add a regression test

Author: David Ungar

validation-test/Serialization/rdar80449046.swift

@@ -0,0 +1,13 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -emit-module %s
+
+@propertyWrapper
+public struct TestWrapper {
+  public var wrappedValue: Int
+  public init(wrappedValue: Int) { self.wrappedValue = wrappedValue }
+}
+
+@frozen public struct Test {
+  @TestWrapper public var x: Int = 42
+}
+