From adc2ae7af2caaea83985fbdfbc7884c159c486f2 Mon Sep 17 00:00:00 2001
From: Motoyuki Kimura <moymoymox@gmail.com>
Date: Thu, 30 Jul 2026 19:29:09 +0900
Subject: [PATCH] rt: add error documentation for `runtime::Builder` (#8297)

---
 tokio/src/runtime/builder.rs               | 10 ++++++++++
 tokio/src/runtime/local_runtime/runtime.rs |  5 +++++
 tokio/src/runtime/runtime.rs               |  5 +++++
 3 files changed, 20 insertions(+)

diff --git a/tokio/src/runtime/builder.rs b/tokio/src/runtime/builder.rs
index 4a8252df2..30dd02b73 100644
--- a/tokio/src/runtime/builder.rs
+++ b/tokio/src/runtime/builder.rs
@@ -1069,6 +1069,11 @@ impl Builder {
     /// });
     /// # }
     /// ```
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the I/O driver or other OS resources required by the
+    /// runtime cannot be initialized.
     pub fn build(&mut self) -> io::Result<Runtime> {
         match &self.kind {
             Kind::CurrentThread => self.build_current_thread_runtime(),
@@ -1100,6 +1105,11 @@ impl Builder {
     ///     println!("Hello from the Tokio runtime");
     /// });
     /// ```
+    ///
+    /// # Errors
+    ///
+    /// Returns an error if the I/O driver or other OS resources required by the
+    /// runtime cannot be initialized.
     pub fn build_local(&mut self, _options: LocalOptions) -> io::Result<LocalRuntime> {
         match &self.kind {
             Kind::CurrentThread => self.build_current_thread_local_runtime(),
diff --git a/tokio/src/runtime/local_runtime/runtime.rs b/tokio/src/runtime/local_runtime/runtime.rs
index 41121622f..6782f425a 100644
--- a/tokio/src/runtime/local_runtime/runtime.rs
+++ b/tokio/src/runtime/local_runtime/runtime.rs
@@ -86,6 +86,11 @@ impl LocalRuntime {
     /// // Use the runtime...
     /// ```
     ///
+    /// # Errors
+    ///
+    /// Returns an error if the I/O driver or other OS resources required by the
+    /// runtime cannot be initialized.
+    ///
     /// [mod]: crate::runtime
     /// [runtime builder]: crate::runtime::Builder
     pub fn new() -> std::io::Result<LocalRuntime> {
diff --git a/tokio/src/runtime/runtime.rs b/tokio/src/runtime/runtime.rs
index 6a1d2e45e..0a1a9b35d 100644
--- a/tokio/src/runtime/runtime.rs
+++ b/tokio/src/runtime/runtime.rs
@@ -165,6 +165,11 @@ impl Runtime {
     /// // Use the runtime...
     /// ```
     ///
+    /// # Errors
+    ///
+    /// Returns an error if the I/O driver or other OS resources required by the
+    /// runtime cannot be initialized.
+    ///
     /// [mod]: index.html
     /// [main]: ../attr.main.html
     /// [threaded scheduler]: index.html#threaded-scheduler