//! checks for attributes use crate::reexport::Name; use crate::utils::{ first_line_of_span, is_present_in_source, match_def_path, paths, snippet_opt, span_lint, span_lint_and_sugg, span_lint_and_then, without_block_comments, }; use if_chain::if_chain; use rustc_ast::ast::{AttrKind, AttrStyle, Attribute, Lit, LitKind, MetaItemKind, NestedMetaItem}; use rustc_ast::util::lev_distance::find_best_match_for_name; use rustc_errors::Applicability; use rustc_hir::{ Block, Expr, ExprKind, ImplItem, ImplItemKind, Item, ItemKind, StmtKind, TraitFn, TraitItem, TraitItemKind, }; use rustc_lint::{CheckLintNameResult, EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext}; use rustc_middle::lint::in_external_macro; use rustc_middle::ty; use rustc_session::{declare_lint_pass, declare_tool_lint}; use rustc_span::source_map::Span; use rustc_span::symbol::Symbol; use semver::Version; declare_clippy_lint! { /// **What it does:** Checks for items annotated with `#[inline(always)]`, /// unless the annotated function is empty or simply panics. /// /// **Why is this bad?** While there are valid uses of this annotation (and once /// you know when to use it, by all means `allow` this lint), it's a common /// newbie-mistake to pepper one's code with it. /// /// As a rule of thumb, before slapping `#[inline(always)]` on a function, /// measure if that additional function call really affects your runtime profile /// sufficiently to make up for the increase in compile time. /// /// **Known problems:** False positives, big time. This lint is meant to be /// deactivated by everyone doing serious performance work. This means having /// done the measurement. /// /// **Example:** /// ```ignore /// #[inline(always)] /// fn not_quite_hot_code(..) { ... } /// ``` pub INLINE_ALWAYS, pedantic, "use of `#[inline(always)]`" } declare_clippy_lint! { /// **What it does:** Checks for `extern crate` and `use` items annotated with /// lint attributes. /// /// This lint whitelists `#[allow(unused_imports)]`, `#[allow(deprecated)]` and /// `#[allow(unreachable_pub)]` on `use` items and `#[allow(unused_imports)]` on /// `extern crate` items with a `#[macro_use]` attribute. /// /// **Why is this bad?** Lint attributes have no effect on crate imports. Most /// likely a `!` was forgotten. /// /// **Known problems:** None. /// /// **Example:** /// ```ignore /// // Bad /// #[deny(dead_code)] /// extern crate foo; /// #[forbid(dead_code)] /// use foo::bar; /// /// // Ok /// #[allow(unused_imports)] /// use foo::baz; /// #[allow(unused_imports)] /// #[macro_use] /// extern crate baz; /// ``` pub USELESS_ATTRIBUTE, correctness, "use of lint attributes on `extern crate` items" } declare_clippy_lint! { /// **What it does:** Checks for `#[deprecated]` annotations with a `since` /// field that is not a valid semantic version. /// /// **Why is this bad?** For checking the version of the deprecation, it must be /// a valid semver. Failing that, the contained information is useless. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// #[deprecated(since = "forever")] /// fn something_else() { /* ... */ } /// ``` pub DEPRECATED_SEMVER, correctness, "use of `#[deprecated(since = \"x\")]` where x is not semver" } declare_clippy_lint! { /// **What it does:** Checks for empty lines after outer attributes /// /// **Why is this bad?** /// Most likely the attribute was meant to be an inner attribute using a '!'