Revert "Remove BinaryOp::result_type"

src/ast.h

Index: src/ast.h
diff --git a/src/ast.h b/src/ast.h
index 6336b3a14b0e144aee345f0f2b91acce270f37ac..b9a98e0b7d12ac7c29593ed4b9efa97bfa06ecf8 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -1884,6 +1884,9 @@ class BinaryOperation: public Expression {
   BailoutId RightId() const { return right_id_; }
 
   TypeFeedbackId BinaryOperationFeedbackId() const { return reuse(id()); }
+  // TODO(rossberg): result_type should be subsumed by lower_type.
+  Handle<Type> result_type() const { return result_type_; }
+  void set_result_type(Handle<Type> type) { result_type_ = type; }
   Maybe<int> fixed_right_arg() const { return fixed_right_arg_; }
   void set_fixed_right_arg(Maybe<int> arg) { fixed_right_arg_ = arg; }
 
@@ -1910,6 +1913,7 @@ class BinaryOperation: public Expression {
   Expression* right_;
   int pos_;
 
+  Handle<Type> result_type_;
   // TODO(rossberg): the fixed arg should probably be represented as a Constant
   // type for the RHS.
   Maybe<int> fixed_right_arg_;