for_loop: Split test into fixable/unfixable, make needless_range_loop use updated range syntax

Author: Manishearth

clippy_lints/src/loops.rs

@@ -1272,7 +1272,7 @@ fn check_for_loop_reverse_range<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, arg: &'tcx
                     let start_snippet = snippet(cx, start.span, "_");
                     let end_snippet = snippet(cx, end.span, "_");
                     let dots = if limits == ast::RangeLimits::Closed {
-                        "..."
+                        "..="
                     } else {
                         ".."
                     };

tests/ui/for_loop.stdout

@@ -0,0 +1,304 @@
+// run-rustfix
+
+#![allow(dead_code, unused)]
+
+use std::collections::*;
+
+#[warn(clippy::all)]
+struct Unrelated(Vec<u8>);
+impl Unrelated {
+    fn next(&self) -> std::slice::Iter<u8> {
+        self.0.iter()
+    }
+
+    fn iter(&self) -> std::slice::Iter<u8> {
+        self.0.iter()
+    }
+}
+
+#[warn(
+    clippy::needless_range_loop,
+    clippy::explicit_iter_loop,
+    clippy::explicit_into_iter_loop,
+    clippy::iter_next_loop,
+    clippy::reverse_range_loop,
+    clippy::for_kv_map
+)]
+#[allow(
+    clippy::linkedlist,
+    clippy::shadow_unrelated,
+    clippy::unnecessary_mut_passed,
+    clippy::cognitive_complexity,
+    clippy::similar_names
+)]
+#[allow(clippy::many_single_char_names, unused_variables, clippy::into_iter_on_array)]
+fn main() {
+    const MAX_LEN: usize = 42;
+    let mut vec = vec![1, 2, 3, 4];
+
+    for i in (0..10).rev() {
+        println!("{}", i);
+    }
+
+    for i in (0..=10).rev() {
+        println!("{}", i);
+    }
+
+    for i in (0..MAX_LEN).rev() {
+        println!("{}", i);
+    }
+
+    for i in 5..=5 {
+        // not an error, this is the range with only one element “5”
+        println!("{}", i);
+    }
+
+    for i in 0..10 {
+        // not an error, the start index is less than the end index
+        println!("{}", i);
+    }
+
+    for i in -10..0 {
+        // not an error
+        println!("{}", i);
+    }
+
+    for i in (10..0).map(|x| x * 2) {
+        // not an error, it can't be known what arbitrary methods do to a range
+        println!("{}", i);
+    }
+
+    // testing that the empty range lint folds constants
+    for i in (5 + 4..10).rev() {
+        println!("{}", i);
+    }
+
+    for i in ((3 - 1)..(5 + 2)).rev() {
+        println!("{}", i);
+    }
+
+    for i in (2 * 2)..(2 * 3) {
+        // no error, 4..6 is fine
+        println!("{}", i);
+    }
+
+    let x = 42;
+    for i in x..10 {
+        // no error, not constant-foldable
+        println!("{}", i);
+    }
+
+    // See #601
+    for i in 0..10 {
+        // no error, id_col does not exist outside the loop
+        let mut id_col = vec![0f64; 10];
+        id_col[i] = 1f64;
+    }
+
+    for _v in &vec {}
+
+    for _v in &mut vec {}
+
+    let out_vec = vec![1, 2, 3];
+    for _v in out_vec {}
+
+    let array = [1, 2, 3];
+    for _v in &array {}
+
+    for _v in &vec {} // these are fine
+    for _v in &mut vec {} // these are fine
+
+    for _v in &[1, 2, 3] {}
+
+    for _v in (&mut [1, 2, 3]).iter() {} // no error
+
+    for _v in &[0; 32] {}
+
+    for _v in [0; 33].iter() {} // no error
+
+    let ll: LinkedList<()> = LinkedList::new();
+    for _v in &ll {}
+
+    let vd: VecDeque<()> = VecDeque::new();
+    for _v in &vd {}
+
+    let bh: BinaryHeap<()> = BinaryHeap::new();
+    for _v in &bh {}
+
+    let hm: HashMap<(), ()> = HashMap::new();
+    for _v in &hm {}
+
+    let bt: BTreeMap<(), ()> = BTreeMap::new();
+    for _v in &bt {}
+
+    let hs: HashSet<()> = HashSet::new();
+    for _v in &hs {}
+
+    let bs: BTreeSet<()> = BTreeSet::new();
+    for _v in &bs {}
+
+    let u = Unrelated(vec![]);
+    for _v in u.next() {} // no error
+    for _v in u.iter() {} // no error
+
+    let mut out = vec![];
+    vec.iter().cloned().map(|x| out.push(x)).collect::<Vec<_>>();
+    let _y = vec.iter().cloned().map(|x| out.push(x)).collect::<Vec<_>>(); // this is fine
+
+    // Loop with explicit counter variable
+
+    // Potential false positives
+    let mut _index = 0;
+    _index = 1;
+    for _v in &vec {
+        _index += 1
+    }
+
+    let mut _index = 0;
+    _index += 1;
+    for _v in &vec {
+        _index += 1
+    }
+
+    let mut _index = 0;
+    if true {
+        _index = 1
+    }
+    for _v in &vec {
+        _index += 1
+    }
+
+    let mut _index = 0;
+    let mut _index = 1;
+    for _v in &vec {
+        _index += 1
+    }
+
+    let mut _index = 0;
+    for _v in &vec {
+        _index += 1;
+        _index += 1
+    }
+
+    let mut _index = 0;
+    for _v in &vec {
+        _index *= 2;
+        _index += 1
+    }
+
+    let mut _index = 0;
+    for _v in &vec {
+        _index = 1;
+        _index += 1
+    }
+
+    let mut _index = 0;
+
+    for _v in &vec {
+        let mut _index = 0;
+        _index += 1
+    }
+
+    let mut _index = 0;
+    for _v in &vec {
+        _index += 1;
+        _index = 0;
+    }
+
+    let mut _index = 0;
+    for _v in &vec {
+        for _x in 0..1 {
+            _index += 1;
+        }
+        _index += 1
+    }
+
+    let mut _index = 0;
+    for x in &vec {
+        if *x == 1 {
+            _index += 1
+        }
+    }
+
+    let mut _index = 0;
+    if true {
+        _index = 1
+    };
+    for _v in &vec {
+        _index += 1
+    }
+
+    let mut _index = 1;
+    if false {
+        _index = 0
+    };
+    for _v in &vec {
+        _index += 1
+    }
+
+    let mut index = 0;
+    {
+        let mut _x = &mut index;
+    }
+    for _v in &vec {
+        _index += 1
+    }
+
+    let mut index = 0;
+    for _v in &vec {
+        index += 1
+    }
+    println!("index: {}", index);
+
+    fn f<T>(_: &T, _: &T) -> bool {
+        unimplemented!()
+    }
+    fn g<T>(_: &mut [T], _: usize, _: usize) {
+        unimplemented!()
+    }
+    for i in 1..vec.len() {
+        if f(&vec[i - 1], &vec[i]) {
+            g(&mut vec, i - 1, i);
+        }
+    }
+
+    for mid in 1..vec.len() {
+        let (_, _) = vec.split_at(mid);
+    }
+}
+
+fn partition<T: PartialOrd + Send>(v: &mut [T]) -> usize {
+    let pivot = v.len() - 1;
+    let mut i = 0;
+    for j in 0..pivot {
+        if v[j] <= v[pivot] {
+            v.swap(i, j);
+            i += 1;
+        }
+    }
+    v.swap(i, pivot);
+    i
+}
+
+#[warn(clippy::needless_range_loop)]
+pub fn manual_copy_same_destination(dst: &mut [i32], d: usize, s: usize) {
+    // Same source and destination - don't trigger lint
+    for i in 0..dst.len() {
+        dst[d + i] = dst[s + i];
+    }
+}
+
+mod issue_2496 {
+    pub trait Handle {
+        fn new_for_index(index: usize) -> Self;
+        fn index(&self) -> usize;
+    }
+
+    pub fn test<H: Handle>() -> H {
+        for x in 0..5 {
+            let next_handle = H::new_for_index(x);
+            println!("{}", next_handle.index());
+        }
+        unimplemented!()
+    }
+}

