Do lint only if the values is cloned, but not copied

Author: pmnoxx

clippy_lints/src/methods/iter_overeager_cloned.rs

@@ -1,9 +1,10 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::snippet;
-use clippy_utils::ty::implements_trait;
+use clippy_utils::ty::{get_iterator_item_ty, implements_trait, is_copy};
 use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_lint::LateContext;
+use rustc_middle::ty;
 use rustc_span::sym;
 
 use super::ITER_OVEREAGER_CLONED;
@@ -17,6 +18,17 @@ pub(super) fn check<'tcx>(
     name: &str,
     map_arg: &[hir::Expr<'_>],
 ) {
+    let recv_ty = cx.typeck_results().expr_ty_adjusted(recv);
+    let inner_ty = match get_iterator_item_ty(cx, recv_ty) {
+        Some(ty) => ty,
+        _ => return,
+    };
+
+    match inner_ty.kind() {
+        ty::Ref(_, ty, _) if is_copy(cx, ty) => return,
+        _ => {},
+    };
+
     // lint if callee is an Iterator
     let recv_impls_iterator = cx.tcx.get_diagnostic_item(sym::Iterator).map_or(false, |id| {
         implements_trait(cx, cx.typeck_results().expr_ty(recv), id, &[])

tests/ui/iter_overeager_cloned.fixed

@@ -41,5 +41,5 @@ fn main() {
     let _ = vec.iter().cloned().any(|x| x.len() == 1);
 
     // Should probably stay as it is.
-    let _ = [0, 1, 2, 3, 4].iter().take(10).cloned();
+    let _ = [0, 1, 2, 3, 4].iter().cloned().take(10);
 }

tests/ui/iter_overeager_cloned.stderr

@@ -54,11 +54,5 @@ LL ~     let _ = [Some(Some("str".to_string())), Some(Some("str".to_string()))]
 LL ~         .iter().flatten().cloned();
    |
 
-error: called `cloned().take(...)` on an `Iterator`. It may be more efficient to call`.take(...).cloned()` instead
-  --> $DIR/iter_overeager_cloned.rs:46:13
-   |
-LL |     let _ = [0, 1, 2, 3, 4].iter().cloned().take(10);
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `[0, 1, 2, 3, 4].iter().take(10).cloned()`
-
-error: aborting due to 8 previous errors
+error: aborting due to 7 previous errors