diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7885bdfb12c..483365b5e91 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2148,6 +2148,7 @@ Released 2018-09-13
[`clone_double_ref`]: https://rust-lang.github.io/rust-clippy/master/index.html#clone_double_ref
[`clone_on_copy`]: https://rust-lang.github.io/rust-clippy/master/index.html#clone_on_copy
[`clone_on_ref_ptr`]: https://rust-lang.github.io/rust-clippy/master/index.html#clone_on_ref_ptr
+[`cloned_instead_of_copied`]: https://rust-lang.github.io/rust-clippy/master/index.html#cloned_instead_of_copied
[`cmp_nan`]: https://rust-lang.github.io/rust-clippy/master/index.html#cmp_nan
[`cmp_null`]: https://rust-lang.github.io/rust-clippy/master/index.html#cmp_null
[`cmp_owned`]: https://rust-lang.github.io/rust-clippy/master/index.html#cmp_owned
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index 93631c5669b..0f48799d339 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -759,6 +759,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
methods::BYTES_NTH,
methods::CHARS_LAST_CMP,
methods::CHARS_NEXT_CMP,
+ methods::CLONED_INSTEAD_OF_COPIED,
methods::CLONE_DOUBLE_REF,
methods::CLONE_ON_COPY,
methods::CLONE_ON_REF_PTR,
@@ -1380,6 +1381,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(matches::MATCH_WILDCARD_FOR_SINGLE_VARIANTS),
LintId::of(matches::MATCH_WILD_ERR_ARM),
LintId::of(matches::SINGLE_MATCH_ELSE),
+ LintId::of(methods::CLONED_INSTEAD_OF_COPIED),
LintId::of(methods::FILTER_MAP_NEXT),
LintId::of(methods::IMPLICIT_CLONE),
LintId::of(methods::INEFFICIENT_TO_STRING),
diff --git a/clippy_lints/src/methods/cloned_instead_of_copied.rs b/clippy_lints/src/methods/cloned_instead_of_copied.rs
new file mode 100644
index 00000000000..ba97ab3900c
--- /dev/null
+++ b/clippy_lints/src/methods/cloned_instead_of_copied.rs
@@ -0,0 +1,38 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::is_trait_method;
+use clippy_utils::ty::{get_iterator_item_ty, is_copy};
+use rustc_errors::Applicability;
+use rustc_hir::Expr;
+use rustc_lint::LateContext;
+use rustc_middle::ty;
+use rustc_span::{sym, Span};
+
+use super::CLONED_INSTEAD_OF_COPIED;
+
+pub fn check(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, span: Span) {
+ let recv_ty = cx.typeck_results().expr_ty_adjusted(recv);
+ let inner_ty = match recv_ty.kind() {
+ // `Option<T>` -> `T`
+ ty::Adt(adt, subst) if cx.tcx.is_diagnostic_item(sym::option_type, adt.did) => subst.type_at(0),
+ _ if is_trait_method(cx, expr, sym::Iterator) => match get_iterator_item_ty(cx, recv_ty) {
+ // <T as Iterator>::Item
+ Some(ty) => ty,
+ _ => return,
+ },
+ _ => return,
+ };
+ match inner_ty.kind() {
+ // &T where T: Copy
+ ty::Ref(_, ty, _) if is_copy(cx, ty) => {},
+ _ => return,
+ };
+ span_lint_and_sugg(
+ cx,
+ CLONED_INSTEAD_OF_COPIED,
+ span,
+ "used `cloned` where `copied` could be used instead",
+ "try",
+ "copied".into(),
+ Applicability::MachineApplicable,
+ )
+}
diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs
index 6c21ff0f6c2..49a9af2a465 100644
--- a/clippy_lints/src/methods/mod.rs
+++ b/clippy_lints/src/methods/mod.rs
@@ -8,6 +8,7 @@ mod chars_next_cmp;
mod chars_next_cmp_with_unwrap;
mod clone_on_copy;
mod clone_on_ref_ptr;
+mod cloned_instead_of_copied;
mod expect_fun_call;
mod expect_used;
mod filetype_is_file;
@@ -73,6 +74,29 @@ use rustc_span::symbol::SymbolStr;
use rustc_span::{sym, Span};
use rustc_typeck::hir_ty_to_ty;
+declare_clippy_lint! {
+ /// **What it does:** Checks for usages of `cloned()` on an `Iterator` or `Option` where
+ /// `copied()` could be used instead.
+ ///
+ /// **Why is this bad?** `copied()` is better because it guarantees that the type being cloned
+ /// implements `Copy`.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ ///
+ /// ```rust
+ /// [1, 2, 3].iter().cloned();
+ /// ```
+ /// Use instead:
+ /// ```rust
+ /// [1, 2, 3].iter().copied();
+ /// ```
+ pub CLONED_INSTEAD_OF_COPIED,
+ pedantic,
+ "used `cloned` where `copied` could be used instead"
+}
+
declare_clippy_lint! {
/// **What it does:** Checks for `.unwrap()` calls on `Option`s and on `Result`s.
