lint for into_iter().count()

TaKO8Ki · TaKO8Ki · commit 204b27937c48 · 2021-02-27T14:16:02.000+09:00
diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs
@@ -1691,7 +1691,7 @@ impl<'tcx> LateLintPass<'tcx> for Methods {
                 lint_search_is_some(cx, expr, "rposition", arg_lists[1], arg_lists[0], method_spans[1])
             },
             ["extend", ..] => lint_extend(cx, expr, arg_lists[0]),
-            ["count", "iter"] => lint_iter_count(cx, expr, &arg_lists[1], false),
+            ["count", "into_iter" | "iter"] => lint_iter_count(cx, expr, &arg_lists[1], false),
             ["count", "iter_mut"] => lint_iter_count(cx, expr, &arg_lists[1], true),
             ["nth", "iter"] => lint_iter_nth(cx, expr, &arg_lists, false),
             ["nth", "iter_mut"] => lint_iter_nth(cx, expr, &arg_lists, true),
@@ -2663,6 +2663,13 @@ fn lint_iter_next<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, iter_
 
 fn lint_iter_count<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, iter_args: &'tcx [Expr<'tcx>], is_mut: bool) {
     let mut_str = if is_mut { "_mut" } else { "" };
+    let iter_method = if method_chain_args(expr, &[format!("iter{}", mut_str).as_str(), "count"]).is_some() {
+        "iter"
+    } else if method_chain_args(expr, &["into_iter", "count"]).is_some() {
+        "into_iter"
+    } else {
+        return;
+    };
     if_chain! {
         let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.typeck_results().expr_ty(&iter_args[0])).is_some() {
             Some("slice")
@@ -2682,7 +2689,7 @@ fn lint_iter_count<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, iter_args: &'t
                 cx,
                 ITER_COUNT,
                 expr.span,
-                &format!("called `.iter{}().count()` on a `{}`", mut_str, caller_type),
+                &format!("called `.{}{}().count()` on a `{}`", iter_method, mut_str, caller_type),
                 "try",
                 format!(
                     "{}.len()",
diff --git a/tests/ui/iter_count.fixed b/tests/ui/iter_count.fixed
@@ -2,8 +2,13 @@
 // aux-build:option_helpers.rs
 
 #![warn(clippy::iter_count)]
-#![allow(unused_variables)]
-#![allow(unused_mut)]
+#![allow(
+    unused_variables,
+    array_into_iter,
+    unused_mut,
+    clippy::into_iter_on_ref,
+    clippy::unnecessary_operation
+)]
 
 extern crate option_helpers;
 
@@ -22,37 +27,36 @@ impl HasIter {
     fn iter_mut(self) -> IteratorFalsePositives {
         IteratorFalsePositives { foo: 0 }
     }
+
+    fn into_iter(self) -> IteratorFalsePositives {
+        IteratorFalsePositives { foo: 0 }
+    }
 }
 
 fn main() {
-    let mut some_vec = vec![0, 1, 2, 3];
+    let mut vec = vec![0, 1, 2, 3];
     let mut boxed_slice: Box<[u8]> = Box::new([0, 1, 2, 3]);
-    let mut some_vec_deque: VecDeque<_> = some_vec.iter().cloned().collect();
-    let mut some_hash_set = HashSet::new();
-    some_hash_set.insert(1);
-
-    {
-        // Make sure we lint `.iter()` for relevant types.
-        let bad_vec = some_vec.len();
-        let bad_slice = &some_vec[..].len();
-        let bad_boxed_slice = boxed_slice.len();
-        let bad_vec_deque = some_vec_deque.len();
-        let bad_hash_set = some_hash_set.len();
-    }
+    let mut vec_deque: VecDeque<_> = vec.iter().cloned().collect();
+    let mut hash_set = HashSet::new();
+    hash_set.insert(1);
 
-    {
-        // Make sure we lint `.iter_mut()` for relevant types.
-        let bad_vec = some_vec.len();
-    }
-    {
-        let bad_slice = &some_vec[..].len();
-    }
-    {
-        let bad_vec_deque = some_vec_deque.len();
-    }
+    &vec[..].len();
+    vec.len();
+    boxed_slice.len();
+    vec_deque.len();
+    hash_set.len();
+
+    vec.len();
+    &vec[..].len();
+    vec_deque.len();
+
+    &vec[..].len();
+    vec.len();
+    vec_deque.len();
 
     // Make sure we don't lint for non-relevant types.
     let false_positive = HasIter;
-    let ok = false_positive.iter().count();
-    let ok_mut = false_positive.iter_mut().count();
+    false_positive.iter().count();
+    false_positive.iter_mut().count();
+    false_positive.into_iter().count();
 }
diff --git a/tests/ui/iter_count.rs b/tests/ui/iter_count.rs
@@ -2,8 +2,13 @@
 // aux-build:option_helpers.rs
 
 #![warn(clippy::iter_count)]
-#![allow(unused_variables)]
-#![allow(unused_mut)]
+#![allow(
+    unused_variables,
+    array_into_iter,
+    unused_mut,
+    clippy::into_iter_on_ref,
+    clippy::unnecessary_operation
+)]
 
 extern crate option_helpers;
 
