Rustup

clippy_lints/src/loops.rs

@@ -2328,8 +2328,10 @@ fn check_needless_collect<'a, 'tcx>(expr: &'tcx Expr, cx: &LateContext<'a, 'tcx>
 }
 
 fn shorten_needless_collect_span(expr: &Expr) -> Span {
-    if let ExprKind::MethodCall(_, _, ref args) = expr.node {
-        if let ExprKind::MethodCall(_, ref span, _) = args[0].node {
+    if_chain! {
+        if let ExprKind::MethodCall(_, _, ref args) = expr.node;
+        if let ExprKind::MethodCall(_, ref span, _) = args[0].node;
+        then {
             return expr.span.with_lo(span.lo() - BytePos(1));
         }
     }

tests/ui/needless_collect.rs

@@ -1,7 +1,9 @@
+#![feature(tool_lints)]
+
 use std::collections::{HashMap, HashSet, BTreeSet};
 
-#[warn(clippy, needless_collect)]
-#[allow(unused_variables, iter_cloned_collect)]
+#[warn(clippy::needless_collect)]
+#[allow(unused_variables, clippy::iter_cloned_collect)]
 fn main() {
     let sample = [1; 5];
     let len = sample.iter().collect::<Vec<_>>().len();

tests/ui/needless_collect.stderr

@@ -1,27 +1,27 @@
 error: avoid using `collect()` when not needed
- --> $DIR/needless_collect.rs:7:28
+ --> $DIR/needless_collect.rs:9:28
   |
-7 |     let len = sample.iter().collect::<Vec<_>>().len();
+9 |     let len = sample.iter().collect::<Vec<_>>().len();
   |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `.count()`
   |
-  = note: `-D needless-collect` implied by `-D warnings`
+  = note: `-D clippy::needless-collect` implied by `-D warnings`
 
 error: avoid using `collect()` when not needed
- --> $DIR/needless_collect.rs:8:21
-  |
-8 |     if sample.iter().collect::<Vec<_>>().is_empty() {
-  |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `.next().is_none()`
-
-error: avoid using `collect()` when not needed
-  --> $DIR/needless_collect.rs:11:27
+  --> $DIR/needless_collect.rs:10:21
    |
-11 |     sample.iter().cloned().collect::<Vec<_>>().contains(&1);
+10 |     if sample.iter().collect::<Vec<_>>().is_empty() {
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `.next().is_none()`
+
+error: avoid using `collect()` when not needed
+  --> $DIR/needless_collect.rs:13:27
+   |
+13 |     sample.iter().cloned().collect::<Vec<_>>().contains(&1);
    |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `.any(|&x| x == 1)`
 
 error: avoid using `collect()` when not needed
-  --> $DIR/needless_collect.rs:12:34
+  --> $DIR/needless_collect.rs:14:34
    |
-12 |     sample.iter().map(|x| (x, x)).collect::<HashMap<_, _>>().len();
+14 |     sample.iter().map(|x| (x, x)).collect::<HashMap<_, _>>().len();
    |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `.count()`
 
 error: aborting due to 4 previous errors