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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,219 @@ | ||
| use clippy_config::Conf; | ||
| use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg}; | ||
| use clippy_utils::{is_none_arm, msrvs, peel_hir_expr_refs}; | ||
| use rustc_errors::Applicability; | ||
| use rustc_hir::def::{DefKind, Res}; | ||
| use rustc_hir::{Arm, Expr, ExprKind, LangItem, Pat, PatKind, QPath, is_range_literal}; | ||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_middle::ty; | ||
| use rustc_session::impl_lint_pass; | ||
| use rustc_span::{Span, Symbol, sym}; | ||
|
|
||
| declare_clippy_lint! { | ||
| /// ### What it does | ||
| /// This detects various manual reimplementations of `Option::as_slice`. | ||
| /// | ||
| /// ### Why is this bad? | ||
| /// Those implementations are both more complex than calling `as_slice` | ||
| /// and unlike that incur a branch, pessimizing performance and leading | ||
| /// to more generated code. | ||
| /// | ||
| /// ### Example | ||
| /// ```no_run | ||
| ///# let opt = Some(1); | ||
| /// _ = opt.as_ref().map_or(&[][..], std::slice::from_ref); | ||
| /// _ = match opt.as_ref() { | ||
| /// Some(f) => std::slice::from_ref(f), | ||
| /// None => &[], | ||
| /// }; | ||
| /// ``` | ||
| /// Use instead: | ||
| /// ```no_run | ||
| ///# let opt = Some(1); | ||
| /// _ = opt.as_slice(); | ||
| /// _ = opt.as_slice(); | ||
| /// ``` | ||
| #[clippy::version = "1.85.0"] | ||
| pub MANUAL_OPTION_AS_SLICE, | ||
| complexity, | ||
| "manual `Option::as_slice`" | ||
| } | ||
|
|
||
| pub struct ManualOptionAsSlice { | ||
| msrv: msrvs::Msrv, | ||
| } | ||
|
|
||
| impl ManualOptionAsSlice { | ||
| pub fn new(conf: &Conf) -> Self { | ||
| Self { | ||
| msrv: conf.msrv.clone(), | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl_lint_pass!(ManualOptionAsSlice => [MANUAL_OPTION_AS_SLICE]); | ||
|
|
||
| impl LateLintPass<'_> for ManualOptionAsSlice { | ||
| extract_msrv_attr!(LateContext); | ||
|
|
||
| fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) { | ||
| let span = expr.span; | ||
| if span.from_expansion() || !self.msrv.meets(msrvs::OPTION_AS_SLICE) { | ||
| return; | ||
| } | ||
| match expr.kind { | ||
| ExprKind::Match(scrutinee, [arm1, arm2], _) => { | ||
| if is_none_arm(cx, arm2) && check_arms(cx, arm2, arm1) | ||
| || is_none_arm(cx, arm1) && check_arms(cx, arm1, arm2) | ||
| { | ||
| check_as_ref(cx, scrutinee, span); | ||
| } | ||
| }, | ||
| ExprKind::If(cond, then, Some(other)) => { | ||
| if let ExprKind::Let(let_expr) = cond.kind | ||
| && let Some(binding) = extract_ident_from_some_pat(cx, let_expr.pat) | ||
| && check_some_body(cx, binding, then) | ||
| && is_empty_slice(cx, other.peel_blocks()) | ||
| { | ||
| check_as_ref(cx, let_expr.init, span); | ||
| } | ||
| }, | ||
| ExprKind::MethodCall(seg, callee, [], _) => { | ||
| if seg.ident.name.as_str() == "unwrap_or_default" { | ||
| check_map(cx, callee, span); | ||
| } | ||
| }, | ||
| ExprKind::MethodCall(seg, callee, [or], _) => match seg.ident.name.as_str() { | ||
| "unwrap_or" => { | ||
| if is_empty_slice(cx, or) { | ||
| check_map(cx, callee, span); | ||
