Change the syntax of availability queries from #available(iOS >= 8.0, OSX >= 10.10, *) to
This change reflects the fact that now that we spell the query '#available()' rather than
'#os()', the specification is about availability of the APIs introduced in a particular OS
release rather than an explicit range of OS versions on which the developer expects the
code to run.
There is a Fix-It to remove '>=' to ease adopting the new syntax.
Swift SVN r28025
On platforms that are not explicitly mentioned in the #os() guard, this new '*'
availability check generates a version comparison against the minimum deployment target.
This construct, based on feedback from API review, is designed to ease porting
to new platforms. Because new platforms typically branch from
existing platforms, the wildcard allows an API availability check to do the "right"
thing (executing the guarded branch accessing newer APIs) on the new platform without
requiring a modification to every availability guard in the program.
So, if the programmer writes:
if #os(OSX >= 10.10, *) {
. . .
}
and then ports the code to iOS, the body will execute.
We still do compile-time availability checking with '*', so the compiler will
emit errors for references to potentially unavailable symbols in the body when compiled
for iOS.
We require a '*' clause on all #os() guards to force developers to
"future proof" their availability checks against the introduction of new a platform.
Swift SVN r26988
This commit adds a new expression (AvailabilityQueryExpr) and a single kind of
specification for when a block of code or function is available
(VersionConstraintAvailabilitySpec). We may add more kinds of specifications
in the future. At the moment, the AvailabilityQueryExpr allows only a
single platform to be queried; I will add support for multiple platforms
in a later commit.
This commit contains just the added AST nodes; no parsing, type checking, etc.
I’ve added assert(false && “Unimplemented”) for places where support for
AvailabilityQueryExpr will need to be added later.
Swift SVN r21760
