Specifiy MethodMirror.isStatic is terms of whether 'this' is permitted.

sdk/lib/mirrors/mirrors.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.
 
 // For the purposes of the mirrors library, we adopt a naming
 // convention with respect to getters and setters.  Specifically, for
 // some variable or field...
 //
 //   var myField;
 //
@@ skipping 882 matching lines @@
    * The source code for the reflectee, if available. Otherwise null.
    */
   String get source;
 
   /**
    * A list of mirrors on the parameters for the reflectee.
    */
   List<ParameterMirror> get parameters;
 
   /**
-   * Is the reflectee static?
+   * A function is considered non-static iff it is permited to refer to 'this'.
    *
-   * For the purposes of the mirrors library, a top-level function is
-   * considered static.
+   * Note that generative constructors are considered non-static, whereas
+   * factory constructors are considered static.
    */
   bool get isStatic;
 
   /**
    * Is the reflectee abstract?
    */
   bool get isAbstract;
 
   /**
    * Returns true if the reflectee is synthetic, and returns false otherwise.
@@ skipping 297 matching lines @@
    *
    * When used as metadata on an import of "dart:mirrors", this metadata does
    * not apply to the library in which the annotation is used, but instead
    * applies to the other libraries (all libraries if "*" is used).
    */
   final override;
 
   const MirrorsUsed(
       {this.symbols, this.targets, this.metaTargets, this.override});
 }