diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2b89170073b..b9e67d361c0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2754,6 +2754,7 @@ Released 2018-09-13
[`manual_ok_or`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_ok_or
[`manual_range_contains`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_range_contains
[`manual_saturating_arithmetic`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_saturating_arithmetic
+[`manual_split_once`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_split_once
[`manual_str_repeat`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_str_repeat
[`manual_strip`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_strip
[`manual_swap`]: https://rust-lang.github.io/rust-clippy/master/index.html#manual_swap
diff --git a/clippy_lints/src/bytecount.rs b/clippy_lints/src/bytecount.rs
index c444984bc13..a07cd5e5f4e 100644
--- a/clippy_lints/src/bytecount.rs
+++ b/clippy_lints/src/bytecount.rs
@@ -1,7 +1,7 @@
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet_with_applicability;
use clippy_utils::ty::match_type;
-use clippy_utils::visitors::LocalUsedVisitor;
+use clippy_utils::visitors::is_local_used;
use clippy_utils::{path_to_local_id, paths, peel_ref_operators, remove_blocks, strip_pat_refs};
use if_chain::if_chain;
use rustc_errors::Applicability;
@@ -65,7 +65,7 @@ impl<'tcx> LateLintPass<'tcx> for ByteCount {
return;
};
if ty::Uint(UintTy::U8) == *cx.typeck_results().expr_ty(needle).peel_refs().kind();
- if !LocalUsedVisitor::new(cx, arg_id).check_expr(needle);
+ if !is_local_used(cx, needle, arg_id);
then {
let haystack = if let ExprKind::MethodCall(path, _, args, _) =
filter_recv.kind {
diff --git a/clippy_lints/src/collapsible_match.rs b/clippy_lints/src/collapsible_match.rs
index a403a9846ba..bd8f9cc7343 100644
--- a/clippy_lints/src/collapsible_match.rs
+++ b/clippy_lints/src/collapsible_match.rs
@@ -1,5 +1,5 @@
use clippy_utils::diagnostics::span_lint_and_then;
-use clippy_utils::visitors::LocalUsedVisitor;
+use clippy_utils::visitors::is_local_used;
use clippy_utils::{is_lang_ctor, path_to_local, peel_ref_operators, SpanlessEq};
use if_chain::if_chain;
use rustc_hir::LangItem::OptionNone;
@@ -83,13 +83,12 @@ fn check_arm<'tcx>(arm: &Arm<'tcx>, wild_outer_arm: &Arm<'tcx>, cx: &LateContext
// the "wild-like" branches must be equal
if SpanlessEq::new(cx).eq_expr(wild_inner_arm.body, wild_outer_arm.body);
// the binding must not be used in the if guard
- let mut used_visitor = LocalUsedVisitor::new(cx, binding_id);
if match arm.guard {
None => true,
- Some(Guard::If(expr) | Guard::IfLet(_, expr)) => !used_visitor.check_expr(expr),
+ Some(Guard::If(expr) | Guard::IfLet(_, expr)) => !is_local_used(cx, expr, binding_id),
};
// ...or anywhere in the inner match
- if !arms_inner.iter().any(|arm| used_visitor.check_arm(arm));
+ if !arms_inner.iter().any(|arm| is_local_used(cx, arm, binding_id));
then {
span_lint_and_then(
cx,
diff --git a/clippy_lints/src/let_if_seq.rs b/clippy_lints/src/let_if_seq.rs
index 13f0d43cf8d..834440e912d 100644
--- a/clippy_lints/src/let_if_seq.rs
+++ b/clippy_lints/src/let_if_seq.rs
@@ -1,6 +1,6 @@
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::source::snippet;
-use clippy_utils::{path_to_local_id, visitors::LocalUsedVisitor};
+use clippy_utils::{path_to_local_id, visitors::is_local_used};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir as hir;
@@ -65,11 +65,10 @@ impl<'tcx> LateLintPass<'tcx> for LetIfSeq {
if let hir::PatKind::Binding(mode, canonical_id, ident, None) = local.pat.kind;
if let hir::StmtKind::Expr(if_) = expr.kind;
if let hir::ExprKind::If(cond, then, ref else_) = if_.kind;
- let mut used_visitor = LocalUsedVisitor::new(cx, canonical_id);
- if !used_visitor.check_expr(cond);
+ if !is_local_used(cx, cond, canonical_id);
if let hir::ExprKind::Block(then, _) = then.kind;
if let Some(value) = check_assign(cx, canonical_id, &*then);
- if !used_visitor.check_expr(value);
+ if !is_local_used(cx, value, canonical_id);
then {
let span = stmt.span.to(if_.span);
@@ -148,15 +147,13 @@ fn check_assign<'tcx>(
if let hir::ExprKind::Assign(var, value, _) = expr.kind;
if path_to_local_id(var, decl);
then {
- let mut v = LocalUsedVisitor::new(cx, decl);
-
- if block.stmts.iter().take(block.stmts.len()-1).any(|stmt| v.check_stmt(stmt)) {
- return None;
+ if block.stmts.iter().take(block.stmts.len()-1).any(|stmt| is_local_used(cx, stmt, decl)) {
+ None
+ } else {
+ Some(value)
}
-
- return Some(value);
+ } else {
+ None
}
}
-
- None
}
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index 8372d681078..1fadaf4770a 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -773,6 +773,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
methods::MANUAL_FILTER_MAP,
methods::MANUAL_FIND_MAP,
methods::MANUAL_SATURATING_ARITHMETIC,
