Deleted the Pass file, replacing it with [[nodiscard]] (#1030)

CMakeLists.txt

@@ -283,7 +283,6 @@ list(APPEND INCLUDE_FILES
     ${PROJECT_SOURCE_DIR}/include/mbgl/util/interpolate.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/util/logging.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/util/noncopyable.hpp
-    ${PROJECT_SOURCE_DIR}/include/mbgl/util/pass_types.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/util/platform.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/util/premultiply.hpp
     ${PROJECT_SOURCE_DIR}/include/mbgl/util/projection.hpp

include/mbgl/actor/scheduler.hpp

@@ -1,6 +1,5 @@
 #pragma once
 
-#include <mbgl/util/pass_types.hpp>
 
 #include <mapbox/std/weak.hpp>
 
@@ -74,7 +73,7 @@ public:
     /// The scheduled tasks might run in parallel on different
     /// threads.
     /// TODO : Rename to GetPool()
-    static PassRefPtr<Scheduler> GetBackground();
+    [[nodiscard]] static std::shared_ptr<Scheduler> GetBackground();
 
     /// Get the *sequenced* scheduler for asynchronous tasks.
     /// Unlike the method above, the returned scheduler
@@ -84,7 +83,7 @@ public:
     ///
     /// Sequenced scheduler can be used for running tasks
     /// on the same thread-unsafe object.
-    static PassRefPtr<Scheduler> GetSequenced();
+    [[nodiscard]] static std::shared_ptr<Scheduler> GetSequenced();
 
 protected:
     template <typename TaskFn, typename ReplyFn>

include/mbgl/storage/file_source_manager.hpp

@@ -1,7 +1,6 @@
 #pragma once
 
 #include <mbgl/storage/file_source.hpp>
-#include <mbgl/util/pass_types.hpp>
 
 namespace mbgl {
 
@@ -31,7 +30,7 @@ public:
     // Returns shared instance of a file source for (type, options) tuple.
     // Creates new instance via registered factory if needed. If new instance cannot be
     // created, nullptr would be returned.
-    PassRefPtr<FileSource> getFileSource(FileSourceType, const ResourceOptions&, const ClientOptions& = ClientOptions()) noexcept;
+    [[nodiscard]] std::shared_ptr<FileSource> getFileSource(FileSourceType, const ResourceOptions&, const ClientOptions& = ClientOptions()) noexcept;
 
     // Registers file source factory for a provided FileSourceType type. If factory for the
     // same type was already registered, will unregister previously registered factory.

include/mbgl/util/pass_types.hpp

@@ -1,24 +0,0 @@
-#pragma once
-
-#include <memory>
-
-namespace mbgl {
-
-/// Using this type as a return type enforces the client to retain the returned object.
-template <typename T>
-class Pass {
-public:
-    Pass(T obj_) : obj(std::move(obj_)) {}
-    Pass(Pass&&) noexcept = default;
-    Pass(const Pass&) = delete;
-    Pass& operator=(const Pass&) = delete;
-    operator T() && { return std::move(obj); }
-
-private:
-    T obj;
-};
-
-template <typename T>
-using PassRefPtr = Pass<std::shared_ptr<T>>;
-
-} // namespace mbgl

src/mbgl/actor/scheduler.cpp

@@ -27,7 +27,7 @@ Scheduler* Scheduler::GetCurrent() {
 }
 
 // static
-PassRefPtr<Scheduler> Scheduler::GetBackground() {
+std::shared_ptr<Scheduler> Scheduler::GetBackground() {
     static std::weak_ptr<Scheduler> weak;
     static std::mutex mtx;
 
@@ -38,11 +38,11 @@ PassRefPtr<Scheduler> Scheduler::GetBackground() {
         weak = scheduler = std::make_shared<ThreadPool>();
     }
 
-    return PassRefPtr<Scheduler>(std::move(scheduler));
+    return scheduler;
 }
 
 // static
-PassRefPtr<Scheduler> Scheduler::GetSequenced() {
+std::shared_ptr<Scheduler> Scheduler::GetSequenced() {
     const std::size_t kSchedulersCount = 10;
     static std::vector<std::weak_ptr<Scheduler>> weaks(kSchedulersCount);
     static std::mutex mtx;
@@ -65,7 +65,7 @@ PassRefPtr<Scheduler> Scheduler::GetSequenced() {
         break;
     }
 
-    return PassRefPtr<Scheduler>(std::move(result));
+    return result;
 }
 
 } //namespace mbgl

src/mbgl/storage/file_source_manager.cpp

@@ -31,7 +31,7 @@ FileSourceManager::FileSourceManager() : impl(std::make_unique<Impl>()) {}
 
 FileSourceManager::~FileSourceManager() = default;
 
-PassRefPtr<FileSource> FileSourceManager::getFileSource(FileSourceType type, const ResourceOptions& resourceOptions, const ClientOptions& clientOptions) noexcept {
+std::shared_ptr<FileSource>  FileSourceManager::getFileSource(FileSourceType type, const ResourceOptions& resourceOptions, const ClientOptions& clientOptions) noexcept {
     std::lock_guard<std::recursive_mutex> lock(impl->mutex);
 
     // Remove released file sources.

test/CMakeLists.txt

@@ -94,7 +94,6 @@ add_library(
     ${PROJECT_SOURCE_DIR}/test/util/memory.test.cpp
     ${PROJECT_SOURCE_DIR}/test/util/merge_lines.test.cpp
     ${PROJECT_SOURCE_DIR}/test/util/number_conversions.test.cpp
-    ${PROJECT_SOURCE_DIR}/test/util/pass.test.cpp
     ${PROJECT_SOURCE_DIR}/test/util/position.test.cpp
     ${PROJECT_SOURCE_DIR}/test/util/projection.test.cpp
     ${PROJECT_SOURCE_DIR}/test/util/rotation.test.cpp

test/util/pass.test.cpp

@@ -1,16 +0,0 @@
-#include <mbgl/test/util.hpp>
-
-#include <mbgl/util/pass_types.hpp>
-
-TEST(Pass, NoCopy) {
-    static int copyCount = 0;
-    struct A {
-        A() = default;
-        A(A&&) = default;
-        A(const A&) { ++copyCount; }
-        static mbgl::Pass<A> create() { return A(); }
-    };
-    A a = A::create();
-    (void)a;
-    EXPECT_EQ(0, copyCount);
-}