[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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@275654 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 0 deletions

diff --git a/lib/Serialization/ASTWriterStmt.cpp b/lib/Serialization/ASTWriterStmt.cpp
index 73f7219ba5..84e718e9ef 100644
--- a/lib/Serialization/ASTWriterStmt.cpp
+++ b/lib/Serialization/ASTWriterStmt.cpp
@@ -1142,6 +1142,13 @@ void ASTStmtWriter::VisitObjCBoolLiteralExpr(ObjCBoolLiteralExpr *E) {
   Code = serialization::EXPR_OBJC_BOOL_LITERAL;
 }
 
+void ASTStmtWriter::VisitObjCAvailabilityCheckExpr(ObjCAvailabilityCheckExpr *E) {
+  VisitExpr(E);
+  Record.AddSourceRange(E->getSourceRange());
+  Record.AddVersionTuple(E->getVersion());
+  Code = serialization::EXPR_OBJC_AVAILABILITY_CHECK;
+}
+
 //===----------------------------------------------------------------------===//
 // C++ Expressions and Statements.
 //===----------------------------------------------------------------------===//