Provide better error message when passing wrong number of arguments.

runtime/vm/object.h

 // 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.
 
 #ifndef VM_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 1442 matching lines @@
     return raw_ptr()->is_optimizable_;
   }
   void set_is_optimizable(bool value) const;
 
   bool is_native() const { return raw_ptr()->is_native_; }
   void set_is_native(bool value) const;
 
   bool HasOptimizedCode() const;
 
   intptr_t NumberOfParameters() const;
+  intptr_t NumberOfImplicitParameters() const;
 
-  bool AreValidArgumentCounts(int num_arguments, int num_named_arguments) const;
-  bool AreValidArguments(int num_arguments, const Array& argument_names) const;
+  // Returns true if the argument counts are valid for calling this function.
+  // Otherwise, it returns false and the reason (if error_message is not NULL).
+  bool AreValidArgumentCounts(int num_arguments,
+                              int num_named_arguments,
+                              String* error_message) const;
+
+  // Returns true if the total argument count and the names of optional
+  // arguments are valid for calling this function.
+  // Otherwise, it returns false and the reason (if error_message is not NULL).
+  bool AreValidArguments(int num_arguments,
+                         const Array& argument_names,
+                         String* error_message) const;
 
   // Fully qualified name uniquely identifying the function under gdb and during
   // ast printing. The special ':' character, if present, is replaced by '_'.
   const char* ToFullyQualifiedCString() const;
 
   // Returns true if this function has parameters that are compatible with the
   // parameters of the other function in order for this function to override the
   // other function. Parameter types are ignored.
   bool HasCompatibleParametersWith(const Function& other) const;
 
@@ skipping 3643 matching lines @@
 }
 
 
 intptr_t Stackmap::SizeInBits() const {
   return (Smi::Value(raw_ptr()->bitmap_size_in_bytes_) * kBitsPerByte);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_