Print the location of duplicated elements.

dart/sdk/lib/_internal/compiler/implementation/resolution/members.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.
 
 part of resolution;
 
 abstract class TreeElements {
   Element get currentElement;
   Set<Node> get superUses;
 
@@ skipping 1457 matching lines @@
       return type;
     }
 
     if (element == null) {
       type = reportFailureAndCreateType(
           MessageKind.CANNOT_RESOLVE_TYPE, {'typeName': node.typeName});
     } else if (element.isAmbiguous()) {
       AmbiguousElement ambiguous = element;
       type = reportFailureAndCreateType(
           ambiguous.messageKind, ambiguous.messageArguments);
+      if (ambiguous.existingElement == ambiguous.newElement) {
+        compiler.reportMessage(
+            compiler.spanFromSpannable(ambiguous.existingElement),
+            MessageKind.GENERIC.error(
+                {'text': 'Giladism: you cannot refer to the same element '

[ahe, 2013/04/17 14:56:25]

Perhaps Gilad can help us come up with a better error message ;-)

+                      'through different imports.'}),
+            Diagnostic.INFO);
+      } else {
+        compiler.reportMessage(
+            compiler.spanFromSpannable(ambiguous.existingElement),
+            MessageKind.GENERIC.error(
+                {'text': 'Note: this is the location of the first element.'}),
+            Diagnostic.INFO);
+        compiler.reportMessage(
+            compiler.spanFromSpannable(ambiguous.newElement),
+            MessageKind.GENERIC.error(
+                {'text': 'Note: this is the location of the second element.'}),
+            Diagnostic.INFO);
+      }
     } else if (!element.impliesType()) {
       type = reportFailureAndCreateType(
           MessageKind.NOT_A_TYPE, {'node': node.typeName});
     } else {
       if (identical(element, compiler.types.voidType.element) ||
           identical(element, compiler.types.dynamicType.element)) {
         type = checkNoTypeArguments(element.computeType(compiler));
       } else if (element.isClass()) {
         ClassElement cls = element;
         compiler.resolver._ensureClassWillBeResolved(cls);
@@ skipping 160 matching lines @@
       if (!inInstanceContext && result.isInstanceMember()) {
         compiler.reportErrorCode(
             node, MessageKind.NO_INSTANCE_AVAILABLE, {'name': name});
         return new ErroneousElementX(MessageKind.NO_INSTANCE_AVAILABLE,
                                      {'name': name},
                                      name, enclosingElement);
       } else if (result.isAmbiguous()) {
         AmbiguousElement ambiguous = result;
         compiler.reportErrorCode(
             node, ambiguous.messageKind, ambiguous.messageArguments);
+        if (ambiguous.existingElement == ambiguous.newElement) {
+          compiler.reportMessage(
+              compiler.spanFromSpannable(ambiguous.existingElement),
+              MessageKind.GENERIC.error(
+                  {'text': 'Giladism: you cannot refer to the same element '
+                        'through different imports.'}),
+              Diagnostic.INFO);
+        } else {
+          compiler.reportMessage(
+              compiler.spanFromSpannable(ambiguous.existingElement),
+              MessageKind.GENERIC.error(
+                  {'text': 'Note: this is the location of the first element.'}),
+              Diagnostic.INFO);
+          compiler.reportMessage(
+              compiler.spanFromSpannable(ambiguous.newElement),
+              MessageKind.GENERIC.error(
+                  {'text':
+                    'Note: this is the location of the second element.'}),
+              Diagnostic.INFO);
+        }
         return new ErroneousElementX(ambiguous.messageKind,
                                      ambiguous.messageArguments,
                                      name, enclosingElement);
       }
     }
     return result;
   }
 
   // Create, or reuse an already created, statement element for a statement.
   TargetElement getOrCreateTargetElement(Node statement) {
@@ skipping 2208 matching lines @@
     return e;
   }
 
   /// Assumed to be called by [resolveRedirectingFactory].
   Element visitReturn(Return node) {
     Node expression = node.expression;
     return finishConstructorReference(visit(expression),
                                       expression, expression);
   }
 }