Test all types supported by [collection_is_never_read]

Demonstrate false negative for `String` as discussed in #10572.

Author: schubart

tests/ui/collection_is_never_read.rs

@@ -163,3 +163,37 @@ fn function_argument() {
     let x = vec![1, 2, 3]; // Ok
     foo(&x);
 }
+
+fn supported_types() {
+    let mut x = std::collections::BTreeMap::new(); // WARNING
+    x.insert(true, 1);
+
+    let mut x = std::collections::BTreeSet::new(); // WARNING
+    x.insert(1);
+
+    let mut x = std::collections::BinaryHeap::new(); // WARNING
+    x.push(1);
+
+    let mut x = std::collections::HashMap::new(); // WARNING
+    x.insert(1, 2);
+
+    let mut x = std::collections::HashSet::new(); // WARNING
+    x.insert(1);
+
+    let mut x = std::collections::LinkedList::new(); // WARNING
+    x.push_front(1);
+
+    let mut x = Some(true); // WARNING
+    x.insert(false);
+
+    // https://github.com/rust-lang/rust-clippy/issues/10572#issuecomment-1498760833
+    let mut x = String::from("hello"); // False negative
+    x.push('!');
+
+    let mut x = Vec::new(); // WARNING
+    x.clear();
+    x.push(1);
+
+    let mut x = std::collections::VecDeque::new(); // WARNING
+    x.push_front(1);
+}

tests/ui/collection_is_never_read.stderr

@@ -48,5 +48,59 @@ error: collection is never read
 LL |     let x = vec![1, 2, 3]; // WARNING
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 8 previous errors
+error: collection is never read
+  --> $DIR/collection_is_never_read.rs:168:5
+   |
+LL |     let mut x = std::collections::BTreeMap::new(); // WARNING
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: collection is never read
+  --> $DIR/collection_is_never_read.rs:171:5
+   |
+LL |     let mut x = std::collections::BTreeSet::new(); // WARNING
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: collection is never read
+  --> $DIR/collection_is_never_read.rs:174:5
+   |
+LL |     let mut x = std::collections::BinaryHeap::new(); // WARNING
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: collection is never read
+  --> $DIR/collection_is_never_read.rs:177:5
+   |
+LL |     let mut x = std::collections::HashMap::new(); // WARNING
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: collection is never read
+  --> $DIR/collection_is_never_read.rs:180:5
+   |
+LL |     let mut x = std::collections::HashSet::new(); // WARNING
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: collection is never read
+  --> $DIR/collection_is_never_read.rs:183:5
+   |
+LL |     let mut x = std::collections::LinkedList::new(); // WARNING
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: collection is never read
+  --> $DIR/collection_is_never_read.rs:186:5
+   |
+LL |     let mut x = Some(true); // WARNING
+   |     ^^^^^^^^^^^^^^^^^^^^^^^
+
+error: collection is never read
+  --> $DIR/collection_is_never_read.rs:193:5
+   |
+LL |     let mut x = Vec::new(); // WARNING
+   |     ^^^^^^^^^^^^^^^^^^^^^^^
+
+error: collection is never read
+  --> $DIR/collection_is_never_read.rs:197:5
+   |
+LL |     let mut x = std::collections::VecDeque::new(); // WARNING
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 17 previous errors