Fix co19 crashes

dart/frog/leg/elements/elements.dart

 // Copyright (c) 2012, 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('elements');
 
 #import('../tree/tree.dart');
 #import('../scanner/scannerlib.dart');
 #import('../leg.dart');  // TODO(karlklose): we only need type.
 #import('../util/util.dart');
@@ skipping 299 matching lines @@
           && e.kind !== ElementKind.PREFIX
           && e.kind !== ElementKind.FOREIGN) {
         if (!e.name.isPrivate()) f(e);
       }
     });
   }
 }
 
 class PrefixElement extends Element {
   Map<SourceString, Element> imported;
+  Token firstPosition;
 
-  PrefixElement(SourceString prefix, Element enclosing)
+  PrefixElement(SourceString prefix, Element enclosing, this.firstPosition)
     : imported = new Map<SourceString, Element>(),
       super(prefix, ElementKind.PREFIX, enclosing);
 
   lookupLocalMember(SourceString memberName) => imported[memberName];
 
   Type computeType(Compiler compiler) => compiler.types.dynamicType;
+
+  Token position() => firstPosition;
 }
 
 class TypedefElement extends Element {
-  TypedefElement(SourceString name, Element enclosing)
+  Token token;
+  TypedefElement(SourceString name, Element enclosing, this.token)
     : super(name, ElementKind.TYPEDEF, enclosing);
+
+  position() => findMyName(token);
 }
 
 class VariableElement extends Element {
   final VariableListElement variables;
   Expression cachedNode; // The send or the identifier in the variables list.
 
   Modifiers get modifiers() => variables.modifiers;
 
   VariableElement(SourceString name,
                   VariableListElement this.variables,
@@ skipping 596 matching lines @@
   final Node node;
   Type bound;
   Type type;
   TypeVariableElement(name, Element enclosing, this.node, this.type,
                       [this.bound])
     : super(name, ElementKind.TYPE_VARIABLE, enclosing);
   Type computeType(compiler) => type;
   Node parseNode(compiler) => node;
   toString() => "${enclosingElement.toString()}.${name.slowToString()}";
 }