These tests were relying on sourcekitd parsing as frontend instead of
using the driver. Update them now to avoid churn when we fix command
line argument parsing in sourcekit.
The changes from clang-importer-sdk to clang-importer-sdk-nosource -I %t
are because clang-importer-sdk implies using -enable-source-import.
Rather than hack them up to use -Xfrontend, it is cleaner to just stop
using source import at all for these tests. Incidentally, this improved
fidelity in a few places. When using the generated swift modules we
also need to pass a target triple to sourcekit, which exposed some tests
that had mac-specific data. This is a systemic issue for sourcekit
tests, but for now just make those few specific tests that we had
problems with run only on mac.
The root cause is that NormalProtocolConformance::forEachValueWitness()
needs to skip protocol members that are not requirements.
Otherwise we end up passing such a non-requirement member down to
NormalProtocolConformance::getWitness() and hit an assert when we
cannot find it.
It looks like this code path was only ever hit from SourceKit.
The fix moves TypeChecker::isRequirement() to a method on ValueDecl,
and calls it in the right places.
Fixes <https://bugs.swift.org/browse/SR-3815>.
