131 lines
3.7 KiB
Rust
131 lines
3.7 KiB
Rust
// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// Test cases where we constrain `<T as Anything<'a, 'b>>::AssocType`
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// to outlive `'a` and there are two bounds in the trait definition of
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// `Anything` -- i.e., we know that `AssocType` outlives `'a` and
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// `'b`. In this case, it's not clear what is the best way to satisfy
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// the trait bound, and hence we propagate it to the caller as a type
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// test.
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// compile-flags:-Zborrowck=mir -Zverbose
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#![allow(warnings)]
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#![feature(rustc_attrs)]
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use std::cell::Cell;
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trait Anything<'a, 'b> {
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type AssocType: 'a + 'b;
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}
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fn with_signature<'a, T, F>(cell: Cell<&'a ()>, t: T, op: F)
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where
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F: FnOnce(Cell<&'a ()>, T),
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{
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op(cell, t)
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}
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fn require<'a, 'b, 'c, T>(_cell: Cell<&'a ()>, _t: T)
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where
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T: Anything<'b, 'c>,
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T::AssocType: 'a,
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{
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}
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#[rustc_regions]
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fn no_relationships_late<'a, 'b, 'c, T>(cell: Cell<&'a ()>, t: T)
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where
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T: Anything<'b, 'c>,
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{
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with_signature(cell, t, |cell, t| require(cell, t));
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//~^ ERROR associated type `<T as Anything<'_#5r, '_#6r>>::AssocType` may not live long enough
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}
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#[rustc_regions]
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fn no_relationships_early<'a, 'b, 'c, T>(cell: Cell<&'a ()>, t: T)
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where
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T: Anything<'b, 'c>,
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'a: 'a,
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{
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with_signature(cell, t, |cell, t| require(cell, t));
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//~^ ERROR associated type `<T as Anything<'_#6r, '_#7r>>::AssocType` may not live long enough
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}
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#[rustc_regions]
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fn projection_outlives<'a, 'b, 'c, T>(cell: Cell<&'a ()>, t: T)
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where
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T: Anything<'b, 'c>,
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T::AssocType: 'a,
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{
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// This error is unfortunate. This code ought to type-check: we
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// are projecting `<T as Anything<'b>>::AssocType`, and we know
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// that this outlives `'a` because of the where-clause. However,
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// the way the region checker works, we don't register this
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// outlives obligation, and hence we get an error: this is because
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// what we see is a projection like `<T as
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// Anything<'?0>>::AssocType`, and we don't yet know if `?0` will
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// equal `'b` or not, so we ignore the where-clause. Obviously we
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// can do better here with a more involved verification step.
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with_signature(cell, t, |cell, t| require(cell, t));
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//~^ ERROR associated type `<T as Anything<'_#6r, '_#7r>>::AssocType` may not live long enough
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}
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#[rustc_regions]
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fn elements_outlive1<'a, 'b, 'c, T>(cell: Cell<&'a ()>, t: T)
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where
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T: Anything<'b, 'c>,
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'b: 'a,
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{
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with_signature(cell, t, |cell, t| require(cell, t));
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}
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#[rustc_regions]
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fn elements_outlive2<'a, 'b, 'c, T>(cell: Cell<&'a ()>, t: T)
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where
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T: Anything<'b, 'c>,
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'c: 'a,
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{
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with_signature(cell, t, |cell, t| require(cell, t));
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}
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#[rustc_regions]
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fn two_regions<'a, 'b, T>(cell: Cell<&'a ()>, t: T)
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where
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T: Anything<'b, 'b>,
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{
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with_signature(cell, t, |cell, t| require(cell, t));
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//~^ ERROR unsatisfied lifetime constraints
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}
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#[rustc_regions]
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fn two_regions_outlive<'a, 'b, T>(cell: Cell<&'a ()>, t: T)
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where
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T: Anything<'b, 'b>,
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'b: 'a,
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{
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with_signature(cell, t, |cell, t| require(cell, t));
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}
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#[rustc_regions]
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fn one_region<'a, T>(cell: Cell<&'a ()>, t: T)
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where
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T: Anything<'a, 'a>,
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{
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// Note that in this case the closure still propagates an external
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// requirement between two variables in its signature, but the
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// creator maps both those two region variables to `'a` on its
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// side.
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with_signature(cell, t, |cell, t| require(cell, t));
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}
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fn main() {}
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