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