Removing use of boost::variant and optional from stlab now that it has moved to C++17 (#531)

* Removing use of boost::variant and optional from stlab now that it has moved to C++17

* fixing one Windows error

* adding using type for clarity

* Update docs/tips/stop-using-out-arguments.md

---------

Co-authored-by: Bryn Aspestrand <[email protected]>

Author: thinlang

CMakeLists.txt

@@ -18,8 +18,6 @@ cmake_dependent_option( stlab.coverage
   "Enable binary instrumentation to collect test coverage information in the DEBUG configuration"
   OFF PROJECT_IS_TOP_LEVEL OFF )
 
-stlab_check_disfunctional_variant_optional(STLAB_DEFAULT_USE_BOOST_CPP17_SHIMS)
-option( STLAB_USE_BOOST_CPP17_SHIMS "Use variant and optional from Boost instead of std. Useful for non-conforming compilers." ${STLAB_DEFAULT_USE_BOOST_CPP17_SHIMS} )
 stlab_check_disfunctional_coroutines(STLAB_DEFAULT_NO_STD_COROUTINES)
 option( STLAB_NO_STD_COROUTINES "Suppress usage of standard coroutines. Useful for non-conforming compilers." ${STLAB_DEFAULT_NO_STD_COROUTINES} )
 stlab_detect_thread_system(STLAB_DEFAULT_THREAD_SYSTEM)
@@ -35,10 +33,6 @@ if( BUILD_TESTING AND NOT Boost_unit_test_framework_FOUND )
   message( SEND_ERROR "BUILD_TESTING is enabled, but an installation of Boost.Test was not found." )
 endif()
 
-if( STLAB_USE_BOOST_CPP17_SHIMS AND NOT Boost_FOUND )
-  message( SEND_ERROR "STLAB_USE_BOOST_CPP17_SHIMS is enabled, but a Boost installation was not found." )
-endif()
-
 if( (NOT STLAB_THREAD_SYSTEM STREQUAL "none") AND NOT Threads_FOUND )
   message( SEND_ERROR "STLAB_THREAD_SYSTEM is not \"none\", but a thread system was not found." )
 endif()
@@ -89,10 +83,6 @@ target_compile_definitions( stlab INTERFACE $<$<CXX_COMPILER_ID:MSVC>:NOMINMAX>
 
 add_subdirectory( stlab )
 
-if ( STLAB_USE_BOOST_CPP17_SHIMS )
-  target_link_libraries( stlab INTERFACE Boost::boost )
-endif()
-
 if ( NOT STLAB_THREAD_SYSTEM STREQUAL "none"  )
   target_link_libraries( stlab INTERFACE Threads::Threads )
 endif()
@@ -109,7 +99,6 @@ elseif (STLAB_MAIN_EXECUTOR STREQUAL "qt6")
   target_link_libraries( stlab INTERFACE Qt6::Core )
 endif()
 
-message(STATUS "stlab: Use Boost C++17 Shims: ${STLAB_USE_BOOST_CPP17_SHIMS}")
 message(STATUS "stlab: Disable Coroutines: ${STLAB_DEFAULT_NO_STD_COROUTINES}")
 message(STATUS "stlab: Thread System: ${STLAB_THREAD_SYSTEM}")
 message(STATUS "stlab: Task System: ${STLAB_TASK_SYSTEM}")

cmake/StlabUtil.cmake

@@ -4,30 +4,6 @@
 include( CheckCXXSymbolExists )
 include( CheckCXXSourceRuns )
 
-# Determine if the selected C++ compiler has functional versions of
-# 'std::variant' and 'std::optional'. Set the specified 'result_var' to 'TRUE'
-# if they are determined to be disfunctional and 'FALSE' otherwise. Note that
-# this check consists of a smoke test and does not check all the ways these
-# library components may be deficient.
-function( stlab_check_disfunctional_variant_optional result_var )
-  check_cxx_source_runs( "
-    #include <variant>
-    #include <optional>
-
-    int main() {
-        std::optional<int> op = 3;
-        op = std::nullopt;
-
-        std::variant<int, char> v = 12;
-        return 0;
-    }" STLAB_HAVE_FUNCTIONAL_VARIANT_OPTIONAL )
-  if( STLAB_HAVE_FUNCTIONAL_VARIANT_OPTIONAL )
-    set( ${result_var} FALSE PARENT_SCOPE )
-  else()
-    set( ${result_var} TRUE PARENT_SCOPE )
-  endif()
-endfunction()
-
 # Determine if the selected C++ compiler has functional coroutines. Set the
 # specified 'result_var' to 'TRUE' if they are determined to be disfunctional
 # and 'FALSE' otherwise. Note that this check consists of a smoke test and does

cmake/stlabConfig.cmake.in

@@ -1,9 +1,5 @@
 include( CMakeFindDependencyMacro )
 
