Provide hook to see if ASTScopes support lookups into inactive clauses

Author: David Ungar

include/swift/AST/NameLookup.h

@@ -627,6 +627,8 @@ class ASTScope {
     return Mem;
   }
 
+  static bool areInactiveIfConfigClausesSupported();
+
 private:
   static ast_scope::ASTSourceFileScope *createScopeTree(SourceFile *);
 };

lib/AST/ASTScopeCreation.cpp

@@ -731,6 +731,10 @@ void ASTScope::
   impl->buildEnoughOfTreeForTopLevelExpressionsButDontRequestGenericsOrExtendedNominals();
 }
 
+bool ASTScope::areInactiveIfConfigClausesSupported() {
+  return ScopeCreator::includeInactiveIfConfigClauses;
+}
+
 ASTSourceFileScope *ASTScope::createScopeTree(SourceFile *SF) {
   ScopeCreator *scopeCreator = new (SF->getASTContext()) ScopeCreator(SF);
   return scopeCreator->sourceFileScope;