[Sema] add reproducer (NFC)

This test case compiled fine before
da96079 and the subsequent
#84828, but now errors. The next
commit will revert those changes.

Author: hnrklssn

test/Sema/access-level-import-both-public-and-private.swift

@@ -0,0 +1,35 @@
+// Regression test for rdar://164588082
+
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t 
+
+// RUN: %target-swift-frontend -verify -verify-additional-file %t%{fs-sep}bar.h -typecheck %t/test.swift -I %t
+
+//--- test.swift
+// expected-note@+1{{struct 'Baz' imported as 'private' from 'Bar' here}}
+private import Foo.Bar
+public import Foo
+
+// expected-error@+2{{function cannot be declared public because its parameter uses a private type}}
+// expected-note@+1{{struct 'Baz' is imported by this file as 'private' from 'Bar'}}
+public func test(x: Baz) {}
+
+//--- foo.h
+#pragma once
+#include "bar.h"
+
+//--- bar.h
+#pragma once
+// expected-note@+1{{type declared here}}
+struct Baz {};
+
+//--- module.modulemap
+module Foo {
+  header "foo.h"
+  export *
+
+  explicit module Bar {
+    header "bar.h"
+    export *
+  }
+}