remove redundant imports

detects redundant imports that can be eliminated.

for #117772 :

In order to facilitate review and modification, split the checking code and
removing redundant imports code into two PR.

src/comment.rs

@@ -1,6 +1,6 @@
 // Formatting and tools for comments.
 
-use std::{self, borrow::Cow, iter};
+use std::{borrow::Cow, iter};
 
 use itertools::{multipeek, MultiPeek};
 use lazy_static::lazy_static;
@@ -1847,7 +1847,6 @@ fn remove_comment_header(comment: &str) -> &str {
 #[cfg(test)]
 mod test {
     use super::*;
-    use crate::shape::{Indent, Shape};
 
     #[test]
     fn char_classes() {

src/config/file_lines.rs

@@ -6,7 +6,7 @@
 use std::{cmp, fmt, iter, str};
 
 use rustc_data_structures::sync::Lrc;
-use rustc_span::{self, SourceFile};
+use rustc_span::SourceFile;
 use serde::{ser, Deserialize, Deserializer, Serialize, Serializer};
 use serde_json as json;
 use thiserror::Error;

src/config/mod.rs

@@ -1,5 +1,4 @@
 use std::cell::Cell;
-use std::default::Default;
 use std::fs::File;
 use std::io::{Error, ErrorKind, Read};
 use std::path::{Path, PathBuf};
@@ -1017,7 +1016,6 @@ fn test_override_single_line_if_else_max_width_exceeds_max_width() {
     #[cfg(test)]
     mod partially_unstable_option {
         use super::mock::{Config, PartiallyUnstableOption};
-        use super::*;
 
         /// From the command line, we can override with a stable variant.
         #[test]

src/emitter/checkstyle.rs

@@ -1,7 +1,6 @@
 use self::xml::XmlEscaped;
 use super::*;
 use crate::rustfmt_diff::{make_diff, DiffLine, Mismatch};
-use std::io::{self, Write};
 
 mod xml;
 

src/emitter/diff.rs

@@ -51,8 +51,6 @@ fn emit_formatted_file(
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::config::Config;
-    use crate::FileName;
     use std::path::PathBuf;
 
     #[test]

src/emitter/json.rs

@@ -2,7 +2,6 @@
 use crate::rustfmt_diff::{make_diff, DiffLine, Mismatch};
 use serde::Serialize;
 use serde_json::to_string as to_json_string;
-use std::io::{self, Write};
 
 #[derive(Debug, Default)]
 pub(crate) struct JsonEmitter {
@@ -106,7 +105,6 @@ fn add_misformatted_file(
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::FileName;
     use std::path::PathBuf;
 
     #[test]

src/emitter/modified_lines.rs

@@ -1,6 +1,5 @@
 use super::*;
 use crate::rustfmt_diff::{make_diff, ModifiedLines};
-use std::io::Write;
 
 #[derive(Debug, Default)]
 pub(crate) struct ModifiedLinesEmitter;

src/emitter/stdout.rs

@@ -1,6 +1,5 @@
 use super::*;
 use crate::config::Verbosity;
-use std::io::Write;
 
 #[derive(Debug)]
 pub(crate) struct StdoutEmitter {

src/ignore_path.rs

@@ -1,4 +1,4 @@
-use ignore::{self, gitignore};
+use ignore::gitignore;
 
 use crate::config::{FileName, IgnoreList};
 

src/imports.rs

@@ -1102,7 +1102,6 @@ enum SharedPrefix {
 #[cfg(test)]
 mod test {
     use super::*;
-    use rustc_span::DUMMY_SP;
 
     // Parse the path part of an import. This parser is not robust and is only
     // suitable for use in a test harness.

src/reorder.rs

@@ -6,7 +6,7 @@
 
 // FIXME(#2455): Reorder trait items.
 
-use std::cmp::{Ord, Ordering};
+use std::cmp::Ordering;
 
 use rustc_ast::{ast, attr};
 use rustc_span::{symbol::sym, Span};

src/types.rs

@@ -1,4 +1,3 @@
-use std::iter::ExactSizeIterator;
 use std::ops::Deref;
 
 use rustc_ast::ast::{self, FnRetTy, Mutability, Term};