Add regression test for https://bugs.swift.org/browse/SR-15792

Author: slavapestov

test/Generics/sr15792_2.swift

@@ -0,0 +1,37 @@
+// RUN: %target-swift-frontend -typecheck %s
+
+// Reduced from Realm open source project: https://github.com/realm/realm-swift.git
+
+internal protocol RealmCollectionImpl: RealmCollection where Index == Int, SubSequence == Slice<Self> {}
+
+public protocol RealmCollection: RealmCollectionBase, Equatable {}
+
+public protocol RealmCollectionBase: RandomAccessCollection, LazyCollectionProtocol, CustomStringConvertible, ThreadConfined where Element: RealmCollectionValue {
+  typealias ElementType = Element
+}
+
+public protocol RealmCollectionValue: Hashable, _HasPersistedType where PersistedType: RealmCollectionValue {}
+
+public protocol _HasPersistedType: _ObjcBridgeable {
+  associatedtype PersistedType: _ObjcBridgeable
+}
+
+public protocol _ObjcBridgeable {}
+
+public protocol ThreadConfined {}
+
+public protocol PersistableEnum: _PersistableInsideOptional, RawRepresentable, CaseIterable, RealmEnum, _RealmCollectionValueInsideOptional, MinMaxType, Comparable where RawValue: Comparable {}
+
+public protocol _PersistableInsideOptional: _Persistable where PersistedType: _PersistableInsideOptional {} 
+
+public protocol _Persistable: _RealmSchemaDiscoverable, _HasPersistedType where PersistedType: _Persistable, PersistedType.PersistedType.PersistedType == PersistedType.PersistedType {}
+
+public protocol RealmEnum: RealmOptionalType, _RealmSchemaDiscoverable {}
+
+public protocol _RealmCollectionValueInsideOptional: RealmCollectionValue where PersistedType: _RealmCollectionValueInsideOptional {}
+
+public protocol MinMaxType {}
+
+public protocol _RealmSchemaDiscoverable {}
+
+public protocol RealmOptionalType: _ObjcBridgeable {}