Auto merge of #8818 - koic:use_rust_2021_prelude, r=flip1995

Use the traits added to the Rust 2021 Edition prelude

Follow up rust-lang/rust#96861.

This PR uses the traits added to the Rust 2021 Edition prelude.

> The `TryInto`, `TryFrom` and `FromIterator` traits are now part of the prelude.

https://doc.rust-lang.org/edition-guide/rust-2021/prelude.html

---

changelog: none

clippy_lints/src/checked_conversions.rs

@@ -30,7 +30,6 @@ declare_clippy_lint! {
     /// Could be written:
     ///
     /// ```rust
-    /// # use std::convert::TryFrom;
     /// # let foo = 1;
     /// # let _ =
     /// i32::try_from(foo).is_ok()

clippy_lints/src/enum_clike.rs

@@ -8,7 +8,6 @@ use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::util::IntTypeExt;
 use rustc_middle::ty::{self, IntTy, UintTy};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
-use std::convert::TryFrom;
 
 declare_clippy_lint! {
     /// ### What it does

clippy_lints/src/excessive_bools.rs

@@ -4,8 +4,6 @@ use rustc_lint::{EarlyContext, EarlyLintPass};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::{sym, Span};
 
-use std::convert::TryInto;
-
 declare_clippy_lint! {
     /// ### What it does
     /// Checks for excessive

clippy_lints/src/fallible_impl_from.rs

@@ -32,7 +32,6 @@ declare_clippy_lint! {
     /// // Good
     /// struct Foo(i32);
     ///
-    /// use std::convert::TryFrom;
     /// impl TryFrom<String> for Foo {
     ///     type Error = ();
     ///     fn try_from(s: String) -> Result<Self, Self::Error> {

clippy_lints/src/index_refutable_slice.rs

@@ -14,7 +14,6 @@ use rustc_middle::ty;
 use rustc_semver::RustcVersion;
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::{symbol::Ident, Span};
-use std::convert::TryInto;
 
 declare_clippy_lint! {
     /// ### What it does

clippy_lints/src/methods/mod.rs

@@ -1776,8 +1776,6 @@ declare_clippy_lint! {
     ///
     /// ### Example
     /// ```rust
-    /// use std::iter::FromIterator;
-    ///
     /// let five_fives = std::iter::repeat(5).take(5);
     ///
     /// let v = Vec::from_iter(five_fives);

clippy_lints/src/redundant_clone.rs

@@ -19,7 +19,6 @@ use rustc_mir_dataflow::{Analysis, AnalysisDomain, CallReturnPlaces, GenKill, Ge
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::source_map::{BytePos, Span};
 use rustc_span::sym;
-use std::convert::TryFrom;
 use std::ops::ControlFlow;
 
 macro_rules! unwrap_or_continue {

clippy_lints/src/regex.rs

@@ -7,7 +7,6 @@ use rustc_hir::{BorrowKind, Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::source_map::{BytePos, Span};
-use std::convert::TryFrom;
 
 declare_clippy_lint! {
     /// ### What it does

clippy_lints/src/tabs_in_doc_comments.rs

@@ -4,7 +4,6 @@ use rustc_errors::Applicability;
 use rustc_lint::{EarlyContext, EarlyLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::source_map::{BytePos, Span};
-use std::convert::TryFrom;
 
 declare_clippy_lint! {
     /// ### What it does

clippy_utils/src/consts.rs

@@ -13,7 +13,6 @@ use rustc_middle::ty::{self, FloatTy, ScalarInt, Ty, TyCtxt};
 use rustc_middle::{bug, span_bug};
 use rustc_span::symbol::Symbol;
 use std::cmp::Ordering::{self, Equal};
-use std::convert::TryInto;
 use std::hash::{Hash, Hasher};
 use std::iter;
 

clippy_utils/src/sugg.rs

@@ -17,7 +17,6 @@ use rustc_middle::ty;
 use rustc_span::source_map::{BytePos, CharPos, Pos, Span, SyntaxContext};
 use rustc_typeck::expr_use_visitor::{Delegate, ExprUseVisitor, PlaceBase, PlaceWithHirId};
 use std::borrow::Cow;
-use std::convert::TryInto;
 use std::fmt::{Display, Write as _};
 use std::iter;
 use std::ops::{Add, Neg, Not, Sub};

