Add tests

tests/cases/conformance/types/conditional/inferTypes1.ts

@@ -33,6 +33,7 @@ type T15 = ReturnType<any>;  // any
 type T16 = ReturnType<never>;  // never
 type T17 = ReturnType<string>;  // Error
 type T18 = ReturnType<Function>;  // Error
+type T19<T extends any[]> = ReturnType<(x: string, ...args: T) => T[]>;  // T[]
 
 type U10 = InstanceType<typeof C>;  // C
 type U11 = InstanceType<any>;  // any
@@ -168,3 +169,13 @@ type EnsureIsString<T> = T extends MustBeString<infer U> ? U : never;
 
 type Test1 = EnsureIsString<"hello">;  // "hello"
 type Test2 = EnsureIsString<42>;  // never
+
+// Repros from #26856
+
+function invoker <K extends string | number | symbol, A extends any[]> (key: K, ...args: A) {
+    return <T extends Record<K, (...args: A) => any>> (obj: T): ReturnType<T[K]> => obj[key](...args)
+}
+
+const result = invoker('test', true)({ test: (a: boolean) => 123 })
+
+type Foo2<A extends any[]> = ReturnType<(...args: A) => string>;