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
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
|
use rustc_hir as hir;
use rustc_hir::intravisit::{self, Visitor};
use rustc_middle::hir::map::Map;
use rustc_middle::hir::nested_filter;
use rustc_middle::middle::resolve_lifetime as rl;
use rustc_middle::ty::{self, Region, TyCtxt};
/// This function calls the `visit_ty` method for the parameters
/// corresponding to the anonymous regions. The `nested_visitor.found_type`
/// contains the anonymous type.
///
/// # Arguments
/// region - the anonymous region corresponding to the anon_anon conflict
/// br - the bound region corresponding to the above region which is of type `BrAnon(_)`
///
/// # Example
/// ```compile_fail,E0623
/// fn foo(x: &mut Vec<&u8>, y: &u8)
/// { x.push(y); }
/// ```
/// The function returns the nested type corresponding to the anonymous region
/// for e.g., `&u8` and `Vec<&u8>`.
pub fn find_anon_type<'tcx>(
tcx: TyCtxt<'tcx>,
region: Region<'tcx>,
br: &ty::BoundRegionKind,
) -> Option<(&'tcx hir::Ty<'tcx>, &'tcx hir::FnSig<'tcx>)> {
let anon_reg = tcx.is_suitable_region(region)?;
let hir_id = tcx.hir().local_def_id_to_hir_id(anon_reg.def_id);
let fn_sig = tcx.hir().get(hir_id).fn_sig()?;
fn_sig
.decl
.inputs
.iter()
.find_map(|arg| find_component_for_bound_region(tcx, arg, br))
.map(|ty| (ty, fn_sig))
}
// This method creates a FindNestedTypeVisitor which returns the type corresponding
// to the anonymous region.
fn find_component_for_bound_region<'tcx>(
tcx: TyCtxt<'tcx>,
arg: &'tcx hir::Ty<'tcx>,
br: &ty::BoundRegionKind,
) -> Option<&'tcx hir::Ty<'tcx>> {
let mut nested_visitor = FindNestedTypeVisitor {
tcx,
bound_region: *br,
found_type: None,
current_index: ty::INNERMOST,
};
nested_visitor.visit_ty(arg);
nested_visitor.found_type
}
// The FindNestedTypeVisitor captures the corresponding `hir::Ty` of the
// anonymous region. The example above would lead to a conflict between
// the two anonymous lifetimes for &u8 in x and y respectively. This visitor
// would be invoked twice, once for each lifetime, and would
// walk the types like &mut Vec<&u8> and &u8 looking for the HIR
// where that lifetime appears. This allows us to highlight the
// specific part of the type in the error message.
struct FindNestedTypeVisitor<'tcx> {
tcx: TyCtxt<'tcx>,
// The bound_region corresponding to the Refree(freeregion)
// associated with the anonymous region we are looking for.
bound_region: ty::BoundRegionKind,
// The type where the anonymous lifetime appears
// for e.g., Vec<`&u8`> and <`&u8`>
found_type: Option<&'tcx hir::Ty<'tcx>>,
current_index: ty::DebruijnIndex,
}
impl<'tcx> Visitor<'tcx> for FindNestedTypeVisitor<'tcx> {
type NestedFilter = nested_filter::OnlyBodies;
fn nested_visit_map(&mut self) -> Self::Map {
self.tcx.hir()
}
fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) {
match arg.kind {
hir::TyKind::BareFn(_) => {
self.current_index.shift_in(1);
intravisit::walk_ty(self, arg);
self.current_index.shift_out(1);
return;
}
hir::TyKind::TraitObject(bounds, ..) => {
for bound in bounds {
self.current_index.shift_in(1);
self.visit_poly_trait_ref(bound);
self.current_index.shift_out(1);
}
}
hir::TyKind::Rptr(ref lifetime, _) => {
// the lifetime of the TyRptr
let hir_id = lifetime.hir_id;
match (self.tcx.named_region(hir_id), self.bound_region) {
// Find the index of the named region that was part of the
// error. We will then search the function parameters for a bound
// region at the right depth with the same index
(Some(rl::Region::EarlyBound(id)), ty::BrNamed(def_id, _)) => {
debug!("EarlyBound id={:?} def_id={:?}", id, def_id);
if id == def_id {
self.found_type = Some(arg);
return; // we can stop visiting now
}
}
// Find the index of the named region that was part of the
// error. We will then search the function parameters for a bound
// region at the right depth with the same index
(
Some(rl::Region::LateBound(debruijn_index, _, id)),
ty::BrNamed(def_id, _),
) => {
debug!(
"FindNestedTypeVisitor::visit_ty: LateBound depth = {:?}",
debruijn_index
);
debug!("LateBound id={:?} def_id={:?}", id, def_id);
if debruijn_index == self.current_index && id == def_id {
self.found_type = Some(arg);
return; // we can stop visiting now
}
}
(
Some(
rl::Region::Static
| rl::Region::Free(_, _)
| rl::Region::EarlyBound(_)
| rl::Region::LateBound(_, _, _),
)
| None,
_,
) => {
debug!("no arg found");
}
}
}
// Checks if it is of type `hir::TyKind::Path` which corresponds to a struct.
