Auto merge of #88865 - guswynn:must_not_suspend, r=oli-obk

[rust.git] / compiler / rustc_lint_defs / src / builtin.rs

diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index b14abb9e5db48a46dce242ffac741a85de944d00..5830ce26fea3ff224d65dae692ed2c2febdff0e6 100644 (file)
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/compiler/rustc_lint_defs/src/builtin.rs
@@ -314,6 +314,44 @@
     "imports that are never used"
 }
 
+declare_lint! {
+    /// The `must_not_suspend` lint guards against values that shouldn't be held across suspend points
+    /// (`.await`)
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// #![feature(must_not_suspend)]
+    ///
+    /// #[must_not_suspend]
+    /// struct SyncThing {}
+    ///
+    /// async fn yield_now() {}
+    ///
+    /// pub async fn uhoh() {
+    ///     let guard = SyncThing {};
+    ///     yield_now().await;
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// The `must_not_suspend` lint detects values that are marked with the `#[must_not_suspend]`
+    /// attribute being held across suspend points. A "suspend" point is usually a `.await` in an async
+    /// function.
+    ///
+    /// This attribute can be used to mark values that are semantically incorrect across suspends
+    /// (like certain types of timers), values that have async alternatives, and values that
+    /// regularly cause problems with the `Send`-ness of async fn's returned futures (like
+    /// `MutexGuard`'s)
+    ///
+    pub MUST_NOT_SUSPEND,
+    Warn,
+    "use of a `#[must_not_suspend]` value across a yield point",
+}
+
 declare_lint! {
     /// The `unused_extern_crates` lint guards against `extern crate` items
     /// that are never used.
@@ -2993,6 +3031,7 @@
         CENUM_IMPL_DROP_CAST,
         CONST_EVALUATABLE_UNCHECKED,
         INEFFECTIVE_UNSTABLE_TRAIT_IMPL,
+        MUST_NOT_SUSPEND,
         UNINHABITED_STATIC,
         FUNCTION_ITEM_REFERENCES,
         USELESS_DEPRECATED,