diff --git a/CHANGELOG.md b/CHANGELOG.md index d74ec71a0e8b..a372f9ea8116 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -3802,6 +3802,8 @@ Released 2018-09-13 [`iter_not_returning_iterator`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_not_returning_iterator [`iter_nth`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_nth [`iter_nth_zero`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_nth_zero +[`iter_on_empty_collections`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_on_empty_collections +[`iter_on_single_items`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_on_single_items [`iter_overeager_cloned`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_overeager_cloned [`iter_skip_next`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_skip_next [`iter_with_drain`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_with_drain diff --git a/clippy_lints/src/dereference.rs b/clippy_lints/src/dereference.rs index 5d41c63928df..e0b94f7190af 100644 --- a/clippy_lints/src/dereference.rs +++ b/clippy_lints/src/dereference.rs @@ -760,7 +760,7 @@ fn walk_parents<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> (Position, & .and_then(|subs| subs.get(1..)) { Some(subs) => cx.tcx.mk_substs(subs.iter().copied()), - None => cx.tcx.mk_substs([].iter()), + None => cx.tcx.mk_substs(std::iter::empty::>()), } && let impl_ty = if cx.tcx.fn_sig(id).skip_binder().inputs()[0].is_ref() { // Trait methods taking `&self` sub_ty diff --git a/clippy_lints/src/derive.rs b/clippy_lints/src/derive.rs index a982990e4186..9ca443b7dff6 100644 --- a/clippy_lints/src/derive.rs +++ b/clippy_lints/src/derive.rs @@ -516,7 +516,10 @@ fn param_env_for_derived_eq(tcx: TyCtxt<'_>, did: DefId, eq_trait_id: DefId) -> tcx.mk_predicates(ty_predicates.iter().map(|&(p, _)| p).chain( params.iter().filter(|&&(_, needs_eq)| needs_eq).map(|&(param, _)| { tcx.mk_predicate(Binder::dummy(PredicateKind::Trait(TraitPredicate { - trait_ref: TraitRef::new(eq_trait_id, tcx.mk_substs([tcx.mk_param_from_def(param)].into_iter())), + trait_ref: TraitRef::new( + eq_trait_id, + tcx.mk_substs(std::iter::once(tcx.mk_param_from_def(param))), + ), constness: BoundConstness::NotConst, polarity: ImplPolarity::Positive, }))) diff --git a/clippy_lints/src/lib.register_lints.rs b/clippy_lints/src/lib.register_lints.rs index c540573b8022..665e3277cb57 100644 --- a/clippy_lints/src/lib.register_lints.rs +++ b/clippy_lints/src/lib.register_lints.rs @@ -315,6 +315,8 @@ store.register_lints(&[ methods::ITER_NEXT_SLICE, methods::ITER_NTH, methods::ITER_NTH_ZERO, + methods::ITER_ON_EMPTY_COLLECTIONS, + methods::ITER_ON_SINGLE_ITEMS, methods::ITER_OVEREAGER_CLONED, methods::ITER_SKIP_NEXT, methods::ITER_WITH_DRAIN, diff --git a/clippy_lints/src/lib.register_nursery.rs b/clippy_lints/src/lib.register_nursery.rs index 7d731d52dbbd..d65901926553 100644 --- a/clippy_lints/src/lib.register_nursery.rs +++ b/clippy_lints/src/lib.register_nursery.rs @@ -14,6 +14,8 @@ store.register_group(true, "clippy::nursery", Some("clippy_nursery"), vec![ LintId::of(index_refutable_slice::INDEX_REFUTABLE_SLICE), LintId::of(let_if_seq::USELESS_LET_IF_SEQ), LintId::of(matches::SIGNIFICANT_DROP_IN_SCRUTINEE), + LintId::of(methods::ITER_ON_EMPTY_COLLECTIONS), + LintId::of(methods::ITER_ON_SINGLE_ITEMS), LintId::of(methods::ITER_WITH_DRAIN), LintId::of(missing_const_for_fn::MISSING_CONST_FOR_FN), LintId::of(mutable_debug_assertion::DEBUG_ASSERT_WITH_MUT_CALL), diff --git a/clippy_lints/src/methods/iter_on_single_or_empty_collections.rs b/clippy_lints/src/methods/iter_on_single_or_empty_collections.rs new file mode 100644 index 000000000000..cea7b0d82ff3 --- /dev/null +++ b/clippy_lints/src/methods/iter_on_single_or_empty_collections.rs @@ -0,0 +1,107 @@ +use clippy_utils::diagnostics::span_lint_and_sugg; +use clippy_utils::source::snippet; +use clippy_utils::{get_expr_use_or_unification_node, is_lang_ctor, is_no_std_crate}; + +use rustc_errors::Applicability; +use rustc_hir::LangItem::{OptionNone, OptionSome}; +use rustc_hir::{Expr, ExprKind, Node}; +use rustc_lint::LateContext; + +use super::{ITER_ON_EMPTY_COLLECTIONS, ITER_ON_SINGLE_ITEMS}; + +enum IterType { + Iter, + IterMut, + IntoIter, +} + +impl IterType { + fn ref_prefix(&self) -> &'static str { + match self { + Self::Iter => "&", + Self::IterMut => "&mut ", + Self::IntoIter => "", + } + } +} + +pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, method_name: &str, recv: &Expr<'_>) { + let item = match &recv.kind { + ExprKind::Array(v) if v.len() <= 1 => v.first(), + ExprKind::Path(p) => { + if is_lang_ctor(cx, p, OptionNone) { + None + } else { + return; + } + }, + ExprKind::Call(f, some_args) if some_args.len() == 1 => { + if let ExprKind::Path(p) = &f.kind { + if is_lang_ctor(cx, p, OptionSome) { + Some(&some_args[0]) + } else { + return; + } + } else { + return; + } + }, + _ => return, + }; + let iter_type = match method_name { + "iter" => IterType::Iter, + "iter_mut" => IterType::IterMut, + "into_iter" => IterType::IntoIter, + _ => return, + }; + + let is_unified = match get_expr_use_or_unification_node(cx.tcx, expr) { + Some((Node::Expr(parent), child_id)) => match parent.kind { + ExprKind::If(e, _, _) | ExprKind::Match(e, _, _) if e.hir_id == child_id => false, + ExprKind::If(_, _, _) + | ExprKind::Match(_, _, _) + | ExprKind::Closure(_) + | ExprKind::Ret(_) + | ExprKind::Break(_, _) => true, + _ => false, + }, + Some((Node::Stmt(_) | Node::Local(_), _)) => false, + _ => true, + }; + + if is_unified { + return; + } + + if let Some(i) = item { + let sugg = format!( + "{}::iter::once({}{})", + if is_no_std_crate(cx) { "core" } else { "std" }, + iter_type.ref_prefix(), + snippet(cx, i.span, "...") + ); + span_lint_and_sugg( + cx, + ITER_ON_SINGLE_ITEMS, + expr.span, + &format!("`{method_name}` call on a collection with only one item"), + "try", + sugg, + Applicability::MaybeIncorrect, + ); + } else { + span_lint_and_sugg( + cx, + ITER_ON_EMPTY_COLLECTIONS, + expr.span, + &format!("`{method_name}` call on an empty collection"), + "try", + if is_no_std_crate(cx) { + "core::iter::empty()".to_string() + } else { + "std::iter::empty()".to_string() + }, + Applicability::MaybeIncorrect, + ); + } +} diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs index b8dba5ba165f..99aae5800ff7 100644 --- a/clippy_lints/src/methods/mod.rs +++ b/clippy_lints/src/methods/mod.rs @@ -33,6 +33,7 @@ mod iter_count; mod iter_next_slice; mod iter_nth; mod iter_nth_zero; +mod iter_on_single_or_empty_collections; mod iter_overeager_cloned; mod iter_skip_next; mod iter_with_drain; @@ -2304,6 +2305,69 @@ declare_clippy_lint! { more clearly with `if .. else ..`" } +declare_clippy_lint! { + /// ### What it does + /// + /// Checks for calls to `iter`, `iter_mut` or `into_iter` on collections containing a single item + /// + /// ### Why is this bad? + /// + /// It is simpler to use the once function from the standard library: + /// + /// ### Example + /// + /// ```rust + /// let a = [123].iter(); + /// let b = Some(123).into_iter(); + /// ``` + /// Use instead: + /// ```rust + /// use std::iter; + /// let a = iter::once(&123); + /// let b = iter::once(123); + /// ``` + /// + /// ### Known problems + /// + /// The type of the resulting iterator might become incompatible with its usage + #[clippy::version = "1.64.0"] + pub ITER_ON_SINGLE_ITEMS, + nursery, + "Iterator for array of length 1" +} + +declare_clippy_lint! { + /// ### What it does + /// + /// Checks for calls to `iter`, `iter_mut` or `into_iter` on empty collections + /// + /// ### Why is this bad? + /// + /// It is simpler to use the empty function from the standard library: + /// + /// ### Example + /// + /// ```rust + /// use std::{slice, option}; + /// let a: slice::Iter = [].iter(); + /// let f: option::IntoIter = None.into_iter(); + /// ``` + /// Use instead: + /// ```rust + /// use std::iter; + /// let a: iter::Empty = iter::empty(); + /// let b: iter::Empty = iter::empty(); + /// ``` + /// + /// ### Known problems + /// + /// The type of the resulting iterator might become incompatible with its usage + #[clippy::version = "1.64.0"] + pub ITER_ON_EMPTY_COLLECTIONS, + nursery, + "Iterator for empty array" +} + pub struct Methods { avoid_breaking_exported_api: bool, msrv: Option, @@ -2406,6 +2470,8 @@ impl_lint_pass!(Methods => [ NEEDLESS_OPTION_TAKE, NO_EFFECT_REPLACE, OBFUSCATED_IF_ELSE, + ITER_ON_SINGLE_ITEMS, + ITER_ON_EMPTY_COLLECTIONS ]); /// Extracts a method call name, args, and `Span` of the method name. @@ -2708,6 +2774,9 @@ impl Methods { ("is_digit", [radix]) => is_digit_ascii_radix::check(cx, expr, recv, radix, self.msrv), ("is_none", []) => check_is_some_is_none(cx, expr, recv, false), ("is_some", []) => check_is_some_is_none(cx, expr, recv, true), + ("iter" | "iter_mut" | "into_iter", []) => { + iter_on_single_or_empty_collections::check(cx, expr, name, recv); + }, ("join", [join_arg]) => { if let Some(("collect", _, span)) = method_call(recv) { unnecessary_join::check(cx, expr, recv, join_arg, span); diff --git a/clippy_lints/src/redundant_slicing.rs b/clippy_lints/src/redundant_slicing.rs index db6c97f3739c..8693ca9af830 100644 --- a/clippy_lints/src/redundant_slicing.rs +++ b/clippy_lints/src/redundant_slicing.rs @@ -11,6 +11,8 @@ use rustc_middle::ty::adjustment::{Adjust, AutoBorrow, AutoBorrowMutability}; use rustc_middle::ty::subst::GenericArg; use rustc_session::{declare_lint_pass, declare_tool_lint}; +use std::iter; + declare_clippy_lint! { /// ### What it does /// Checks for redundant slicing expressions which use the full range, and @@ -134,7 +136,7 @@ impl<'tcx> LateLintPass<'tcx> for RedundantSlicing { } else if let Some(target_id) = cx.tcx.lang_items().deref_target() { if let Ok(deref_ty) = cx.tcx.try_normalize_erasing_regions( cx.param_env, - cx.tcx.mk_projection(target_id, cx.tcx.mk_substs([GenericArg::from(indexed_ty)].into_iter())), + cx.tcx.mk_projection(target_id, cx.tcx.mk_substs(iter::once(GenericArg::from(indexed_ty)))), ) { if deref_ty == expr_ty { let snip = snippet_with_context(cx, indexed.span, ctxt, "..", &mut app).0; diff --git a/clippy_lints/src/utils/conf.rs b/clippy_lints/src/utils/conf.rs index 3faae9ac0d2b..47b72f4783e3 100644 --- a/clippy_lints/src/utils/conf.rs +++ b/clippy_lints/src/utils/conf.rs @@ -350,7 +350,7 @@ define_Conf! { /// Lint: DISALLOWED_SCRIPT_IDENTS. /// /// The list of unicode scripts allowed to be used in the scope. - (allowed_scripts: Vec = ["Latin"].iter().map(ToString::to_string).collect()), + (allowed_scripts: Vec = vec!