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add new lint [once_cell_lazy] to detect usage of static Lazy type
#12968
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,259 @@ | ||
| use clippy_config::msrvs::Msrv; | ||
| use clippy_utils::diagnostics::span_lint_and_then; | ||
| use clippy_utils::visitors::for_each_expr; | ||
| use clippy_utils::{def_path_def_ids, fn_def_id, match_def_path, path_def_id}; | ||
| use rustc_data_structures::fx::FxIndexMap; | ||
| use rustc_errors::Applicability; | ||
| use rustc_hir::def::{DefKind, Res}; | ||
| use rustc_hir::def_id::DefId; | ||
| use rustc_hir::{self as hir, BodyId, Expr, ExprKind, Item, ItemKind}; | ||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_session::impl_lint_pass; | ||
| use rustc_span::Span; | ||
|
|
||
| declare_clippy_lint! { | ||
| /// ### What it does | ||
| /// Lints when a `static` is declared with `once_cell::sync::Lazy` type, | ||
| /// which can mostly be done with `std::sync::LazyLock` without relying on | ||
| /// additional dependency. | ||
| /// | ||
| /// Note: This lint will not trigger in crate with `no_std` context, or with MSRV < 1.80.0. | ||
| /// | ||
| /// ### Why restrict this? | ||
| /// Such usage can be replaced with the `std::sync::LazyLock` type, | ||
| /// to reduce dependence of the `once_cell` crate. | ||
| /// | ||
| /// ### Example | ||
| /// ```ignore | ||
| /// static FOO: once_cell::sync::Lazy<String> = once_cell::sync::Lazy::new(|| "FOO".to_lowercase()); | ||
| /// ``` | ||
| /// Use instead: | ||
| /// ```ignore | ||
| /// static FOO: std::sync::LazyLock<String> = std::sync::LazyLock::new(|| "FOO".to_lowercase()); | ||
| /// ``` | ||
| #[clippy::version = "1.81.0"] | ||
| pub ONCE_CELL_LAZY, | ||
| restriction, | ||
| "using `once_cell::sync::Lazy` type that could be replaced by `std::sync::LazyLock`" | ||
| } | ||
|
|
||
| /// A list containing functions with coresponding replacements in `LazyLock`. | ||
| /// | ||
| /// Some functions could be replaced as well if we have replaced `Lazy` to `LazyLock`, | ||
| /// therefore after suggesting replace the type, we need to make sure the function calls can be | ||
| /// replaced, otherwise the suggestions cannot be applied thus the applicability should be | ||
| /// `Unspecified` or `MaybeIncorret`. | ||
| static FUNCTION_REPLACEMENTS: &[(&str, Option<&str>)] = &[ | ||
| ("once_cell::sync::Lazy::force", Some("std::sync::LazyLock::force")), | ||
| ("once_cell::sync::Lazy::get", None), | ||
| ("once_cell::sync::Lazy::new", Some("std::sync::LazyLock::new")), | ||
| // Note: `Lazy::{into_value, get_mut, force_mut}` are not in the list. | ||
| // Because the lint only checks for `static`s, and using these functions with statics | ||
| // will either be a hard error or triggers `static_mut_ref` that will be hard errors. | ||
| // But keep in mind that if somehow we decide to expand this lint to catch non-statics, | ||
| // add those functions into the list. | ||
| ]; | ||
|
|
||
| pub struct OnceCellLazy { | ||
| msrv: Msrv, | ||
| sugg_map: FxIndexMap<DefId, Option<String>>, | ||
| lazy_type_defs: FxIndexMap<DefId, LazyInfo>, | ||
| } | ||
|
|
||
| impl OnceCellLazy { | ||
| #[must_use] | ||
| pub fn new(msrv: Msrv) -> Self { | ||
| Self { | ||
| msrv, | ||
| sugg_map: FxIndexMap::default(), | ||
| lazy_type_defs: FxIndexMap::default(), | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl_lint_pass!(OnceCellLazy => [ONCE_CELL_LAZY]); | ||
|
|
||
| /// Return if current MSRV does not meet the requirement for `lazy_cell` feature, | ||
| /// or current context has `no_std` attribute. | ||
| macro_rules! ensure_prerequisite { | ||