+ methods::MANUAL_SPLIT_ONCE,
methods::MANUAL_STR_REPEAT,
methods::MAP_COLLECT_RESULT_UNIT,
methods::MAP_FLATTEN,
@@ -1319,6 +1320,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(methods::MANUAL_FILTER_MAP),
LintId::of(methods::MANUAL_FIND_MAP),
LintId::of(methods::MANUAL_SATURATING_ARITHMETIC),
+ LintId::of(methods::MANUAL_SPLIT_ONCE),
LintId::of(methods::MANUAL_STR_REPEAT),
LintId::of(methods::MAP_COLLECT_RESULT_UNIT),
LintId::of(methods::MAP_IDENTITY),
@@ -1617,6 +1619,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(methods::ITER_COUNT),
LintId::of(methods::MANUAL_FILTER_MAP),
LintId::of(methods::MANUAL_FIND_MAP),
+ LintId::of(methods::MANUAL_SPLIT_ONCE),
LintId::of(methods::MAP_IDENTITY),
LintId::of(methods::OPTION_AS_REF_DEREF),
LintId::of(methods::OPTION_FILTER_MAP),
diff --git a/clippy_lints/src/loops/for_kv_map.rs b/clippy_lints/src/loops/for_kv_map.rs
index 82bf49f5b49..68bef2f4c8b 100644
--- a/clippy_lints/src/loops/for_kv_map.rs
+++ b/clippy_lints/src/loops/for_kv_map.rs
@@ -3,7 +3,7 @@ use clippy_utils::diagnostics::{multispan_sugg, span_lint_and_then};
use clippy_utils::source::snippet;
use clippy_utils::sugg;
use clippy_utils::ty::is_type_diagnostic_item;
-use clippy_utils::visitors::LocalUsedVisitor;
+use clippy_utils::visitors::is_local_used;
use rustc_hir::{BorrowKind, Expr, ExprKind, Mutability, Pat, PatKind};
use rustc_lint::LateContext;
use rustc_middle::ty;
@@ -66,9 +66,7 @@ pub(super) fn check<'tcx>(
fn pat_is_wild<'tcx>(cx: &LateContext<'tcx>, pat: &'tcx PatKind<'_>, body: &'tcx Expr<'_>) -> bool {
match *pat {
PatKind::Wild => true,
- PatKind::Binding(_, id, ident, None) if ident.as_str().starts_with('_') => {
- !LocalUsedVisitor::new(cx, id).check_expr(body)
- },
+ PatKind::Binding(_, id, ident, None) if ident.as_str().starts_with('_') => !is_local_used(cx, body, id),
_ => false,
}
}
diff --git a/clippy_lints/src/loops/manual_flatten.rs b/clippy_lints/src/loops/manual_flatten.rs
index d8153abc965..2af6cfe35b5 100644
--- a/clippy_lints/src/loops/manual_flatten.rs
+++ b/clippy_lints/src/loops/manual_flatten.rs
@@ -1,7 +1,7 @@
use super::utils::make_iterator_snippet;
use super::MANUAL_FLATTEN;
use clippy_utils::diagnostics::span_lint_and_then;
-use clippy_utils::visitors::LocalUsedVisitor;
+use clippy_utils::visitors::is_local_used;
use clippy_utils::{is_lang_ctor, path_to_local_id};
use if_chain::if_chain;
use rustc_errors::Applicability;
@@ -49,7 +49,7 @@ pub(super) fn check<'tcx>(
let ok_ctor = is_lang_ctor(cx, qpath, ResultOk);
if some_ctor || ok_ctor;
// Ensure epxr in `if let` is not used afterwards
- if !LocalUsedVisitor::new(cx, pat_hir_id).check_arm(true_arm);
+ if !is_local_used(cx, true_arm, pat_hir_id);
then {
let if_let_type = if some_ctor { "Some" } else { "Ok" };
// Prepare the error message
diff --git a/clippy_lints/src/loops/needless_range_loop.rs b/clippy_lints/src/loops/needless_range_loop.rs
index 3810d0dcc05..fa33d068d3d 100644
--- a/clippy_lints/src/loops/needless_range_loop.rs
+++ b/clippy_lints/src/loops/needless_range_loop.rs
@@ -2,10 +2,8 @@ use super::NEEDLESS_RANGE_LOOP;
use clippy_utils::diagnostics::{multispan_sugg, span_lint_and_then};
use clippy_utils::source::snippet;
use clippy_utils::ty::has_iter_method;
-use clippy_utils::visitors::LocalUsedVisitor;
-use clippy_utils::{
- contains_name, higher, is_integer_const, match_trait_method, path_to_local_id, paths, sugg, SpanlessEq,
-};
+use clippy_utils::visitors::is_local_used;
+use clippy_utils::{contains_name, higher, is_integer_const, match_trait_method, paths, sugg, SpanlessEq};
use if_chain::if_chain;
use rustc_ast::ast;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
@@ -256,43 +254,36 @@ impl<'a, 'tcx> VarVisitor<'a, 'tcx> {
if let ExprKind::Path(ref seqpath) = seqexpr.kind;
if let QPath::Resolved(None, seqvar) = *seqpath;
if seqvar.segments.len() == 1;
- let index_used_directly = path_to_local_id(idx, self.var);
- let indexed_indirectly = {
- let mut used_visitor = LocalUsedVisitor::new(self.cx, self.var);
- walk_expr(&mut used_visitor, idx);
- used_visitor.used
- };
- if indexed_indirectly || index_used_directly;
+ if is_local_used(self.cx, idx, self.var);
then {
if self.prefer_mutable {
self.indexed_mut.insert(seqvar.segments[0].ident.name);
}
+ let index_used_directly = matches!(idx.kind, ExprKind::Path(_));
let res = self.cx.qpath_res(seqpath, seqexpr.hir_id);
match res {
Res::Local(hir_id) => {
let parent_id = self.cx.tcx.hir().get_parent_item(expr.hir_id);
let parent_def_id = self.cx.tcx.hir().local_def_id(parent_id);
let extent = self.cx.tcx.region_scope_tree(parent_def_id).var_scope(hir_id.local_id);
- if indexed_indirectly {
- self.indexed_indirectly.insert(seqvar.segments[0].ident.name, Some(extent));
- }
if index_used_directly {
self.indexed_directly.insert(
seqvar.segments[0].ident.name,
