Fix supervisor example child builder and clippy lint config

- remove incorrect global std::fs bans from clippy config comments
- correct worker child spec builder return in supervisor example

Author: developerworks

clippy.toml

@@ -1,10 +1,8 @@
-# Disallow blocking I/O, synchronous locks, and raw OS process spawns in
-# asynchronous contexts. Subtask code must use tokio::fs, tokio::net,
-# tokio::sync::Mutex, tokio::time::sleep, and tokio::process::Command instead.
+# This lint is global and cannot detect whether a call is inside an async
+# runtime context. Keep only APIs that should be banned everywhere. Blocking
+# filesystem calls are intentionally not listed because sync CLI and test code
+# use them outside async runtime contexts.
 disallowed-methods = [
-    "std::fs::read",
-    "std::fs::write",
-    { path = "std::fs::File", allow-invalid = true },
     { path = "std::net::TcpStream", allow-invalid = true },
     "std::thread::sleep",
     { path = "std::sync::Mutex", allow-invalid = true },

examples/supervisor_tree_story.rs

@@ -100,7 +100,7 @@ fn worker(id: &str, name: &str) -> Result<ChildSpec, SupervisorError> {
     });
 
     // Create the worker child specification.
-    Ok(ChildSpec::worker(
+    ChildSpec::worker(
         // Set the child identifier.
         ChildId::new(id),
         // Set the child name.
@@ -110,7 +110,7 @@ fn worker(id: &str, name: &str) -> Result<ChildSpec, SupervisorError> {
         // Store the task factory behind shared ownership.
         Arc::new(factory),
         // Finish the worker child specification.
-    )?)
+    )
     // Finish the worker builder.
 }