Fix crashes in String natives.

runtime/lib/string.cc

 // Copyright (c) 2011, 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.
 
 #include "vm/bootstrap_natives.h"
 
 #include "vm/exceptions.h"
 #include "vm/native_entry.h"
 #include "vm/object.h"
 
@@ skipping 67 matching lines @@
     Smi& smi = Smi::Handle();
     smi ^= index.raw();
     int32_t index = smi.Value();
     if ((index < 0) || (index >= str.Length())) {
       GrowableArray<const Object*> arguments;
       arguments.Add(&smi);
       Exceptions::ThrowByType(Exceptions::kIndexOutOfRange, arguments);
     }
     return str.CharAt(index);
   } else {
-    // TODO(srdjan): Bigint index not supported.
-    UNIMPLEMENTED();
+    // An index larger than Smi is always illegal.
+    GrowableArray<const Object*> arguments;
+    arguments.Add(&index);
+    Exceptions::ThrowByType(Exceptions::kIndexOutOfRange, arguments);
     return 0;
   }
 }
 
 
 DEFINE_NATIVE_ENTRY(String_charAt, 2) {
   const String& str = String::CheckedHandle(arguments->At(0));
   const Instance& index_instance = Instance::CheckedHandle(arguments->At(1));
   if (!index_instance.IsInteger()) {
     GrowableArray<const Object*> args;
@@ skipping 52 matching lines @@
   const String& str = String::CheckedHandle(arguments->At(0));
   ASSERT(!str.IsNull());
   const String& result = String::Handle(String::ToUpperCase(str));
   arguments->SetReturn(result);
 }
 
 
 DEFINE_NATIVE_ENTRY(Strings_concatAll, 1) {
   const Array& strings = Array::CheckedHandle(arguments->At(0));
   ASSERT(!strings.IsNull());
+  // Check that the array contains strings.
+  Instance& elem = Instance::Handle();
+  for (intptr_t i = 0; i < strings.Length(); i++) {
+    elem ^= strings.At(i);
+    if (elem.IsNull()) {
+      GrowableArray<const Object*> args;
+      Exceptions::ThrowByType(Exceptions::kNullPointer, args);
+    }
+    if (!elem.IsString()) {
+      GrowableArray<const Object*> args;
+      args.Add(&elem);
+      Exceptions::ThrowByType(Exceptions::kIllegalArgument, args);
+    }
+  }
   const String& result = String::Handle(String::ConcatAll(strings));
   arguments->SetReturn(result);
 }
 
 }  // namespace dart