AST: Add AnyRequest::isDependencySource()

Author: slavapestov

include/swift/AST/AnyRequest.h

@@ -83,6 +83,7 @@ struct AnyRequestVTable {
   const std::function<void(const void *, DiagnosticEngine &)> noteCycleStep;
   const std::function<SourceLoc(const void *)> getNearestLoc;
   const std::function<bool(const void *)> isCached;
+  bool isDependencySource;
 
   template <typename Request,
             typename std::enable_if<Request::isEverCached>::type * = nullptr>
@@ -99,6 +100,7 @@ struct AnyRequestVTable {
         &Impl<Request>::noteCycleStep,
         &Impl<Request>::getNearestLoc,
         &Impl<Request>::isCached,
+        Request::isDependencySource,
     };
     return &vtable;
   }
@@ -118,6 +120,7 @@ struct AnyRequestVTable {
         &Impl<Request>::noteCycleStep,
         &Impl<Request>::getNearestLoc,
         [](auto){ return false; },
+        Request::isDependencySource,
     };
     return &vtable;
   }
@@ -224,6 +227,10 @@ class AnyRequestBase {
     return getVTable()->isCached(getRawStorage());
   }
 
+  bool isDependencySource() const {
+    return getVTable()->isDependencySource;
+  }
+
   /// Compare two instances for equality.
   friend bool operator==(const AnyRequestBase<Derived> &lhs,
                          const AnyRequestBase<Derived> &rhs) {