Implement DeclarationMirror.location for all but ParameterMirrors.

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 268 matching lines @@
 
   /**
    * Is this declaration top-level?
    *
    * This is defined to be equivalent to:
    *    [:mirror.owner != null && mirror.owner is LibraryMirror:]
    */
   bool get isTopLevel;
 
   /**
-   * The source location of this Dart language entity.
+   * The source location of this Dart language entity, or [:null:] if the
+   * entity is synthetic.
    *
-   * This operation is optional and may return [:null:].
+   * If the reflectee is a variable, the returned location gives the position of   * the variable name at its point of declaration.
+   *
+   * If the reflectee is a library, class, typedef, function or type variable
+   * with associated metadata, the returned location gives the position of the
+   * first metadata declaration associated with the reflectee.
+   *
+   * Otherwise:
+   * If the reflectee is a library, the returned location gives the position of
+   * the keyword 'library' at the reflectee's point of declaration, if the
+   * reflectee is a named library, or the first character of the first line in
+   * the compilation unit defining the reflectee if the reflectee is anonymous.
+   *
+   * If the reflectee is an abstract class, the returned location gives the
+   * position of the keyword 'abstract' at the reflectee's point of declaration.   * Otherwise, if the reflectee is a class, the returned location gives the
+   * position of the keyword 'class' at the reflectee's point of declaration.
+   *
+   * If the reflectee is a typedef the returned location gives the position of
+   * the of the keyword 'typedef' at the reflectee's point of declaration.
+   *
+   * If the reflectee is a function with a declared return type, the returned
+   * location gives the position of the function's return type at the
+   * reflectee's point of declaration. Otherwise. the returned location gives
+   * the position of the function's name at the reflectee's point of
+   * declaration.
+   *
+   * This operation is optional and may throw an [UnsupportedError].
    */
   SourceLocation get location;
 
   /**
    * A list of the metadata associated with this declaration.
    *
    * Let *D* be the declaration this mirror reflects.
    * If *D* is decorated with annotations *A1, ..., An*
    * where *n > 0*, then for each annotation *Ai* associated
    * with *D, 1 <= i <= n*, let *ci* be the constant object
@@ skipping 924 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});
 }