hir::TyKind::Path(_) => {
let subvisitor = &mut TyPathVisitor {
tcx: self.tcx,
found_it: false,
bound_region: self.bound_region,
current_index: self.current_index,
};
intravisit::walk_ty(subvisitor, arg); // call walk_ty; as visit_ty is empty,
// this will visit only outermost type
if subvisitor.found_it {
self.found_type = Some(arg);
}
}
_ => {}
}
// walk the embedded contents: e.g., if we are visiting `Vec<&Foo>`,
// go on to visit `&Foo`
intravisit::walk_ty(self, arg);
}
}
// The visitor captures the corresponding `hir::Ty` of the anonymous region
// in the case of structs ie. `hir::TyKind::Path`.
// This visitor would be invoked for each lifetime corresponding to a struct,
// and would walk the types like Vec<Ref> in the above example and Ref looking for the HIR
// where that lifetime appears. This allows us to highlight the
// specific part of the type in the error message.
struct TyPathVisitor<'tcx> {
tcx: TyCtxt<'tcx>,
found_it: bool,
bound_region: ty::BoundRegionKind,
current_index: ty::DebruijnIndex,
}
impl<'tcx> Visitor<'tcx> for TyPathVisitor<'tcx> {
type NestedFilter = nested_filter::OnlyBodies;
fn nested_visit_map(&mut self) -> Map<'tcx> {
self.tcx.hir()
}
fn visit_lifetime(&mut self, lifetime: &hir::Lifetime) {
match (self.tcx.named_region(lifetime.hir_id), self.bound_region) {
// the lifetime of the TyPath!
(Some(rl::Region::EarlyBound(id)), ty::BrNamed(def_id, _)) => {
debug!("EarlyBound id={:?} def_id={:?}", id, def_id);
if id == def_id {
self.found_it = true;
return; // we can stop visiting now
}
}
(Some(rl::Region::LateBound(debruijn_index, _, id)), ty::BrNamed(def_id, _)) => {
debug!("FindNestedTypeVisitor::visit_ty: LateBound depth = {:?}", debruijn_index,);
debug!("id={:?}", id);
debug!("def_id={:?}", def_id);
if debruijn_index == self.current_index && id == def_id {
self.found_it = true;
return; // we can stop visiting now
}
}
(
Some(
rl::Region::Static
| rl::Region::EarlyBound(_)
| rl::Region::LateBound(_, _, _)
| rl::Region::Free(_, _),
)
| None,
_,
) => {
debug!("no arg found");
}
}
}
fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) {
// ignore nested types
//
// If you have a type like `Foo<'a, &Ty>` we
// are only interested in the immediate lifetimes ('a).
//
// Making `visit_ty` empty will ignore the `&Ty` embedded
// inside, it will get reached by the outer visitor.
debug!("`Ty` corresponding to a struct is {:?}", arg);
}
}
|
