message: Don't check src/doc directory.
diff: @@ -6,11 +6,18 @@ fn check_forbidden_code() {
  // Do not use certain macros, functions, etc.
  if !cargo::util::is_ci() {
  // Only check these on CI, otherwise it could be annoying.
  + use std::io::Write;
  + writeln!(
  + std::io::stderr(),
  + "\nSkipping check_forbidden_code test, set CI=1 to enable"
  + )
  + .unwrap();
  return;
  }
  - let path = std::path::Path::new(env!("CARGO_MANIFEST_DIR")).join("src");
  - for entry in walkdir::WalkDir::new(path)
  + let root_path = std::path::Path::new(env!("CARGO_MANIFEST_DIR")).join("src");
  + for entry in walkdir::WalkDir::new(&root_path)
  .into_iter()
  + .filter_entry(|e| e.path() != root_path.join("doc"))
  .filter_map(|e| e.ok())
  {
  let path = entry.path();
  @@ -22,6 +29,7 @@ fn check_forbidden_code() {
  {
  continue;
  }
  + eprintln!("checking {}", path.display());
  let c = fs::read_to_string(path).unwrap();
  for (line_index, line) in c.lines().enumerate() {
  if line.trim().starts_with("//") {
  