@@ -22,37 +27,36 @@ impl HasIter {
     fn iter_mut(self) -> IteratorFalsePositives {
         IteratorFalsePositives { foo: 0 }
     }
+
+    fn into_iter(self) -> IteratorFalsePositives {
+        IteratorFalsePositives { foo: 0 }
+    }
 }
 
 fn main() {
-    let mut some_vec = vec![0, 1, 2, 3];
+    let mut vec = vec![0, 1, 2, 3];
     let mut boxed_slice: Box<[u8]> = Box::new([0, 1, 2, 3]);
-    let mut some_vec_deque: VecDeque<_> = some_vec.iter().cloned().collect();
-    let mut some_hash_set = HashSet::new();
-    some_hash_set.insert(1);
-
-    {
-        // Make sure we lint `.iter()` for relevant types.
-        let bad_vec = some_vec.iter().count();
-        let bad_slice = &some_vec[..].iter().count();
-        let bad_boxed_slice = boxed_slice.iter().count();
-        let bad_vec_deque = some_vec_deque.iter().count();
-        let bad_hash_set = some_hash_set.iter().count();
-    }
+    let mut vec_deque: VecDeque<_> = vec.iter().cloned().collect();
+    let mut hash_set = HashSet::new();
+    hash_set.insert(1);
 
-    {
-        // Make sure we lint `.iter_mut()` for relevant types.
-        let bad_vec = some_vec.iter_mut().count();
-    }
-    {
-        let bad_slice = &some_vec[..].iter_mut().count();
-    }
-    {
-        let bad_vec_deque = some_vec_deque.iter_mut().count();
-    }
+    &vec[..].iter().count();
+    vec.iter().count();
+    boxed_slice.iter().count();
+    vec_deque.iter().count();
+    hash_set.iter().count();
+
+    vec.iter_mut().count();
+    &vec[..].iter_mut().count();
+    vec_deque.iter_mut().count();
+
+    &vec[..].into_iter().count();
+    vec.into_iter().count();
+    vec_deque.into_iter().count();
 
     // Make sure we don't lint for non-relevant types.
     let false_positive = HasIter;
-    let ok = false_positive.iter().count();
-    let ok_mut = false_positive.iter_mut().count();
+    false_positive.iter().count();
+    false_positive.iter_mut().count();
+    false_positive.into_iter().count();
 }
diff --git a/tests/ui/iter_count.stderr b/tests/ui/iter_count.stderr
@@ -1,52 +1,70 @@
-error: called `.iter().count()` on a `Vec`
-  --> $DIR/iter_count.rs:36:23
+error: called `.iter().count()` on a `slice`
+  --> $DIR/iter_count.rs:43:6
    |
-LL |         let bad_vec = some_vec.iter().count();
-   |                       ^^^^^^^^^^^^^^^^^^^^^^^ help: try: `some_vec.len()`
+LL |     &vec[..].iter().count();
+   |      ^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec[..].len()`
    |
    = note: `-D clippy::iter-count` implied by `-D warnings`
 
-error: called `.iter().count()` on a `slice`
-  --> $DIR/iter_count.rs:37:26
+error: called `.iter().count()` on a `Vec`
+  --> $DIR/iter_count.rs:44:5
    |
-LL |         let bad_slice = &some_vec[..].iter().count();
-   |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `some_vec[..].len()`
+LL |     vec.iter().count();
+   |     ^^^^^^^^^^^^^^^^^^ help: try: `vec.len()`
 
 error: called `.iter().count()` on a `slice`
-  --> $DIR/iter_count.rs:38:31
+  --> $DIR/iter_count.rs:45:5
    |
-LL |         let bad_boxed_slice = boxed_slice.iter().count();
-   |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `boxed_slice.len()`
+LL |     boxed_slice.iter().count();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `boxed_slice.len()`
 
 error: called `.iter().count()` on a `VecDeque`
-  --> $DIR/iter_count.rs:39:29
+  --> $DIR/iter_count.rs:46:5
    |
-LL |         let bad_vec_deque = some_vec_deque.iter().count();
-   |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `some_vec_deque.len()`
+LL |     vec_deque.iter().count();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec_deque.len()`
 
 error: called `.iter().count()` on a `std::iter::Iterator`
-  --> $DIR/iter_count.rs:40:28
+  --> $DIR/iter_count.rs:47:5
    |
-LL |         let bad_hash_set = some_hash_set.iter().count();
-   |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `some_hash_set.len()`
+LL |     hash_set.iter().count();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^ help: try: `hash_set.len()`
 
 error: called `.iter_mut().count()` on a `Vec`
-  --> $DIR/iter_count.rs:45:23
+  --> $DIR/iter_count.rs:49:5
    |
-LL |         let bad_vec = some_vec.iter_mut().count();
-   |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `some_vec.len()`
+LL |     vec.iter_mut().count();
+   |     ^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec.len()`
 
 error: called `.iter_mut().count()` on a `slice`
-  --> $DIR/iter_count.rs:48:26
+  --> $DIR/iter_count.rs:50:6
    |
-LL |         let bad_slice = &some_vec[..].iter_mut().count();
-   |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `some_vec[..].len()`
+LL |     &vec[..].iter_mut().count();
+   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec[..].len()`
 
 error: called `.iter_mut().count()` on a `VecDeque`
-  --> $DIR/iter_count.rs:51:29
+  --> $DIR/iter_count.rs:51:5
+   |
+LL |     vec_deque.iter_mut().count();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec_deque.len()`
+
+error: called `.into_iter().count()` on a `slice`
+  --> $DIR/iter_count.rs:53:6
+   |
+LL |     &vec[..].into_iter().count();
+   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec[..].len()`
+
+error: called `.into_iter().count()` on a `Vec`
+  --> $DIR/iter_count.rs:54:5
+   |
+LL |     vec.into_iter().count();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec.len()`
+
+error: called `.into_iter().count()` on a `VecDeque`
+  --> $DIR/iter_count.rs:55:5
    |
-LL |         let bad_vec_deque = some_vec_deque.iter_mut().count();
-   |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `some_vec_deque.len()`
+LL |     vec_deque.into_iter().count();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec_deque.len()`
 
-error: aborting due to 8 previous errors
+error: aborting due to 11 previous errors
 
