Refactor the dart api a bit:

runtime/include/dart_api.h

Index: runtime/include/dart_api.h
===================================================================
--- runtime/include/dart_api.h	(revision 775)
+++ runtime/include/dart_api.h	(working copy)
@@ -45,28 +45,7 @@
 typedef void* Dart_Isolate;
 typedef void* Dart_Handle;
 typedef void* Dart_NativeArguments;
-typedef enum {
-  kRetCIntptr = 0,
-  kRetCBool,
-  kRetCString,
-  kRetObject,
-  kRetCInt64,
-  kRetCDouble,
-  kRetLibSpec,
-} Dart_ReturnType;
 
-typedef struct {
-  Dart_ReturnType type_;
-  union {
-    intptr_t int_value;
-    bool bool_value;
-    const char* str_value;
-    Dart_Handle obj_value;
-    int64_t int64_value;
-    double double_value;
-  } retval_;
-} Dart_Result;
-
 typedef enum {
   kLibraryTag = 0,
   kImportTag,
@@ -94,78 +73,17 @@
 typedef void (*Dart_NativeFunction)(Dart_NativeArguments arguments);
 typedef Dart_NativeFunction (*Dart_NativeEntryResolver)(Dart_Handle name,
                                                         int num_of_arguments);
-typedef Dart_Result (*Dart_LibraryTagHandler)(Dart_LibraryTag tag,
+typedef Dart_Handle (*Dart_LibraryTagHandler)(Dart_LibraryTag tag,
                                               Dart_Handle library,
                                               Dart_Handle url);
 
 // TODO(iposva): This is a placeholder for the eventual external Dart API.
 
 // Return value handling after a Dart API call.
-DART_EXPORT bool Dart_IsValidResult(const Dart_Result& result);
+DART_EXPORT bool Dart_IsValid(const Dart_Handle& result);
 
-inline intptr_t Dart_GetResultAsCIntptr(const Dart_Result& result) {
-  assert(result.type_ == kRetCIntptr);  // Valid to access result as C int.
-  return result.retval_.int_value;
-}
-inline  Dart_Result Dart_ResultAsCIntptr(intptr_t value) {
-  Dart_Result result;
-  result.type_ = kRetCIntptr;
-  result.retval_.int_value = value;
-  return result;
-}
-inline bool Dart_GetResultAsCBoolean(const Dart_Result& result) {
-  assert(result.type_ == kRetCBool);  // Valid to access result as C bool.
-  return result.retval_.bool_value;
-}
-inline  Dart_Result Dart_ResultAsCBoolean(bool value) {
-  Dart_Result result;
-  result.type_ = kRetCBool;
-  result.retval_.bool_value = value;
-  return result;
-}
-inline const char* Dart_GetResultAsCString(const Dart_Result& result) {
-  assert(result.type_ == kRetCString);  // Valid to access result as C string.
-  return result.retval_.str_value;
-}
-inline  Dart_Result Dart_ResultAsCString(const char* value) {
-  // Assumes passed in string value will be available on return.
-  Dart_Result result;
-  result.type_ = kRetCString;
-  result.retval_.str_value = value;
-  return result;
-}
-inline Dart_Handle Dart_GetResult(const Dart_Result& result) {
-  assert(result.type_ == kRetObject);  // Valid to access result as Dart obj.
-  return result.retval_.obj_value;
-}
-inline  Dart_Result Dart_ResultAsObject(Dart_Handle value) {
-  Dart_Result result;
-  result.type_ = kRetObject;
-  result.retval_.obj_value = value;
-  return result;
-}
-inline int64_t Dart_GetResultAsCInt64(const Dart_Result& result) {
-  assert(result.type_ == kRetCInt64);  // Valid to access result as C int64_t.
-  return result.retval_.int64_value;
-}
-inline  Dart_Result Dart_ResultAsCInt64(int64_t value) {
-  Dart_Result result;
-  result.type_ = kRetCInt64;
-  result.retval_.int64_value = value;
-  return result;
-}
-inline double Dart_GetResultAsCDouble(const Dart_Result& result) {
-  assert(result.type_ == kRetCDouble);  // Valid to access result as C double.
-  return result.retval_.double_value;
-}
-inline  Dart_Result Dart_ResultAsCDouble(double value) {
-  Dart_Result result;
-  result.type_ = kRetCDouble;
-  result.retval_.double_value = value;
-  return result;
-}
-DART_EXPORT const char* Dart_GetErrorCString(const Dart_Result& result);
-DART_EXPORT Dart_Result Dart_ErrorResult(const char* value);
+DART_EXPORT const char* Dart_GetError(const Dart_Handle& result);
+DART_EXPORT Dart_Handle Dart_Error(const char* value);
 