tests/ui-toml/unwrap_used/unwrap_used.rs

@@ -7,7 +7,6 @@
 use std::collections::BTreeMap;
 use std::collections::HashMap;
 use std::collections::VecDeque;
-use std::iter::FromIterator;
 
 struct GetFalsePositive {
     arr: [u32; 3],

tests/ui-toml/unwrap_used/unwrap_used.stderr

@@ -1,5 +1,5 @@
 error: called `.get().unwrap()` on a slice. Using `[]` is more clear and more concise
-  --> $DIR/unwrap_used.rs:36:17
+  --> $DIR/unwrap_used.rs:35:17
    |
 LL |         let _ = boxed_slice.get(1).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `&boxed_slice[1]`
@@ -11,7 +11,7 @@ LL | #![deny(clippy::get_unwrap)]
    |         ^^^^^^^^^^^^^^^^^^
 
 error: used `unwrap()` on `an Option` value
-  --> $DIR/unwrap_used.rs:36:17
+  --> $DIR/unwrap_used.rs:35:17
    |
 LL |         let _ = boxed_slice.get(1).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -20,175 +20,175 @@ LL |         let _ = boxed_slice.get(1).unwrap();
    = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a slice. Using `[]` is more clear and more concise
-  --> $DIR/unwrap_used.rs:37:17
+  --> $DIR/unwrap_used.rs:36:17
    |
 LL |         let _ = some_slice.get(0).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `&some_slice[0]`
 
 error: used `unwrap()` on `an Option` value
-  --> $DIR/unwrap_used.rs:37:17
+  --> $DIR/unwrap_used.rs:36:17
    |
 LL |         let _ = some_slice.get(0).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a Vec. Using `[]` is more clear and more concise
-  --> $DIR/unwrap_used.rs:38:17
+  --> $DIR/unwrap_used.rs:37:17
    |
 LL |         let _ = some_vec.get(0).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `&some_vec[0]`
 
 error: used `unwrap()` on `an Option` value
-  --> $DIR/unwrap_used.rs:38:17
+  --> $DIR/unwrap_used.rs:37:17
    |
 LL |         let _ = some_vec.get(0).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a VecDeque. Using `[]` is more clear and more concise
-  --> $DIR/unwrap_used.rs:39:17
+  --> $DIR/unwrap_used.rs:38:17
    |
 LL |         let _ = some_vecdeque.get(0).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `&some_vecdeque[0]`
 
 error: used `unwrap()` on `an Option` value
-  --> $DIR/unwrap_used.rs:39:17
+  --> $DIR/unwrap_used.rs:38:17
    |
 LL |         let _ = some_vecdeque.get(0).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a HashMap. Using `[]` is more clear and more concise
-  --> $DIR/unwrap_used.rs:40:17
+  --> $DIR/unwrap_used.rs:39:17
    |
 LL |         let _ = some_hashmap.get(&1).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `&some_hashmap[&1]`
 
 error: used `unwrap()` on `an Option` value
-  --> $DIR/unwrap_used.rs:40:17
+  --> $DIR/unwrap_used.rs:39:17
    |
 LL |         let _ = some_hashmap.get(&1).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a BTreeMap. Using `[]` is more clear and more concise
-  --> $DIR/unwrap_used.rs:41:17
+  --> $DIR/unwrap_used.rs:40:17
    |
 LL |         let _ = some_btreemap.get(&1).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `&some_btreemap[&1]`
 
 error: used `unwrap()` on `an Option` value
-  --> $DIR/unwrap_used.rs:41:17
+  --> $DIR/unwrap_used.rs:40:17
    |
 LL |         let _ = some_btreemap.get(&1).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a slice. Using `[]` is more clear and more concise
-  --> $DIR/unwrap_used.rs:45:21
+  --> $DIR/unwrap_used.rs:44:21
    |
 LL |         let _: u8 = *boxed_slice.get(1).unwrap();
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `boxed_slice[1]`
 
 error: used `unwrap()` on `an Option` value
-  --> $DIR/unwrap_used.rs:45:22
+  --> $DIR/unwrap_used.rs:44:22
    |
 LL |         let _: u8 = *boxed_slice.get(1).unwrap();
    |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
 
 error: called `.get_mut().unwrap()` on a slice. Using `[]` is more clear and more concise
-  --> $DIR/unwrap_used.rs:50:9
+  --> $DIR/unwrap_used.rs:49:9
    |
 LL |         *boxed_slice.get_mut(0).unwrap() = 1;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `boxed_slice[0]`
 
