Add a few includes of Optional.h and Hashing.h. These files are failing
ot build in the "next" branch due to changes in llvm's own includes, but
it's general goodness to include them on main as well.
This cleans up 90 instances of this warning and reduces the build spew
when building on Linux. This helps identify actual issues when
building which can get lost in the stream of warning messages. It also
helps restore the ability to build the compiler with gcc.
When building with MSVC, this would fail to compile due to the `buffer`
type (`uint8_t [8]`) being treated as `unsigned char *`, which is
expecting to be SFINAE'd to fail find an overload for the hash
combination.
Switch from a string core to a 128-bit integral core. This should make
Fingerprints much cheaper to copy around and sets us up for a future
where we can provide alternative implementations of the ambient hashing
algorithm.
rdar://72313506
MSVC2017 seems to not fallback to the correct overloaded constructor
when an initializer list constructor seems to be used, but only fails
because the conversion rules. Using parenthesis instead of braces seems
to indicate MSVC2017 the right constructor to use, and should work in
the rest of the compilers as well.
Seems that MSVC2019 is more resilient to this ambiguity.
Introduced in #34808 and started failing https://ci-external.swift.org/job/oss-swift-windows-x86_64/5953/
A fingerprint is a stable hash of a particular piece of compiler data. This formalizes the stable notion of identity that the dependency trackers use for type body fingerprints in iterable decl contexts and the file-level interface hash