(Some(extent), self.cx.typeck_results().node_type(seqexpr.hir_id)),
);
+ } else {
+ self.indexed_indirectly.insert(seqvar.segments[0].ident.name, Some(extent));
}
return false; // no need to walk further *on the variable*
}
Res::Def(DefKind::Static | DefKind::Const, ..) => {
- if indexed_indirectly {
- self.indexed_indirectly.insert(seqvar.segments[0].ident.name, None);
- }
if index_used_directly {
self.indexed_directly.insert(
seqvar.segments[0].ident.name,
(None, self.cx.typeck_results().node_type(seqexpr.hir_id)),
);
+ } else {
+ self.indexed_indirectly.insert(seqvar.segments[0].ident.name, None);
}
return false; // no need to walk further *on the variable*
}
diff --git a/clippy_lints/src/matches.rs b/clippy_lints/src/matches.rs
index 5360c02f905..149c9bee9fb 100644
--- a/clippy_lints/src/matches.rs
+++ b/clippy_lints/src/matches.rs
@@ -5,7 +5,7 @@ use clippy_utils::diagnostics::{
use clippy_utils::source::{expr_block, indent_of, snippet, snippet_block, snippet_opt, snippet_with_applicability};
use clippy_utils::sugg::Sugg;
use clippy_utils::ty::{implements_trait, is_type_diagnostic_item, match_type, peel_mid_ty_refs};
-use clippy_utils::visitors::LocalUsedVisitor;
+use clippy_utils::visitors::is_local_used;
use clippy_utils::{
get_parent_expr, in_macro, is_expn_of, is_lang_ctor, is_lint_allowed, is_refutable, is_wild, meets_msrv, msrvs,
path_to_local, path_to_local_id, peel_hir_pat_refs, peel_n_hir_expr_refs, recurse_or_patterns, remove_blocks,
@@ -953,9 +953,7 @@ fn check_wild_err_arm<'tcx>(cx: &LateContext<'tcx>, ex: &Expr<'tcx>, arms: &[Arm
// Looking for unused bindings (i.e.: `_e`)
for pat in inner.iter() {
if let PatKind::Binding(_, id, ident, None) = pat.kind {
- if ident.as_str().starts_with('_')
- && !LocalUsedVisitor::new(cx, id).check_expr(arm.body)
- {
+ if ident.as_str().starts_with('_') && !is_local_used(cx, arm.body, id) {
ident_bind_name = (&ident.name.as_str()).to_string();
matching_wild = true;
}
diff --git a/clippy_lints/src/methods/manual_split_once.rs b/clippy_lints/src/methods/manual_split_once.rs
new file mode 100644
index 00000000000..e273186d051
--- /dev/null
+++ b/clippy_lints/src/methods/manual_split_once.rs
@@ -0,0 +1,213 @@
+use clippy_utils::consts::{constant, Constant};
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::source::snippet_with_context;
+use clippy_utils::{is_diag_item_method, match_def_path, paths};
+use if_chain::if_chain;
+use rustc_errors::Applicability;
+use rustc_hir::{Expr, ExprKind, HirId, LangItem, Node, QPath};
+use rustc_lint::LateContext;
+use rustc_middle::ty::{self, adjustment::Adjust};
+use rustc_span::{symbol::sym, Span, SyntaxContext};
+
+use super::MANUAL_SPLIT_ONCE;
+
+pub(super) fn check(cx: &LateContext<'_>, method_name: &str, expr: &Expr<'_>, self_arg: &Expr<'_>, pat_arg: &Expr<'_>) {
+ if !cx.typeck_results().expr_ty_adjusted(self_arg).peel_refs().is_str() {
+ return;
+ }
+
+ let ctxt = expr.span.ctxt();
+ let usage = match parse_iter_usage(cx, ctxt, cx.tcx.hir().parent_iter(expr.hir_id)) {
+ Some(x) => x,
+ None => return,
+ };
+ let (method_name, msg) = if method_name == "splitn" {
+ ("split_once", "manual implementation of `split_once`")
+ } else {
+ ("rsplit_once", "manual implementation of `rsplit_once`")
+ };
+
+ let mut app = Applicability::MachineApplicable;
+ let self_snip = snippet_with_context(cx, self_arg.span, ctxt, "..", &mut app).0;
+ let pat_snip = snippet_with_context(cx, pat_arg.span, ctxt, "..", &mut app).0;
+
+ match usage.kind {
+ IterUsageKind::NextTuple => {
+ span_lint_and_sugg(
+ cx,
+ MANUAL_SPLIT_ONCE,
+ usage.span,
+ msg,
+ "try this",
+ format!("{}.{}({})", self_snip, method_name, pat_snip),
+ app,
+ );
+ },
+ IterUsageKind::Next => {
+ let self_deref = {
+ let adjust = cx.typeck_results().expr_adjustments(self_arg);
+ if adjust.is_empty() {
+ String::new()
+ } else if cx.typeck_results().expr_ty(self_arg).is_box()
+ || adjust
+ .iter()
+ .any(|a| matches!(a.kind, Adjust::Deref(Some(_))) || a.target.is_box())
+ {
+ format!("&{}", "*".repeat(adjust.len() - 1))
+ } else {
+ "*".repeat(adjust.len() - 2)
+ }
+ };
+ let sugg = if usage.unwrap_kind.is_some() {
+ format!(
+ "{}.{}({}).map_or({}{}, |x| x.0)",
+ &self_snip, method_name, pat_snip, self_deref, &self_snip
+ )
+ } else {
+ format!(
+ "Some({}.{}({}).map_or({}{}, |x| x.0))",
+ &self_snip, method_name, pat_snip, self_deref, &self_snip
+ )
+ };
+
+ span_lint_and_sugg(cx, MANUAL_SPLIT_ONCE, usage.span, msg, "try this", sugg, app);
+ },
+ IterUsageKind::Second => {
+ let access_str = match usage.unwrap_kind {
+ Some(UnwrapKind::Unwrap) => ".unwrap().1",
+ Some(UnwrapKind::QuestionMark) => "?.1",
+ None => ".map(|x| x.1)",
+ };
+ span_lint_and_sugg(
+ cx,
+ MANUAL_SPLIT_ONCE,
+ usage.span,
+ msg,
+ "try this",
+ format!("{}.{}({}){}", self_snip, method_name, pat_snip, access_str),
+ app,
