AST: Handle PoundDiagnosticDecl in DeclExportabilityVisitor.

Author: tshortli

include/swift/AST/DeclExportabilityVisitor.h

@@ -150,7 +150,6 @@ class DeclExportabilityVisitor
   }
   UNREACHABLE(Module);
   UNREACHABLE(TopLevelCode);
-  UNREACHABLE(PoundDiagnostic);
   UNREACHABLE(Missing);
   UNREACHABLE(MissingMember);
   UNREACHABLE(GenericTypeParam);
@@ -168,6 +167,7 @@ class DeclExportabilityVisitor
   bool visit##KIND##Decl(const KIND##Decl *D) { return true; }
   UNINTERESTING(IfConfig);
   UNINTERESTING(Import);
+  UNINTERESTING(PoundDiagnostic);
   UNINTERESTING(PrecedenceGroup);
   UNINTERESTING(EnumCase);
   UNINTERESTING(Operator);

test/SILGen/skip_non_exportable_decls.swift

@@ -4,6 +4,8 @@
 
 import Swift
 
+#warning("!")
+
 // CHECK-NO-SKIP: sil_global private @$s4Test17internalGlobalVar_Wz : $Builtin.Word
 // CHECK-SKIP-NOT: s4Test17internalGlobalVar_Wz