. /// If it was meant to be an outer attribute, then the following item /// should not be separated by empty lines. /// /// **Known problems:** Can cause false positives. /// /// From the clippy side it's difficult to detect empty lines between an attributes and the /// following item because empty lines and comments are not part of the AST. The parsing /// currently works for basic cases but is not perfect. /// /// **Example:** /// ```rust /// // Good (as inner attribute) /// #![inline(always)] /// /// fn this_is_fine() { } /// /// // Bad /// #[inline(always)] /// /// fn not_quite_good_code() { } /// /// // Good (as outer attribute) /// #[inline(always)] /// fn this_is_fine_too() { } /// ``` pub EMPTY_LINE_AFTER_OUTER_ATTR, nursery, "empty line after outer attribute" } declare_clippy_lint! { /// **What it does:** Checks for `allow`/`warn`/`deny`/`forbid` attributes with scoped clippy /// lints and if those lints exist in clippy. If there is an uppercase letter in the lint name /// (not the tool name) and a lowercase version of this lint exists, it will suggest to lowercase /// the lint name. /// /// **Why is this bad?** A lint attribute with a mistyped lint name won't have an effect. /// /// **Known problems:** None. /// /// **Example:** /// Bad: /// ```rust /// #![warn(if_not_els)] /// #![deny(clippy::All)] /// ``` /// /// Good: /// ```rust /// #![warn(if_not_else)] /// #![deny(clippy::all)] /// ``` pub UNKNOWN_CLIPPY_LINTS, style, "unknown_lints for scoped Clippy lints" } declare_clippy_lint! { /// **What it does:** Checks for `#[cfg_attr(rustfmt, rustfmt_skip)]` and suggests to replace it /// with `#[rustfmt::skip]`. /// /// **Why is this bad?** Since tool_attributes ([rust-lang/rust#44690](https://github.com/rust-lang/rust/issues/44690)) /// are stable now, they should be used instead of the old `cfg_attr(rustfmt)` attributes. /// /// **Known problems:** This lint doesn't detect crate level inner attributes, because they get /// processed before the PreExpansionPass lints get executed. See /// [#3123](https://github.com/rust-lang/rust-clippy/pull/3123#issuecomment-422321765) /// /// **Example:** /// /// Bad: /// ```rust /// #[cfg_attr(rustfmt, rustfmt_skip)] /// fn main() { } /// ``` /// /// Good: /// ```rust /// #[rustfmt::skip] /// fn main() { } /// ``` pub DEPRECATED_CFG_ATTR, complexity, "usage of `cfg_attr(rustfmt)` instead of tool attributes" } declare_lint_pass!(Attributes => [ INLINE_ALWAYS, DEPRECATED_SEMVER, USELESS_ATTRIBUTE, EMPTY_LINE_AFTER_OUTER_ATTR, UNKNOWN_CLIPPY_LINTS, ]); impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Attributes { fn check_attribute(&mut self, cx: &LateContext<'a, 'tcx>, attr: &'tcx Attribute) { if let Some(items) = &attr.meta_item_list() { if let Some(ident) = attr.ident() { match &*ident.as_str() { "allow" | "warn" | "deny" | "forbid" => { check_clippy_lint_names(cx, items); }, _ => {}, } if items.is_empty() || !attr.check_name(sym!(deprecated)) { return; } for item in items { if_chain! { if let NestedMetaItem::MetaItem(mi) = &item; if let MetaItemKind::NameValue(lit) = &mi.kind; if mi.check_name(sym!(since)); then { check_semver(cx, item.span(), lit); } } } } } } fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item<'_>) { if is_relevant_item(cx, item) { check_attrs(cx, item.span, item.ident.name, &item.attrs) } match item.kind { ItemKind::ExternCrate(..) | ItemKind::Use(..) => { let skip_unused_imports = item.attrs.iter().any(|attr| attr.check_name(sym!