From cd7de8c8a22123fc1b418bce2dcb33496fcfced4 Mon Sep 17 00:00:00 2001
From: David Herberth <github@dav1d.de>
Date: Fri, 26 Apr 2024 15:18:44 +0200
Subject: [PATCH] Annotate metric types with must_use (#475)

---
 metrics/src/handles.rs                    | 3 +++
 metrics/tests/macros/02_trailing_comma.rs | 4 ++--
 metrics/tests/macros/03_mod_aliasing.rs   | 2 +-
 3 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/metrics/src/handles.rs b/metrics/src/handles.rs
index 490e4df3..33dc62d2 100644
--- a/metrics/src/handles.rs
+++ b/metrics/src/handles.rs
@@ -40,18 +40,21 @@ pub trait HistogramFn {
 
 /// A counter.
 #[derive(Clone)]
+#[must_use = "counters do nothing unless you use them"]
 pub struct Counter {
     inner: Option<Arc<dyn CounterFn + Send + Sync>>,
 }
 
 /// A gauge.
 #[derive(Clone)]
+#[must_use = "gauges do nothing unless you use them"]
 pub struct Gauge {
     inner: Option<Arc<dyn GaugeFn + Send + Sync>>,
 }
 
 /// A histogram.
 #[derive(Clone)]
+#[must_use = "histograms do nothing unless you use them"]
 pub struct Histogram {
     inner: Option<Arc<dyn HistogramFn + Send + Sync>>,
 }
diff --git a/metrics/tests/macros/02_trailing_comma.rs b/metrics/tests/macros/02_trailing_comma.rs
index fa7863f5..badeed52 100644
--- a/metrics/tests/macros/02_trailing_comma.rs
+++ b/metrics/tests/macros/02_trailing_comma.rs
@@ -12,9 +12,9 @@ fn no_trailing_comma() {
 
 #[allow(dead_code)]
 fn with_trailing_comma() {
-    counter!("qwe",);
+    counter!("qwe",).increment(1);
     counter!(
-        "qwe", 
+        "qwe",
         "foo" => "bar",
     ).increment(1);
     counter!("qwe", vec![],).increment(1);
diff --git a/metrics/tests/macros/03_mod_aliasing.rs b/metrics/tests/macros/03_mod_aliasing.rs
index dac8537f..acacf700 100644
--- a/metrics/tests/macros/03_mod_aliasing.rs
+++ b/metrics/tests/macros/03_mod_aliasing.rs
@@ -13,7 +13,7 @@ use framework::*; // This exposes mod `framework::metrics`.
 
 #[inline]
 pub fn register_metrics() {
-    ::metrics::counter!(
+    let _ = ::metrics::counter!(
         metrics::UPLOAD_METRIC_NAME,
         &[
             (metrics::UPLOAD_METRIC_LABEL_PROCESS_TYPE, ""),