SymbolGraph: Simplify availability check.

Getting a result from `DeclAttrs::getUnavailable()` already indicates that the
declaration is either fully unavailable or obsoleted. Checking
`AvailableAttr::getVersionAvailability()` is redundant.

Author: tshortli

lib/SymbolGraphGen/SymbolGraphASTWalker.cpp

@@ -110,26 +110,17 @@ SymbolGraph *SymbolGraphASTWalker::getModuleSymbolGraph(const Decl *D) {
   return SG;
 }
 
-namespace {
-bool isUnavailableOrObsoleted(const Decl *D) {
+static bool isUnavailableOrObsoletedOnPlatform(const Decl *D) {
   if (const auto *Avail =
         D->getAttrs().getUnavailable(D->getASTContext())) {
-    if (Avail->getPlatform() != PlatformKind::none) {
-      switch (Avail->getVersionAvailability(D->getASTContext())) {
-        case AvailableVersionComparison::Unavailable:
-        case AvailableVersionComparison::Obsoleted:
-          return true;
-        default:
-          break;
-      }
-    }
+    if (Avail->getPlatform() != PlatformKind::none)
+      return true;
   }
   return false;
 }
-} // end anonymous namespace
 
 bool SymbolGraphASTWalker::walkToDeclPre(Decl *D, CharSourceRange Range) {
-  if (isUnavailableOrObsoleted(D)) {
+  if (isUnavailableOrObsoletedOnPlatform(D)) {
     return false;
   }
 
@@ -171,7 +162,7 @@ bool SymbolGraphASTWalker::walkToDeclPre(Decl *D, CharSourceRange Range) {
       return false;
     }
 
-    if (isUnavailableOrObsoleted(ExtendedNominal)) {
+    if (isUnavailableOrObsoletedOnPlatform(ExtendedNominal)) {
       return false;
     }