Add constexpr to pair

[miscco]

I somehow missed to add the description to the PR so here it is:

This implements the changes to utility as described by the misc_constexpr paper.

While there I tried to overhaul the tests to get rid of the local classes that should be able to be replaced by the archetypes

[miscco]

Ping, a second *pair* of eyes wouldn't hurt.

I am terrible at jokes ...

[miscco]

Took the opportunity to look through this again. Mostly nits about the tests

libcxx/test/std/utilities/utility/pairs/pairs.pair/assign_rv_pair.pass.cpp

39

I believe I have to check this one here, It seems moving to ConstexprTestTypes::MoveOnly should suffice

libcxx/test/std/utilities/utility/pairs/pairs.pair/assign_rv_pair_U_V.pass.cpp

43

I am really not too happy with this dance. I guess one should add one additional section for C++20 only

libcxx/test/std/utilities/utility/pairs/pairs.pair/swap.pass.cpp

24 ↗

(On Diff #266217)

Could we remove those by the way? I do not see any use for them

[miscco]

Could someone have a look at this?

[miscco]

Updated tests

[miscco]

Missed some changes

[ldionne]

Mostly LGTM with nits.

libcxx/test/std/utilities/utility/pairs/pairs.pair/assign_rv_pair.pass.cpp

27

This isn't used.

libcxx/test/std/utilities/utility/pairs/pairs.pair/assign_rv_pair_U_V.pass.cpp

43

I think this is acceptable, we do it in a bunch of other places for testing constexpr. I do agree that something in the test runner would be better, but eh.

libcxx/test/std/utilities/utility/pairs/pairs.pair/swap.pass.cpp

24 ↗

(On Diff #266217)

Do you mean remove S altogether? It's used below.

[miscco]

libcxx/test/std/utilities/utility/pairs/pairs.pair/assign_rv_pair.pass.cpp

27

True, will remove

libcxx/test/std/utilities/utility/pairs/pairs.pair/swap.pass.cpp

24 ↗

(On Diff #266217)

I think that was from a previous revision where I did not yet removed those two lines

S * operator& () { assert(false); return this; }
S const * operator& () const { assert(false); return this; }

[miscco]

Remove the unused member function from CountAssign

[miscco]

Please use all the changes

[miscco]

Once again into the breach

[miscco]

• Fix formatting of meow.version.pass.cpp

[ldionne]

Thanks!

libcxx/test/std/utilities/utility/pairs/pairs.pair/assign_pair.pass.cpp

 #include <cassert>
 
 #include "test_macros.h"
 #include "archetypes.h"
 
 struct CountAssign {
   int copied = 0;
   int moved = 0;
-  TEST_CONSTEXPR_CXX20 void reset() { copied = moved = 0; }
   TEST_CONSTEXPR_CXX20 CountAssign() = default;
   TEST_CONSTEXPR_CXX20 CountAssign& operator=(CountAssign const&) {
     ++copied;
     return *this;
   }
   TEST_CONSTEXPR_CXX20 CountAssign& operator=(CountAssign&&) {
     ++moved;
     return *this;

libcxx/test/std/utilities/utility/pairs/pairs.pair/assign_rv_pair.pass.cpp

 #include <cassert>
 
 #include "test_macros.h"
 #include "archetypes.h"
 
 struct CountAssign {
   int copied = 0;
   int moved = 0;
-  TEST_CONSTEXPR_CXX20 void reset() { copied = moved = 0; }
   TEST_CONSTEXPR_CXX20 CountAssign() = default;
   TEST_CONSTEXPR_CXX20 CountAssign& operator=(CountAssign const&) {
     ++copied;
     return *this;
   }
   TEST_CONSTEXPR_CXX20 CountAssign& operator=(CountAssign&&) {
     ++moved;
     return *this;
   }
 };
 
 TEST_CONSTEXPR_CXX20 bool test() {
   {
     typedef std::pair<ConstexprTestTypes::MoveOnly, int> P;
     P p1(3, 4);
     P p2;
     p2 = std::move(p1);
     assert(p2.first.value == 3);
     assert(p2.second == 4);
   }
   {

libcxx/test/std/utilities/utility/pairs/pairs.pair/assign_rv_pair_U_V.pass.cpp

 
 struct Derived : ConstexprTestTypes::MoveOnly {
   Derived() = default;
   TEST_CONSTEXPR_CXX20 Derived(ConstexprTestTypes::MoveOnly&&){};
 };
 struct CountAssign {
   int copied = 0;
   int moved = 0;
-  TEST_CONSTEXPR_CXX20 void reset() { copied = moved = 0; }
   TEST_CONSTEXPR_CXX20 CountAssign() = default;
   TEST_CONSTEXPR_CXX20 CountAssign(const int){};
   TEST_CONSTEXPR_CXX20 CountAssign& operator=(CountAssign const&) {
     ++copied;
     return *this;
   }
   TEST_CONSTEXPR_CXX20 CountAssign& operator=(CountAssign&&) {
     ++moved;
     return *this;
   }
 };
 
 TEST_CONSTEXPR_CXX20 bool test() {
   {
     typedef std::pair<Derived, short> P1;
     typedef std::pair<ConstexprTestTypes::MoveOnly, long> P2;
     P1 p1(Derived(), static_cast<short>(4));
     P2 p2;
     p2 = std::move(p1);
     assert(p2.second == 4);
   }