This change adds support for WASI in stdlib tests. Some tests that expect a crash to happen had to be disabled, since there's currently no way to observe such crash from a WASI host.
Within the (single) implementation of abs(_:), dynamically check whether
the numeric type and its `Magnitude` are of the same type and, if so,
return the result of `magnitude`. This ensures that we do the right thing
with respect to (e.g.) floating point values like -0.0, without resorting
to overloading of abs(_:).
StdlibUnittest uses gyb to avoid duplicating many source-context
arguments. However, this means that any test that wishes to add new
expect helpers has to also be gybbed. Given that this structure hasn't
changed in years, and we should have a real language support
eventually, de-gyb it.
* Make the underlying builtins for FP + Vector match Integer.
For stdlib integer types, these are named `_value` and `init(_ _value: Builtin.xxx)`. This patch adopts the same scheme for stdlib floating point and SDK overlay vector types, and removes a legacy init for integers that was only needed to support them. There should be no changes visible outside of the stdlib, and no functional change within the stdlib; the naming of some implementation details is simply more uniform now.
All unoptimized tests should now pass when Swift is built with
'build-script -- --swift-stdlib-enable-resilience=1'.
There are still some issues when the tests themselves are built
with optimizations via 'check-swift-validation-optimize'.
Fixes <rdar://problem/28409189>.