["Latin".to_string()]), /// Lint: NON_SEND_FIELDS_IN_SEND_TY. /// /// Whether to apply the raw pointer heuristic to determine if a type is `Send`. diff --git a/clippy_lints/src/utils/internal_lints/metadata_collector.rs b/clippy_lints/src/utils/internal_lints/metadata_collector.rs index 92cf42c7ad43..b1148bccc2a2 100644 --- a/clippy_lints/src/utils/internal_lints/metadata_collector.rs +++ b/clippy_lints/src/utils/internal_lints/metadata_collector.rs @@ -797,7 +797,7 @@ fn get_lint_group_and_level_or_lint( let result = cx.lint_store.check_lint_name( lint_name, Some(sym::clippy), - &[Ident::with_dummy_span(sym::clippy)].into_iter().collect(), + &std::iter::once(Ident::with_dummy_span(sym::clippy)).collect(), ); if let CheckLintNameResult::Tool(Ok(lint_lst)) = result { if let Some(group) = get_lint_group(cx, lint_lst[0]) { diff --git a/tests/ui/iter_on_empty_collections.fixed b/tests/ui/iter_on_empty_collections.fixed new file mode 100644 index 000000000000..bd9b07aefbfb --- /dev/null +++ b/tests/ui/iter_on_empty_collections.fixed @@ -0,0 +1,63 @@ +// run-rustfix +#![warn(clippy::iter_on_empty_collections)] +#![allow(clippy::iter_next_slice, clippy::redundant_clone)] + +fn array() { + assert_eq!(std::iter::empty().next(), Option::::None); + assert_eq!(std::iter::empty().next(), Option::<&mut i32>::None); + assert_eq!(std::iter::empty().next(), Option::<&i32>::None); + assert_eq!(std::iter::empty().next(), Option::::None); + assert_eq!(std::iter::empty().next(), Option::<&mut i32>::None); + assert_eq!(std::iter::empty().next(), Option::<&i32>::None); + + // Don't trigger on non-iter methods + let _: Option = None.clone(); + let _: [String; 0] = [].clone(); + + // Don't trigger on match or if branches + let _ = match 123 { + 123 => [].iter(), + _ => ["test"].iter(), + }; + + let _ = if false { ["test"].iter() } else { [].iter() }; +} + +macro_rules! in_macros { + () => { + assert_eq!([].into_iter().next(), Option::::None); + assert_eq!([].iter_mut().next(), Option::<&mut i32>::None); + assert_eq!([].iter().next(), Option::<&i32>::None); + assert_eq!(None.into_iter().next(), Option::::None); + assert_eq!(None.iter_mut().next(), Option::<&mut i32>::None); + assert_eq!(None.iter().next(), Option::<&i32>::None); + }; +} + +// Don't trigger on a `None` that isn't std's option +mod custom_option { + #[allow(unused)] + enum CustomOption { + Some(i32), + None, + } + + impl CustomOption { + fn iter(&self) {} + fn iter_mut(&mut self) {} + fn into_iter(self) {} + } + use CustomOption::*; + + pub fn custom_option() { + None.iter(); + None.iter_mut(); + None.into_iter(); + } +} + +fn main() { + array(); + custom_option::custom_option(); + in_macros!(); +} diff --git a/tests/ui/iter_on_empty_collections.rs b/tests/ui/iter_on_empty_collections.rs new file mode 100644 index 000000000000..e15ba94bd465 --- /dev/null +++ b/tests/ui/iter_on_empty_collections.rs @@ -0,0 +1,63 @@ +// run-rustfix +#![warn(clippy::iter_on_empty_collections)] +#![allow(clippy::iter_next_slice, clippy::redundant_clone)] + +fn array() { + assert_eq!([].into_iter().next(), Option::::None); + assert_eq!([].iter_mut().next(), Option::<&mut i32>::None); + assert_eq!([].iter().next(), Option::<&i32>::None); + assert_eq!(None.into_iter().next(), Option::::None); + assert_eq!(None.iter_mut().next(), Option::<&mut i32>::None); + assert_eq!(None.iter().next(), Option::<&i32>::None); + + // Don't trigger on non-iter methods + let _: Option = None.clone(); + let _: [String; 0] = [].clone(); + + // Don't trigger on match or if branches + let _ = match 123 { + 123 => [].iter(), + _ => ["test"].iter(), + }; + + let _ = if false { ["test"].iter() } else { [].iter() }; +} + +macro_rules! in_macros { + () => { + assert_eq!([].into_iter().next(), Option::::None); + assert_eq!([].iter_mut().next(), Option::<&mut i32>::None); + assert_eq!([].iter().next(), Option::<&i32>::None); + assert_eq!(None.into_iter().next(), Option::::None); + assert_eq!(None.iter_mut().next(), Option::<&mut i32>::None); + assert_eq!