mirror of https://github.com/rust-lang/rust
84 lines
1.9 KiB
Rust
84 lines
1.9 KiB
Rust
// Test cases where we constrain `<T as Anything<'b>>::AssocType` to
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// outlive `'a` and there are no bounds in the trait definition of
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// `Anything`. This means that the constraint can only be satisfied in two
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// ways:
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//
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// - by ensuring that `T: 'a` and `'b: 'a`, or
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// - by something in the where clauses.
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//
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// As of this writing, the where clause option does not work because
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// of limitations in our region inferencing system (this is true both
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// with and without NLL). See `projection_outlives`.
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//
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// Ensuring that both `T: 'a` and `'b: 'a` holds does work (`elements_outlive`).
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//@ compile-flags:-Zverbose-internals
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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> {
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type AssocType;
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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, T>(_cell: Cell<&'a ()>, _t: T)
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where
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T: Anything<'b>,
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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, T>(cell: Cell<&'a ()>, t: T)
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where
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T: Anything<'b>,
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{
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with_signature(cell, t, |cell, t| require(cell, t));
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//~^ ERROR the parameter type `T` may not live long enough
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//~| ERROR
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}
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#[rustc_regions]
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fn no_relationships_early<'a, 'b, T>(cell: Cell<&'a ()>, t: T)
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where
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T: Anything<'b>,
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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 the parameter type `T` may not live long enough
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//~| ERROR
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}
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#[rustc_regions]
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fn projection_outlives<'a, 'b, T>(cell: Cell<&'a ()>, t: T)
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where
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T: Anything<'b>,
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T::AssocType: 'a,
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{
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// We are projecting `<T as Anything<'b>>::AssocType`, and we know
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// that this outlives `'a` because of the where-clause.
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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_outlive<'a, 'b, T>(cell: Cell<&'a ()>, t: T)
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where
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T: Anything<'b>,
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T: 'a,
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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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fn main() {}
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