Implement P0739R0: 'Some improvements to class template argument deduction integration into the standard library' This is an API change (not ABI change) due to a late change in the c++17 standard

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@309296 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/thread/thread.mutex/thread.lock/thread.lock.scoped/adopt_lock.pass.cpp

@@ -14,7 +14,7 @@
 
 // template <class ...Mutex> class scoped_lock;
 
-// scoped_lock(Mutex&..., adopt_lock_t);
+// scoped_lock(adopt_lock_t, Mutex&...);
 
 #include <mutex>
 #include <cassert>
@@ -43,7 +43,7 @@ int main()
         using LG = std::scoped_lock<TestMutex>;
         m1.lock();
         {
-            LG lg(m1, std::adopt_lock);
+            LG lg(std::adopt_lock, m1);
             assert(m1.locked);
         }
         assert(!m1.locked);
@@ -53,7 +53,7 @@ int main()
         using LG = std::scoped_lock<TestMutex, TestMutex>;
         m1.lock(); m2.lock();
         {
-            LG lg(m1, m2, std::adopt_lock);
+            LG lg(std::adopt_lock, m1, m2);
             assert(m1.locked && m2.locked);
         }
         assert(!m1.locked && !m2.locked);
@@ -63,7 +63,7 @@ int main()
         using LG = std::scoped_lock<TestMutex, TestMutex, TestMutex>;
         m1.lock(); m2.lock(); m3.lock();
         {
-            LG lg(m1, m2, m3, std::adopt_lock);
+            LG lg(std::adopt_lock, m1, m2, m3);
             assert(m1.locked && m2.locked && m3.locked);
         }
         assert(!m1.locked && !m2.locked && !m3.locked);

test/std/utilities/variant/variant.variant/variant.ctor/copy.pass.cpp

@@ -261,4 +261,9 @@ int main() {
   test_copy_ctor_valueless_by_exception();
   test_copy_ctor_sfinae();
   test_constexpr_copy_ctor_extension();
+{ // This is the motivating example from P0739R0
+  std::variant<int, double> v1(3);
+  std::variant v2 = v1;
+  (void) v2;
+}
 }