Diagnose compiler crashes.

dart/lib/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.
 
 class WorkItem {
   final Element element;
   TreeElements resolutionTree;
   bool allowSpeculativeOptimization = true;
   List<HTypeGuard> guards = const <HTypeGuard>[];
 
   WorkItem(this.element, this.resolutionTree);
 
   bool isAnalyzed() => resolutionTree !== null;
 
   int hashCode() => element.hashCode();
 
   String run(Compiler compiler) {
     String code = compiler.universe.generatedCode[element];
     if (code !== null) return code;
-    if (!isAnalyzed()) compiler.analyze(this);
-    return compiler.codegen(this);
+    try {
+      if (!isAnalyzed()) compiler.analyze(this);
+      return compiler.codegen(this);
+    } catch (CompilerCancelledException ex) {
+      throw;
+    } catch (var ex) {
+      compiler.unhandledExceptionOnElement(element);
+      throw;
+    }
   }
 }
 
 class Compiler implements DiagnosticListener {
   Queue<WorkItem> codegenQueue;
   Universe universe;
   World world;
   String assembledCode;
   Namer namer;
   Types types;
@@ skipping 99 matching lines @@
     cancel("${red('internal error:')} $message",
            node, token, instruction, element);
   }
 
   void internalErrorOnElement(Element element, String message) {
     withCurrentElement(element, () {
       internalError(message, element: element);
     });
   }
 
+  void unhandledExceptionOnElement(Element element) {
+    internalErrorOnElement(element, '''
+An unhandled exception was thrown.
+Please report this problem at http://dartbug.com/new.''');
+  }
+
   void cancel([String reason, Node node, Token token,
                HInstruction instruction, Element element]) {
     SourceSpan span = const SourceSpan(null, null, null);
     if (node !== null) {
       span = spanFromNode(node);
     } else if (token !== null) {
       span = spanFromTokens(token, token);
     } else if (instruction !== null) {
       span = spanFromElement(currentElement);
     } else if (element !== null) {
@@ skipping 399 matching lines @@
   }
 }
 
 class SourceSpan {
   final Uri uri;
   final int begin;
   final int end;
 
   const SourceSpan(this.uri, this.begin, this.end);
 }