rust/src/test/compile-fail/wf-static-method.rs

// Copyright 2015 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.

// check that static methods don't get to assume their trait-ref
// is well-formed.
// FIXME(#27579): this is just a bug. However, our checking with
// static inherent methods isn't quite working - need to
// fix that before removing the check.

trait Foo<'a, 'b, T>: Sized {
    fn make_me() -> Self { loop {} }
    fn static_evil(u: &'b u32) -> &'a u32;
}

struct Evil<'a, 'b: 'a>(Option<&'a &'b ()>);

impl<'a, 'b> Foo<'a, 'b, Evil<'a, 'b>> for () {
    fn make_me() -> Self { }
    fn static_evil(u: &'b u32) -> &'a u32 {
        u //~ ERROR cannot infer an appropriate lifetime
    }
}

struct IndirectEvil<'a, 'b: 'a>(Option<&'a &'b ()>);

impl<'a, 'b> Foo<'a, 'b, ()> for IndirectEvil<'a, 'b> {
    fn make_me() -> Self { IndirectEvil(None) }
    fn static_evil(u: &'b u32) -> &'a u32 {
        let me = Self::make_me(); //~ ERROR lifetime bound not satisfied
        loop {} // (`me` could be used for the lifetime transmute).
    }
}

impl<'a, 'b> Evil<'a, 'b> {
    fn inherent_evil(u: &'b u32) -> &'a u32 {
        u //~ ERROR cannot infer an appropriate lifetime
    }
}

// while static methods don't get to *assume* this, we still
// *check* that they hold.

fn evil<'a, 'b>(b: &'b u32) -> &'a u32 {
    <()>::static_evil(b) //~ ERROR cannot infer an appropriate lifetime
}

fn indirect_evil<'a, 'b>(b: &'b u32) -> &'a u32 {
    <IndirectEvil>::static_evil(b)
    //~^ ERROR cannot infer an appropriate lifetime
}

fn inherent_evil<'a, 'b>(b: &'b u32) -> &'a u32 {
    <Evil>::inherent_evil(b) // bug? shouldn't this be an error
}


fn main() {}