(None.iter().next(), Option::<&i32>::None); + }; +} + +// Don't trigger on a `None` that isn't std's option +mod custom_option { + #[allow(unused)] + enum CustomOption { + Some(i32), + None, + } + + impl CustomOption { + fn iter(&self) {} + fn iter_mut(&mut self) {} + fn into_iter(self) {} + } + use CustomOption::*; + + pub fn custom_option() { + None.iter(); + None.iter_mut(); + None.into_iter(); + } +} + +fn main() { + array(); + custom_option::custom_option(); + in_macros!(); +} diff --git a/tests/ui/iter_on_empty_collections.stderr b/tests/ui/iter_on_empty_collections.stderr new file mode 100644 index 000000000000..cbd611769569 --- /dev/null +++ b/tests/ui/iter_on_empty_collections.stderr @@ -0,0 +1,40 @@ +error: `into_iter` call on an empty collection + --> $DIR/iter_on_empty_collections.rs:6:16 + | +LL | assert_eq!([].into_iter().next(), Option::::None); + | ^^^^^^^^^^^^^^ help: try: `std::iter::empty()` + | + = note: `-D clippy::iter-on-empty-collections` implied by `-D warnings` + +error: `iter_mut` call on an empty collection + --> $DIR/iter_on_empty_collections.rs:7:16 + | +LL | assert_eq!([].iter_mut().next(), Option::<&mut i32>::None); + | ^^^^^^^^^^^^^ help: try: `std::iter::empty()` + +error: `iter` call on an empty collection + --> $DIR/iter_on_empty_collections.rs:8:16 + | +LL | assert_eq!([].iter().next(), Option::<&i32>::None); + | ^^^^^^^^^ help: try: `std::iter::empty()` + +error: `into_iter` call on an empty collection + --> $DIR/iter_on_empty_collections.rs:9:16 + | +LL | assert_eq!(None.into_iter().next(), Option::::None); + | ^^^^^^^^^^^^^^^^ help: try: `std::iter::empty()` + +error: `iter_mut` call on an empty collection + --> $DIR/iter_on_empty_collections.rs:10:16 + | +LL | assert_eq!(None.iter_mut().next(), Option::<&mut i32>::None); + | ^^^^^^^^^^^^^^^ help: try: `std::iter::empty()` + +error: `iter` call on an empty collection + --> $DIR/iter_on_empty_collections.rs:11:16 + | +LL | assert_eq!(None.iter().next(), Option::<&i32>::None); + | ^^^^^^^^^^^ help: try: `std::iter::empty()` + +error: aborting due to 6 previous errors + diff --git a/tests/ui/iter_on_single_items.fixed b/tests/ui/iter_on_single_items.fixed new file mode 100644 index 000000000000..1fa4b03641bc --- /dev/null +++ b/tests/ui/iter_on_single_items.fixed @@ -0,0 +1,63 @@ +// run-rustfix +#![warn(clippy::iter_on_single_items)] +#![allow(clippy::iter_next_slice, clippy::redundant_clone)] + +fn array() { + assert_eq!(std::iter::once(123).next(), Some(123)); + assert_eq!(std::iter::once(&mut 123).next(), Some(&mut 123)); + assert_eq!(std::iter::once(&123).next(), Some(&123)); + assert_eq!(std::iter::once(123).next(), Some(123)); + assert_eq!(std::iter::once(&mut 123).next(), Some(&mut 123)); + assert_eq!(std::iter::once(&123).next(), Some(&123)); + + // Don't trigger on non-iter methods + let _: Option = Some("test".to_string()).clone(); + let _: [String; 1] = ["test".to_string()].clone(); + + // Don't trigger on match or if branches + let _ = match 123 { + 123 => [].iter(), + _ => ["test"].iter(), + }; + + let _ = if false { ["test"].iter() } else { [].iter() }; +} + +macro_rules! in_macros { + () => { + assert_eq!([123].into_iter().next(), Some(123)); + assert_eq!([123].iter_mut().next(), Some(&mut 123)); + assert_eq!([123].iter().next(), Some(&123)); + assert_eq!(Some(123).into_iter().next(), Some(123)); + assert_eq!(Some(123).iter_mut().next(), Some(&mut 123)); + assert_eq!(Some(123).iter().next(), Some(&123)); + }; +} + +// Don't trigger on a `Some` that isn't std's option +mod custom_option { + #[allow(unused)] + enum CustomOption { + Some(i32), + None, + } + + impl CustomOption { + fn iter(&self) {} + fn iter_mut(&mut self) {} + fn into_iter(self) {} + } + use CustomOption::*; + + pub fn custom_option() { + Some(3).iter(); + Some(3).iter_mut(); + Some(3).into_iter(); + } +} + +fn main() { + array(); + custom_option::custom_option(); + in_macros!