Add regression test

ahejlsberg · ahejlsberg · commit 21c397dd5a7a · 2018-02-03T14:45:16.000-08:00
diff --git a/tests/cases/compiler/typeAliasFunctionTypeSharedSymbol.ts b/tests/cases/compiler/typeAliasFunctionTypeSharedSymbol.ts
@@ -0,0 +1,12 @@
+// Repro from comment in #21496
+
+function Mixin<TBase extends {new (...args: any[]): {}}>(Base: TBase) {
+    return class extends Base {
+    };
+}
+
+type Mixin = ReturnTypeOf<typeof Mixin>
+
+type ReturnTypeOf<V> = V extends (...args: any[])=>infer R ? R : never;
+
+type Crashes = number & Mixin;
