Apply suggestions from code review

Co-authored-by: Alejandra González <blyxyas@gmail.com>

clippy_lints/src/loops/mod.rs

@@ -580,7 +580,7 @@ declare_clippy_lint! {
 
 declare_clippy_lint! {
     /// ### What it does
-    /// Checks for `for (_, v) in a.iter().enumerate()`
+    /// Checks for uses of the `enumerate` method where the index is unused (`_`)
     ///
     /// ### Why is this bad?
     /// The index from `.enumerate()` is immediately dropped.
@@ -589,20 +589,20 @@ declare_clippy_lint! {
     /// ```rust
     /// let v = vec![1, 2, 3, 4];
     /// for (_, x) in v.iter().enumerate() {
-    ///     print!("{x}")
+    ///     println!("{x}");
     /// }
     /// ```
     /// Use instead:
     /// ```rust
     /// let v = vec![1, 2, 3, 4];
     /// for x in v.iter() {
-    ///     print!("{x}")
+    ///     println!("{x}");
     /// }
     /// ```
-    #[clippy::version = "1.69.0"]
+    #[clippy::version = "1.75.0"]
     pub UNUSED_ENUMERATE_INDEX,
     style,
-    "using .enumerate() and immediately dropping the index"
+    "using `.enumerate()` and immediately dropping the index"
 }
 
 declare_clippy_lint! {

clippy_lints/src/loops/unused_enumerate_index.rs

@@ -3,40 +3,27 @@ use clippy_utils::diagnostics::{multispan_sugg, span_lint_and_then};
 use clippy_utils::source::snippet;
 use clippy_utils::sugg;
 use clippy_utils::visitors::is_local_used;
+use rustc_hir::def::DefKind;
 use rustc_hir::{Expr, ExprKind, Pat, PatKind};
 use rustc_lint::LateContext;
 use rustc_middle::ty;
 
 /// Checks for the `UNUSED_ENUMERATE_INDEX` lint.
 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, arg: &'tcx Expr<'_>, body: &'tcx Expr<'_>) {
-    let pat_span = pat.span;
-
-    let PatKind::Tuple(pat, _) = pat.kind else {
+    let PatKind::Tuple(tuple, _) = pat.kind else {
         return;
     };
 
-    if pat.len() != 2 {
-        return;
-    }
-
-    let arg_span = arg.span;
-
-    let ExprKind::MethodCall(method, self_arg, [], _) = arg.kind else {
+    let ExprKind::MethodCall(_method, self_arg, [], _) = arg.kind else {
         return;
     };
 
-    if method.ident.as_str() != "enumerate" {
-        return;
-    }
-
     let ty = cx.typeck_results().expr_ty(arg);
 
-    if !pat_is_wild(cx, &pat[0].kind, body) {
+    if !pat_is_wild(cx, &tuple[0].kind, body) {
         return;
     }
 
-    let new_pat_span = pat[1].span;
-
     let name = match *ty.kind() {
         ty::Adt(base, _substs) => cx.tcx.def_path_str(base.did()),
         _ => return,
@@ -46,10 +33,20 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, arg: &'tcx
         return;
     }
 
+    let Some((DefKind::AssocFn, call_id)) = cx.typeck_results().type_dependent_def(arg.hir_id) else {
+        return;
+    };
+
+    let call_name = cx.tcx.def_path_str(call_id);
+
+    if call_name != "std::iter::Iterator::enumerate" && call_name != "core::iter::Iterator::enumerate" {
+        return;
+    }
+
     span_lint_and_then(
         cx,
         UNUSED_ENUMERATE_INDEX,
-        arg_span,
+        arg.span,
         "you seem to use `.enumerate()` and immediately discard the index",
         |diag| {
             let base_iter = sugg::Sugg::hir(cx, self_arg, "base iter");
@@ -57,8 +54,8 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, arg: &'tcx
                 diag,
                 "remove the `.enumerate()` call",
                 vec![
-                    (pat_span, snippet(cx, new_pat_span, "value").into_owned()),
-                    (arg_span, base_iter.to_string()),
+                    (pat.span, snippet(cx, tuple[1].span, "..").into_owned()),
+                    (arg.span, base_iter.to_string()),
                 ],
             );
         },

tests/ui/unused_enumerate_index.fixed

@@ -1,10 +1,58 @@
-// run-rustfix
 #![allow(unused)]
 #![warn(clippy::unused_enumerate_index)]
 
