Add locations to diagnostics.

dart/lib/compiler/implementation/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 628 matching lines @@
       : this.constructor = constructor,
         super(constructor.name,
               ElementKind.GENERATIVE_CONSTRUCTOR_BODY,
               null,
               constructor.enclosingElement) {
     functionSignature = constructor.functionSignature;
   }
 
   bool isInstanceMember() => true;
 
-  FunctionType computeType(Compiler compiler) { unreachable(); }
+  FunctionType computeType(Compiler compiler) {
+    compiler.reportFatalError('Internal error: $this.computeType', this);
+  }
 
   Node parseNode(DiagnosticListener listener) {
     if (cachedNode !== null) return cachedNode;
     cachedNode = constructor.parseNode(listener);
     assert(cachedNode !== null);
     return cachedNode;
   }
 
   Token position() => constructor.position();
 }
@@ skipping 384 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()}";
 }