 
 // Initialize the VM with commmand line flags.
@@ -188,7 +106,7 @@
 //
 // This routine may only be used when the embedder has not provided an
 // alternate message delivery mechanism with Dart_SetPostMessageCallback.
-DART_EXPORT Dart_Result Dart_RunLoop();
+DART_EXPORT Dart_Handle Dart_RunLoop();
 
 // Messages/ports
 
@@ -243,17 +161,21 @@
 
 
 // Object.
-DART_EXPORT Dart_Result Dart_ObjectToString(Dart_Handle object);
+DART_EXPORT Dart_Handle Dart_ObjectToString(Dart_Handle object);
 DART_EXPORT bool Dart_IsNull(Dart_Handle object);
 
 
 // Returns true if the two objects are equal.
-DART_EXPORT Dart_Result Dart_Objects_Equal(Dart_Handle obj1, Dart_Handle obj2);
+DART_EXPORT Dart_Handle Dart_Objects_Equal(Dart_Handle obj1,
+                                           Dart_Handle obj2,
+                                           bool* value);
 
 
 // Classes.
-DART_EXPORT Dart_Result Dart_GetClass(Dart_Handle library, Dart_Handle name);
-DART_EXPORT Dart_Result Dart_IsInstanceOf(Dart_Handle object, Dart_Handle cls);
+DART_EXPORT Dart_Handle Dart_GetClass(Dart_Handle library, Dart_Handle name);
+DART_EXPORT Dart_Handle Dart_IsInstanceOf(Dart_Handle object,
+                                          Dart_Handle cls,
+                                          bool* value);
 
 
 // Number.
@@ -264,26 +186,29 @@
 DART_EXPORT bool Dart_IsInteger(Dart_Handle object);
 DART_EXPORT Dart_Handle Dart_NewInteger(int64_t value);
 DART_EXPORT Dart_Handle Dart_NewIntegerFromHexCString(const char* value);
-DART_EXPORT Dart_Result Dart_IntegerValue(Dart_Handle integer);
-DART_EXPORT Dart_Result Dart_IntegerFitsIntoInt64(Dart_Handle integer);
+DART_EXPORT Dart_Handle Dart_IntegerValue(Dart_Handle integer, int64_t* value);
+DART_EXPORT Dart_Handle Dart_IntegerValueHexCString(Dart_Handle integer,
+                                                    const char** value);
+DART_EXPORT Dart_Handle Dart_IntegerFitsIntoInt64(Dart_Handle integer,
+                                                  bool* value);
 
 
 // Boolean.
 DART_EXPORT bool Dart_IsBoolean(Dart_Handle object);
 DART_EXPORT Dart_Handle Dart_NewBoolean(bool value);
-DART_EXPORT Dart_Result Dart_BooleanValue(Dart_Handle bool_object);
+DART_EXPORT Dart_Handle Dart_BooleanValue(Dart_Handle bool_object, bool* value);
 
 
 // Double.
 DART_EXPORT bool Dart_IsDouble(Dart_Handle object);
 DART_EXPORT Dart_Handle Dart_NewDouble(double value);
-DART_EXPORT Dart_Result Dart_DoubleValue(Dart_Handle integer);
+DART_EXPORT Dart_Handle Dart_DoubleValue(Dart_Handle integer, double* result);
 
 
 // String.
 DART_EXPORT bool Dart_IsString(Dart_Handle object);
 
-DART_EXPORT Dart_Result Dart_StringLength(Dart_Handle str);
+DART_EXPORT Dart_Handle Dart_StringLength(Dart_Handle str, intptr_t* len);
 
 DART_EXPORT Dart_Handle Dart_NewString(const char* str);
 DART_EXPORT Dart_Handle Dart_NewString8(const uint8_t* codepoints,
@@ -298,33 +223,34 @@
 DART_EXPORT bool Dart_IsString8(Dart_Handle object);
 DART_EXPORT bool Dart_IsString16(Dart_Handle object);
 
-DART_EXPORT Dart_Result Dart_StringGet8(Dart_Handle str,
+DART_EXPORT Dart_Handle Dart_StringGet8(Dart_Handle str,
                                         uint8_t* codepoints,
-                                        intptr_t length);
-DART_EXPORT Dart_Result Dart_StringGet16(Dart_Handle str,
+                                        intptr_t* length);
+DART_EXPORT Dart_Handle Dart_StringGet16(Dart_Handle str,
                                          uint16_t* codepoints,
-                                         intptr_t length);
-DART_EXPORT Dart_Result Dart_StringGet32(Dart_Handle str,
+                                         intptr_t* length);
+DART_EXPORT Dart_Handle Dart_StringGet32(Dart_Handle str,
                                          uint32_t* codepoints,
-                                         intptr_t length);
+                                         intptr_t* length);
 
