[ObjC] Implement @available in the Parser and AST

This patch adds a new AST node: ObjCAvailabilityCheckExpr, and teaches the
Parser and Sema to generate it. This node represents an availability check of
the form:

  @available(macos 10.10, *);

Which will eventually compile to a runtime check of the host's OS version. This
is the first patch of the feature I proposed here:
http://lists.llvm.org/pipermail/cfe-dev/2016-July/049851.html

Differential Revision: https://reviews.llvm.org/D22171

llvm-svn: 275654

1 files changed, 5 insertions, 0 deletions

diff --git a/clang/lib/AST/StmtProfile.cpp b/clang/lib/AST/StmtProfile.cpp
index 5ce6e5e13a2a..0a39413853a0 100644
--- a/clang/lib/AST/StmtProfile.cpp
+++ b/clang/lib/AST/StmtProfile.cpp
@@ -1632,6 +1632,11 @@ void StmtProfiler::VisitObjCBridgedCastExpr(const ObjCBridgedCastExpr *S) {
   ID.AddBoolean(S->getBridgeKind());
 }
 
+void StmtProfiler::VisitObjCAvailabilityCheckExpr(
+    const ObjCAvailabilityCheckExpr *S) {
+  VisitExpr(S);
+}
+
 void StmtProfiler::VisitDecl(const Decl *D) {
   ID.AddInteger(D? D->getKind() : 0);