Clear the LV cache when merging the availability attribute.

The availability implies default visibility, so it can change the computed
visibility.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@171840 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 84b0d3f..3b37890 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -1790,12 +1790,16 @@
 
 bool Sema::mergeDeclAttribute(Decl *D, InheritableAttr *Attr) {
   InheritableAttr *NewAttr = NULL;
-  if (AvailabilityAttr *AA = dyn_cast<AvailabilityAttr>(Attr))
+  if (AvailabilityAttr *AA = dyn_cast<AvailabilityAttr>(Attr)) {
     NewAttr = mergeAvailabilityAttr(D, AA->getRange(), AA->getPlatform(),
                                     AA->getIntroduced(), AA->getDeprecated(),
                                     AA->getObsoleted(), AA->getUnavailable(),
                                     AA->getMessage());
-  else if (VisibilityAttr *VA = dyn_cast<VisibilityAttr>(Attr)) {
+    if (NewAttr) {
+      NamedDecl *ND = cast<NamedDecl>(D);
+      ND->ClearLVCache();
+    }
+  } else if (VisibilityAttr *VA = dyn_cast<VisibilityAttr>(Attr)) {
     NewAttr = mergeVisibilityAttr(D, VA->getRange(), VA->getVisibility());
     if (NewAttr) {
       NamedDecl *ND = cast<NamedDecl>(D);