TLDR: This makes it so that we always can parse sending/transferring but changes
the semantic language effects to be keyed on RegionBasedIsolation instead.
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The key thing that makes this all work is that I changed all of the "special"
semantic changes originally triggered on *ArgsAndResults to now be triggered
based on RegionBasedIsolation being enabled. This makes a lot of sense since we
want these semantic changes specifically to be combined with the checkers that
RegionBasedIsolation turns on. As a result, even though this causes these two
features to always be enabled, we just parse it but we do not use it for
anything semantically.
rdar://128961672
I had to change the APIs to always be always emit into client instead of back
deployable since silgen_name seems to interfere with @backDeployment. So I
switched the implementation so that it instead uses an always emit into client
thunk with the in source function name and a usableFromInline function that has
the silgen_name. This ensures that we still appropriately export the same symbol
as we did before, so it is ABI stable.
This was approved as part of se-0414.
rdar://122030520
