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Diffstat (limited to '')
-rw-r--r-- | src/test/ui/issues/issue-20831-debruijn.rs | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/src/test/ui/issues/issue-20831-debruijn.rs b/src/test/ui/issues/issue-20831-debruijn.rs new file mode 100644 index 000000000..20d980763 --- /dev/null +++ b/src/test/ui/issues/issue-20831-debruijn.rs @@ -0,0 +1,39 @@ +// Regression test for #20831: debruijn index account was thrown off +// by the (anonymous) lifetime in `<Self as Publisher>::Output` +// below. Note that changing to a named lifetime made the problem go +// away. + +use std::cell::RefCell; +use std::ops::{Shl, Shr}; + +pub trait Subscriber { + type Input; +} + +pub trait Publisher<'a> { + type Output; + fn subscribe(&mut self, _: Box<dyn Subscriber<Input=Self::Output> + 'a>); +} + +pub trait Processor<'a> : Subscriber + Publisher<'a> { } + +impl<'a, P> Processor<'a> for P where P : Subscriber + Publisher<'a> { } + +struct MyStruct<'a> { + sub: Box<dyn Subscriber<Input=u64> + 'a> +} + +impl<'a> Publisher<'a> for MyStruct<'a> { + type Output = u64; + fn subscribe(&mut self, t : Box<dyn Subscriber<Input=<Self as Publisher>::Output> + 'a>) { + // Not obvious, but there is an implicit lifetime here -------^ + //~^^ ERROR cannot infer + // + // The fact that `Publisher` is using an implicit lifetime is + // what was causing the debruijn accounting to be off, so + // leave it that way! + self.sub = t; + } +} + +fn main() {} |