+ );
+ },
+ }
+}
+
+enum IterUsageKind {
+ Next,
+ Second,
+ NextTuple,
+}
+
+enum UnwrapKind {
+ Unwrap,
+ QuestionMark,
+}
+
+struct IterUsage {
+ kind: IterUsageKind,
+ unwrap_kind: Option<UnwrapKind>,
+ span: Span,
+}
+
+fn parse_iter_usage(
+ cx: &LateContext<'tcx>,
+ ctxt: SyntaxContext,
+ mut iter: impl Iterator<Item = (HirId, Node<'tcx>)>,
+) -> Option<IterUsage> {
+ let (kind, span) = match iter.next() {
+ Some((_, Node::Expr(e))) if e.span.ctxt() == ctxt => {
+ let (name, args) = if let ExprKind::MethodCall(name, _, [_, args @ ..], _) = e.kind {
+ (name, args)
+ } else {
+ return None;
+ };
+ let did = cx.typeck_results().type_dependent_def_id(e.hir_id)?;
+ let iter_id = cx.tcx.get_diagnostic_item(sym::Iterator)?;
+
+ match (&*name.ident.as_str(), args) {
+ ("next", []) if cx.tcx.trait_of_item(did) == Some(iter_id) => (IterUsageKind::Next, e.span),
+ ("next_tuple", []) => {
+ if_chain! {
+ if match_def_path(cx, did, &paths::ITERTOOLS_NEXT_TUPLE);
+ if let ty::Adt(adt_def, subs) = cx.typeck_results().expr_ty(e).kind();
+ if cx.tcx.is_diagnostic_item(sym::option_type, adt_def.did);
+ if let ty::Tuple(subs) = subs.type_at(0).kind();
+ if subs.len() == 2;
+ then {
+ return Some(IterUsage { kind: IterUsageKind::NextTuple, span: e.span, unwrap_kind: None });
+ } else {
+ return None;
+ }
+ }
+ },
+ ("nth" | "skip", [idx_expr]) if cx.tcx.trait_of_item(did) == Some(iter_id) => {
+ if let Some((Constant::Int(idx), _)) = constant(cx, cx.typeck_results(), idx_expr) {
+ let span = if name.ident.as_str() == "nth" {
+ e.span
+ } else {
+ if_chain! {
+ if let Some((_, Node::Expr(next_expr))) = iter.next();
+ if let ExprKind::MethodCall(next_name, _, [_], _) = next_expr.kind;
+ if next_name.ident.name == sym::next;
+ if next_expr.span.ctxt() == ctxt;
+ if let Some(next_id) = cx.typeck_results().type_dependent_def_id(next_expr.hir_id);
+ if cx.tcx.trait_of_item(next_id) == Some(iter_id);
+ then {
+ next_expr.span
+ } else {
+ return None;
+ }
+ }
+ };
+ match idx {
+ 0 => (IterUsageKind::Next, span),
+ 1 => (IterUsageKind::Second, span),
+ _ => return None,
+ }
+ } else {
+ return None;
+ }
+ },
+ _ => return None,
+ }
+ },
+ _ => return None,
+ };
+
+ let (unwrap_kind, span) = if let Some((_, Node::Expr(e))) = iter.next() {
+ match e.kind {
+ ExprKind::Call(
+ Expr {
+ kind: ExprKind::Path(QPath::LangItem(LangItem::TryTraitBranch, _)),
+ ..
+ },
+ _,
+ ) => {
+ let parent_span = e.span.parent().unwrap();
+ if parent_span.ctxt() == ctxt {
+ (Some(UnwrapKind::QuestionMark), parent_span)
+ } else {
+ (None, span)
+ }
+ },
+ _ if e.span.ctxt() != ctxt => (None, span),
+ ExprKind::MethodCall(name, _, [_], _)
+ if name.ident.name == sym::unwrap
+ && cx
+ .typeck_results()
+ .type_dependent_def_id(e.hir_id)
+ .map_or(false, |id| is_diag_item_method(cx, id, sym::option_type)) =>
+ {
+ (Some(UnwrapKind::Unwrap), e.span)
+ },
+ _ => (None, span),
+ }
+ } else {
+ (None, span)
+ };
+
+ Some(IterUsage {
+ kind,
+ unwrap_kind,
+ span,
+ })
+}
diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs
index 91606ed3b2b..b6438bce874 100644
--- a/clippy_lints/src/methods/mod.rs
+++ b/clippy_lints/src/methods/mod.rs
@@ -33,6 +33,7 @@ mod iter_nth_zero;
mod iter_skip_next;
mod iterator_step_by_zero;
mod manual_saturating_arithmetic;
+mod manual_split_once;
mod manual_str_repeat;
mod map_collect_result_unit;
mod map_flatten;
@@ -64,6 +65,7 @@ mod wrong_self_convention;
mod zst_offset;
use bind_instead_of_map::BindInsteadOfMap;
+use clippy_utils::consts::{constant, Constant};
use clippy_utils::diagnostics::{span_lint, span_lint_and_help};
use clippy_utils::ty::{contains_adt_constructor, contains_ty, implements_trait, is_copy, is_type_diagnostic_item};
use clippy_utils::{contains_return, get_trait_def_id, in_macro, iter_input_pats, meets_msrv, msrvs, paths, return_ty};
@@ -1771,6 +1773,29 @@ declare_clippy_lint! {
"manual implementation of `str::repeat`"
}
+declare_clippy_lint! {
+ /// **What it does:** Checks for usages of `str::splitn(2, _)`
+ ///
+ /// **Why is this bad?** `split_once` is both clearer in intent and slightly more efficient.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ ///
+ /// ```rust,ignore
+ /// // Bad
+ /// let (key, value) = _.splitn(2, '=').next_tuple()?;
+ /// let value = _.splitn(2, '=').nth(1)?;
+ ///
+ /// // Good
+ /// let (key, value) = _.split_once('=')?;
+ /// let value = _.split_once('=')?.1;
+ /// ```
+ pub MANUAL_SPLIT_ONCE,
+ complexity,
+ "replace `.splitn(2, pat)` with `.split_once(pat)`"
+}
+
pub struct Methods {
avoid_breaking_exported_api: bool,
msrv: Option<RustcVersion>,
@@ -1848,7 +1873,8 @@ impl_lint_pass!(Methods => [
IMPLICIT_CLONE,
SUSPICIOUS_SPLITN,
MANUAL_STR_REPEAT,
- EXTEND_WITH_DRAIN
+ EXTEND_WITH_DRAIN,
+ MANUAL_SPLIT_ONCE
]);
/// Extracts a method call name, args, and `Span` of the method name.
