rust/src/test/run-pass/recursion.rs

// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// ignore-test

enum Nil {Nil}
struct Cons<T> {head:int, tail:T}
trait Dot {fn dot(other:self) -> int;}
impl Dot for Nil {
  fn dot(_:Nil) -> int {0}
}
impl<T:Dot> Dot for Cons<T> {
  fn dot(other:Cons<T>) -> int {
    self.head * other.head + self.tail.dot(other.tail)
  }
}
fn test<T:Dot> (n:int, i:int, first:T, second:T) ->int {
  match n {
    0 => {first.dot(second)}
      // Error message should be here. It should be a type error
      // to instantiate `test` at a type other than T. (See #4287)
    _ => {test (n-1, i+1, Cons {head:2*i+1, tail:first}, Cons{head:i*i, tail:second})}
  }
}
pub fn main() {
  let n = test(1, 0, Nil, Nil);
  println!("{}", n);
}