Limit reporting as an error imports of a non-library-evolution module
from a library-evolution enabled module to sources that are part of the
SDK. The error also requires having enabled `InternalImportsByDefault`.
This should help prevent SDK breaking regressions while loosening the
restriction elsewhere.
Framework owners can enable `-library-level api` or `spi` to get this
check as an error, along with more sanity checks.
Other cases remain as a warning. We should look to silence it in some
cases or offer a flag to do so.
rdar://160414667
Find all the usages of `--enable-experimental-feature` or
`--enable-upcoming-feature` in the tests and replace some of the
`REQUIRES: asserts` to use `REQUIRES: swift-feature-Foo` instead, which
should correctly apply to depending on the asserts/noasserts mode of the
toolchain for each feature.
Remove some comments that talked about enabling asserts since they don't
apply anymore (but I might had miss some).
All this was done with an automated script, so some formatting weirdness
might happen, but I hope I fixed most of those.
There might be some tests that were `REQUIRES: asserts` that might run
in `noasserts` toolchains now. This will normally be because their
feature went from experimental to upcoming/base and the tests were not
updated.
