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
|
// run-pass
#![allow(dead_code)]
// Test that this fairly specialized, but also reasonable, pattern
// typechecks. The pattern involves regions bound in closures that
// wind up related to inference variables.
//
// NB. Changes to the region implementations have broken this pattern
// a few times, but it happens to be used in the compiler so those
// changes were caught. However, those uses in the compiler could
// easily get changed or refactored away in the future.
struct Ctxt<'tcx> {
x: &'tcx Vec<isize>
}
struct Foo<'a,'tcx:'a> {
cx: &'a Ctxt<'tcx>,
}
impl<'a,'tcx> Foo<'a,'tcx> {
fn bother(&mut self) -> isize {
self.elaborate_bounds(Box::new(|this| {
// (*) Here: type of `this` is `&'f0 Foo<&'f1, '_2>`,
// where `'f0` and `'f1` are fresh, free regions that
// result from the bound regions on the closure, and `'2`
// is a region inference variable created by the call. Due
// to the constraints on the type, we find that `'_2 : 'f1
// + 'f2` must hold (and can be assumed by the callee).
// Region inference has to do some clever stuff to avoid
// inferring `'_2` to be `'static` in this case, because
// it is created outside the closure but then related to
// regions bound by the closure itself. See the
// `region_constraints.rs` file (and the `givens` field, in
// particular) for more details.
this.foo()
}))
}
fn foo(&mut self) -> isize {
22
}
fn elaborate_bounds(
&mut self,
mut mk_cand: Box<dyn for<'b> FnMut(&mut Foo<'b, 'tcx>) -> isize>)
-> isize
{
mk_cand(self)
}
}
fn main() {
let v = vec![];
let cx = Ctxt { x: &v };
let mut foo = Foo { cx: &cx };
assert_eq!(foo.bother(), 22); // just so the code is not dead, basically
}
|
