tidy: println! -> eprintln!

src/tools/tidy/src/error_codes.rs

@@ -38,7 +38,7 @@ const IGNORE_UI_TEST_CHECK: &[&str] =
 macro_rules! verbose_print {
     ($verbose:expr, $($fmt:tt)*) => {
         if $verbose {
-            println!("{}", format_args!($($fmt)*));
+            eprintln!("{}", format_args!($($fmt)*));
         }
     };
 }
@@ -49,8 +49,8 @@ pub fn check(root_path: &Path, search_paths: &[&Path], verbose: bool, bad: &mut
     // Stage 1: create list
     let error_codes = extract_error_codes(root_path, &mut errors);
     if verbose {
-        println!("Found {} error codes", error_codes.len());
-        println!("Highest error code: `{}`", error_codes.iter().max().unwrap());
+        eprintln!("Found {} error codes", error_codes.len());
+        eprintln!("Highest error code: `{}`", error_codes.iter().max().unwrap());
     }
 
     // Stage 2: check list has docs

src/tools/tidy/src/features.rs

@@ -158,14 +158,14 @@ pub fn check(
         .collect::<Vec<_>>();
 
     for &(name, _) in gate_untested.iter() {
-        println!("Expected a gate test for the feature '{name}'.");
-        println!(
+        eprintln!("Expected a gate test for the feature '{name}'.");
+        eprintln!(
             "Hint: create a failing test file named 'tests/ui/feature-gates/feature-gate-{}.rs',\
                 \n      with its failures due to missing usage of `#![feature({})]`.",
             name.replace("_", "-"),
             name
         );
-        println!(
+        eprintln!(
             "Hint: If you already have such a test and don't want to rename it,\
                 \n      you can also add a // gate-test-{} line to the test file.",
             name
@@ -218,7 +218,7 @@ pub fn check(
 
         lines.sort();
         for line in lines {
-            println!("* {line}");
+            eprintln!("* {line}");
         }
     }
 

src/tools/tidy/src/unstable_book.rs

@@ -118,16 +118,16 @@ pub fn check(path: &Path, features: CollectedFeatures, bad: &mut bool) {
     // List unstable features that don't have Unstable Book sections.
     // Remove the comment marker if you want the list printed.
     /*
-    println!("Lib features without unstable book sections:");
+    eprintln!("Lib features without unstable book sections:");
     for feature_name in &unstable_lang_feature_names -
                         &unstable_book_lang_features_section_file_names {
-        println!("    * {} {:?}", feature_name, lib_features[&feature_name].tracking_issue);
+        eprintln!("    * {} {:?}", feature_name, lib_features[&feature_name].tracking_issue);
     }
 
-    println!("Lang features without unstable book sections:");
+    eprintln!("Lang features without unstable book sections:");
     for feature_name in &unstable_lib_feature_names-
                         &unstable_book_lib_features_section_file_names {
-        println!("    * {} {:?}", feature_name, lang_features[&feature_name].tracking_issue);
+        eprintln!("    * {} {:?}", feature_name, lang_features[&feature_name].tracking_issue);
     }
     // */
 }

src/tools/tidy/src/x_version.rs

@@ -42,7 +42,7 @@ pub fn check(root: &Path, cargo: &Path, bad: &mut bool) {
 
         if let Some(expected) = get_x_wrapper_version(root, cargo) {
             if installed < expected {
-                return println!(
+                return eprintln!(
                     "Current version of x is {installed}, but the latest version is {expected}\nConsider updating to the newer version of x by running `cargo install --path src/tools/x`"
                 );
             }