From 9a8e7e666aa9c4fad3cd3f4da375e8a41c545b7c Mon Sep 17 00:00:00 2001
From: Kartavya Vashishtha <sendtokartavya@gmail.com>
Date: Wed, 10 Aug 2022 16:54:36 -0700
Subject: [PATCH] subscriber: add `must_use` for `CollectorBuilder::finish`
 (#2271)

## Motivation

Follow up to #2239.

Discovered that

```rust
    tracing_subscriber::fmt().with_ansi(false).finish();
    tracing::info!("hello");
```
doesn't actually do anything, because `finish` returns a `Collector` and
`init` is the thing that actually installs the collector.

## Solution

Added `#[must_use]` which suggests using `try_init` instead.
---
 tracing-subscriber/src/fmt/mod.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tracing-subscriber/src/fmt/mod.rs b/tracing-subscriber/src/fmt/mod.rs
index f34ff691cd..2230362d0e 100644
--- a/tracing-subscriber/src/fmt/mod.rs
+++ b/tracing-subscriber/src/fmt/mod.rs
@@ -476,6 +476,7 @@ where
         subscribe::Subscribe<Registry> + Send + Sync + 'static,
 {
     /// Finish the builder, returning a new `FmtCollector`.
+    #[must_use = "you may want to use `try_init` or similar to actually install the collector."]
     pub fn finish(self) -> Collector<N, E, F, W> {
         let collector = self.inner.with_collector(Registry::default());
         Collector {