Another round of cleanups for http://www.dartbug.com/15922

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 "include/dart_api.h"
 #include "vm/exceptions.h"
 #include "vm/dart_api_impl.h"
 #include "vm/isolate.h"
@@ skipping 55 matching lines @@
   int32_t* utf32_array = zone->Alloc<int32_t>(array_len);
   Instance& index_object = Instance::Handle(isolate);
   for (intptr_t i = 0; i < array_len; i++) {
     index_object ^= a.At(i);
     if (!index_object.IsSmi()) {
       Exceptions::ThrowArgumentError(index_object);
     }
     intptr_t value = Smi::Cast(index_object).Value();
     if (Utf::IsOutOfRange(value)) {
       Exceptions::ThrowByType(Exceptions::kArgument, Object::empty_array());
-    } else {
-      if (!Utf::IsLatin1(value)) {
-        is_one_byte_string = false;
-        if (Utf::IsSupplementary(value)) {
-          utf16_len += 1;
-        }
+      UNREACHABLE();
+    }
+    // Now it is safe to cast the value.
+    int32_t value32 = static_cast<int32_t>(value);
+    if (!Utf::IsLatin1(value32)) {
+      is_one_byte_string = false;
+      if (Utf::IsSupplementary(value32)) {
+        utf16_len += 1;
       }
     }
-    utf32_array[i] = value;
+    utf32_array[i] = value32;
   }
   if (is_one_byte_string) {
     return OneByteString::New(utf32_array, array_len, Heap::kNew);
   }
   return TwoByteString::New(utf16_len, utf32_array, array_len, Heap::kNew);
 }
 
 
 DEFINE_NATIVE_ENTRY(StringBase_substringUnchecked, 3) {
   const String& receiver = String::CheckedHandle(arguments->NativeArgAt(0));
@@ skipping 135 matching lines @@
 
 DEFINE_NATIVE_ENTRY(String_getLength, 1) {
   const String& receiver = String::CheckedHandle(arguments->NativeArgAt(0));
   return Smi::New(receiver.Length());
 }
 
 
 static int32_t StringValueAt(const String& str, const Integer& index) {
   if (index.IsSmi()) {
     const Smi& smi = Smi::Cast(index);
-    int32_t index = smi.Value();
+    intptr_t index = smi.Value();
     if ((index < 0) || (index >= str.Length())) {
       const Array& args = Array::Handle(Array::New(1));
       args.SetAt(0, smi);
       Exceptions::ThrowByType(Exceptions::kRange, args);
     }
     return str.CharAt(index);
   } else {
     // An index larger than Smi is always illegal.
     const Array& args = Array::Handle(Array::New(1));
     args.SetAt(0, index);
@@ skipping 95 matching lines @@
       ? String::Handle(OneByteString::New(length_value, Heap::kNew))
       : String::Handle(TwoByteString::New(length_value, Heap::kNew));
   NoGCScope no_gc;
 
   uint16_t* data_position = reinterpret_cast<uint16_t*>(codeUnits.DataAddr(0));
   String::Copy(result, 0, data_position, length_value);
   return result.raw();
 }
 
 }  // namespace dart