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// Test cases where we constrain `<T as Anything<'b>>::AssocType` to
// outlive `'a` and there is a unique bound in the trait definition of
// `Anything` -- i.e., we know that `AssocType` outlives `'b`. In this
// case, the best way to satisfy the trait bound is to show that `'b:
// 'a`, which can be done in various ways.
// compile-flags:-Zverbose
#![allow(warnings)]
#![feature(rustc_attrs)]
use std::cell::Cell;
trait Anything<'a> {
type AssocType: 'a;
}
fn with_signature<'a, T, F>(cell: Cell<&'a ()>, t: T, op: F)
where
F: FnOnce(Cell<&'a ()>, T),
{
op(cell, t)
}
fn require<'a, 'b, T>(_cell: Cell<&'a ()>, _t: T)
where
T: Anything<'b>,
T::AssocType: 'a,
{
}
#[rustc_regions]
fn no_relationships_late<'a, 'b, T>(cell: Cell<&'a ()>, t: T)
where
T: Anything<'b>,
{
with_signature(cell, t, |cell, t| require(cell, t));
//~^ ERROR
}
#[rustc_regions]
fn no_relationships_early<'a, 'b, T>(cell: Cell<&'a ()>, t: T)
where
T: Anything<'b>,
'a: 'a,
{
with_signature(cell, t, |cell, t| require(cell, t));
//~^ ERROR
}
#[rustc_regions]
fn projection_outlives<'a, 'b, T>(cell: Cell<&'a ()>, t: T)
where
T: Anything<'b>,
T::AssocType: 'a,
{
// We are projecting `<T as Anything<'b>>::AssocType`, and we know
// that this outlives `'a` because of the where-clause.
with_signature(cell, t, |cell, t| require(cell, t));
}
#[rustc_regions]
fn elements_outlive<'a, 'b, T>(cell: Cell<&'a ()>, t: T)
where
T: Anything<'b>,
'b: 'a,
{
with_signature(cell, t, |cell, t| require(cell, t));
}
#[rustc_regions]
fn one_region<'a, T>(cell: Cell<&'a ()>, t: T)
where
T: Anything<'a>,
{
// Note that in this case the closure still propagates an external
// requirement between two variables in its signature, but the
// creator maps both those two region variables to `'a` on its
// side.
with_signature(cell, t, |cell, t| require(cell, t));
}
fn main() {}
|