| } | ||
| }, | ||
| "unwrap_or_else" => { | ||
| if returns_empty_slice(cx, or) { | ||
| check_map(cx, callee, span); | ||
| } | ||
| }, | ||
| _ => {}, | ||
| }, | ||
| ExprKind::MethodCall(seg, callee, [or_else, map], _) => match seg.ident.name.as_str() { | ||
| "map_or" => { | ||
| if is_empty_slice(cx, or_else) && is_slice_from_ref(cx, map) { | ||
| check_as_ref(cx, callee, span); | ||
| } | ||
| }, | ||
| "map_or_else" => { | ||
| if returns_empty_slice(cx, or_else) && is_slice_from_ref(cx, map) { | ||
| check_as_ref(cx, callee, span); | ||
| } | ||
| }, | ||
| _ => {}, | ||
| }, | ||
| _ => {}, | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn check_map(cx: &LateContext<'_>, map: &Expr<'_>, span: Span) { | ||
| if let ExprKind::MethodCall(seg, callee, [mapping], _) = map.kind | ||
| && seg.ident.name == sym::map | ||
| && is_slice_from_ref(cx, mapping) | ||
| { | ||
| check_as_ref(cx, callee, span); | ||
| } | ||
| } | ||
|
|
||
| fn check_as_ref(cx: &LateContext<'_>, expr: &Expr<'_>, span: Span) { | ||
| if let ExprKind::MethodCall(seg, callee, [], _) = expr.kind | ||
| && seg.ident.name == sym::as_ref | ||
| && let ty::Adt(adtdef, ..) = cx.typeck_results().expr_ty(callee).kind() | ||
| && cx.tcx.is_diagnostic_item(sym::Option, adtdef.did()) | ||
| { | ||
| if let Some(snippet) = clippy_utils::source::snippet_opt(cx, callee.span) { | ||
| span_lint_and_sugg( | ||
| cx, | ||
| MANUAL_OPTION_AS_SLICE, | ||
| span, | ||
| "use `Option::as_slice`", | ||
| "use", | ||
| format!("{snippet}.as_slice()"), | ||
| Applicability::MachineApplicable, | ||
| ); | ||
| } else { | ||
| span_lint(cx, MANUAL_OPTION_AS_SLICE, span, "use `Option_as_slice`"); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn extract_ident_from_some_pat(cx: &LateContext<'_>, pat: &Pat<'_>) -> Option<Symbol> { | ||
| if let PatKind::TupleStruct(QPath::Resolved(None, path), [binding], _) = pat.kind | ||
| && let Res::Def(DefKind::Ctor(..), def_id) = path.res | ||
| && let PatKind::Binding(_mode, _hir_id, ident, _inner_pat) = binding.kind | ||
| && clippy_utils::is_lang_item_or_ctor(cx, def_id, LangItem::OptionSome) | ||
| { | ||
| Some(ident.name) | ||
| } else { | ||
| None | ||
| } | ||
| } | ||
|
|
||
| /// Returns true if `expr` is `std::slice::from_ref(<name>)`. Used in `if let`s. | ||
| fn check_some_body(cx: &LateContext<'_>, name: Symbol, expr: &Expr<'_>) -> bool { | ||
| if let ExprKind::Call(slice_from_ref, [arg]) = expr.peel_blocks().kind | ||
| && is_slice_from_ref(cx, slice_from_ref) | ||
| && let ExprKind::Path(QPath::Resolved(None, path)) = arg.kind | ||
| && let [seg] = path.segments | ||
| { | ||
| seg.ident.name == name | ||
| } else { | ||
| false | ||
| } | ||
| } | ||
|
|
||
| fn check_arms(cx: &LateContext<'_>, none_arm: &Arm<'_>, some_arm: &Arm<'_>) -> bool { | ||
| if none_arm.guard.is_none() | ||
| && some_arm.guard.is_none() | ||
| && is_empty_slice(cx, none_arm.body) | ||
| && let Some(name) = extract_ident_from_some_pat(cx, some_arm.pat) | ||
| { | ||
| check_some_body(cx, name, some_arm.body) | ||
| } else { | ||
| false | ||
| } | ||
| } | ||
|
|
||
| fn returns_empty_slice(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool { | ||