(macro_use))); for attr in item.attrs { if in_external_macro(cx.sess(), attr.span) { return; } if let Some(lint_list) = &attr.meta_item_list() { if let Some(ident) = attr.ident() { match &*ident.as_str() { "allow" | "warn" | "deny" | "forbid" => { // whitelist `unused_imports`, `deprecated` and `unreachable_pub` for `use` items // and `unused_imports` for `extern crate` items with `macro_use` for lint in lint_list { match item.kind { ItemKind::Use(..) => { if is_word(lint, sym!(unused_imports)) || is_word(lint, sym!(deprecated)) || is_word(lint, sym!(unreachable_pub)) || is_word(lint, sym!(unused)) { return; } }, ItemKind::ExternCrate(..) => { if is_word(lint, sym!(unused_imports)) && skip_unused_imports { return; } if is_word(lint, sym!(unused_extern_crates)) { return; } }, _ => {}, } } let line_span = first_line_of_span(cx, attr.span); if let Some(mut sugg) = snippet_opt(cx, line_span) { if sugg.contains("#[") { span_lint_and_then( cx, USELESS_ATTRIBUTE, line_span, "useless lint attribute", |db| { sugg = sugg.replacen("#[", "#![", 1); db.span_suggestion( line_span, "if you just forgot a `!`, use", sugg, Applicability::MaybeIncorrect, ); }, ); } } }, _ => {}, } } } } }, _ => {}, } } fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem<'_>) { if is_relevant_impl(cx, item) { check_attrs(cx, item.span, item.ident.name, &item.attrs) } } fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem<'_>) { if is_relevant_trait(cx, item) { check_attrs(cx, item.span, item.ident.name, &item.attrs) } } } #[allow(clippy::single_match_else)] fn check_clippy_lint_names(cx: &LateContext<'_, '_>, items: &[NestedMetaItem]) { let lint_store = cx.lints(); for lint in items { if_chain! { if let Some(meta_item) = lint.meta_item(); if meta_item.path.segments.len() > 1; if let tool_name = meta_item.path.segments[0].ident; if tool_name.as_str() == "clippy"; let name = meta_item.path.segments.last().unwrap().ident.name; if let CheckLintNameResult::Tool(Err((None, _))) = lint_store.check_lint_name( &name.as_str(), Some(tool_name.name), ); then { span_lint_and_then( cx, UNKNOWN_CLIPPY_LINTS, lint.span(), &format!("unknown clippy lint: clippy::{}", name), |db| { let name_lower = name.as_str().to_lowercase(); let symbols = lint_store.get_lints().iter().map( |l| Symbol::intern(&l.name_lower()) ).collect::>(); let sugg = find_best_match_for_name( symbols.iter(), &format!("clippy::{}", name_lower), None, ); if name.as_str().chars().any(char::is_uppercase) && lint_store.find_lints(&format!("clippy::{}", name_lower)).is_ok() { db.span_suggestion( lint.span(), "lowercase the lint name", format!("clippy::{}", name_lower), Applicability::MachineApplicable, ); } else if let Some(sugg) = sugg { db.span_suggestion( lint.span(), "did you mean", sugg.to_string(), Applicability::MachineApplicable, ); } } ); } }; } } fn is_relevant_item(cx: &LateContext<'_, '_>, item: &Item<'_>) -> bool { if let ItemKind::Fn(_, _, eid) = item.kind { is_relevant_expr(cx, cx.tcx.body_tables(eid), &cx.tcx.hir().body(eid).value) } else { true } } fn is_relevant_impl(cx: &LateContext<'_, '_>, item: &ImplItem<'_>) -> bool { match item.kind { ImplItemKind::Fn(_, eid) => is_relevant_expr(cx, cx.tcx.body_tables(eid), &cx.tcx.hir().body(eid).value), _ => false, } } fn is_relevant_trait(cx: &LateContext<'_, '_>, item: &TraitItem<'_>) -> bool { match item.kind { TraitItemKind::Fn(_, TraitFn::Required(_)) => true, TraitItemKind::Fn(_, TraitFn::Provided(eid)) => { is_relevant_expr(cx, cx.tcx.body_tables(eid), &cx.tcx.hir().body(eid).value) }, _ => false, } } fn is_relevant_block(cx: &LateContext<'_, '_>, tables: &ty::TypeckTables<'_>, block: &Block<'_>) -> bool { if let Some(stmt) = block.stmts.first() { match &stmt.kind { StmtKind::Local(_) => true, StmtKind::Expr(expr) | StmtKind::Semi(expr) => is_relevant_expr(cx, tables, expr), _ => false, } } else { block.expr.as_ref().map_or(false, |e| is_relevant_expr(cx, tables, e)) } } fn is_relevant_expr(cx: &LateContext<'_, '_>, tables: &ty::TypeckTables<'_>, expr: &Expr<'_>) -> bool { match &expr.kind { ExprKind::Block(block, _) => is_relevant_block(cx, tables, block), ExprKind::Ret(Some(e)) => is_relevant_expr(cx, tables, e), ExprKind::Ret(None) | ExprKind::Break(_, None) => false, ExprKind::Call(path_expr, _) => { if let ExprKind::Path(qpath) = &path_expr.kind { if let Some(fun_id) = tables.qpath_res(qpath, path_expr.hir_id).opt_def_id() { !match_def_path(cx, fun_id, &paths::BEGIN_PANIC) } else { true } } else { true } }, _ => true, } } fn check_attrs(cx: &LateContext<'_, '_>, span: Span, name: Name, attrs: &[Attribute]) { if span.from_expansion() { return; } for attr in attrs { let attr_item = if let AttrKind::Normal(ref attr) = attr.kind { attr } else { continue; }; if attr.style == AttrStyle::Outer { if attr_item.args.inner_tokens().is_empty() || !is_present_in_source(cx, attr.span) { return; } let begin_of_attr_to_item = Span::new(attr.span.lo(), span.lo(), span.ctxt()); let end_of_attr_to_item = Span::new(attr.span.hi(), span.lo(), span.ctxt()); if let Some(snippet) = snippet_opt(cx, end_of_attr_to_item) { let lines = snippet.split('\n').collect::>(); let lines = without_block_comments(lines); if lines.iter().filter(|l| l.trim().is_empty()).count() > 2 { span_lint( cx, EMPTY_LINE_AFTER_OUTER_ATTR, begin_of_attr_to_item, "Found an empty line after an outer attribute. \ Perhaps you forgot to add a `!` to make it an inner attribute?", ); } } } if let Some(values) = attr.meta_item_list() { if values.len() != 1 || !attr.check_name(sym!(inline)) { continue; } if is_word(&values[0], sym!(always)) { span_lint( cx, INLINE_ALWAYS, attr.span, &format!( "you have declared `#[inline(always)]` on `{}`. This is usually a bad idea", name ), ); } } } } fn check_semver(cx: &LateContext<'_, '_>, span: Span, lit: &Lit) { if let LitKind::Str(is, _) = lit.kind { if Version::parse(&is.as_str()).is_ok() { return; } } span_lint( cx, DEPRECATED_SEMVER, span, "the since field must contain a semver-compliant version", ); } fn is_word(nmi: &NestedMetaItem, expected: Symbol) -> bool { if let NestedMetaItem::MetaItem(mi) = &nmi { mi.is_word() && mi.check_name(expected) } else { false } } declare_lint_pass!(DeprecatedCfgAttribute => [DEPRECATED_CFG_ATTR]); impl EarlyLintPass for DeprecatedCfgAttribute { fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &Attribute) { if_chain! { // check cfg_attr if attr.check_name(sym!(cfg_attr)); if let Some(items) = attr.meta_item_list(); if items.len() == 2; // check for `rustfmt` if let Some(feature_item) = items[0].meta_item(); if feature_item.check_name(sym!(rustfmt)); // check for `rustfmt_skip` and `rustfmt::skip` if let Some(skip_item) = &items[1].meta_item(); if skip_item.check_name(sym!(rustfmt_skip)) || skip_item.path.segments.last().expect("empty path in attribute").ident.name == sym!(skip); // Only lint outer attributes, because custom inner attributes are unstable // Tracking issue: https://github.com/rust-lang/rust/issues/54726 if let AttrStyle::Outer = attr.style; then { span_lint_and_sugg( cx, DEPRECATED_CFG_ATTR, attr.span, "`cfg_attr` is deprecated for rustfmt and got replaced by tool attributes", "use", "#[rustfmt::skip]".to_string(), Applicability::MachineApplicable, ); } } } }