Fix ExperimentalFlags operator== ambiguity

After switching to C++20, ExperimentalFlags doesn't compile:

art/runtime/runtime.h:809:42: error: use of overloaded operator '!=' is ambiguous (with operand types 'ExperimentalFlags' and 'art::ExperimentalFlags::(unnamed enum at art/runtime/experimental_flags.h:29:3)')
  809 |     return (experimental_flags_ & flags) != ExperimentalFlags::kNone;
      |            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^  ~~~~~~~~~~~~~~~~~~~~~~~~
art/runtime/experimental_flags.h:60:18: note: candidate function
   60 |   constexpr bool operator==(const ExperimentalFlags& b) const {
      |                  ^
art/runtime/runtime.h:809:42: note: built-in candidate operator!=(enum art::ExperimentalFlags::(unnamed at art/runtime/experimental_flags.h:29:3), enum art::ExperimentalFlags::(unnamed at art/runtime/experimental_flags.h:29:3))
  809 |     return (experimental_flags_ & flags) != ExperimentalFlags::kNone;
      |                                          ^

There are two ways to compile ExperimentalFlags != unnamed-enum in
C++20:

 * Convert the LHS ExperimentalFlags to unnamed-enum using the
   user-declared conversion operator, then call the built-in
   operator!=(unnamed-enum, unnamed-enum) function.

 * Starting with C++20: convert unnamed-enum to ExperimentalFlags and
   call the user-declared
   operator==(ExperimentalFlags, ExperimentalFlags), negating the
   result.

C++20 adds the ability for operator== to be called using != syntax, but
the ambiguity exists even in C++17 if this line:

    return (experimental_flags_ & flags) != ExperimentalFlags::kNone;

is changed to:

    return !((experimental_flags_ & flags) == ExperimentalFlags::kNone);

Removing the implicit ExperimentalFlags to unnamed-enum conversion
seems to be a sufficient fix, but this code can be simplified a lot
while only losing the operator bool, so do that instead.

Bug: 311052584
Test: remove cpp_std override and build Android
Test: atest art_standalone_cmdline_tests
Change-Id: I16e29705294c850118aec41d423cfbb02222b629

0 files changed, 0 insertions, 0 deletions