+use std::iter::Enumerate;
+
 fn main() {
     let v = [1, 2, 3];
     for x in v.iter() {
-        print!("{x}");
+        println!("{x}");
+    }
+
+    struct Dummy1;
+    impl Dummy1 {
+        fn enumerate(self) -> Vec<usize> {
+            vec![]
+        }
+    }
+    let dummy = Dummy1;
+    for x in dummy.enumerate() {
+        println!("{x}");
+    }
+
+    struct Dummy2;
+    impl Dummy2 {
+        fn enumerate(self) -> Enumerate<std::vec::IntoIter<usize>> {
+            vec![1, 2].into_iter().enumerate()
+        }
+    }
+    let dummy = Dummy2;
+    for (_, x) in dummy.enumerate() {
+        println!("{x}");
+    }
+
+    let mut with_used_iterator = [1, 2, 3].into_iter().enumerate();
+    with_used_iterator.next();
+    for (_, x) in with_used_iterator {
+        println!("{x}");
+    }
+
+    struct Dummy3(std::vec::IntoIter<usize>);
+
+    impl Iterator for Dummy3 {
+        type Item = usize;
+
+        fn next(&mut self) -> Option<Self::Item> {
+            self.0.next()
+        }
+
+        fn size_hint(&self) -> (usize, Option<usize>) {
+            self.0.size_hint()
+        }
+    }
+
+    let dummy = Dummy3(vec![1, 2, 3].into_iter());
+    for x in dummy {
+        println!("{x}");
     }
 }

tests/ui/unused_enumerate_index.rs

@@ -1,10 +1,58 @@
-// run-rustfix
 #![allow(unused)]
 #![warn(clippy::unused_enumerate_index)]
 
+use std::iter::Enumerate;
+
 fn main() {
     let v = [1, 2, 3];
     for (_, x) in v.iter().enumerate() {
-        print!("{x}");
+        println!("{x}");
+    }
+
+    struct Dummy1;
+    impl Dummy1 {
+        fn enumerate(self) -> Vec<usize> {
+            vec![]
+        }
+    }
+    let dummy = Dummy1;
+    for x in dummy.enumerate() {
+        println!("{x}");
+    }
+
+    struct Dummy2;
+    impl Dummy2 {
+        fn enumerate(self) -> Enumerate<std::vec::IntoIter<usize>> {
+            vec![1, 2].into_iter().enumerate()
+        }
+    }
+    let dummy = Dummy2;
+    for (_, x) in dummy.enumerate() {
+        println!("{x}");
+    }
+
+    let mut with_used_iterator = [1, 2, 3].into_iter().enumerate();
+    with_used_iterator.next();
+    for (_, x) in with_used_iterator {
+        println!("{x}");
+    }
+
+    struct Dummy3(std::vec::IntoIter<usize>);
+
+    impl Iterator for Dummy3 {
+        type Item = usize;
+
+        fn next(&mut self) -> Option<Self::Item> {
+            self.0.next()
+        }
+
+        fn size_hint(&self) -> (usize, Option<usize>) {
+            self.0.size_hint()
+        }
+    }
+
+    let dummy = Dummy3(vec![1, 2, 3].into_iter());
+    for (_, x) in dummy.enumerate() {
+        println!("{x}");
     }
 }

tests/ui/unused_enumerate_index.stderr

@@ -1,5 +1,5 @@
 error: you seem to use `.enumerate()` and immediately discard the index
-  --> $DIR/unused_enumerate_index.rs:7:19
+  --> $DIR/unused_enumerate_index.rs:8:19
    |
 LL |     for (_, x) in v.iter().enumerate() {
    |                   ^^^^^^^^^^^^^^^^^^^^
@@ -11,5 +11,16 @@ help: remove the `.enumerate()` call
 LL |     for x in v.iter() {
    |         ~    ~~~~~~~~
 
-error: aborting due to previous error
+error: you seem to use `.enumerate()` and immediately discard the index
+  --> $DIR/unused_enumerate_index.rs:55:19
+   |
+LL |     for (_, x) in dummy.enumerate() {
+   |                   ^^^^^^^^^^^^^^^^^
+   |
+help: remove the `.enumerate()` call
+   |
+LL |     for x in dummy {
+   |         ~    ~~~~~
+
+error: aborting due to 2 previous errors