Bump to C++17

Author: hamishknight

CMakeLists.txt

@@ -5,7 +5,7 @@ list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules)
 project(IndexStoreDB
   LANGUAGES C CXX Swift)
 
-set(CMAKE_CXX_STANDARD 14)
+set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED YES)
 set(CMAKE_CXX_EXTENSIONS NO)
 

Package.swift

@@ -142,5 +142,5 @@ let package = Package(
       ]),
   ],
 
-  cxxLanguageStandard: .cxx14
+  cxxLanguageStandard: .cxx17
 )

lib/Index/IndexDatastore.cpp

@@ -1003,13 +1003,12 @@ void UnitMonitor::markOutOfDate(OutOfDateFileTriggerRef trigger,
     // Note we have to be careful with the memory management here since the
     // key for OutOfDateTriggers is a reference into the stored trigger value.
     sys::ScopedLock L(StateMtx);
-    auto iterAndInserted =
+    auto [iter, inserted] =
         OutOfDateTriggers.try_emplace(trigger->getPathRef(), trigger);
-    if (!iterAndInserted.second) {
+    if (!inserted) {
       // If we have the same or newer mod time for this trigger already stored,
       // we've seen it before, and have already informed the delegate that the
       // unit is out of date.
-      auto iter = iterAndInserted.first;
       if (iter->second->getModTime() >= trigger->getModTime())
         return;