Lint `needless_collect` on non-std collection types

3 files changed, 83 insertions, 1 deletions

diff --git a/tests/ui/needless_collect.fixed b/tests/ui/needless_collect.fixed
index 6ecbbcb6249..2659ad38488 100644
--- a/tests/ui/needless_collect.fixed
+++ b/tests/ui/needless_collect.fixed
@@ -33,4 +33,33 @@ fn main() {
     // `BinaryHeap` doesn't have `contains` method
     sample.iter().count();
     sample.iter().next().is_none();
+
+    // Don't lint string from str
+    let _ = ["", ""].into_iter().collect::<String>().is_empty();
+
+    let _ = sample.iter().next().is_none();
+    let _ = sample.iter().any(|x| x == &0);
+
+    struct VecWrapper<T>(Vec<T>);
+    impl<T> core::ops::Deref for VecWrapper<T> {
+        type Target = Vec<T>;
+        fn deref(&self) -> &Self::Target {
+            &self.0
+        }
+    }
+    impl<T> IntoIterator for VecWrapper<T> {
+        type IntoIter = <Vec<T> as IntoIterator>::IntoIter;
+        type Item = <Vec<T> as IntoIterator>::Item;
+        fn into_iter(self) -> Self::IntoIter {
+            self.0.into_iter()
+        }
+    }
+    impl<T> FromIterator<T> for VecWrapper<T> {
+        fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
+            Self(Vec::from_iter(iter))
+        }
+    }
+
+    let _ = sample.iter().next().is_none();
+    let _ = sample.iter().any(|x| x == &0);
 }
diff --git a/tests/ui/needless_collect.rs b/tests/ui/needless_collect.rs
index 8dc69bcf5b3..535ec82982b 100644
--- a/tests/ui/needless_collect.rs
+++ b/tests/ui/needless_collect.rs
@@ -33,4 +33,33 @@ fn main() {
     // `BinaryHeap` doesn't have `contains` method
     sample.iter().collect::<BinaryHeap<_>>().len();
     sample.iter().collect::<BinaryHeap<_>>().is_empty();
+
+    // Don't lint string from str
+    let _ = ["", ""].into_iter().collect::<String>().is_empty();
+
+    let _ = sample.iter().collect::<HashSet<_>>().is_empty();
+    let _ = sample.iter().collect::<HashSet<_>>().contains(&&0);
+
+    struct VecWrapper<T>(Vec<T>);
+    impl<T> core::ops::Deref for VecWrapper<T> {
+        type Target = Vec<T>;
+        fn deref(&self) -> &Self::Target {
+            &self.0
+        }
+    }
+    impl<T> IntoIterator for VecWrapper<T> {
+        type IntoIter = <Vec<T> as IntoIterator>::IntoIter;
+        type Item = <Vec<T> as IntoIterator>::Item;
+        fn into_iter(self) -> Self::IntoIter {
+            self.0.into_iter()
+        }
+    }
+    impl<T> FromIterator<T> for VecWrapper<T> {
+        fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
+            Self(Vec::from_iter(iter))
+        }
+    }
+
+    let _ = sample.iter().collect::<VecWrapper<_>>().is_empty();
+    let _ = sample.iter().collect::<VecWrapper<_>>().contains(&&0);
 }
diff --git a/tests/ui/needless_collect.stderr b/tests/ui/needless_collect.stderr
index 039091627a8..584d2a1d835 100644
--- a/tests/ui/needless_collect.stderr
+++ b/tests/ui/needless_collect.stderr
@@ -66,5 +66,29 @@ error: avoid using `collect()` when not needed
 LL |     sample.iter().collect::<BinaryHeap<_>>().is_empty();
    |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `next().is_none()`
 
-error: aborting due to 11 previous errors
+error: avoid using `collect()` when not needed
+  --> $DIR/needless_collect.rs:40:27
+   |
+LL |     let _ = sample.iter().collect::<HashSet<_>>().is_empty();
+   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `next().is_none()`
+
+error: avoid using `collect()` when not needed
+  --> $DIR/needless_collect.rs:41:27
+   |
+LL |     let _ = sample.iter().collect::<HashSet<_>>().contains(&&0);
+   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `any(|x| x == &0)`
+
+error: avoid using `collect()` when not needed
+  --> $DIR/needless_collect.rs:63:27
+   |
+LL |     let _ = sample.iter().collect::<VecWrapper<_>>().is_empty();
+   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `next().is_none()`
+
+error: avoid using `collect()` when not needed
+  --> $DIR/needless_collect.rs:64:27
+   |
+LL |     let _ = sample.iter().collect::<VecWrapper<_>>().contains(&&0);
+   |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `any(|x| x == &0)`
+
+error: aborting due to 15 previous errors