[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, 11 insertions, 0 deletions

diff --git a/clang/lib/Serialization/ASTReaderStmt.cpp b/clang/lib/Serialization/ASTReaderStmt.cpp
index 2fa3a4400bc..395da42d4f2 100644
--- a/clang/lib/Serialization/ASTReaderStmt.cpp
+++ b/clang/lib/Serialization/ASTReaderStmt.cpp
@@ -1182,6 +1182,14 @@ void ASTStmtReader::VisitObjCBoolLiteralExpr(ObjCBoolLiteralExpr *E) {
   E->setLocation(ReadSourceLocation(Record, Idx));
 }
 
+void ASTStmtReader::VisitObjCAvailabilityCheckExpr(ObjCAvailabilityCheckExpr *E) {
+  VisitExpr(E);
+  SourceRange R = Reader.ReadSourceRange(F, Record, Idx);
+  E->AtLoc = R.getBegin();
+  E->RParen = R.getEnd();
+  E->VersionToCheck = Reader.ReadVersionTuple(Record, Idx);
+}
+
 //===----------------------------------------------------------------------===//
 // C++ Expressions and Statements
 //===----------------------------------------------------------------------===//
@@ -3221,6 +3229,9 @@ Stmt *ASTReader::ReadStmtFromStream(ModuleFile &F) {
     case EXPR_OBJC_BOOL_LITERAL:
       S = new (Context) ObjCBoolLiteralExpr(Empty);
       break;
+    case EXPR_OBJC_AVAILABILITY_CHECK:
+      S = new (Context) ObjCAvailabilityCheckExpr(Empty);
+      break;
     case STMT_SEH_LEAVE:
       S = new (Context) SEHLeaveStmt(Empty);
       break;