11984340bf
Currently, we consider region subtyping a failure if a skolemized lifetime is relatable to any other lifetime in any way at all. But a more precise formulation is to say that a skolemized lifetime: - must not have any *incoming* edges in the region graph - only has *outgoing* edges to nodes that are `'static` To enforce the latter requirement, we add edges from `'static -> 'x` for each lifetime '`x' reachable from a skolemized region. We now have to add a new `pop_skolemized` routine to do cleanup. Whereas before if there were *any* edges relating to a skolemized region, we would return `Err` and hence rollback the transaction, we now tolerate some edges and return `Ok`. Therefore, the `pop_skolemized` routine runs and cleans up those edges.
49 lines
1.3 KiB
Rust
49 lines
1.3 KiB
Rust
// Copyright 2015 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 that two distinct impls which match subtypes of one another
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// yield coherence errors (or not) depending on the variance.
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trait Contravariant {
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fn foo(&self) { }
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}
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impl Contravariant for for<'a,'b> fn(&'a u8, &'b u8) -> &'a u8 {
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}
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impl Contravariant for for<'a> fn(&'a u8, &'a u8) -> &'a u8 {
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}
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///////////////////////////////////////////////////////////////////////////
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trait Covariant {
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fn foo(&self) { }
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}
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impl Covariant for for<'a,'b> fn(&'a u8, &'b u8) -> &'a u8 {
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}
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impl Covariant for for<'a> fn(&'a u8, &'a u8) -> &'a u8 {
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}
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///////////////////////////////////////////////////////////////////////////
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trait Invariant {
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fn foo(&self) { }
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}
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impl Invariant for for<'a,'b> fn(&'a u8, &'b u8) -> &'a u8 {
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}
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impl Invariant for for<'a> fn(&'a u8, &'a u8) -> &'a u8 {
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}
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fn main() { }
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