Add regression test for https://bugs.swift.org/browse/SR-11030 / rdar://problem/52266834

Author: slavapestov

validation-test/compiler_crashers_2_fixed/sr11030.swift

@@ -0,0 +1,45 @@
+// RUN: %target-swift-frontend -O -emit-ir %s
+
+public class Coordinator: ConcreteCoordinator {
+    public func coordinate() {
+
+    }
+}
+
+public typealias ConcreteCoordinator = InternalBaseCoordinator & CoordinatorProtocol
+
+public protocol CoordinatorProtocol {
+    func coordinate()
+}
+
+public protocol ViewBridgeProtocol {
+    func createCoordinator() -> ConcreteCoordinator
+}
+
+public class InternalBaseViewBridge {
+
+    public func startCoordinator() {
+        abstract().createCoordinator()
+            .with(success: nil)
+            .coordinate()
+    }
+
+    private func abstract() -> ViewBridgeProtocol {
+        return self as! ViewBridgeProtocol
+    }
+
+}
+
+public class InternalBaseCoordinator: InternalCoordinatorProtocol {
+    
+}
+
+public protocol InternalCoordinatorProtocol: AnyObject {
+    
+}
+
+extension InternalCoordinatorProtocol {
+    public func with(success: ((ConcreteCoordinator) -> Void)?) -> Self {
+        return self
+    }
+}