gistfile1.txt

$ cat -n associated-types-project-from-hrtb-in-fn-body.rs
     1  // Copyright 2014 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  // Check projection of an associated type out of a higher-ranked
    12  // trait-bound in the context of a function body.
    13
    14  pub trait Foo<T> {
    15      type A;
    16
    17      fn get(&self, t: T) -> Self::A;
    18  }
    19
    20  fn foo<'a, I : for<'x> Foo<&'x isize>>(
    21      x: <I as Foo<&'a isize>>::A)
    22  {
    23      let y: I::A = x;
    24  }
    25
    26  fn bar<'a, 'b, I : for<'x> Foo<&'x isize>>(
    27      x: <I as Foo<&'a isize>>::A,
    28      y: <I as Foo<&'b isize>>::A,
    29      cond: bool)
    30  {
    31      // x and y here have two distinct lifetimes:
    32      let z: I::A = if cond { x } else { y };
    33      //~^ ERROR cannot infer
    34  }
    35
    36  pub fn main() {}


######## Expected error message ########


$ rustc associated-types-project-from-hrtb-in-fn-body.rs
associated-types-project-from-hrtb-in-fn-body.rs:32:12: 32:16 error: cannot infer an appropriate lifetime for lifetime parameter 'x in trait containing associated type `A` due to conflicting requirements [E0495]
associated-types-project-from-hrtb-in-fn-body.rs:32     let z: I::A = if cond { x } else { y };
                                                               ^~~~
associated-types-project-from-hrtb-in-fn-body.rs:26:1: 34:2 help: consider using an explicit lifetime parameter as shown: fn bar<'a,
       I: for<'x>Foo<&'x isize>>(x: <I as Foo<&'a isize>>::A,
                                 y: <I as Foo<&'b isize>>::A, cond: bool)
associated-types-project-from-hrtb-in-fn-body.rs:26 fn bar<'a, 'b, I : for<'x> Foo<&'x isize>>(
                                                    ^
error: aborting due to previous error

    
######## What I got instead ########


$ ./rustc associated-types-project-from-hrtb-in-fn-body.rs
associated-types-project-from-hrtb-in-fn-body.rs:26:1: 34:2 error: mismatched types [E0308]
associated-types-project-from-hrtb-in-fn-body.rs:26 fn bar<'a, 'b, I : for<'x> Foo<&'x isize>>(
                                                    ^
associated-types-project-from-hrtb-in-fn-body.rs:26:1: 34:2 help: run `rustc --explain E0308` to see a detailed explanation
associated-types-project-from-hrtb-in-fn-body.rs:26:1: 34:2 note: expected type `std::marker::Sized`
associated-types-project-from-hrtb-in-fn-body.rs:26:1: 34:2 note:    found type `std::marker::Sized`
associated-types-project-from-hrtb-in-fn-body.rs:30:1: 34:2 note: the lifetime 'a as defined on the block at 30:0...
associated-types-project-from-hrtb-in-fn-body.rs:30 {
                                                    ^
associated-types-project-from-hrtb-in-fn-body.rs:30:1: 34:2 note: ...does not necessarily outlive the lifetime 'b as defined on the block at 30:0
associated-types-project-from-hrtb-in-fn-body.rs:30 {
                                                    ^
associated-types-project-from-hrtb-in-fn-body.rs:26:1: 34:2 error: mismatched types [E0308]
associated-types-project-from-hrtb-in-fn-body.rs:26 fn bar<'a, 'b, I : for<'x> Foo<&'x isize>>(
                                                    ^
associated-types-project-from-hrtb-in-fn-body.rs:26:1: 34:2 help: run `rustc --explain E0308` to see a detailed explanation
associated-types-project-from-hrtb-in-fn-body.rs:26:1: 34:2 note: expected type `std::marker::Sized`
associated-types-project-from-hrtb-in-fn-body.rs:26:1: 34:2 note:    found type `std::marker::Sized`
associated-types-project-from-hrtb-in-fn-body.rs:30:1: 34:2 note: the lifetime 'b as defined on the block at 30:0...
associated-types-project-from-hrtb-in-fn-body.rs:30 {
                                                    ^
associated-types-project-from-hrtb-in-fn-body.rs:30:1: 34:2 note: ...does not necessarily outlive the lifetime 'a as defined on the block at 30:0
associated-types-project-from-hrtb-in-fn-body.rs:30 {
                                                    ^
associated-types-project-from-hrtb-in-fn-body.rs:26:1: 34:2 help: consider using an explicit lifetime parameter as shown: fn bar<'a,
       I: for<'x>Foo<&'x isize>>(x: <I as Foo<&'a isize>>::A,
                                 y: <I as Foo<&'b isize>>::A, cond: bool)
associated-types-project-from-hrtb-in-fn-body.rs:26 fn bar<'a, 'b, I : for<'x> Foo<&'x isize>>(
                                                    ^
error: aborting due to 2 previous errors