[Support] Simplify has_StreamOperator (NFC) (#159242)

Without this patch, we are doing a roundtrip on types.  Specifically,
if decltype(...) is well formed, std::is_same_v evaluates to a boolean
value.  We then pass the boolean value to std::enable_if_t, go through
the sizeof(char)/sizeof(double) trick, and then come back to a boolean
value.

This patch simplifies all this by having test() return
std::is_same<...>.  The "caller" attaches ::value, so effectively we
are using std::is_same<...>::value when decltype(...) is well formed,
bypassing std::enable_if_t and the sizeof(char)/sizeof(double) trick.

If we did not care about the return type of the shift operator, we
could use llvm::is_detected, but the return type check doesn't allow
us to simplify things that far.

0 files changed, 0 insertions, 0 deletions