-if ( @STLAB_USE_BOOST_CPP17_SHIMS@ )
-  find_dependency( Boost 1.74.0 )
-endif()
-
 if ( @STLAB_TASK_SYSTEM@ STREQUAL "libdispatch" )
   find_dependency( libdispatch )
 endif()

docs/README.md

@@ -68,7 +68,6 @@ Specify the following options:
  STLAB_NO_STD_COROUTINES          ON
  STLAB_TASK_SYSTEM                portable
  STLAB_THREAD_SYSTEM              pthread
- STLAB_USE_BOOST_CPP17_SHIMS      OFF
  stlab.coverage                   OFF
 ```
 

docs/libraries/concurrency/future.hpp/future3CT2C20enable_if_.6354105c/m_error.md

@@ -7,10 +7,10 @@ tags:
   - method
 defined_in_file: concurrency/future.hpp
 overloads:
-  stlab::optional<std::exception_ptr> error() const &:
+  std::optional<std::exception_ptr> error() const &:
     annotation:
       - deprecated (Use exception() instead)
     description: __OPTIONAL__
     return: __OPTIONAL__
-    signature_with_names: stlab::optional<std::exception_ptr> error() const &
+    signature_with_names: std::optional<std::exception_ptr> error() const &
 ---

docs/libraries/concurrency/future.hpp/future3CT2C20enable_if_.e055d50a/m_error.md

@@ -7,12 +7,12 @@ tags:
   - method
 defined_in_file: concurrency/future.hpp
 overloads:
-  stlab::optional<std::exception_ptr> error() const &:
+  std::optional<std::exception_ptr> error() const &:
     annotation:
       - deprecated (Use exception() instead)
     description: Iff an error occurred, returns the stored exception pointer.
     return: __OPTIONAL__
-    signature_with_names: stlab::optional<std::exception_ptr> error() const &
+    signature_with_names: std::optional<std::exception_ptr> error() const &
 ---
 Returns a potentially stored exception pointer. This function will be removed in future versions of the library. Use `exception()` instead.
 

docs/libraries/concurrency/future.hpp/future3Cvoid2C20void3E/m_error.md

@@ -7,10 +7,10 @@ tags:
   - method
 defined_in_file: concurrency/future.hpp
 overloads:
-  stlab::optional<std::exception_ptr> error() const &:
+  std::optional<std::exception_ptr> error() const &:
     annotation:
       - deprecated (Use exception() instead)
     description: __OPTIONAL__
     return: __OPTIONAL__
-    signature_with_names: stlab::optional<std::exception_ptr> error() const &
+    signature_with_names: std::optional<std::exception_ptr> error() const &
 ---

docs/libraries/concurrency/future/future/error.md

@@ -6,10 +6,10 @@ defined-in-header: stlab/concurrency/future.hpp
 tags:
   - function
 overloads:
-  stlab::optional<std::exception_ptr> error():
+  std::optional<std::exception_ptr> error():
     description: In case an error occurred, it returns the stored exception pointer.
     return: __OPTIONAL__
-    signature_with_names: "[[deprecated]] stlab::optional<std::exception_ptr> error() const"
+    signature_with_names: "[[deprecated]] std::optional<std::exception_ptr> error() const"
 ---
 Returns a potentially stored exception pointer. This function will be removed in future versions of the library. Use `exception()` instead.
 

docs/libraries/concurrency/future/future/get_try.md

@@ -6,10 +6,10 @@ defined-in-header: stlab/concurrency/future.hpp
 tags:
   - function
 overloads:
-  stlab::optional<T> get_try():
+  std::optional<T> get_try():
     description: If `T` is not `void`, it returns an initialized `optional` if the future has succeeded, otherwise an empty `optional<T>`. In case that an error occurred it rethrows the captured exception.
     return: __OPTIONAL__
-    signature_with_names: stlab::optional<T> get_try()
+    signature_with_names: std::optional<T> get_try()
   bool get_try():
     description: If `T` is void it returns `true` if the future succeeded, otherwise `false`. In case that an error occurred it rethrows the captured exception.
     return: __OPTIONAL__