| ($msrv:expr, $cx:ident) => { | ||
| if !$msrv.meets(clippy_config::msrvs::LAZY_CELL) || clippy_utils::is_no_std_crate($cx) { | ||
| return; | ||
| } | ||
| }; | ||
| } | ||
|
|
||
| impl<'hir> LateLintPass<'hir> for OnceCellLazy { | ||
| extract_msrv_attr!(LateContext); | ||
|
|
||
| fn check_crate(&mut self, cx: &LateContext<'hir>) { | ||
| // Do not lint if current crate does not support `LazyLock`. | ||
| ensure_prerequisite!(self.msrv, cx); | ||
|
|
||
| // Convert hardcoded fn replacement list into a map with def_id | ||
| for (path, sugg) in FUNCTION_REPLACEMENTS { | ||
| let path_vec = path.split("::").collect::<Vec<_>>(); | ||
| for did in def_path_def_ids(cx, &path_vec) { | ||
| self.sugg_map.insert(did, sugg.map(ToOwned::to_owned)); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn check_item(&mut self, cx: &LateContext<'hir>, item: &Item<'hir>) { | ||
| ensure_prerequisite!(self.msrv, cx); | ||
|
|
||
| if let Some(lazy_info) = LazyInfo::from_item(cx, item) { | ||
| self.lazy_type_defs.insert(item.owner_id.to_def_id(), lazy_info); | ||
| } | ||
| } | ||
|
|
||
| fn check_expr(&mut self, cx: &LateContext<'hir>, expr: &Expr<'hir>) { | ||
| ensure_prerequisite!(self.msrv, cx); | ||
|
|
||
| // All functions in the `FUNCTION_REPLACEMENTS` have only one args | ||
| if let ExprKind::Call(callee, [arg]) = expr.kind | ||
| && let Some(call_def_id) = fn_def_id(cx, expr) | ||
| && self.sugg_map.contains_key(&call_def_id) | ||
| && let ExprKind::Path(qpath) = arg.peel_borrows().kind | ||
| && let Some(arg_def_id) = cx.typeck_results().qpath_res(&qpath, arg.hir_id).opt_def_id() | ||
| && let Some(lazy_info) = self.lazy_type_defs.get_mut(&arg_def_id) | ||
| { | ||
| lazy_info.calls_span_and_id.insert(callee.span, call_def_id); | ||
| } | ||
| } | ||
|
|
||
| fn check_crate_post(&mut self, cx: &LateContext<'hir>) { | ||
| ensure_prerequisite!(self.msrv, cx); | ||
|
|
||
| for (_, lazy_info) in &self.lazy_type_defs { | ||
| lazy_info.lint(cx, &self.sugg_map); | ||
| } | ||
|
|
||
| self.sugg_map = FxIndexMap::default(); | ||
| } | ||
| } | ||
|
|
||
| struct LazyInfo { | ||
| /// Span of the [`hir::Ty`] without including args. | ||
| /// i.e.: | ||
| /// ```ignore | ||
| /// static FOO: Lazy<String> = Lazy::new(...); | ||
| /// // ^^^^ | ||
| /// ``` | ||
| ty_span_no_args: Span, | ||
| /// `Span` and `DefId` of calls on `Lazy` type. | ||
| /// i.e.: | ||
| /// ```ignore | ||
| /// static FOO: Lazy<String> = Lazy::new(...); | ||
| /// // ^^^^^^^^^ | ||
| /// ``` | ||
| calls_span_and_id: FxIndexMap<Span, DefId>, | ||
| } | ||
|
|
||
| impl LazyInfo { | ||
| fn from_item(cx: &LateContext<'_>, item: &Item<'_>) -> Option<Self> { | ||
| // Check if item is a `once_cell:sync::Lazy` static. | ||
| if let ItemKind::Static(ty, _, body_id) = item.kind | ||
| && let Some(path_def_id) = path_def_id(cx, ty) | ||
| && let hir::TyKind::Path(hir::QPath::Resolved(_, path)) = ty.kind | ||
| && match_def_path(cx, path_def_id, &["once_cell", "sync", "Lazy"]) | ||
| { | ||
| let ty_span_no_args = path_span_without_args(path); | ||
| let body = cx.tcx.hir().body(body_id); | ||
|
|
||
| // visit body to collect `Lazy::new` calls | ||
| let mut new_fn_calls = FxIndexMap::default(); | ||
| for_each_expr::<(), ()>(cx, body, |ex| { | ||
| if let Some((fn_did, call_span)) = fn_def_id_and_span_from_body(cx, ex, body_id) | ||
| && match_def_path(cx, fn_did, &["once_cell", "sync", "Lazy", "new"]) | ||
| { | ||
| new_fn_calls.insert(call_span, fn_did); | ||
| } | ||
| std::ops::ControlFlow::Continue(()) | ||
| }); | ||
|
|
||
| Some(LazyInfo { | ||
| ty_span_no_args, | ||
| calls_span_and_id: new_fn_calls, | ||
| }) | ||