 error: used `unwrap()` on `an Option` value
-  --> $DIR/unwrap_used.rs:50:10
+  --> $DIR/unwrap_used.rs:49:10
    |
 LL |         *boxed_slice.get_mut(0).unwrap() = 1;
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
 
 error: called `.get_mut().unwrap()` on a slice. Using `[]` is more clear and more concise
-  --> $DIR/unwrap_used.rs:51:9
+  --> $DIR/unwrap_used.rs:50:9
    |
 LL |         *some_slice.get_mut(0).unwrap() = 1;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `some_slice[0]`
 
 error: used `unwrap()` on `an Option` value
-  --> $DIR/unwrap_used.rs:51:10
+  --> $DIR/unwrap_used.rs:50:10
    |
 LL |         *some_slice.get_mut(0).unwrap() = 1;
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
 
 error: called `.get_mut().unwrap()` on a Vec. Using `[]` is more clear and more concise
-  --> $DIR/unwrap_used.rs:52:9
+  --> $DIR/unwrap_used.rs:51:9
    |
 LL |         *some_vec.get_mut(0).unwrap() = 1;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `some_vec[0]`
 
 error: used `unwrap()` on `an Option` value
-  --> $DIR/unwrap_used.rs:52:10
+  --> $DIR/unwrap_used.rs:51:10
    |
 LL |         *some_vec.get_mut(0).unwrap() = 1;
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
 
 error: called `.get_mut().unwrap()` on a VecDeque. Using `[]` is more clear and more concise
-  --> $DIR/unwrap_used.rs:53:9
+  --> $DIR/unwrap_used.rs:52:9
    |
 LL |         *some_vecdeque.get_mut(0).unwrap() = 1;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `some_vecdeque[0]`
 
 error: used `unwrap()` on `an Option` value
-  --> $DIR/unwrap_used.rs:53:10
+  --> $DIR/unwrap_used.rs:52:10
    |
 LL |         *some_vecdeque.get_mut(0).unwrap() = 1;
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a Vec. Using `[]` is more clear and more concise
-  --> $DIR/unwrap_used.rs:65:17
+  --> $DIR/unwrap_used.rs:64:17
    |
 LL |         let _ = some_vec.get(0..1).unwrap().to_vec();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `some_vec[0..1]`
 
 error: used `unwrap()` on `an Option` value
-  --> $DIR/unwrap_used.rs:65:17
+  --> $DIR/unwrap_used.rs:64:17
    |
 LL |         let _ = some_vec.get(0..1).unwrap().to_vec();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
 
 error: called `.get_mut().unwrap()` on a Vec. Using `[]` is more clear and more concise
-  --> $DIR/unwrap_used.rs:66:17
+  --> $DIR/unwrap_used.rs:65:17
    |
 LL |         let _ = some_vec.get_mut(0..1).unwrap().to_vec();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `some_vec[0..1]`
 
 error: used `unwrap()` on `an Option` value
-  --> $DIR/unwrap_used.rs:66:17
+  --> $DIR/unwrap_used.rs:65:17
    |
 LL |         let _ = some_vec.get_mut(0..1).unwrap().to_vec();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
 
 error: called `.get().unwrap()` on a slice. Using `[]` is more clear and more concise
-  --> $DIR/unwrap_used.rs:73:13
+  --> $DIR/unwrap_used.rs:72:13
    |
 LL |     let _ = boxed_slice.get(1).unwrap();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `&boxed_slice[1]`

tests/ui/auxiliary/proc_macro_suspicious_else_formatting.rs

@@ -5,7 +5,6 @@
 
 extern crate proc_macro;
 use proc_macro::{token_stream, Delimiter, Group, Ident, Span, TokenStream, TokenTree};
-use std::iter::FromIterator;
 
 fn read_ident(iter: &mut token_stream::IntoIter) -> Ident {
     match iter.next() {

tests/ui/checked_conversions.fixed

@@ -7,8 +7,6 @@
 )]
 #![warn(clippy::checked_conversions)]
 
-use std::convert::TryFrom;
-
 // Positive tests
 
 // Signed to unsigned

tests/ui/checked_conversions.rs

@@ -7,8 +7,6 @@
 )]
 #![warn(clippy::checked_conversions)]
 
-use std::convert::TryFrom;
-
 // Positive tests
 
 // Signed to unsigned