| match expr.kind { | ||
| ExprKind::Path(_) => clippy_utils::is_path_diagnostic_item(cx, expr, sym::default_fn), | ||
| ExprKind::Closure(cl) => is_empty_slice(cx, cx.tcx.hir().body(cl.body).value), | ||
| _ => false, | ||
| } | ||
| } | ||
|
|
||
| /// Returns if expr returns an empty slice. If: | ||
| /// - An indexing operation to an empty array with a built-in range. `[][..]` | ||
| /// - An indexing operation with a zero-ended range. `expr[..0]` | ||
| /// - A reference to an empty array. `&[]` | ||
| /// - Or a call to `Default::default`. | ||
| fn is_empty_slice(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool { | ||
| let expr = peel_hir_expr_refs(expr.peel_blocks()).0; | ||
| match expr.kind { | ||
| ExprKind::Index(arr, range, _) => match arr.kind { | ||
| ExprKind::Array([]) => is_range_literal(range), | ||
| ExprKind::Array(_) => { | ||
| let Some(range) = clippy_utils::higher::Range::hir(range) else { | ||
| return false; | ||
| }; | ||
| range.end.is_some_and(|e| clippy_utils::is_integer_const(cx, e, 0)) | ||
| }, | ||
| _ => false, | ||
| }, | ||
| ExprKind::Array([]) => true, | ||
| ExprKind::Call(def, []) => clippy_utils::is_path_diagnostic_item(cx, def, sym::default_fn), | ||
| _ => false, | ||
| } | ||
| } | ||
|
|
||
| fn is_slice_from_ref(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool { | ||
| clippy_utils::is_expr_path_def_path(cx, expr, &["core", "slice", "raw", "from_ref"]) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,62 @@ | ||
| #![warn(clippy::manual_option_as_slice)] | ||
| #![allow(clippy::redundant_closure, clippy::unwrap_or_default)] | ||
|
|
||
| fn check(x: Option<u32>) { | ||
| _ = x.as_slice(); | ||
|
|
||
| _ = x.as_slice(); | ||
|
|
||
| _ = x.as_slice(); | ||
| //~^ manual_option_as_slice | ||
|
|
||
| _ = x.as_slice(); | ||
| //~^ manual_option_as_slice | ||
|
|
||
| _ = x.as_slice(); | ||
| //~^ manual_option_as_slice | ||
|
|
||
| _ = x.as_slice(); | ||
| //~^ manual_option_as_slice | ||
|
|
||
| { | ||
| use std::slice::from_ref; | ||
| _ = x.as_slice(); | ||
| //~^ manual_option_as_slice | ||
| } | ||
|
|
||
| // possible false positives | ||
| let y = x.as_ref(); | ||
| _ = match y { | ||
| // as_ref outside | ||
| Some(f) => &[f][..], | ||
| None => &[][..], | ||
| }; | ||
| _ = match x.as_ref() { | ||
| Some(f) => std::slice::from_ref(f), | ||
| None => &[0], | ||
| }; | ||
| _ = match x.as_ref() { | ||
| Some(42) => &[23], | ||
| Some(f) => std::slice::from_ref(f), | ||
| None => &[], | ||
| }; | ||
| let b = &[42]; | ||
| _ = if let Some(_f) = x.as_ref() { | ||
| std::slice::from_ref(b) | ||
| } else { | ||
| &[] | ||
| }; | ||
| _ = x.as_ref().map_or(&[42][..], std::slice::from_ref); | ||
| _ = x.as_ref().map_or_else(|| &[42][..1], std::slice::from_ref); | ||
| _ = x.as_ref().map(|f| std::slice::from_ref(f)).unwrap_or_default(); | ||
| } | ||
|
|
||
| #[clippy::msrv = "1.74"] | ||
| fn check_msrv(x: Option<u32>) { | ||
| _ = x.as_ref().map_or(&[][..], std::slice::from_ref); | ||
| } | ||
|
|
||
| fn main() { | ||
| check(Some(1)); | ||
| check_msrv(Some(175)); | ||
| } |
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