@@ -2176,8 +2202,18 @@ fn check_methods<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, msrv: Optio
unnecessary_lazy_eval::check(cx, expr, recv, arg, "or");
}
},
- ("splitn" | "splitn_mut" | "rsplitn" | "rsplitn_mut", [count_arg, _]) => {
- suspicious_splitn::check(cx, name, expr, recv, count_arg);
+ ("splitn" | "rsplitn", [count_arg, pat_arg]) => {
+ if let Some((Constant::Int(count), _)) = constant(cx, cx.typeck_results(), count_arg) {
+ suspicious_splitn::check(cx, name, expr, recv, count);
+ if count == 2 && meets_msrv(msrv, &msrvs::STR_SPLIT_ONCE) {
+ manual_split_once::check(cx, name, expr, recv, pat_arg);
+ }
+ }
+ },
+ ("splitn_mut" | "rsplitn_mut", [count_arg, _]) => {
+ if let Some((Constant::Int(count), _)) = constant(cx, cx.typeck_results(), count_arg) {
+ suspicious_splitn::check(cx, name, expr, recv, count);
+ }
},
("step_by", [arg]) => iterator_step_by_zero::check(cx, expr, arg),
("to_os_string" | "to_owned" | "to_path_buf" | "to_vec", []) => {
diff --git a/clippy_lints/src/methods/suspicious_splitn.rs b/clippy_lints/src/methods/suspicious_splitn.rs
index a271df60572..1c546a15bf6 100644
--- a/clippy_lints/src/methods/suspicious_splitn.rs
+++ b/clippy_lints/src/methods/suspicious_splitn.rs
@@ -1,4 +1,3 @@
-use clippy_utils::consts::{constant, Constant};
use clippy_utils::diagnostics::span_lint_and_note;
use if_chain::if_chain;
use rustc_ast::LitKind;
@@ -8,15 +7,8 @@ use rustc_span::source_map::Spanned;
use super::SUSPICIOUS_SPLITN;
-pub(super) fn check(
- cx: &LateContext<'_>,
- method_name: &str,
- expr: &Expr<'_>,
- self_arg: &Expr<'_>,
- count_arg: &Expr<'_>,
-) {
+pub(super) fn check(cx: &LateContext<'_>, method_name: &str, expr: &Expr<'_>, self_arg: &Expr<'_>, count: u128) {
if_chain! {
- if let Some((Constant::Int(count), _)) = constant(cx, cx.typeck_results(), count_arg);
if count <= 1;
if let Some(call_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
if let Some(impl_id) = cx.tcx.impl_of_method(call_id);
@@ -24,9 +16,9 @@ pub(super) fn check(
if lang_items.slice_impl() == Some(impl_id) || lang_items.str_impl() == Some(impl_id);
then {
// Ignore empty slice and string literals when used with a literal count.
- if (matches!(self_arg.kind, ExprKind::Array([]))
+ if matches!(self_arg.kind, ExprKind::Array([]))
|| matches!(self_arg.kind, ExprKind::Lit(Spanned { node: LitKind::Str(s, _), .. }) if s.is_empty())
- ) && matches!(count_arg.kind, ExprKind::Lit(_))
+
{
return;
}
diff --git a/clippy_lints/src/unused_self.rs b/clippy_lints/src/unused_self.rs
index 658ac81f6ea..e7e249c79a2 100644
--- a/clippy_lints/src/unused_self.rs
+++ b/clippy_lints/src/unused_self.rs
@@ -1,5 +1,5 @@
use clippy_utils::diagnostics::span_lint_and_help;
-use clippy_utils::visitors::LocalUsedVisitor;
+use clippy_utils::visitors::is_local_used;
use if_chain::if_chain;
use rustc_hir::{Impl, ImplItem, ImplItemKind, ItemKind};
use rustc_lint::{LateContext, LateLintPass};
@@ -50,8 +50,7 @@ impl<'tcx> LateLintPass<'tcx> for UnusedSelf {
if let ImplItemKind::Fn(.., body_id) = &impl_item.kind;
let body = cx.tcx.hir().body(*body_id);
if let [self_param, ..] = body.params;
- let self_hir_id = self_param.pat.hir_id;
- if !LocalUsedVisitor::new(cx, self_hir_id).check_body(body);
+ if !is_local_used(cx, body, self_param.pat.hir_id);
then {
span_lint_and_help(
cx,
diff --git a/clippy_lints/src/utils/conf.rs b/clippy_lints/src/utils/conf.rs
index ad341fbbda9..97062bcb282 100644
--- a/clippy_lints/src/utils/conf.rs
+++ b/clippy_lints/src/utils/conf.rs
@@ -132,7 +132,7 @@ define_Conf! {
///
/// Suppress lints whenever the suggested change would cause breakage for other crates.
(avoid_breaking_exported_api: bool = true),
- /// Lint: MANUAL_STR_REPEAT, CLONED_INSTEAD_OF_COPIED, REDUNDANT_FIELD_NAMES, REDUNDANT_STATIC_LIFETIMES, FILTER_MAP_NEXT, CHECKED_CONVERSIONS, MANUAL_RANGE_CONTAINS, USE_SELF, MEM_REPLACE_WITH_DEFAULT, MANUAL_NON_EXHAUSTIVE, OPTION_AS_REF_DEREF, MAP_UNWRAP_OR, MATCH_LIKE_MATCHES_MACRO, MANUAL_STRIP, MISSING_CONST_FOR_FN, UNNESTED_OR_PATTERNS, FROM_OVER_INTO, PTR_AS_PTR, IF_THEN_SOME_ELSE_NONE.