(); +} diff --git a/tests/ui/iter_on_single_items.rs b/tests/ui/iter_on_single_items.rs new file mode 100644 index 000000000000..ea96d8066c56 --- /dev/null +++ b/tests/ui/iter_on_single_items.rs @@ -0,0 +1,63 @@ +// run-rustfix +#![warn(clippy::iter_on_single_items)] +#![allow(clippy::iter_next_slice, clippy::redundant_clone)] + +fn array() { + assert_eq!([123].into_iter().next(), Some(123)); + assert_eq!([123].iter_mut().next(), Some(&mut 123)); + assert_eq!([123].iter().next(), Some(&123)); + assert_eq!(Some(123).into_iter().next(), Some(123)); + assert_eq!(Some(123).iter_mut().next(), Some(&mut 123)); + assert_eq!(Some(123).iter().next(), Some(&123)); + + // Don't trigger on non-iter methods + let _: Option = Some("test".to_string()).clone(); + let _: [String; 1] = ["test".to_string()].clone(); + + // Don't trigger on match or if branches + let _ = match 123 { + 123 => [].iter(), + _ => ["test"].iter(), + }; + + let _ = if false { ["test"].iter() } else { [].iter() }; +} + +macro_rules! in_macros { + () => { + assert_eq!([123].into_iter().next(), Some(123)); + assert_eq!([123].iter_mut().next(), Some(&mut 123)); + assert_eq!([123].iter().next(), Some(&123)); + assert_eq!(Some(123).into_iter().next(), Some(123)); + assert_eq!(Some(123).iter_mut().next(), Some(&mut 123)); + assert_eq!(Some(123).iter().next(), Some(&123)); + }; +} + +// Don't trigger on a `Some` that isn't std's option +mod custom_option { + #[allow(unused)] + enum CustomOption { + Some(i32), + None, + } + + impl CustomOption { + fn iter(&self) {} + fn iter_mut(&mut self) {} + fn into_iter(self) {} + } + use CustomOption::*; + + pub fn custom_option() { + Some(3).iter(); + Some(3).iter_mut(); + Some(3).into_iter(); + } +} + +fn main() { + array(); + custom_option::custom_option(); + in_macros!(); +} diff --git a/tests/ui/iter_on_single_items.stderr b/tests/ui/iter_on_single_items.stderr new file mode 100644 index 000000000000..d6c547116363 --- /dev/null +++ b/tests/ui/iter_on_single_items.stderr @@ -0,0 +1,40 @@ +error: `into_iter` call on a collection with only one item + --> $DIR/iter_on_single_items.rs:6:16 + | +LL | assert_eq!([123].into_iter().next(), Some(123)); + | ^^^^^^^^^^^^^^^^^ help: try: `std::iter::once(123)` + | + = note: `-D clippy::iter-on-single-items` implied by `-D warnings` + +error: `iter_mut` call on a collection with only one item + --> $DIR/iter_on_single_items.rs:7:16 + | +LL | assert_eq!([123].iter_mut().next(), Some(&mut 123)); + | ^^^^^^^^^^^^^^^^ help: try: `std::iter::once(&mut 123)` + +error: `iter` call on a collection with only one item + --> $DIR/iter_on_single_items.rs:8:16 + | +LL | assert_eq!([123].iter().next(), Some(&123)); + | ^^^^^^^^^^^^ help: try: `std::iter::once(&123)` + +error: `into_iter` call on a collection with only one item + --> $DIR/iter_on_single_items.rs:9:16 + | +LL | assert_eq!(Some(123).into_iter().next(), Some(123)); + | ^^^^^^^^^^^^^^^^^^^^^ help: try: `std::iter::once(123)` + +error: `iter_mut` call on a collection with only one item + --> $DIR/iter_on_single_items.rs:10:16 + | +LL | assert_eq!(Some(123).iter_mut().next(), Some(&mut 123)); + | ^^^^^^^^^^^^^^^^^^^^ help: try: `std::iter::once(&mut 123)` + +error: `iter` call on a collection with only one item + --> $DIR/iter_on_single_items.rs:11:16 + | +LL | assert_eq!(Some(123).iter().next(), Some(&123)); + | ^^^^^^^^^^^^^^^^ help: try: `std::iter::once(&123)` + +error: aborting due to 6 previous errors +