Add regression test for rdar://57549596 / https://bugs.swift.org/browse/SR-11874

Author: slavapestov

test/IDE/print_swift_module.swift

@@ -1,7 +1,9 @@
 // RUN: %empty-directory(%t)
 // RUN: %target-swift-frontend -emit-module-path %t/print_swift_module.swiftmodule -emit-module-doc -emit-module-doc-path %t/print_swift_module.swiftdoc %s
 // RUN: %target-swift-ide-test -print-module -print-interface -no-empty-line-between-members -module-to-print=print_swift_module -I %t -source-filename=%s > %t.syn.txt
+// RUN: %target-swift-ide-test -print-module -access-filter-internal -no-empty-line-between-members -module-to-print=print_swift_module -I %t -source-filename=%s > %t.syn.internal.txt
 // RUN: %FileCheck %s -check-prefix=CHECK1 < %t.syn.txt
+// RUN: %FileCheck %s -check-prefix=CHECK2 < %t.syn.internal.txt
 
 public protocol P1 {
   /// foo1 comment from P1
@@ -53,3 +55,14 @@ public struct City {
 
 // CHECK1:      /// returnsAlias() comment
 // CHECK1-NEXT: func returnsAlias() -> print_swift_module.Alias<Int>
+
+// CHECK2: struct Event {
+public struct Event {
+  public var start: Int
+  public var end: Int?
+  public var repeating: ((), Int?)
+  public var name = "untitled event"
+
+  // CHECK2: init(start: Int, end: Int? = nil, repeating: ((), Int?) = ((), nil), name: String = "untitled event")
+}
+// CHECK2: }