tests/ui/for_loop_fixable.fixed

@@ -1,8 +1,8 @@
-use std::collections::*;
-use std::rc::Rc;
+// run-rustfix
+
+#![allow(dead_code, unused)]
 
-static STATIC: [usize; 4] = [0, 1, 8, 16];
-const CONST: [usize; 4] = [0, 1, 8, 16];
+use std::collections::*;
 
 #[warn(clippy::all)]
 struct Unrelated(Vec<u8>);
@@ -48,10 +48,6 @@ fn main() {
         println!("{}", i);
     }
 
-    for i in 5..5 {
-        println!("{}", i);
-    }
-
     for i in 5..=5 {
         // not an error, this is the range with only one element “5”
         println!("{}", i);
@@ -81,10 +77,6 @@ fn main() {
         println!("{}", i);
     }
 
-    for i in (5 + 2)..(8 - 1) {
-        println!("{}", i);
-    }
-
     for i in (2 * 2)..(2 * 3) {
         // no error, 4..6 is fine
         println!("{}", i);
@@ -145,8 +137,6 @@ fn main() {
     let bs: BTreeSet<()> = BTreeSet::new();
     for _v in bs.iter() {}
 
-    for _v in vec.iter().next() {}
-
     let u = Unrelated(vec![]);
     for _v in u.next() {} // no error
     for _v in u.iter() {} // no error
@@ -275,17 +265,8 @@ fn main() {
     for mid in 1..vec.len() {
         let (_, _) = vec.split_at(mid);
     }
-
-    const ZERO: usize = 0;
-
-    for i in ZERO..vec.len() {
-        if f(&vec[i], &vec[i]) {
-            panic!("at the disco");
-        }
-    }
 }
 
-#[allow(dead_code)]
 fn partition<T: PartialOrd + Send>(v: &mut [T]) -> usize {
     let pivot = v.len() - 1;
     let mut i = 0;