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
|
//! An iterator over the type substructure.
//! WARNING: this does not keep track of the region depth.
use crate::ty::subst::{GenericArg, GenericArgKind};
use crate::ty::{self, Ty};
use rustc_data_structures::sso::SsoHashSet;
use smallvec::{self, SmallVec};
// The TypeWalker's stack is hot enough that it's worth going to some effort to
// avoid heap allocations.
type TypeWalkerStack<'tcx> = SmallVec<[GenericArg<'tcx>; 8]>;
pub struct TypeWalker<'tcx> {
stack: TypeWalkerStack<'tcx>,
last_subtree: usize,
pub visited: SsoHashSet<GenericArg<'tcx>>,
}
/// An iterator for walking the type tree.
///
/// It's very easy to produce a deeply
/// nested type tree with a lot of
/// identical subtrees. In order to work efficiently
/// in this situation walker only visits each type once.
/// It maintains a set of visited types and
/// skips any types that are already there.
impl<'tcx> TypeWalker<'tcx> {
pub fn new(root: GenericArg<'tcx>) -> Self {
Self { stack: smallvec![root], last_subtree: 1, visited: SsoHashSet::new() }
}
/// Skips the subtree corresponding to the last type
/// returned by `next()`.
///
/// Example: Imagine you are walking `Foo<Bar<i32>, usize>`.
///
/// ```ignore (illustrative)
/// let mut iter: TypeWalker = ...;
/// iter.next(); // yields Foo
/// iter.next(); // yields Bar<i32>
/// iter.skip_current_subtree(); // skips i32
/// iter.next(); // yields usize
/// ```
pub fn skip_current_subtree(&mut self) {
self.stack.truncate(self.last_subtree);
}
}
impl<'tcx> Iterator for TypeWalker<'tcx> {
type Item = GenericArg<'tcx>;
fn next(&mut self) -> Option<GenericArg<'tcx>> {
debug!("next(): stack={:?}", self.stack);
loop {
let next = self.stack.pop()?;
self.last_subtree = self.stack.len();
if self.visited.insert(next) {
push_inner(&mut self.stack, next);
debug!("next: stack={:?}", self.stack);
return Some(next);
}
}
}
}
impl<'tcx> GenericArg<'tcx> {
/// Iterator that walks `self` and any types reachable from
/// `self`, in depth-first order. Note that just walks the types
/// that appear in `self`, it does not descend into the fields of
/// structs or variants. For example:
///
/// ```text
/// isize => { isize }
/// Foo<Bar<isize>> => { Foo<Bar<isize>>, Bar<isize>, isize }
/// [isize] => { [isize], isize }
/// ```
pub fn walk(self) -> TypeWalker<'tcx> {
TypeWalker::new(self)
}
/// Iterator that walks the immediate children of `self`. Hence
/// `Foo<Bar<i32>, u32>` yields the sequence `[Bar<i32>, u32]`
/// (but not `i32`, like `walk`).
///
/// Iterator only walks items once.
/// It accepts visited set, updates it with all visited types
/// and skips any types that are already there.
pub fn walk_shallow(
self,
visited: &mut SsoHashSet<GenericArg<'tcx>>,
) -> impl Iterator<Item = GenericArg<'tcx>> {
let mut stack = SmallVec::new();
push_inner(&mut stack, self);
stack.retain(|a| visited.insert(*a));
stack.into_iter()
}
}
impl<'tcx> Ty<'tcx> {
/// Iterator that walks `self` and any types reachable from
/// `self`, in depth-first order. Note that just walks the types
/// that appear in `self`, it does not descend into the fields of
/// structs or variants. For example:
///
/// ```text
/// isize => { isize }
/// Foo<Bar<isize>> => { Foo<Bar<isize>>, Bar<isize>, isize }
/// [isize] => { [isize], isize }
/// ```
pub fn walk(self) -> TypeWalker<'tcx> {
TypeWalker::new(self.into())
}
}
/// We push `GenericArg`s on the stack in reverse order so as to
/// maintain a pre-order traversal. As of the time of this
/// writing, the fact that the traversal is pre-order is not
/// known to be significant to any code, but it seems like the
/// natural order one would expect (basically, the order of the
/// types as they are written).
fn push_inner<'tcx>(stack: &mut TypeWalkerStack<'tcx>, parent: GenericArg<'tcx>) {
match parent.unpack() {
GenericArgKind::Type(parent_ty) => match *parent_ty.kind() {
ty::Bool
| ty::Char
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Str
| ty::Infer(_)
| ty::Param(_)
| ty::Never
| ty::Error(_)
| ty::Placeholder(..)
| ty::Bound(..)
| ty::Foreign(..) => {}
ty::Array(ty, len) => {
stack.push(len.into());
stack.push(ty.into());
}
ty::Slice(ty) => {
stack.push(ty.into());
}
ty::RawPtr(mt) => {
stack.push(mt.ty.into());
}
ty::Ref(lt, ty, _) => {
stack.push(ty.into());
stack.push(lt.into());
}
ty::Projection(data) => {
stack.extend(data.substs.iter().rev());
}
ty::Dynamic(obj, lt) => {
stack.push(lt.into());
stack.extend(obj.iter().rev().flat_map(|predicate| {
let (substs, opt_ty) = match predicate.skip_binder() {
ty::ExistentialPredicate::Trait(tr) => (tr.substs, None),
ty::ExistentialPredicate::Projection(p) => (p.substs, Some(p.term)),
ty::ExistentialPredicate::AutoTrait(_) =>
// Empty iterator
{
(ty::InternalSubsts::empty(), None)
}
};
substs.iter().rev().chain(opt_ty.map(|term| match term {
ty::Term::Ty(ty) => ty.into(),
ty::Term::Const(ct) => ct.into(),
}))
}));
}
ty::Adt(_, substs)
| ty::Opaque(_, substs)
| ty::Closure(_, substs)
| ty::Generator(_, substs, _)
| ty::FnDef(_, substs) => {
stack.extend(substs.iter().rev());
}
ty::Tuple(ts) => stack.extend(ts.as_substs().iter().rev()),
ty::GeneratorWitness(ts) => {
stack.extend(ts.skip_binder().iter().rev().map(|ty| ty.into()));
}
ty::FnPtr(sig) => {
stack.push(sig.skip_binder().output().into());
stack.extend(sig.skip_binder().inputs().iter().copied().rev().map(|ty| ty.into()));
}
},
GenericArgKind::Lifetime(_) => {}
GenericArgKind::Const(parent_ct) => {
stack.push(parent_ct.ty().into());
match parent_ct.kind() {
ty::ConstKind::Infer(_)
| ty::ConstKind::Param(_)
| ty::ConstKind::Placeholder(_)
| ty::ConstKind::Bound(..)
| ty::ConstKind::Value(_)
| ty::ConstKind::Error(_) => {}
ty::ConstKind::Unevaluated(ct) => {
stack.extend(ct.substs.iter().rev());
}
}
}
}
}
|