///
@@ -1638,6 +1662,7 @@ impl_lint_pass!(Methods => [
CLONE_ON_COPY,
CLONE_ON_REF_PTR,
CLONE_DOUBLE_REF,
+ CLONED_INSTEAD_OF_COPIED,
INEFFICIENT_TO_STRING,
NEW_RET_NO_SELF,
SINGLE_CHAR_PATTERN,
@@ -1909,6 +1934,7 @@ fn check_methods<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, msrv: Optio
("as_mut", []) => useless_asref::check(cx, expr, "as_mut", recv),
("as_ref", []) => useless_asref::check(cx, expr, "as_ref", recv),
("assume_init", []) => uninit_assumed_init::check(cx, expr, recv),
+ ("cloned", []) => cloned_instead_of_copied::check(cx, expr, recv, span),
("collect", []) => match method_call!(recv) {
Some(("cloned", [recv2], _)) => iter_cloned_collect::check(cx, expr, recv2),
Some(("map", [m_recv, m_arg], _)) => {
diff --git a/clippy_utils/src/ty.rs b/clippy_utils/src/ty.rs
index 807cfbc4c7f..64a80f2554f 100644
--- a/clippy_utils/src/ty.rs
+++ b/clippy_utils/src/ty.rs
@@ -13,7 +13,7 @@ use rustc_lint::LateContext;
use rustc_middle::ty::subst::{GenericArg, GenericArgKind};
use rustc_middle::ty::{self, AdtDef, IntTy, Ty, TypeFoldable, UintTy};
use rustc_span::sym;
-use rustc_span::symbol::Symbol;
+use rustc_span::symbol::{Ident, Symbol};
use rustc_span::DUMMY_SP;
use rustc_trait_selection::traits::query::normalize::AtExt;
@@ -52,6 +52,25 @@ pub fn contains_adt_constructor(ty: Ty<'_>, adt: &AdtDef) -> bool {
})
}
+/// Resolves `<T as Iterator>::Item` for `T`
+/// Do not invoke without first verifying that the type implements `Iterator`
+pub fn get_iterator_item_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
+ cx.tcx
+ .get_diagnostic_item(sym::Iterator)
+ .and_then(|iter_did| {
+ cx.tcx.associated_items(iter_did).find_by_name_and_kind(
+ cx.tcx,
+ Ident::from_str("Item"),
+ ty::AssocKind::Type,
+ iter_did,
+ )
+ })
+ .map(|assoc| {
+ let proj = cx.tcx.mk_projection(assoc.def_id, cx.tcx.mk_substs_trait(ty, &[]));
+ cx.tcx.normalize_erasing_regions(cx.param_env, proj)
+ })
+}
+
/// Returns true if ty has `iter` or `iter_mut` methods
pub fn has_iter_method(cx: &LateContext<'_>, probably_ref_ty: Ty<'_>) -> Option<Symbol> {
// FIXME: instead of this hard-coded list, we should check if `<adt>::iter`
diff --git a/tests/ui/cloned_instead_of_copied.fixed b/tests/ui/cloned_instead_of_copied.fixed
new file mode 100644
index 00000000000..4eb999e18e6
--- /dev/null
+++ b/tests/ui/cloned_instead_of_copied.fixed
@@ -0,0 +1,15 @@
+// run-rustfix
+#![warn(clippy::cloned_instead_of_copied)]
+
+fn main() {
+ // yay
+ let _ = [1].iter().copied();
+ let _ = vec!["hi"].iter().copied();
+ let _ = Some(&1).copied();
+ let _ = Box::new([1].iter()).copied();
+ let _ = Box::new(Some(&1)).copied();
+
+ // nay
+ let _ = [String::new()].iter().cloned();
+ let _ = Some(&String::new()).cloned();
+}
diff --git a/tests/ui/cloned_instead_of_copied.rs b/tests/ui/cloned_instead_of_copied.rs
new file mode 100644
index 00000000000..894496c0ebb
--- /dev/null
+++ b/tests/ui/cloned_instead_of_copied.rs
@@ -0,0 +1,15 @@
+// run-rustfix
+#![warn(clippy::cloned_instead_of_copied)]
+
+fn main() {
+ // yay
+ let _ = [1].iter().cloned();
+ let _ = vec!["hi"].iter().cloned();
+ let _ = Some(&1).cloned();
+ let _ = Box::new([1].iter()).cloned();
+ let _ = Box::new(Some(&1)).cloned();
+
+ // nay
+ let _ = [String::new()].iter().cloned();
+ let _ = Some(&String::new()).cloned();
+}
diff --git a/tests/ui/cloned_instead_of_copied.stderr b/tests/ui/cloned_instead_of_copied.stderr
new file mode 100644
index 00000000000..e0707d32146
--- /dev/null
+++ b/tests/ui/cloned_instead_of_copied.stderr
@@ -0,0 +1,34 @@
+error: used `cloned` where `copied` could be used instead
+ --> $DIR/cloned_instead_of_copied.rs:6:24
+ |
+LL | let _ = [1].iter().cloned();
+ | ^^^^^^ help: try: `copied`
+ |
+ = note: `-D clippy::cloned-instead-of-copied` implied by `-D warnings`
+
+error: used `cloned` where `copied` could be used instead
+ --> $DIR/cloned_instead_of_copied.rs:7:31
+ |
+LL | let _ = vec!["hi"].iter().cloned();
+ | ^^^^^^ help: try: `copied`
+
+error: used `cloned` where `copied` could be used instead
+ --> $DIR/cloned_instead_of_copied.rs:8:22
+ |
+LL | let _ = Some(&1).cloned();
+ | ^^^^^^ help: try: `copied`
+
+error: used `cloned` where `copied` could be used instead
+ --> $DIR/cloned_instead_of_copied.rs:9:34
+ |
+LL | let _ = Box::new([1].iter()).cloned();
+ | ^^^^^^ help: try: `copied`
+
+error: used `cloned` where `copied` could be used instead
+ --> $DIR/cloned_instead_of_copied.rs:10:32
+ |
+LL | let _ = Box::new(Some(&1)).cloned();
+ | ^^^^^^ help: try: `copied`
+
+error: aborting due to 5 previous errors
+