VM: Fix bug with ??= expressions using await.

runtime/vm/flow_graph_builder.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/flow_graph_builder.h"
 
 #include "lib/invocation_mirror.h"
 #include "vm/ast_printer.h"
 #include "vm/bit_vector.h"
 #include "vm/compiler.h"
@@ skipping 1320 matching lines @@
     } else {
       EffectGraphVisitor for_right(owner());
       node->right()->Visit(&for_right);
       if (node->kind() == Token::kAND) {
         Join(for_left, for_right, empty);
       } else {
         Join(for_left, empty, for_right);
       }
     }
     return;
-  } else if (node->kind() == Token::kIFNULL) {
-    // left ?? right. This operation cannot be overloaded.
-    // temp = left; temp === null ? right : temp
-    ValueGraphVisitor for_left_value(owner());
-    node->left()->Visit(&for_left_value);
-    Append(for_left_value);
-    Do(BuildStoreExprTemp(for_left_value.value()));
-
-    LocalVariable* temp_var = owner()->parsed_function().expression_temp_var();
-    LoadLocalNode* load_temp =
-        new(Z) LoadLocalNode(Scanner::kNoSourcePos, temp_var);
-    LiteralNode* null_constant =
-        new(Z) LiteralNode(Scanner::kNoSourcePos, Object::null_instance());
-    ComparisonNode* check_is_null =
-        new(Z) ComparisonNode(Scanner::kNoSourcePos,
-                              Token::kEQ_STRICT,
-                              load_temp,
-                              null_constant);
-    TestGraphVisitor for_test(owner(), Scanner::kNoSourcePos);
-    check_is_null->Visit(&for_test);
-
-    ValueGraphVisitor for_right_value(owner());
-    node->right()->Visit(&for_right_value);
-    for_right_value.Do(BuildStoreExprTemp(for_right_value.value()));
-
-    ValueGraphVisitor for_temp(owner());
-    // Nothing to do, left value is already loaded into temp.
-
-    Join(for_test, for_right_value, for_temp);
-    return;
   }
+  ASSERT(node->kind() != Token::kIFNULL);
   ValueGraphVisitor for_left_value(owner());
   node->left()->Visit(&for_left_value);
   Append(for_left_value);
   PushArgumentInstr* push_left = PushArgument(for_left_value.value());
 
   ValueGraphVisitor for_right_value(owner());
   node->right()->Visit(&for_right_value);
   Append(for_right_value);
   PushArgumentInstr* push_right = PushArgument(for_right_value.value());
 
@@ skipping 53 matching lines @@
       Join(for_test, for_right, for_false);
     } else {
       ASSERT(node->kind() == Token::kOR);
       ValueGraphVisitor for_true(owner());
       Value* constant_true = for_true.Bind(new(Z) ConstantInstr(Bool::True()));
       for_true.Do(BuildStoreExprTemp(constant_true));
       Join(for_test, for_true, for_right);
     }
     ReturnDefinition(BuildLoadExprTemp());
     return;
-  } else if (node->kind() == Token::kIFNULL) {
-    // left ?? right. This operation cannot be overloaded.
-    // temp = left; temp === null ? right : temp
-    ValueGraphVisitor for_left_value(owner());
-    node->left()->Visit(&for_left_value);
-    Append(for_left_value);
-    Do(BuildStoreExprTemp(for_left_value.value()));
-
-    LocalVariable* temp_var = owner()->parsed_function().expression_temp_var();
-    LoadLocalNode* load_temp =
-        new(Z) LoadLocalNode(Scanner::kNoSourcePos, temp_var);
-    LiteralNode* null_constant =
-        new(Z) LiteralNode(Scanner::kNoSourcePos, Object::null_instance());
-    ComparisonNode* check_is_null =
-        new(Z) ComparisonNode(Scanner::kNoSourcePos,
-                              Token::kEQ_STRICT,
-                              load_temp,
-                              null_constant);
-    TestGraphVisitor for_test(owner(), Scanner::kNoSourcePos);
-    check_is_null->Visit(&for_test);
-
-    ValueGraphVisitor for_right_value(owner());
-    node->right()->Visit(&for_right_value);
-    for_right_value.Do(BuildStoreExprTemp(for_right_value.value()));
-
-    ValueGraphVisitor for_temp(owner());
-    // Nothing to do, left value is already loaded into temp.
-
-    Join(for_test, for_right_value, for_temp);
-    ReturnDefinition(BuildLoadExprTemp());
-    return;
   }
 
   EffectGraphVisitor::VisitBinaryOpNode(node);
 }
 
 
 static const String& BinaryOpAndMaskName(BinaryOpNode* node) {
   if (node->kind() == Token::kSHL) {
     return Library::PrivateCoreLibName(Symbols::_leftShiftWithMask32());
   }
@@ skipping 3187 matching lines @@
   Report::MessageF(Report::kBailout,
                    Script::Handle(function.script()),
                    function.token_pos(),
                    "FlowGraphBuilder Bailout: %s %s",
                    String::Handle(function.name()).ToCString(),
                    reason);
   UNREACHABLE();
 }
 
 }  // namespace dart