Use std::optional instead of mbgl::optional (#911)

include/mbgl/storage/database_file_source.hpp

@@ -3,7 +3,6 @@
 #include <mbgl/storage/file_source.hpp>
 #include <mbgl/storage/offline.hpp>
 #include <mbgl/util/expected.hpp>
-#include <mbgl/util/optional.hpp>
 
 namespace mbgl {
 

include/mbgl/storage/offline.hpp

@@ -3,7 +3,6 @@
 #include <mbgl/util/geo.hpp>
 #include <mbgl/util/geometry.hpp>
 #include <mbgl/util/range.hpp>
-#include <mbgl/util/optional.hpp>
 #include <mbgl/util/variant.hpp>
 #include <mbgl/style/types.hpp>
 #include <mbgl/storage/response.hpp>

include/mbgl/storage/online_file_source.hpp

@@ -3,7 +3,8 @@
 #include <mbgl/storage/file_source.hpp>
 #include <mbgl/storage/resource_options.hpp>
 #include <mbgl/util/client_options.hpp>
-#include <mbgl/util/optional.hpp>
+
+#include <optional>
 
 namespace mbgl {
 

include/mbgl/storage/resource.hpp

@@ -2,11 +2,11 @@
 
 #include <mbgl/storage/response.hpp>
 #include <mbgl/util/bitmask_operations.hpp>
-#include <mbgl/util/optional.hpp>
 #include <mbgl/util/font_stack.hpp>
 #include <mbgl/util/tileset.hpp>
 
 #include <string>
+#include <optional>
 
 namespace mbgl {
 
@@ -55,7 +55,7 @@ public:
 
     Resource(Kind kind_,
              std::string url_,
-             optional<TileData> tileData_ = {},
+             std::optional<TileData> tileData_ = std::nullopt,
              LoadingMethod loadingMethod_ = LoadingMethod::All)
         : kind(kind_),
           loadingMethod(loadingMethod_),
@@ -91,11 +91,11 @@ public:
     std::string url;
 
     // Includes auxiliary data if this is a tile request.
-    optional<TileData> tileData;
+    std::optional<TileData> tileData;
 
-    optional<Timestamp> priorModified = {};
-    optional<Timestamp> priorExpires = {};
-    optional<std::string> priorEtag = {};
+    std::optional<Timestamp> priorModified = std::nullopt;
+    std::optional<Timestamp> priorExpires = std::nullopt;
+    std::optional<std::string> priorEtag = std::nullopt;
     std::shared_ptr<const std::string> priorData;
     Duration minimumUpdateInterval{Duration::zero()};
     StoragePolicy storagePolicy{StoragePolicy::Permanent};

include/mbgl/storage/response.hpp

@@ -1,8 +1,8 @@
 #pragma once
 
 #include <mbgl/util/chrono.hpp>
-#include <mbgl/util/optional.hpp>
 
+#include <optional>
 #include <string>
 #include <memory>
 
@@ -33,9 +33,9 @@ public:
     // The actual data of the response. Present only for non-error, non-notModified responses.
     std::shared_ptr<const std::string> data;
 
-    optional<Timestamp> modified;
-    optional<Timestamp> expires;
-    optional<std::string> etag;
+    std::optional<Timestamp> modified;
+    std::optional<Timestamp> expires;
+    std::optional<std::string> etag;
 
     bool isFresh() const {
         return expires ? *expires > util::now() : !error;
@@ -63,10 +63,10 @@ public:
     // informing the user about the reason for the failure.
     std::string message;
 
-    optional<Timestamp> retryAfter;
+    std::optional<Timestamp> retryAfter;
 
 public:
-    Error(Reason, std::string = "", optional<Timestamp> = {});
+    Error(Reason, std::string = "", std::optional<Timestamp> = std::nullopt);
 };
 
 } // namespace mbgl