+ /// Lint: MANUAL_SPLIT_ONCE, MANUAL_STR_REPEAT, CLONED_INSTEAD_OF_COPIED, REDUNDANT_FIELD_NAMES, REDUNDANT_STATIC_LIFETIMES, FILTER_MAP_NEXT, CHECKED_CONVERSIONS, MANUAL_RANGE_CONTAINS, USE_SELF, MEM_REPLACE_WITH_DEFAULT, MANUAL_NON_EXHAUSTIVE, OPTION_AS_REF_DEREF, MAP_UNWRAP_OR, MATCH_LIKE_MATCHES_MACRO, MANUAL_STRIP, MISSING_CONST_FOR_FN, UNNESTED_OR_PATTERNS, FROM_OVER_INTO, PTR_AS_PTR, IF_THEN_SOME_ELSE_NONE.
///
/// The minimum rust version that the project supports
(msrv: Option<String> = None),
diff --git a/clippy_utils/src/diagnostics.rs b/clippy_utils/src/diagnostics.rs
index 71cfa196fc3..9302e5c21fa 100644
--- a/clippy_utils/src/diagnostics.rs
+++ b/clippy_utils/src/diagnostics.rs
@@ -21,7 +21,7 @@ fn docs_link(diag: &mut DiagnosticBuilder<'_>, lint: &'static Lint) {
"for further information visit https://rust-lang.github.io/rust-clippy/{}/index.html#{}",
&option_env!("RUST_RELEASE_NUM").map_or("master".to_string(), |n| {
// extract just major + minor version and ignore patch versions
- format!("rust-{}", n.rsplitn(2, '.').nth(1).unwrap())
+ format!("rust-{}", n.rsplit_once('.').unwrap().1)
}),
lint
));
diff --git a/clippy_utils/src/lib.rs b/clippy_utils/src/lib.rs
index bd229402f41..603e831459d 100644
--- a/clippy_utils/src/lib.rs
+++ b/clippy_utils/src/lib.rs
@@ -2,6 +2,7 @@
#![feature(in_band_lifetimes)]
#![feature(iter_zip)]
#![feature(rustc_private)]
+#![feature(control_flow_enum)]
#![recursion_limit = "512"]
#![cfg_attr(feature = "deny-warnings", deny(warnings))]
#![allow(clippy::missing_errors_doc, clippy::missing_panics_doc, clippy::must_use_candidate)]
diff --git a/clippy_utils/src/msrvs.rs b/clippy_utils/src/msrvs.rs
index 4a9c4fd0276..14234d9c9cb 100644
--- a/clippy_utils/src/msrvs.rs
+++ b/clippy_utils/src/msrvs.rs
@@ -13,6 +13,7 @@ macro_rules! msrv_aliases {
// names may refer to stabilized feature flags or library items
msrv_aliases! {
1,53,0 { OR_PATTERNS }
+ 1,52,0 { STR_SPLIT_ONCE }
1,50,0 { BOOL_THEN }
1,46,0 { CONST_IF_MATCH }
1,45,0 { STR_STRIP_PREFIX }
diff --git a/clippy_utils/src/paths.rs b/clippy_utils/src/paths.rs
index b0c3fe1e5a7..d7e46c2d3eb 100644
--- a/clippy_utils/src/paths.rs
+++ b/clippy_utils/src/paths.rs
@@ -68,6 +68,7 @@ pub const IO_WRITE: [&str; 3] = ["std", "io", "Write"];
pub const IPADDR_V4: [&str; 5] = ["std", "net", "ip", "IpAddr", "V4"];
pub const IPADDR_V6: [&str; 5] = ["std", "net", "ip", "IpAddr", "V6"];
pub const ITER_REPEAT: [&str; 5] = ["core", "iter", "sources", "repeat", "repeat"];
+pub const ITERTOOLS_NEXT_TUPLE: [&str; 3] = ["itertools", "Itertools", "next_tuple"];
#[cfg(feature = "internal-lints")]
pub const KW_MODULE: [&str; 3] = ["rustc_span", "symbol", "kw"];
#[cfg(feature = "internal-lints")]
diff --git a/clippy_utils/src/visitors.rs b/clippy_utils/src/visitors.rs
index ce00106dd4d..503effbdad5 100644
--- a/clippy_utils/src/visitors.rs
+++ b/clippy_utils/src/visitors.rs
@@ -4,6 +4,7 @@ use rustc_hir::intravisit::{self, walk_expr, ErasedMap, NestedVisitorMap, Visito
use rustc_hir::{def::Res, Arm, Block, Body, BodyId, Destination, Expr, ExprKind, HirId, Stmt};
use rustc_lint::LateContext;
use rustc_middle::hir::map::Map;
+use std::ops::ControlFlow;
/// returns `true` if expr contains match expr desugared from try
fn contains_try(expr: &hir::Expr<'_>) -> bool {
@@ -133,62 +134,6 @@ where
}
}
-pub struct LocalUsedVisitor<'hir> {
- hir: Map<'hir>,
- pub local_hir_id: HirId,
- pub used: bool,
-}
-
-impl<'hir> LocalUsedVisitor<'hir> {
- pub fn new(cx: &LateContext<'hir>, local_hir_id: HirId) -> Self {
- Self {
- hir: cx.tcx.hir(),
- local_hir_id,
- used: false,
- }
- }
-
- fn check<T>(&mut self, t: T, visit: fn(&mut Self, T)) -> bool {
- visit(self, t);
- std::mem::replace(&mut self.used, false)
- }
-
- pub fn check_arm(&mut self, arm: &'hir Arm<'_>) -> bool {
- self.check(arm, Self::visit_arm)
- }
-
- pub fn check_body(&mut self, body: &'hir Body<'_>) -> bool {
- self.check(body, Self::visit_body)
- }
-
- pub fn check_expr(&mut self, expr: &'hir Expr<'_>) -> bool {
- self.check(expr, Self::visit_expr)
- }
-
- pub fn check_stmt(&mut self, stmt: &'hir Stmt<'_>) -> bool {
- self.check(stmt, Self::visit_stmt)
- }
-}
-
-impl<'v> Visitor<'v> for LocalUsedVisitor<'v> {
- type Map = Map<'v>;
-
- fn visit_expr(&mut self, expr: &'v Expr<'v>) {
- if self.used {
- return;
- }
- if path_to_local_id(expr, self.local_hir_id) {
- self.used = true;
- } else {
- walk_expr(self, expr);
- }
- }
-
- fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
- NestedVisitorMap::OnlyBodies(self.hir)
- }
-}
-
/// A type which can be visited.
