src/test/compile-fail/variance-unused-type-param.rs

   1 // Copyright 2012 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 #![allow(dead_code)]
  12
  13 // Test that we report an error for unused type parameters in types and traits,
  14 // and that we offer a helpful suggestion.
  15
  16 struct SomeStruct<A> { x: u32 }
  17 //~^ ERROR parameter `A` is never used
  18 //~| HELP PhantomData
  19 //~| HELP run `rustc --explain E0392` to see a detailed explanation
  20
  21 enum SomeEnum<A> { Nothing }
  22 //~^ ERROR parameter `A` is never used
  23 //~| HELP PhantomData
  24 //~| HELP run `rustc --explain E0392` to see a detailed explanation
  25
  26 // Here T might *appear* used, but in fact it isn't.
  27 enum ListCell<T> {
  28 //~^ ERROR parameter `T` is never used
  29 //~| HELP PhantomData
  30 //~| HELP run `rustc --explain E0392` to see a detailed explanation
  31     Cons(Box<ListCell<T>>),
  32     Nil
  33 }
  34
  35 fn main() {}