lint: use eprintln for human-facing outputs

Author: weihanglo

crates/mdman/src/main.rs

@@ -48,7 +48,7 @@ fn run() -> Result<(), Error> {
         if same_file::is_same_file(source, &out_path).unwrap_or(false) {
             bail!("cannot output to the same file as the source");
         }
-        println!("Converting {} -> {}", source.display(), out_path.display());
+        eprintln!("Converting {} -> {}", source.display(), out_path.display());
         let result = mdman::convert(&source, opts.format, opts.url.clone(), opts.man_map.clone())
             .with_context(|| format!("failed to translate {}", source.display()))?;
 

crates/resolver-tests/src/lib.rs

@@ -163,7 +163,7 @@ pub fn resolve_with_config_raw(
             if std::thread::panicking() && self.list.len() != self.used.len() {
                 // we found a case that causes a panic and did not use all of the input.
                 // lets print the part of the input that was used for minimization.
-                println!(
+                eprintln!(
                     "{:?}",
                     PrettyPrintRegistry(
                         self.list

crates/semver-check/src/main.rs

@@ -20,7 +20,7 @@ use std::process::{Command, Output};
 
 fn main() {
     if let Err(e) = doit() {
-        println!("error: {}", e);
+        eprintln!("error: {}", e);
         std::process::exit(1);
     }
 }
@@ -103,7 +103,7 @@ fn doit() -> Result<(), Box<dyn Error>> {
             result
         };
         let expect_success = parts[0][0].contains("MINOR");
-        println!("Running test from line {}", block_start);
+        eprintln!("Running test from line {}", block_start);
 
         let result = run_test(
             join(parts[1]),