[test] Fix logic error in <compare> tests; enable for MSVC Dev16

Submitted upstream as https://reviews.llvm.org/D53763.

llvm-svn: 351148

Author: CaseyCarter

libcxx/test/std/language.support/cmp/cmp.partialord/partialord.pass.cpp

@@ -130,7 +130,7 @@ constexpr bool test_constexpr() {
   };
   for (auto TC : SpaceshipTestCases)
   {
-    std::partial_ordering Res = (0 <=> TC.Value);
+    std::partial_ordering Res = (TC.Value <=> 0);
     switch (TC.Expect) {
     case ER_Equiv:
       assert(Res == 0);

libcxx/test/std/language.support/cmp/cmp.strongord/strongord.pass.cpp

@@ -185,7 +185,7 @@ constexpr bool test_constexpr() {
   };
   for (auto TC : SpaceshipTestCases)
   {
-    std::strong_ordering Res = (0 <=> TC.Value);
+    std::strong_ordering Res = (TC.Value <=> 0);
     switch (TC.Expect) {
     case ER_Equiv:
       assert(Res == 0);

libcxx/test/std/language.support/cmp/cmp.weakord/weakord.pass.cpp

@@ -142,7 +142,7 @@ constexpr bool test_constexpr() {
   };
   for (auto TC : SpaceshipTestCases)
   {
-    std::weak_ordering Res = (0 <=> TC.Value);
+    std::weak_ordering Res = (TC.Value <=> 0);
     switch (TC.Expect) {
     case ER_Equiv:
       assert(Res == 0);

libcxx/test/support/test_macros.h

@@ -210,8 +210,9 @@
 
 // FIXME: Fix this feature check when either (A) a compiler provides a complete
 // implementation, or (b) a feature check macro is specified
+#if !defined(_MSC_VER) || defined(__clang__) || _MSC_VER < 1920 || _MSVC_LANG <= 201703L
 #define TEST_HAS_NO_SPACESHIP_OPERATOR
-
+#endif
 
 #if TEST_STD_VER < 11
 #define ASSERT_NOEXCEPT(...)