Squashed 'third_party/optional/' content from commit 1baad184f

Change-Id: I9b2473a84dcf6d9892f1f7a9fd21b340796b6ff5
git-subtree-dir: third_party/optional
git-subtree-split: 1baad184f022a3a7502db094a984a86adedf9626
diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..63720f6
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,52 @@
+cmake_minimum_required(VERSION 3.0)
+
+project(optional)
+
+option(OPTIONAL_ENABLE_TESTS "Enable tests." ON)
+option(OPTIONAL_ENABLE_DOCS "Enable documentation." ON)
+
+add_library(optional INTERFACE)
+target_sources(optional INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}/tl/optional.hpp)
+target_include_directories(optional INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}/tl)
+
+if(OPTIONAL_ENABLE_TESTS)
+  # Prepare "Catch" library for other executables
+  set(CATCH_INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/test)
+  add_library(Catch INTERFACE)
+  target_include_directories(Catch INTERFACE ${CATCH_INCLUDE_DIR})
+
+  # Make test executable
+  set(TEST_SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/tests/main.cpp
+                   ${CMAKE_CURRENT_SOURCE_DIR}/tests/noexcept.cpp
+                   ${CMAKE_CURRENT_SOURCE_DIR}/tests/make_optional.cpp
+                   ${CMAKE_CURRENT_SOURCE_DIR}/tests/in_place.cpp
+                   ${CMAKE_CURRENT_SOURCE_DIR}/tests/relops.cpp
+                   ${CMAKE_CURRENT_SOURCE_DIR}/tests/observers.cpp
+                   ${CMAKE_CURRENT_SOURCE_DIR}/tests/extensions.cpp
+                   ${CMAKE_CURRENT_SOURCE_DIR}/tests/emplace.cpp
+                   ${CMAKE_CURRENT_SOURCE_DIR}/tests/constexpr.cpp
+                   ${CMAKE_CURRENT_SOURCE_DIR}/tests/constructors.cpp
+                   ${CMAKE_CURRENT_SOURCE_DIR}/tests/assignment.cpp
+                   ${CMAKE_CURRENT_SOURCE_DIR}/tests/issues.cpp  
+                   ${CMAKE_CURRENT_SOURCE_DIR}/tests/bases.cpp
+                   ${CMAKE_CURRENT_SOURCE_DIR}/tests/nullopt.cpp)
+
+  add_executable(tests ${TEST_SOURCES})
+
+  target_link_libraries(tests Catch optional)
+
+  set(CXXSTD 14 CACHE STRING "C++ standard to use, default C++14")
+  set_property(TARGET tests PROPERTY CXX_STANDARD ${CXXSTD})
+endif()
+
+if(OPTIONAL_ENABLE_DOCS)
+  find_package(standardese) # find standardese after installation
+
+  # generates a custom target that will run standardese to generate the documentation
+  if(standardese_FOUND)
+    standardese_generate(optional
+                         INCLUDE_DIRECTORY tl
+                         CONFIG ${CMAKE_CURRENT_SOURCE_DIR}/standardese.config
+                         INPUT tl/optional.hpp)
+  endif()
+endif()