gn: Fix integer subtraction.

tools/gn/operators.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tools/gn/operators.h"
 
 #include <stddef.h>
 #include <algorithm>
 
 #include "base/strings/string_number_conversions.h"
@@ skipping 401 matching lines @@
   return Value();
 }
 
 // Left is passed by value because it will be modified in-place and returned
 // for the list case.
 Value ExecuteMinus(const BinaryOpNode* op_node,
                    Value left,
                    const Value& right,
                    Err* err) {
   // Left-hand-side int. The only thing to do is subtract another int.
-  if (left.type() == Value::INTEGER && right.type() != Value::INTEGER) {
+  if (left.type() == Value::INTEGER && right.type() == Value::INTEGER) {
     // Int - int -> subtraction.
     return Value(op_node, left.int_value() - right.int_value());
   }
 
   // Left-hand-side list. The only thing to do is subtract another list.
   if (left.type() == Value::LIST && right.type() == Value::LIST) {
     // In-place modify left and return it.
     RemoveMatchesFromList(op_node, &left, right, err);
     return left;
   }
@@ skipping 341 matching lines @@
     return ExecuteGreaterEquals(scope, op_node, left_value, right_value, err);
   if (op.type() == Token::LESS_EQUAL)
     return ExecuteLessEquals(scope, op_node, left_value, right_value, err);
   if (op.type() == Token::GREATER_THAN)
     return ExecuteGreater(scope, op_node, left_value, right_value, err);
   if (op.type() == Token::LESS_THAN)
     return ExecuteLess(scope, op_node, left_value, right_value, err);
 
   return Value();
 }