pub trait Visitable<'tcx> {
/// Calls the corresponding `visit_*` function on the visitor.
@@ -203,7 +148,22 @@ macro_rules! visitable_ref {
}
};
}
+visitable_ref!(Arm, visit_arm);
visitable_ref!(Block, visit_block);
+visitable_ref!(Body, visit_body);
+visitable_ref!(Expr, visit_expr);
+visitable_ref!(Stmt, visit_stmt);
+
+// impl<'tcx, I: IntoIterator> Visitable<'tcx> for I
+// where
+// I::Item: Visitable<'tcx>,
+// {
+// fn visit<V: Visitor<'tcx>>(self, visitor: &mut V) {
+// for x in self {
+// x.visit(visitor);
+// }
+// }
+// }
/// Calls the given function for each break expression.
pub fn visit_break_exprs<'tcx>(
@@ -260,3 +220,48 @@ pub fn is_res_used(cx: &LateContext<'_>, res: Res, body: BodyId) -> bool {
v.visit_expr(&cx.tcx.hir().body(body).value);
v.found
}
+
+/// Calls the given function for each usage of the given local.
+pub fn for_each_local_usage<'tcx, B>(
+ cx: &LateContext<'tcx>,
+ visitable: impl Visitable<'tcx>,
+ id: HirId,
+ f: impl FnMut(&'tcx Expr<'tcx>) -> ControlFlow<B>,
+) -> ControlFlow<B> {
+ struct V<'tcx, B, F> {
+ map: Map<'tcx>,
+ id: HirId,
+ f: F,
+ res: ControlFlow<B>,
+ }
+ impl<'tcx, B, F: FnMut(&'tcx Expr<'tcx>) -> ControlFlow<B>> Visitor<'tcx> for V<'tcx, B, F> {
+ type Map = Map<'tcx>;
+ fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
+ NestedVisitorMap::OnlyBodies(self.map)
+ }
+
+ fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
+ if self.res.is_continue() {
+ if path_to_local_id(e, self.id) {
+ self.res = (self.f)(e);
+ } else {
+ walk_expr(self, e);
+ }
+ }
+ }
+ }
+
+ let mut v = V {
+ map: cx.tcx.hir(),
+ id,
+ f,
+ res: ControlFlow::CONTINUE,
+ };
+ visitable.visit(&mut v);
+ v.res
+}
+
+/// Checks if the given local is used.
+pub fn is_local_used(cx: &LateContext<'tcx>, visitable: impl Visitable<'tcx>, id: HirId) -> bool {
+ for_each_local_usage(cx, visitable, id, |_| ControlFlow::BREAK).is_break()
+}
diff --git a/tests/compile-test.rs b/tests/compile-test.rs
index 0a82377a10e..6116acffe07 100644
--- a/tests/compile-test.rs
+++ b/tests/compile-test.rs
@@ -39,6 +39,7 @@ fn third_party_crates() -> String {
"clippy_lints",
"clippy_utils",
"if_chain",
+ "itertools",
"quote",
"regex",
"serde",
diff --git a/tests/ui/manual_split_once.fixed b/tests/ui/manual_split_once.fixed
new file mode 100644
index 00000000000..3a0332939d4
--- /dev/null
+++ b/tests/ui/manual_split_once.fixed
@@ -0,0 +1,50 @@
+// run-rustfix
+
+#![feature(custom_inner_attributes)]
+#![warn(clippy::manual_split_once)]
+#![allow(clippy::iter_skip_next, clippy::iter_nth_zero)]
+
+extern crate itertools;
+
+#[allow(unused_imports)]
+use itertools::Itertools;
+
+fn main() {
+ let _ = Some("key=value".split_once('=').map_or("key=value", |x| x.0));
+ let _ = "key=value".splitn(2, '=').nth(2);
+ let _ = "key=value".split_once('=').map_or("key=value", |x| x.0);
+ let _ = "key=value".split_once('=').map_or("key=value", |x| x.0);
+ let _ = "key=value".split_once('=').unwrap().1;
+ let _ = "key=value".split_once('=').unwrap().1;
+ let (_, _) = "key=value".split_once('=').unwrap();
+
+ let s = String::from("key=value");
+ let _ = s.split_once('=').map_or(&*s, |x| x.0);
+
+ let s = Box::<str>::from("key=value");
+ let _ = s.split_once('=').map_or(&*s, |x| x.0);
+
+ let s = &"key=value";
+ let _ = s.split_once('=').map_or(*s, |x| x.0);
+
+ fn _f(s: &str) -> Option<&str> {
+ let _ = s.split_once("key=value").map_or(s, |x| x.0);
+ let _ = s.split_once("key=value")?.1;
+ let _ = s.split_once("key=value")?.1;
+ None
+ }
+
+ // Don't lint, slices don't have `split_once`
+ let _ = [0, 1, 2].splitn(2, |&x| x == 1).nth(1).unwrap();
+}
+
+fn _msrv_1_51() {
+ #![clippy::msrv = "1.51"]
+ // `str::split_once` was stabilized in 1.16. Do not lint this
+ let _ = "key=value".splitn(2, '=').nth(1).unwrap();
+}
+
+fn _msrv_1_52() {
+ #![clippy::msrv = "1.52"]
+ let _ = "key=value".split_once('=').unwrap().1;
+}
diff --git a/tests/ui/manual_split_once.rs b/tests/ui/manual_split_once.rs
new file mode 100644
index 00000000000..e6093b63fe8
--- /dev/null
+++ b/tests/ui/manual_split_once.rs
@@ -0,0 +1,50 @@
+// run-rustfix
+
+#![feature(custom_inner_attributes)]
+#![warn(clippy::manual_split_once)]
+#![allow(clippy::iter_skip_next, clippy::iter_nth_zero)]
+
+extern crate itertools;
+
+#[allow(unused_imports)]
+use itertools::Itertools;
+
+fn main() {
+ let _ = "key=value".splitn(2, '=').next();
+ let _ = "key=value".splitn(2, '=').nth(2);
+ let _ = "key=value".splitn(2, '=').next().unwrap();
+ let _ = "key=value".splitn(2, '=').nth(0).unwrap();