-DART_EXPORT Dart_Result Dart_StringToCString(Dart_Handle str);
+DART_EXPORT Dart_Handle Dart_StringToCString(Dart_Handle str,
+                                             const char** result);
 
 
 // Array.
 DART_EXPORT bool Dart_IsArray(Dart_Handle object);
 DART_EXPORT Dart_Handle Dart_NewArray(intptr_t length);
-DART_EXPORT Dart_Result Dart_GetLength(Dart_Handle array);
-DART_EXPORT Dart_Result Dart_ArrayGetAt(Dart_Handle array,
+DART_EXPORT Dart_Handle Dart_GetLength(Dart_Handle array, intptr_t* len);
+DART_EXPORT Dart_Handle Dart_ArrayGetAt(Dart_Handle array,
                                         intptr_t index);
-DART_EXPORT Dart_Result Dart_ArrayGet(Dart_Handle array,
+DART_EXPORT Dart_Handle Dart_ArrayGet(Dart_Handle array,
                                       intptr_t offset,
                                       uint8_t* native_array,
                                       intptr_t length);
-DART_EXPORT Dart_Result Dart_ArraySetAt(Dart_Handle array,
+DART_EXPORT Dart_Handle Dart_ArraySetAt(Dart_Handle array,
                                         intptr_t index,
                                         Dart_Handle value);
-DART_EXPORT Dart_Result Dart_ArraySet(Dart_Handle array,
+DART_EXPORT Dart_Handle Dart_ArraySet(Dart_Handle array,
                                       intptr_t offset,
                                       uint8_t* native_array,
                                       intptr_t length);
@@ -332,21 +258,21 @@
 // Closure.
 DART_EXPORT bool Dart_IsClosure(Dart_Handle object);
 // DEPRECATED: The API below is a temporary hack.
-DART_EXPORT Dart_Result Dart_ClosureSmrck(Dart_Handle object);
+DART_EXPORT int64_t Dart_ClosureSmrck(Dart_Handle object);
 DART_EXPORT void Dart_ClosureSetSmrck(Dart_Handle object, int64_t value);
 
 
 // Invocation of methods.
-DART_EXPORT Dart_Result Dart_InvokeStatic(Dart_Handle library,
+DART_EXPORT Dart_Handle Dart_InvokeStatic(Dart_Handle library,
                                           Dart_Handle class_name,
                                           Dart_Handle function_name,
                                           int number_of_arguments,
                                           Dart_Handle* arguments);
-DART_EXPORT Dart_Result Dart_InvokeDynamic(Dart_Handle receiver,
+DART_EXPORT Dart_Handle Dart_InvokeDynamic(Dart_Handle receiver,
                                            Dart_Handle function_name,
                                            int number_of_arguments,
                                            Dart_Handle* arguments);
-DART_EXPORT Dart_Result Dart_InvokeClosure(Dart_Handle closure,
+DART_EXPORT Dart_Handle Dart_InvokeClosure(Dart_Handle closure,
                                            int number_of_arguments,
                                            Dart_Handle* arguments);
 
@@ -360,36 +286,36 @@
 
 // Library.
 DART_EXPORT bool Dart_IsLibrary(Dart_Handle object);
-DART_EXPORT Dart_Result Dart_LibraryUrl(Dart_Handle library);
-DART_EXPORT Dart_Result Dart_LibraryImportLibrary(Dart_Handle library,
+DART_EXPORT Dart_Handle Dart_LibraryUrl(Dart_Handle library);
+DART_EXPORT Dart_Handle Dart_LibraryImportLibrary(Dart_Handle library,
                                                   Dart_Handle import);
 
-DART_EXPORT Dart_Result Dart_LookupLibrary(Dart_Handle url);
+DART_EXPORT Dart_Handle Dart_LookupLibrary(Dart_Handle url);
 
-DART_EXPORT Dart_Result Dart_LoadLibrary(Dart_Handle url,
+DART_EXPORT Dart_Handle Dart_LoadLibrary(Dart_Handle url,
                                          Dart_Handle source);
-DART_EXPORT Dart_Result Dart_LoadSource(Dart_Handle library,
+DART_EXPORT Dart_Handle Dart_LoadSource(Dart_Handle library,
                                         Dart_Handle url,
                                         Dart_Handle source);
-DART_EXPORT Dart_Result Dart_SetNativeResolver(
+DART_EXPORT Dart_Handle Dart_SetNativeResolver(
     Dart_Handle library,
     Dart_NativeEntryResolver resolver);
 
