List abstract classes separately in Dartdoc

pkg/dartdoc/lib/dartdoc.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.
 
 /**
  * To generate docs for a library, run this script with the path to an
  * entrypoint .dart file, like:
  *
  *     $ dart dartdoc.dart foo.dart
  *
@@ skipping 726 matching lines @@
     // Look for a comment for the entire library.
     final comment = getLibraryComment(library);
     if (comment != null) {
       writeln('<div class="doc">${comment.html}</div>');
     }
 
     // Document the top-level members.
     docMembers(library);
 
     // Document the types.
+    final interfaces = <ClassMirror>[];
+    final abstractClasses = <ClassMirror>[];
     final classes = <ClassMirror>[];
-    final interfaces = <ClassMirror>[];
     final typedefs = <TypedefMirror>[];
     final exceptions = <ClassMirror>[];
 
     for (ClassMirror type in orderByName(library.classes.values)) {
       if (!showPrivate && type.isPrivate) continue;
 
       if (isException(type)) {
         exceptions.add(type);
       } else if (type.isClass) {
-        classes.add(type);
+        if (type.isAbstract) {
+          abstractClasses.add(type);
+        } else {
+          classes.add(type);
+        }
       } else if (type.isInterface){
         interfaces.add(type);
       } else if (type is TypedefMirror) {
         typedefs.add(type);
       } else {
         throw new InternalError("internal error: unknown type $type.");
       }
     }
 
+    docTypes(interfaces, 'Interfaces');
+    docTypes(abstractClasses, 'Abstract Classes');
     docTypes(classes, 'Classes');
-    docTypes(interfaces, 'Interfaces');
     docTypes(typedefs, 'Typedefs');
     docTypes(exceptions, 'Exceptions');
 
     writeFooter();
     endFile();
 
     for (final type in library.classes.values) {
       if (!showPrivate && type.isPrivate) continue;
 
       docType(type);
@@ skipping 1046 matching lines @@
       Path relativeFilePath = filePath.relativeTo(outputDir);
       write("$relativeFilePath\n");
     };
     toCacheLister.onDone = (done) => endFile();
   }
 
   /**
    * Returns [:true:] if [type] should be regarded as an exception.
    */
   bool isException(TypeMirror type) {
-    return type.simpleName.endsWith('Exception');
+    return type.simpleName.endsWith('Exception') ||
+        type.simpleName.endsWith('Error');
   }
 }
 
 /**
  * Used to report an unexpected error in the DartDoc tool or the
  * underlying data
  */
 class InternalError {
   final String message;
   const InternalError(this.message);
   String toString() => "InternalError: '$message'";
 }
 
 class DocComment {
   final String text;
 
   /**
    * Non-null if the comment is inherited from another declaration.
    */
   final ClassMirror inheritedFrom;
 
   DocComment(this.text, [this.inheritedFrom = null]) {
     assert(text != null && !text.trim().isEmpty);
   }
 
   String get html => md.markdownToHtml(text);
 
   String toString() => text;
 }