+ let _ = "key=value".splitn(2, '=').nth(1).unwrap();
+ let _ = "key=value".splitn(2, '=').skip(1).next().unwrap();
+ let (_, _) = "key=value".splitn(2, '=').next_tuple().unwrap();
+
+ let s = String::from("key=value");
+ let _ = s.splitn(2, '=').next().unwrap();
+
+ let s = Box::<str>::from("key=value");
+ let _ = s.splitn(2, '=').nth(0).unwrap();
+
+ let s = &"key=value";
+ let _ = s.splitn(2, '=').skip(0).next().unwrap();
+
+ fn _f(s: &str) -> Option<&str> {
+ let _ = s.splitn(2, "key=value").next()?;
+ let _ = s.splitn(2, "key=value").nth(1)?;
+ let _ = s.splitn(2, "key=value").skip(1).next()?;
+ None
+ }
+
+ // Don't lint, slices don't have `split_once`
+ let _ = [0, 1, 2].splitn(2, |&x| x == 1).nth(1).unwrap();
+}
+
+fn _msrv_1_51() {
+ #![clippy::msrv = "1.51"]
+ // `str::split_once` was stabilized in 1.16. Do not lint this
+ let _ = "key=value".splitn(2, '=').nth(1).unwrap();
+}
+
+fn _msrv_1_52() {
+ #![clippy::msrv = "1.52"]
+ let _ = "key=value".splitn(2, '=').nth(1).unwrap();
+}
diff --git a/tests/ui/manual_split_once.stderr b/tests/ui/manual_split_once.stderr
new file mode 100644
index 00000000000..4f15196b469
--- /dev/null
+++ b/tests/ui/manual_split_once.stderr
@@ -0,0 +1,82 @@
+error: manual implementation of `split_once`
+ --> $DIR/manual_split_once.rs:13:13
+ |
+LL | let _ = "key=value".splitn(2, '=').next();
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `Some("key=value".split_once('=').map_or("key=value", |x| x.0))`
+ |
+ = note: `-D clippy::manual-split-once` implied by `-D warnings`
+
+error: manual implementation of `split_once`
+ --> $DIR/manual_split_once.rs:15:13
+ |
+LL | let _ = "key=value".splitn(2, '=').next().unwrap();
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `"key=value".split_once('=').map_or("key=value", |x| x.0)`
+
+error: manual implementation of `split_once`
+ --> $DIR/manual_split_once.rs:16:13
+ |
+LL | let _ = "key=value".splitn(2, '=').nth(0).unwrap();
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `"key=value".split_once('=').map_or("key=value", |x| x.0)`
+
+error: manual implementation of `split_once`
+ --> $DIR/manual_split_once.rs:17:13
+ |
+LL | let _ = "key=value".splitn(2, '=').nth(1).unwrap();
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `"key=value".split_once('=').unwrap().1`
+
+error: manual implementation of `split_once`
+ --> $DIR/manual_split_once.rs:18:13
+ |
+LL | let _ = "key=value".splitn(2, '=').skip(1).next().unwrap();
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `"key=value".split_once('=').unwrap().1`
+
+error: manual implementation of `split_once`
+ --> $DIR/manual_split_once.rs:19:18
+ |
+LL | let (_, _) = "key=value".splitn(2, '=').next_tuple().unwrap();
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `"key=value".split_once('=')`
+
+error: manual implementation of `split_once`
+ --> $DIR/manual_split_once.rs:22:13
+ |
+LL | let _ = s.splitn(2, '=').next().unwrap();
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `s.split_once('=').map_or(&*s, |x| x.0)`
+
+error: manual implementation of `split_once`
+ --> $DIR/manual_split_once.rs:25:13
+ |
+LL | let _ = s.splitn(2, '=').nth(0).unwrap();
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `s.split_once('=').map_or(&*s, |x| x.0)`
+
+error: manual implementation of `split_once`
+ --> $DIR/manual_split_once.rs:28:13
+ |
+LL | let _ = s.splitn(2, '=').skip(0).next().unwrap();
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `s.split_once('=').map_or(*s, |x| x.0)`
+
+error: manual implementation of `split_once`
+ --> $DIR/manual_split_once.rs:31:17
+ |
+LL | let _ = s.splitn(2, "key=value").next()?;
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `s.split_once("key=value").map_or(s, |x| x.0)`
+
+error: manual implementation of `split_once`
+ --> $DIR/manual_split_once.rs:32:17
+ |
+LL | let _ = s.splitn(2, "key=value").nth(1)?;
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `s.split_once("key=value")?.1`
+
+error: manual implementation of `split_once`
+ --> $DIR/manual_split_once.rs:33:17
+ |
+LL | let _ = s.splitn(2, "key=value").skip(1).next()?;
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `s.split_once("key=value")?.1`
+
+error: manual implementation of `split_once`
+ --> $DIR/manual_split_once.rs:49:13
+ |
+LL | let _ = "key=value".splitn(2, '=').nth(1).unwrap();
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `"key=value".split_once('=').unwrap().1`
+
+error: aborting due to 13 previous errors
+