1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
|
use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
use rustc_data_structures::transitive_relation::TransitiveRelationBuilder;
use rustc_middle::{bug, ty};
use tracing::debug;
use super::explicit_outlives_bounds;
use crate::infer::GenericKind;
use crate::infer::free_regions::FreeRegionMap;
use crate::traits::query::OutlivesBound;
/// The `OutlivesEnvironment` collects information about what outlives
/// what in a given type-checking setting. For example, if we have a
/// where-clause like `where T: 'a` in scope, then the
/// `OutlivesEnvironment` would record that (in its
/// `region_bound_pairs` field). Similarly, it contains methods for
/// processing and adding implied bounds into the outlives
/// environment.
///
/// Other code at present does not typically take a
/// `&OutlivesEnvironment`, but rather takes some of its fields (e.g.,
/// `process_registered_region_obligations` wants the
/// region-bound-pairs). There is no mistaking it: the current setup
/// of tracking region information is quite scattered! The
/// `OutlivesEnvironment`, for example, needs to sometimes be combined
/// with the `middle::RegionRelations`, to yield a full picture of how
/// (lexical) lifetimes interact. However, I'm reluctant to do more
/// refactoring here, since the setup with NLL is quite different.
/// For example, NLL has no need of `RegionRelations`, and is solely
/// interested in the `OutlivesEnvironment`. -nmatsakis
#[derive(Clone)]
pub struct OutlivesEnvironment<'tcx> {
pub param_env: ty::ParamEnv<'tcx>,
free_region_map: FreeRegionMap<'tcx>,
/// FIXME: Your first reaction may be that this is a bit strange. `RegionBoundPairs`
/// does not contain lifetimes, which are instead in the `FreeRegionMap`, and other
/// known type outlives are stored in the `known_type_outlives` set. So why do we
/// have these at all? It turns out that removing these and using `known_type_outlives`
/// everywhere is just enough of a perf regression to matter. This can/should be
/// optimized in the future, though.
region_bound_pairs: RegionBoundPairs<'tcx>,
known_type_outlives: Vec<ty::PolyTypeOutlivesPredicate<'tcx>>,
/// Assumptions that come from the well-formedness of coroutines that we prove
/// auto trait bounds for during the type checking of this body.
higher_ranked_assumptions: FxHashSet<ty::ArgOutlivesPredicate<'tcx>>,
}
/// "Region-bound pairs" tracks outlives relations that are known to
/// be true, either because of explicit where-clauses like `T: 'a` or
/// because of implied bounds.
pub type RegionBoundPairs<'tcx> = FxIndexSet<ty::OutlivesPredicate<'tcx, GenericKind<'tcx>>>;
impl<'tcx> OutlivesEnvironment<'tcx> {
/// Create a new `OutlivesEnvironment` from normalized outlives bounds.
pub fn from_normalized_bounds(
param_env: ty::ParamEnv<'tcx>,
known_type_outlives: Vec<ty::PolyTypeOutlivesPredicate<'tcx>>,
extra_bounds: impl IntoIterator<Item = OutlivesBound<'tcx>>,
higher_ranked_assumptions: FxHashSet<ty::ArgOutlivesPredicate<'tcx>>,
) -> Self {
let mut region_relation = TransitiveRelationBuilder::default();
let mut region_bound_pairs = RegionBoundPairs::default();
// Record relationships such as `T:'x` that don't go into the
// free-region-map but which we use here.
for outlives_bound in explicit_outlives_bounds(param_env).chain(extra_bounds) {
debug!("add_outlives_bounds: outlives_bound={:?}", outlives_bound);
match outlives_bound {
OutlivesBound::RegionSubParam(r_a, param_b) => {
region_bound_pairs
.insert(ty::OutlivesPredicate(GenericKind::Param(param_b), r_a));
}
OutlivesBound::RegionSubAlias(r_a, alias_b) => {
region_bound_pairs
.insert(ty::OutlivesPredicate(GenericKind::Alias(alias_b), r_a));
}
OutlivesBound::RegionSubRegion(r_a, r_b) => match (r_a.kind(), r_b.kind()) {
(
ty::ReStatic | ty::ReEarlyParam(_) | ty::ReLateParam(_),
ty::ReStatic | ty::ReEarlyParam(_) | ty::ReLateParam(_),
) => region_relation.add(r_a, r_b),
(ty::ReError(_), _) | (_, ty::ReError(_)) => {}
// FIXME(#109628): We shouldn't have existential variables in implied bounds.
// Panic here once the linked issue is resolved!
(ty::ReVar(_), _) | (_, ty::ReVar(_)) => {}
_ => bug!("add_outlives_bounds: unexpected regions: ({r_a:?}, {r_b:?})"),
},
}
}
OutlivesEnvironment {
param_env,
known_type_outlives,
free_region_map: FreeRegionMap { relation: region_relation.freeze() },
region_bound_pairs,
higher_ranked_assumptions,
}
}
pub fn free_region_map(&self) -> &FreeRegionMap<'tcx> {
&self.free_region_map
}
pub fn region_bound_pairs(&self) -> &RegionBoundPairs<'tcx> {
&self.region_bound_pairs
}
pub fn known_type_outlives(&self) -> &[ty::PolyTypeOutlivesPredicate<'tcx>] {
&self.known_type_outlives
}
pub fn higher_ranked_assumptions(&self) -> &FxHashSet<ty::ArgOutlivesPredicate<'tcx>> {
&self.higher_ranked_assumptions
}
}
|
