Discard non-indexed relations instead of entire references.

References for function calls where there would normally be a received-by relationship were being discarded. This happened when the receiver type is a non-indexed type, e.g. a private type in a system framework. The function call could be public or defined in any module though, so discarding it entirely because of the receiver type is not desirable.

Follow up to refine the behavior of [previous commit](b65d8c2).

Author: dylansturg

lib/Index/Index.cpp

@@ -1762,9 +1762,11 @@ bool IndexSwiftASTWalker::reportIsDynamicRef(ValueDecl *D, IndexSymbol &Info) {
   SmallVector<NominalTypeDecl *, 1> Types;
   ide::getReceiverType(BaseE, Types);
   for (auto *ReceiverTy : Types) {
-    if (addRelation(Info, (SymbolRoleSet) SymbolRole::RelationReceivedBy,
-                    ReceiverTy))
-      return true;
+    // Adding the received-by "fails" if the receiver type isn't indexed.
+    // Allow the relation to be silently discarded, while keeping the
+    // reference.
+    addRelation(Info, (SymbolRoleSet)SymbolRole::RelationReceivedBy,
+                ReceiverTy);
   }
 
   return false;

test/Index/index_private_type_receiver.swift

@@ -0,0 +1,22 @@
+// RUN: %target-swift-ide-test -print-indexed-symbols -source-filename %s  | %FileCheck %s
+
+import SwiftUI
+
+private struct Mod: ViewModifier {
+  func body(content: Content) -> some View {
+    content
+      .background(Color.red)
+      // CHECK: [[@LINE-1]]:8 | instance-method/Swift | background(_:ignoresSafeAreaEdges:) | {{.*}} | Ref,Call{{.*}} |
+      .foregroundColor(.green)
+
+  }
+}
+
+private struct V: View {
+  var body: some View {
+    Capsule()
+      .fill(.red)
+      .background(.green)
+    // CHECK: [[@LINE-1]]:8 | instance-method/Swift | background(_:ignoresSafeAreaEdges:) | {{.*}} | Ref,Call{{.*}} |
+  }
+}