Extend type nullability qualifiers for Objective-C.

Introduce context-sensitive, non-underscored nullability specifiers
(nonnull, nullable, null_unspecified) for Objective-C method return
types, method parameter types, and properties.

Introduce Objective-C-specific semantics, including computation of the
nullability of the result of a message send, merging of nullability
information from the @interface of a class into its @implementation,
etc .

This is the Objective-C part of rdar://problem/18868820.

llvm-svn: 240154

clang/lib/Basic/IdentifierTable.cpp

@@ -16,6 +16,7 @@
 #include "clang/Basic/IdentifierTable.h"
 #include "clang/Basic/LangOptions.h"
 #include "clang/Basic/OperatorKinds.h"
+#include "clang/Basic/Specifiers.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/FoldingSet.h"
 #include "llvm/ADT/SmallString.h"
@@ -645,3 +646,16 @@ const char *clang::getOperatorSpelling(OverloadedOperatorKind Operator) {
 
   llvm_unreachable("Invalid OverloadedOperatorKind!");
 }
+
+StringRef clang::getNullabilitySpelling(NullabilityKind kind) {
+  switch (kind) {
+  case NullabilityKind::NonNull:
+    return "__nonnull";
+
+  case NullabilityKind::Nullable:
+    return "__nullable";
+
+  case NullabilityKind::Unspecified:
+    return "__null_unspecified";
+  }
+}