| } else { | ||
| None | ||
| } | ||
| } | ||
|
|
||
| fn lint(&self, cx: &LateContext<'_>, sugg_map: &FxIndexMap<DefId, Option<String>>) { | ||
| // Applicability might get adjusted to `MachineApplicable` later if | ||
| // all calls in `calls_span_and_id` is replaceable judging by the `sugg_map`. | ||
| let mut appl = Applicability::Unspecified; | ||
| let mut suggs = vec![(self.ty_span_no_args, "std::sync::LazyLock".to_string())]; | ||
|
|
||
| if self | ||
| .calls_span_and_id | ||
| .iter() | ||
| // Filtering the calls that DOES NOT have a suggested replacement. | ||
| .filter(|(span, def_id)| { | ||
| let maybe_sugg = sugg_map.get(*def_id).cloned().flatten(); | ||
| if let Some(sugg) = maybe_sugg { | ||
| suggs.push((**span, sugg)); | ||
| false | ||
| } else { | ||
| true | ||
| } | ||
| }) | ||
| .collect::<Vec<_>>() | ||
| .is_empty() | ||
| { | ||
| appl = Applicability::MachineApplicable; | ||
| } | ||
|
|
||
| span_lint_and_then( | ||
| cx, | ||
| ONCE_CELL_LAZY, | ||
| self.ty_span_no_args, | ||
| "this type has been superceded by `std::sync::LazyLock`", | ||
| |diag| { | ||
| diag.multipart_suggestion("use `std::sync::LazyLock` instead", suggs, appl); | ||
| }, | ||
| ); | ||
| } | ||
| } | ||
|
|
||
| /// Return the span of a given `Path` without including any of its args. | ||
| /// | ||
| /// NB: Re-write of a private function `rustc_lint::non_local_def::path_span_without_args`. | ||
| fn path_span_without_args(path: &hir::Path<'_>) -> Span { | ||
| path.segments | ||
| .last() | ||
| .and_then(|seg| seg.args) | ||
| .map_or(path.span, |args| path.span.until(args.span_ext)) | ||
| } | ||
|
|
||
| /// Returns the `DefId` and `Span` of the callee if the given expression is a function call. | ||
| /// | ||
| /// NB: Modified from [`clippy_utils::fn_def_id`], to support calling in an static `Item`'s body. | ||
| fn fn_def_id_and_span_from_body(cx: &LateContext<'_>, expr: &Expr<'_>, body_id: BodyId) -> Option<(DefId, Span)> { | ||
| // FIXME: find a way to cache the result. | ||
| let typeck = cx.tcx.typeck_body(body_id); | ||
| match &expr.kind { | ||
| ExprKind::Call( | ||
| Expr { | ||
| kind: ExprKind::Path(qpath), | ||
| hir_id: path_hir_id, | ||
| span, | ||
| .. | ||
| }, | ||
| .., | ||
| ) => { | ||
| // Only return Fn-like DefIds, not the DefIds of statics/consts/etc that contain or | ||
| // deref to fn pointers, dyn Fn, impl Fn - #8850 | ||
| if let Res::Def(DefKind::Fn | DefKind::Ctor(..) | DefKind::AssocFn, id) = | ||
| typeck.qpath_res(qpath, *path_hir_id) | ||
| { | ||
| Some((id, *span)) | ||
| } else { | ||
| None | ||
| } | ||
| }, | ||
| _ => None, | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,39 @@ | ||
| //! **FAKE** once_cell crate. | ||
| pub mod sync { | ||
| use std::marker::PhantomData; | ||
|
|
||
| pub struct Lazy<T, F = fn() -> T> { | ||
| cell: PhantomData<T>, | ||
| init: F, | ||
| } | ||
| unsafe impl<T, F: Send> Sync for Lazy<T, F> {} | ||
| impl<T, F> Lazy<T, F> { | ||
| pub const fn new(f: F) -> Lazy<T, F> { | ||
| Lazy { | ||
| cell: PhantomData, | ||
| init: f, | ||
| } | ||
| } | ||
|
|
||
| pub fn into_value(this: Lazy<T, F>) -> Result<T, F> { | ||
| unimplemented!() | ||
| } | ||
|
|
||
| pub fn force(_this: &Lazy<T, F>) -> &T { | ||
| unimplemented!() | ||
| } | ||
|
|
||
| pub fn force_mut(_this: &mut Lazy<T, F>) -> &mut T { | ||
| unimplemented!() | ||
| } | ||
|
|
||
| pub fn get(_this: &Lazy<T, F>) -> Option<&T> { | ||
| unimplemented!() | ||
| } | ||
|
|
||
| pub fn get_mut(_this: &mut Lazy<T, F>) -> Option<&mut T> { | ||
| unimplemented!() | ||
| } | ||
| } | ||
| } | ||
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