 
 // Script handling.
-DART_EXPORT Dart_Result Dart_LoadScript(Dart_Handle url,
+DART_EXPORT Dart_Handle Dart_LoadScript(Dart_Handle url,
                                         Dart_Handle source,
                                         Dart_LibraryTagHandler handler);
 
 // Compile all loaded classes and functions eagerly.
-DART_EXPORT Dart_Result Dart_CompileAll();
+DART_EXPORT Dart_Handle Dart_CompileAll();
 
 // Exception related.
 DART_EXPORT bool Dart_ExceptionOccurred(Dart_Handle result);
-DART_EXPORT Dart_Result Dart_GetException(Dart_Handle result);
-DART_EXPORT Dart_Result Dart_GetStacktrace(Dart_Handle unhandled_exception);
-DART_EXPORT Dart_Result Dart_ThrowException(Dart_Handle exception);
-DART_EXPORT Dart_Result Dart_ReThrowException(Dart_Handle exception,
+DART_EXPORT Dart_Handle Dart_GetException(Dart_Handle result);
+DART_EXPORT Dart_Handle Dart_GetStacktrace(Dart_Handle unhandled_exception);
+DART_EXPORT Dart_Handle Dart_ThrowException(Dart_Handle exception);
+DART_EXPORT Dart_Handle Dart_ReThrowException(Dart_Handle exception,
                                               Dart_Handle stacktrace);
 
 // Global Handles and Scope for local handles and zone based memory allocation.
@@ -402,36 +328,37 @@
 DART_EXPORT void Dart_DeletePersistentHandle(Dart_Handle object);
 
 // Fields.
-DART_EXPORT Dart_Result Dart_GetStaticField(Dart_Handle cls, Dart_Handle name);
-DART_EXPORT Dart_Result Dart_SetStaticField(Dart_Handle cls,
+DART_EXPORT Dart_Handle Dart_GetStaticField(Dart_Handle cls, Dart_Handle name);
+DART_EXPORT Dart_Handle Dart_SetStaticField(Dart_Handle cls,
                                             Dart_Handle name,
                                             Dart_Handle value);
-DART_EXPORT Dart_Result Dart_GetInstanceField(Dart_Handle obj,
+DART_EXPORT Dart_Handle Dart_GetInstanceField(Dart_Handle obj,
                                               Dart_Handle name);
-DART_EXPORT Dart_Result Dart_SetInstanceField(Dart_Handle obj,
+DART_EXPORT Dart_Handle Dart_SetInstanceField(Dart_Handle obj,
                                               Dart_Handle name,
                                               Dart_Handle value);
 
 // Native fields.
-DART_EXPORT Dart_Result Dart_CreateNativeWrapperClass(Dart_Handle library,
+DART_EXPORT Dart_Handle Dart_CreateNativeWrapperClass(Dart_Handle library,
                                                       Dart_Handle class_name,
                                                       int field_count);
-DART_EXPORT Dart_Result Dart_GetNativeInstanceField(Dart_Handle obj,
-                                                    int index);
-DART_EXPORT Dart_Result Dart_SetNativeInstanceField(Dart_Handle obj,
+DART_EXPORT Dart_Handle Dart_GetNativeInstanceField(Dart_Handle obj,
                                                     int index,
+                                                    intptr_t* value);
+DART_EXPORT Dart_Handle Dart_SetNativeInstanceField(Dart_Handle obj,
+                                                    int index,
                                                     intptr_t value);
 
 // Snapshot creation.
-DART_EXPORT Dart_Result Dart_CreateSnapshot(uint8_t** snaphot_buffer,
+DART_EXPORT Dart_Handle Dart_CreateSnapshot(uint8_t** snaphot_buffer,
                                             intptr_t* snapshot_size);
 
 // Message communication.
-DART_EXPORT Dart_Result Dart_PostIntArray(Dart_Port port,
-                                          int field_count,
-                                          intptr_t* data);
+DART_EXPORT bool Dart_PostIntArray(Dart_Port port,
+                                   int field_count,
+                                   intptr_t* data);
 
-DART_EXPORT Dart_Result Dart_Post(Dart_Port port, Dart_Handle value);
+DART_EXPORT bool Dart_Post(Dart_Port port, Dart_Handle value);
 
 // External pprof support for gathering and dumping symbolic information
 // that can be used for better profile reports for dynamically generated