src/test/compile-fail/variance-types-bounds.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 // Test that we correctly infer variance for type parameters in
  12 // various types and traits.
  13
  14 #![feature(rustc_attrs)]
  15
  16 #[rustc_variance]
  17 struct TestImm<A, B> { //~ ERROR [+, +]
  18     x: A,
  19     y: B,
  20 }
  21
  22 #[rustc_variance]
  23 struct TestMut<A, B:'static> { //~ ERROR [+, o]
  24     x: A,
  25     y: &'static mut B,
  26 }
  27
  28 #[rustc_variance]
  29 struct TestIndirect<A:'static, B:'static> { //~ ERROR [+, o]
  30     m: TestMut<A, B>
  31 }
  32
  33 #[rustc_variance]
  34 struct TestIndirect2<A:'static, B:'static> { //~ ERROR [o, o]
  35     n: TestMut<A, B>,
  36     m: TestMut<B, A>
  37 }
  38
  39 #[rustc_variance]
  40 trait Getter<A> { //~ ERROR [o, o]
  41     fn get(&self) -> A;
  42 }
  43
  44 #[rustc_variance]
  45 trait Setter<A> { //~ ERROR [o, o]
  46     fn set(&mut self, a: A);
  47 }
  48
  49 #[rustc_variance]
  50 trait GetterSetter<A> { //~ ERROR [o, o]
  51     fn get(&self) -> A;
  52     fn set(&mut self, a: A);
  53 }
  54
  55 #[rustc_variance]
  56 trait GetterInTypeBound<A> { //~ ERROR [o, o]
  57     // Here, the use of `A` in the method bound *does* affect
  58     // variance.  Think of it as if the method requested a dictionary
  59     // for `T:Getter<A>`.  Since this dictionary is an input, it is
  60     // contravariant, and the Getter is covariant w/r/t A, yielding an
  61     // overall contravariant result.
  62     fn do_it<T:Getter<A>>(&self);
  63 }
  64
  65 #[rustc_variance]
  66 trait SetterInTypeBound<A> { //~ ERROR [o, o]
  67     fn do_it<T:Setter<A>>(&self);
  68 }
  69
  70 #[rustc_variance]
  71 struct TestObject<A, R> { //~ ERROR [o, o]
  72     n: Box<Setter<A>+Send>,
  73     m: Box<Getter<R>+Send>,
  74 }
  75
  76 fn main() {}