Cygwin is considered a distinct target with a distinct ABI, environment
conditions, and data types. Though the goal of the project is
native Windows integration with UNIX-likes, that is not compatible with
the idea that the platform can be ignored as Win-like enough to have the
existing os(Windows) condition apply.
Specifically, objc_setUncaughtExceptionHandler, whose nullability is
now annotated in Swift 4 mode when using the Xcode 9 SDKs. That means
it has a different signature in Swift 3 and Swift 4 mode, which means
that references from SIL will fail when deserialized in the other
mode. (The recovery support added in earlier commits doesn't cover
serialized SIL.)
This resulted in crashes when building with
-build-serialized-stdlib-unittest, which enables -sil-serialize-all /
"magic performance mode" when building the StdlibUnittest module like
it does the standard libarry.
None of this affects developer code, because developer code doesn't
serialize anything (if they're playing by the rules).
Part of ABI FIXME #99, this gives us some nice consistency that
ensures that slicing a SubSequence gives us another SubSequence. There
are two source-compatibility implications to this change:
* Collections now need to satisfy this property, which could not be
expressed in Swift 3. There might be some Collections that don't
satisfy this property, and will break with the Swift 4 compiler
*even in Swift 3 compatibility mode*. Case in point...
* The Lazy collection types were formulated as a lazy collection of
the base slice (e.g., LazyCollection<ArraySlice<T>>) rather than as
a slice of the lazy collection (e.g.,
Slice<LazyCollection<Array<T>>). The former doesn't meet the new
requirements, so change to the latter.
Address ABI FIXME #68 by using same-type constraints directly on an
associated type to describe the requirements on the Indices associated
type of the Collection protocol. ABI FIXMEs #89, #90, #91 are all in
StdlibUnittest, and provoke warnings once #68 is fixed, but it's nice
to clear them out.
Fixes SR-2121.
- CYGWIN symbol is used to distinguish Cygwin environment from other OS
and other environment in Windows.
- Added windows and windowsCygnus to OSVersion in StdlibUnittest
From the Swift documentation:
"If you define an optional variable without providing a default value,
the variable is automatically set to nil for you."
The new names are what people generally expect. The old names made more
sense in the old times when the 'Optional.None' case could not be
created with the 'nil' keyword.
Implements part of SE-0110. Single argument in closures will not be accepted if
there exists explicit type with a number of arguments that's not 1.
```swift
let f: (Int, Int) -> Void = { x in } // this is now an error
```
Note there's a second part of SE-0110 which could be considered additive,
which says one must add an extra pair of parens to specify a single arugment
type that is a tuple:
```swift
let g ((Int, Int)) -> Void = { y in } // y should have type (Int, Int)
```
This patch does not implement that part.
Adds an explicit @escaping throughout the standard library, validation
test suite, and tests. This will be necessary as soon as noescape is
the default for closure parameters.
