tracing_subscriber::Registry misbehaves when exiting span while some other subscriber is default #1656
Description
Bug Report
Version
asdf-tracing v0.1.0 (/Users/lily/Dev/Scratch/asdf-tracing)
├── tracing v0.1.29
│ ├── tracing-attributes v0.1.18 (proc-macro)
│ └── tracing-core v0.1.21
└── tracing-subscriber v0.2.25
├── tracing v0.1.29 (*)
├── tracing-core v0.1.21 (*)
├── tracing-log v0.1.2
│ └── tracing-core v0.1.21 (*)
└── tracing-serde v0.1.2
└── tracing-core v0.1.21 (*)
Platform
Darwin DeerBook 20.6.0 Darwin Kernel Version 20.6.0: Mon Aug 30 06:12:21 PDT 2021; root:xnu-7195.141.6~3/RELEASE_X86_64 x86_64
Crates
tracing-subscriber
Description
If I exit a span created from something using Registry (such as FmtSubscriber) while its associated dispatch is not the default dispatch, Registry will ask the default dispatch to try_close() the span id. This means it's asking the wrong dispatch to close it, which can lead to panics.
Reproduction
let outer = tracing_subscriber::fmt().set_default();
let one = info_span!("one").entered();
let inner = tracing_subscriber::fmt().set_default();
let two = info_span!("two").entered();
drop(one); // this closes span two
drop(two); // this panicsthread 'main' panicked at 'tried to drop a ref to Id(1), but no such span exists!', /Users/lily/.cargo/registry/src/github.com-1ecc6299db9ec823/tracing-subscriber-0.2.25/src/registry/sharded.rs:346:21