Diagnose illegal lvalues better.

dart/sdk/lib/_internal/compiler/implementation/compiler.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 dart2js;
 
 /**
  * If true, print a warning for each method that was resolved, but not
  * compiled.
  */
@@ skipping 144 matching lines @@
   Element get currentElement => _currentElement;
   withCurrentElement(Element element, f()) {
     Element old = currentElement;
     _currentElement = element;
     try {
       return f();
     } on SpannableAssertionFailure catch (ex) {
       if (!hasCrashed) {
         SourceSpan span = spanFromSpannable(ex.node);
         reportDiagnostic(span, ex.message, api.Diagnostic.ERROR);
+        pleaseReportCrash();
       }
       hasCrashed = true;
       throw;
     } on CompilerCancelledException catch (ex) {
       throw;
     } on StackOverflowError catch (ex) {
       // We cannot report anything useful in this case, because we
       // do not have enough stack space.
       throw;
     } catch (ex) {
@@ skipping 122 matching lines @@
   void internalErrorOnElement(Element element, String message) {
     internalError(message, element: element);
   }
 
   void unhandledExceptionOnElement(Element element) {
     if (hasCrashed) return;
     hasCrashed = true;
     reportDiagnostic(spanFromElement(element),
                      MessageKind.COMPILER_CRASHED.error().toString(),
                      api.Diagnostic.CRASH);
+    pleaseReportCrash();
+  }
+
+  void pleaseReportCrash() {
     print(MessageKind.PLEASE_REPORT_THE_CRASH.message([BUILD_ID]));
   }
 
   void cancel(String reason, {Node node, Token token,
                HInstruction instruction, Element element}) {
     assembledCode = null; // Compilation failed. Make sure that we
                           // don't return a bogus result.
     SourceSpan span = null;
     if (node != null) {
       span = spanFromNode(node);
@@ skipping 622 matching lines @@
   // TODO(johnniwinther): Use [spannable] and [message] to provide better
   // information on assertion errors.
   if (condition is Function){
     condition = condition();
   }
   if (spannable == null || !condition) {
     throw new SpannableAssertionFailure(spannable, message);
   }
   return true;
 }