style: enable clippy::print_std(err|out) when applicable

Author: rami3l

src/cli/rustup_mode.rs

@@ -588,7 +588,8 @@ pub async fn main(
     }
 
     let Some(subcmd) = matches.subcmd else {
-        eprintln!("{}", Rustup::command().render_long_help());
+        let help = Rustup::command().render_long_help();
+        writeln!(process.stderr().lock(), "{help}")?;
         return Ok(utils::ExitCode(1));
     };
 

src/diskio/threaded.rs

@@ -268,6 +268,7 @@ impl<'a> Executor for Threaded<'a> {
                 prev_files as u64,
             ));
         }
+        #[allow(clippy::print_stderr)]
         if prev_files > 50 {
             eprintln!("{prev_files} deferred IO operations");
         }

src/lib.rs

@@ -3,6 +3,11 @@
     clippy::result_large_err, // 288 bytes is our 'large' variant today, which is unlikely to be a performance problem
     clippy::arc_with_non_send_sync, // will get resolved as we move further into async
 )]
+#![cfg_attr(not(test), warn(
+    // We use the logging system instead of printing directly.
+    clippy::print_stdout,
+    clippy::print_stderr,
+))]
 #![recursion_limit = "1024"]
 
 use anyhow::{anyhow, Result};

src/test.rs

@@ -1,4 +1,4 @@
-#![allow(clippy::box_default)]
+#![allow(clippy::box_default, clippy::print_stdout, clippy::print_stderr)]
 //! Test support module; public to permit use from integration tests.
 
 pub mod mock;