From 3d04388907f0433dc4d957790520c440f48e33a7 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Sun, 25 Mar 2018 11:30:08 -0700
Subject: [PATCH] Add tests

---
 .../types/conditional/conditionalTypes2.ts    | 65 +++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 tests/cases/conformance/types/conditional/conditionalTypes2.ts

diff --git a/tests/cases/conformance/types/conditional/conditionalTypes2.ts b/tests/cases/conformance/types/conditional/conditionalTypes2.ts
new file mode 100644
index 00000000000..d08700a0119
--- /dev/null
+++ b/tests/cases/conformance/types/conditional/conditionalTypes2.ts
@@ -0,0 +1,65 @@
+// @strict: true
+// @declaration: true
+
+interface Covariant<T> {
+    foo: T extends string ? T : number;
+}
+
+interface Contravariant<T> {
+    foo: T extends string ? keyof T : number;
+}
+
+interface Invariant<T> {
+    foo: T extends string ? keyof T : T;
+}
+
+interface A { a: string }
+interface B extends A { b: string }
+
+
+function f1(a: Covariant<A>, b: Covariant<B>) {
+    a = b;
+    b = a;  // Error
+}
+
+function f2(a: Contravariant<A>, b: Contravariant<B>) {
+    a = b;  // Error
+    b = a;
+}
+
+function f3(a: Invariant<A>, b: Invariant<B>) {
+    a = b;  // Error
+    b = a;  // Error
+}
+
+// Repros from #22860
+
+export class Option<T> {
+    toVector(): Vector<T> {
+        return <any>undefined;
+    }
+}
+
+interface Seq<T> {
+    tail(): Option<Seq<T>>;
+}
+
+class Vector<T> implements Seq<T> {
+    tail(): Option<Vector<T>> {
+        return <any>undefined;
+    }
+    partition2<U extends T>(predicate:(v:T)=>v is U): [Vector<U>,Vector<Exclude<T, U>>];
+    partition2(predicate:(x:T)=>boolean): [Vector<T>,Vector<T>];
+    partition2<U extends T>(predicate:(v:T)=>boolean): [Vector<U>,Vector<any>] {
+        return <any>undefined;
+    }
+}
+
+interface A1<T> {
+    bat: B1<A1<T>>;
+}
+
+interface B1<T> extends A1<T> {
+    bat: B1<B1<T>>;
+    boom: T extends any ? true : true
+}