add error anotations

Author: Kither12

clippy_lints/src/methods/mod.rs

@@ -4281,7 +4281,7 @@ restriction,
 }
 declare_clippy_lint! {
     /// ### What it does
-    /// Checks for usage of `.drain(x..)` for the sole purpose of truncate a container.
+    /// Checks for usage of `.drain(x..)` for the sole purpose of truncating a container.
     ///
     /// ### Why is this bad?
     /// This creates an unnecessary iterator that is dropped immediately.
@@ -4301,7 +4301,7 @@ declare_clippy_lint! {
     #[clippy::version = "1.84.0"]
     pub TRUNCATE_WITH_DRAIN,
     nursery,
-    "calling `drain` in order to `truncate` a `Vec`"
+    "calling `drain` in order to truncate a `Vec`"
 }
 
 pub struct Methods {

tests/ui/truncate_with_drain.rs

@@ -10,45 +10,39 @@ fn vec_range() {
 
     // Do not lint because iterator is used
     let mut v = vec![1, 2, 3];
-    let n = v.drain(1..v.len()).count();
-
-    // Do not lint because iterator is assigned and used
-    let mut v = vec![1, 2, 3];
-    let iter = v.drain(1..v.len());
-    let n = iter.count();
+    v.drain(1..v.len()).next();
 
     // Do lint
     let mut v = vec![1, 2, 3];
     v.drain(1..v.len());
+    //~^ ERROR: `drain` used to truncate a `Vec`
 
     // Do lint
     let x = 1;
     let mut v = vec![1, 2, 3];
     v.drain(x..v.len());
+    //~^ ERROR: `drain` used to truncate a `Vec`
 }
 
 fn vec_range_from() {
     // Do not lint because iterator is assigned
     let mut v = vec![1, 2, 3];
     let iter = v.drain(1..);
 
-    // Do not lint because iterator is assigned and used
-    let mut v = vec![1, 2, 3];
-    let mut iter = v.drain(1..);
-    let next = iter.next();
-
     // Do not lint because iterator is used
     let mut v = vec![1, 2, 3];
-    let next = v.drain(1..).next();
+    v.drain(1..).next();
 
     // Do lint
     let mut v = vec![1, 2, 3];
     v.drain(1..);
+    //~^ ERROR: `drain` used to truncate a `Vec`
 
     // Do lint
     let x = 1;
     let mut v = vec![1, 2, 3];
     v.drain(x..);
+    //~^ ERROR: `drain` used to truncate a `Vec`
 }
 
 fn vec_partial_drains() {
@@ -102,45 +96,39 @@ fn vec_deque_range() {
 
     // Do not lint because iterator is used
     let mut deque = VecDeque::from([1, 2, 3]);
-    let n = deque.drain(1..deque.len()).count();
-
-    // Do not lint because iterator is assigned and used
-    let mut deque = VecDeque::from([1, 2, 3]);
-    let iter = deque.drain(1..deque.len());
-    let n = iter.count();
+    deque.drain(1..deque.len()).next();
 
     // Do lint
     let mut v = VecDeque::from([1, 2, 3]);
     v.drain(1..v.len());
+    //~^ ERROR: `drain` used to truncate a `VecDeque`
 
     // Do lint
     let x = 1;
     let mut v = VecDeque::from([1, 2, 3]);
     v.drain(x..v.len());
+    //~^ ERROR: `drain` used to truncate a `VecDeque`
 }
 
 fn vec_deque_range_from() {
     // Do not lint because iterator is assigned
     let mut deque = VecDeque::from([1, 2, 3]);
     let iter = deque.drain(1..);
 
-    // Do not lint because iterator is assigned and used
-    let mut deque = VecDeque::from([1, 2, 3]);
-    let mut iter = deque.drain(1..);
-    let next = iter.next();
-
     // Do not lint because iterator is used
     let mut deque = VecDeque::from([1, 2, 3]);
-    let next = deque.drain(1..).next();
+    deque.drain(1..).next();
 
     // Do lint
     let mut deque = VecDeque::from([1, 2, 3]);
     deque.drain(1..);
+    //~^ ERROR: `drain` used to truncate a `VecDeque`
 
     // Do lint
     let x = 1;
     let mut v = VecDeque::from([1, 2, 3]);
     v.drain(x..);
+    //~^ ERROR: `drain` used to truncate a `VecDeque`
 }
 
 fn vec_deque_partial_drains() {
@@ -194,45 +182,39 @@ fn string_range() {
 
     // Do not lint because iterator is used
     let mut s = String::from("Hello, world!");
-    let n = s.drain(1..s.len()).count();
-
-    // Do not lint because iterator is assigned and used
-    let mut s = String::from("Hello, world!");
-    let iter = s.drain(1..s.len());
-    let n = iter.count();
+    s.drain(1..s.len()).next();
 
     // Do lint
     let mut s = String::from("Hello, world!");
     s.drain(1..s.len());
+    //~^ ERROR: `drain` used to truncate a `String`
 
     // Do lint
     let x = 1;
     let mut v = String::from("Hello, world!");
     v.drain(x..s.len());
+    //~^ ERROR: `drain` used to truncate a `String`
 }
 
 fn string_range_from() {
     // Do not lint because iterator is assigned
     let mut s = String::from("Hello, world!");
     let iter = s.drain(1..);
 
-    // Do not lint because iterator is assigned and used
-    let mut s = String::from("Hello, world!");
-    let mut iter = s.drain(1..);
-    let next = iter.next();
-
     // Do not lint because iterator is used
     let mut s = String::from("Hello, world!");
-    let next = s.drain(1..).next();
+    s.drain(1..).next();
 
     // Do lint
     let mut s = String::from("Hello, world!");
     s.drain(1..);
+    //~^ ERROR: `drain` used to truncate a `String`
 
     // Do lint
     let x = 1;
-    let mut v = String::from("Hello, world!");
-    v.drain(x..);
+    let mut s = String::from("Hello, world!");
+    s.drain(x..);
+    //~^ ERROR: `drain` used to truncate a `String`
 }
 
 fn string_partial_drains() {