';
+  }
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the length of the list are disallowed.
    */
-  E removeLast() { _throw(); }
+  E removeLast() {
+    _throw();
+    throw 'unreachable';
+  }
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the length of the list are disallowed.
    */
   void removeWhere(bool test(E element)) => _throw();
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the length of the list are disallowed.
@@ skipping 41 matching lines @@
   void _throw() {
     throw new UnsupportedError("Cannot modify an unmodifiable Set");
   }
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the set are disallowed.
    */
   bool add(E value) {
     _throw();
+    throw 'unreachable';
   }
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the set are disallowed.
    */
   void addAll(Iterable<E> elements) => _throw();
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the set are disallowed.
    */
-  bool remove(Object value) { _throw(); }
+  bool remove(Object value) {
+    _throw();
+    throw 'unreachable';
+  }
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the set are disallowed.
    */
   void removeAll(Iterable elements) => _throw();
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the set are disallowed.
@@ skipping 45 matching lines @@
   /**
    * Throws an [UnsupportedError];
    * operations that change the map are disallowed.
    */
   void operator []=(K key, V value) => _throw();
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the map are disallowed.
    */
-  V putIfAbsent(K key, V ifAbsent()) { _throw(); }
+  V putIfAbsent(K key, V ifAbsent()) {
+    _throw();
+    throw 'unreachable';
+  }
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the map are disallowed.
    */
   void addAll(Map<K, V> other) => _throw();
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the map are disallowed.
    */
-  V remove(K key) { _throw(); }
+  V remove(K key) {
+    _throw();
+    throw 'unreachable';
+  }
 
   /**
    * Throws an [UnsupportedError];
    * operations that change the map are disallowed.
    */
   void clear() => _throw();
 }