--- /dev/null
+use crate::utils::{is_copy, match_path, paths, span_lint_and_note};
+use rustc_hir::{Impl, Item, ItemKind};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for types that implement `Copy` as well as
+ /// `Iterator`.
+ ///
+ /// **Why is this bad?** Implicit copies can be confusing when working with
+ /// iterator combinators.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust,ignore
+ /// #[derive(Copy, Clone)]
+ /// struct Countdown(u8);
+ ///
+ /// impl Iterator for Countdown {
+ /// // ...
+ /// }
+ ///
+ /// let a: Vec<_> = my_iterator.take(1).collect();
+ /// let b: Vec<_> = my_iterator.collect();
+ /// ```
+ pub COPY_ITERATOR,
+ pedantic,
+ "implementing `Iterator` on a `Copy` type"
+}
+
+declare_lint_pass!(CopyIterator => [COPY_ITERATOR]);
+
+impl<'tcx> LateLintPass<'tcx> for CopyIterator {
+ fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
+ if let ItemKind::Impl(Impl {
+ of_trait: Some(ref trait_ref),
+ ..
+ }) = item.kind
+ {
+ let ty = cx.tcx.type_of(item.def_id);
+
+ if is_copy(cx, ty) && match_path(&trait_ref.path, &paths::ITERATOR) {
+ span_lint_and_note(
+ cx,
+ COPY_ITERATOR,
+ item.span,
+ "you are implementing `Iterator` on a `Copy` type",
+ None,
+ "consider implementing `IntoIterator` instead",
+ );
+ }
+ }
+ }
+}