Update function subtyping rules to latest spec (issue 9057).

runtime/vm/object.cc

 // 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.
 
 #include "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/bigint_operations.h"
@@ skipping 3883 matching lines @@
   const intptr_t other_num_fixed_params = other.num_fixed_parameters();
   const intptr_t other_num_opt_pos_params =
       other.NumOptionalPositionalParameters();
   const intptr_t other_num_opt_named_params =
       other.NumOptionalNamedParameters();
   // A generative constructor may be compared to a redirecting factory and be
   // compatible although it has an additional phase parameter.
   const intptr_t num_ignored_params =
       (other.IsRedirectingFactory() && IsConstructor()) ? 1 : 0;
   // The default values of optional parameters can differ.
-  if (((num_fixed_params - num_ignored_params) != other_num_fixed_params) ||
-      (num_opt_pos_params < other_num_opt_pos_params) ||
+  // This function requires the same arguments or less and accepts the same
+  // arguments or more.
+  if (((num_fixed_params - num_ignored_params) > other_num_fixed_params) ||
+      ((num_fixed_params - num_ignored_params) + num_opt_pos_params <
+       other_num_fixed_params + other_num_opt_pos_params) ||
       (num_opt_named_params < other_num_opt_named_params)) {
     return false;
   }
   if (other_num_opt_named_params == 0) {
     return true;
   }
   // Check that for each optional named parameter of the other function there
   // exists an optional named parameter of this function with an identical
   // name.
   // Note that SetParameterNameAt() guarantees that names are symbols, so we
@@ skipping 76 matching lines @@
                         const AbstractTypeArguments& other_type_arguments,
                         Error* malformed_error) const {
   const intptr_t num_fixed_params = num_fixed_parameters();
   const intptr_t num_opt_pos_params = NumOptionalPositionalParameters();
   const intptr_t num_opt_named_params = NumOptionalNamedParameters();
   const intptr_t other_num_fixed_params = other.num_fixed_parameters();
   const intptr_t other_num_opt_pos_params =
       other.NumOptionalPositionalParameters();
   const intptr_t other_num_opt_named_params =
       other.NumOptionalNamedParameters();
-  if ((num_fixed_params != other_num_fixed_params) ||
-      (num_opt_pos_params < other_num_opt_pos_params) ||
+  // This function requires the same arguments or less and accepts the same
+  // arguments or more.
+  if ((num_fixed_params > other_num_fixed_params) ||
+      (num_fixed_params + num_opt_pos_params <
+       other_num_fixed_params + other_num_opt_pos_params) ||
       (num_opt_named_params < other_num_opt_named_params)) {
     return false;
   }
   // Check the result type.
   AbstractType& other_res_type = AbstractType::Handle(other.result_type());
   if (!other_res_type.IsInstantiated()) {
     other_res_type = other_res_type.InstantiateFrom(other_type_arguments,
                                                     malformed_error);
     ASSERT((malformed_error == NULL) || malformed_error->IsNull());
   }
@@ skipping 12 matching lines @@
         return false;
       }
     } else {
       ASSERT(test_kind == kIsMoreSpecificThan);
       if (!res_type.IsMoreSpecificThan(other_res_type, malformed_error)) {
         return false;
       }
     }
   }
   // Check the types of fixed and optional positional parameters.
-  for (intptr_t i = 0; i < num_fixed_params + other_num_opt_pos_params; i++) {
+  for (intptr_t i = 0;
+       i < other_num_fixed_params + other_num_opt_pos_params; i++) {
     if (!TestParameterType(test_kind,
                            i, i, type_arguments, other, other_type_arguments,
                            malformed_error)) {
       return false;
     }
   }
   // Check the names and types of optional named parameters.
   if (other_num_opt_named_params == 0) {
     return true;
   }
@@ skipping 9622 matching lines @@
   }
   return result.raw();
 }
 
 
 const char* WeakProperty::ToCString() const {
   return "_WeakProperty";
 }
 
 }  // namespace dart