src/test/compile-fail/defaulted-unit-warning.rs

   1 // Copyright 2016 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 #![allow(unreachable_code)]
  13 #![deny(resolve_trait_on_defaulted_unit)]
  14
  15 trait Deserialize: Sized {
  16     fn deserialize() -> Result<Self, String>;
  17 }
  18
  19 impl Deserialize for () {
  20     fn deserialize() -> Result<(), String> {
  21         Ok(())
  22     }
  23 }
  24
  25 fn doit() -> Result<(), String> {
  26     let _ = match Deserialize::deserialize() {
  27         //~^ ERROR code relies on type
  28         //~| WARNING previously accepted
  29         Ok(x) => x,
  30         Err(e) => return Err(e),
  31     };
  32     Ok(())
  33 }
  34
  35 trait ImplementedForUnitButNotNever {}
  36
  37 impl ImplementedForUnitButNotNever for () {}
  38
  39 fn foo<T: ImplementedForUnitButNotNever>(_t: T) {}
  40
  41 fn smeg() {
  42     let _x = return;
  43     foo(_x);
  44     //~^ ERROR code relies on type
  45     //~| WARNING previously accepted
  46 }
  47
  48 fn main() {
  49     let _ = doit();
  50 }
  51