needless_collect: fix suggestion, make test rustfixable

Author: Manishearth

clippy_lints/src/loops.rs

@@ -2427,12 +2427,17 @@ fn check_needless_collect<'a, 'tcx>(expr: &'tcx Expr, cx: &LateContext<'a, 'tcx>
                     let contains_arg = snippet(cx, args[1].span, "??");
                     let span = shorten_needless_collect_span(expr);
                     span_lint_and_then(cx, NEEDLESS_COLLECT, span, NEEDLESS_COLLECT_MSG, |db| {
+                        let (arg, pred) = if contains_arg.starts_with('&') {
+                            ("x", &contains_arg[1..])
+                        } else {
+                            ("&x", &*contains_arg)
+                        };
                         db.span_suggestion(
                             span,
                             "replace with",
                             format!(
-                                ".any(|&x| x == {})",
-                                if contains_arg.starts_with('&') { &contains_arg[1..] } else { &contains_arg }
+                                ".any(|{}| x == {})",
+                                arg, pred
                             ),
                             Applicability::MachineApplicable,
                         );

tests/ui/needless_collect.fixed

@@ -0,0 +1,21 @@
+// run-rustfix
+
+#![allow(unused, clippy::suspicious_map)]
+
+use std::collections::{BTreeSet, HashMap, HashSet};
+
+#[warn(clippy::needless_collect)]
+#[allow(unused_variables, clippy::iter_cloned_collect)]
+fn main() {
+    let sample = [1; 5];
+    let len = sample.iter().count();
+    if sample.iter().next().is_none() {
+        // Empty
+    }
+    sample.iter().cloned().any(|x| x == 1);
+    sample.iter().map(|x| (x, x)).count();
+    // Notice the `HashSet`--this should not be linted
+    sample.iter().collect::<HashSet<_>>().len();
+    // Neither should this
+    sample.iter().collect::<BTreeSet<_>>().len();
+}

tests/ui/needless_collect.rs

@@ -1,3 +1,7 @@
+// run-rustfix
+
+#![allow(unused, clippy::suspicious_map)]
+
 use std::collections::{BTreeSet, HashMap, HashSet};
 
 #[warn(clippy::needless_collect)]

tests/ui/needless_collect.stderr

@@ -1,25 +1,25 @@
 error: avoid using `collect()` when not needed
-  --> $DIR/needless_collect.rs:7:28
+  --> $DIR/needless_collect.rs:11:28
    |
 LL |     let len = sample.iter().collect::<Vec<_>>().len();
    |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `.count()`
    |
    = note: `-D clippy::needless-collect` implied by `-D warnings`
 
 error: avoid using `collect()` when not needed
-  --> $DIR/needless_collect.rs:8:21
+  --> $DIR/needless_collect.rs:12:21
    |
 LL |     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:15:27
    |
 LL |     sample.iter().cloned().collect::<Vec<_>>().contains(&1);
-   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `.any(|&x| x == 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:16:34
    |
 LL |     sample.iter().map(|x| (x, x)).collect::<HashMap<_, _>>().len();
    |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `.count()`