Add regression test for rdar://64759168

Author: slavapestov

validation-test/compiler_crashers_2_fixed/rdar64759168.swift

@@ -0,0 +1,15 @@
+// RUN: %target-swift-frontend -emit-ir %s
+
+public class Clazz {}
+
+public protocol SelectableFieldValueProtocol {}
+
+public protocol FieldProtocol {
+    associatedtype SelectableValue : SelectableFieldValueProtocol
+}
+
+public protocol SelectFieldValueCoordinatorDelegate  {
+    associatedtype Field : Clazz, FieldProtocol
+}
+
+public class SelectFieldValueCoordinator<Field, Delegate : SelectFieldValueCoordinatorDelegate> where Field == Delegate.Field {}