//! checks for attributes use reexport::*; use rustc::lint::*; use rustc::hir::*; use rustc::ty::{self, TyCtxt}; use semver::Version; use syntax::ast::{Attribute, Lit, LitKind, MetaItemKind, NestedMetaItem, NestedMetaItemKind}; use syntax::codemap::Span; use utils::{in_macro, match_def_path, paths, span_lint, span_lint_and_then, snippet_opt}; /// **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:** /// ```rust /// #[inline(always)] /// fn not_quite_hot_code(..) { ... } /// ``` declare_lint! { pub INLINE_ALWAYS, Warn, "use of `#[inline(always)]`" } /// **What it does:** Checks for `extern crate` and `use` items annotated with lint attributes /// /// **Why is this bad?** Lint attributes have no effect on crate imports. Most likely a `!` was /// forgotten /// /// **Known problems:** Technically one might allow `unused_import` on a `use` item, /// but it's easier to remove the unused item. /// /// **Example:** /// ```rust /// #[deny(dead_code)] /// extern crate foo; /// #[allow(unused_import)] /// use foo::bar; /// ``` declare_lint! { pub USELESS_ATTRIBUTE, Warn, "use of lint attributes on `extern crate` items" } /// **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(..) { ... } /// ``` declare_lint! { pub DEPRECATED_SEMVER, Warn, "use of `#[deprecated(since = \"x\")]` where x is not semver" } #[derive(Copy,Clone)] pub struct AttrPass; impl LintPass for AttrPass { fn get_lints(&self) -> LintArray { lint_array!(INLINE_ALWAYS, DEPRECATED_SEMVER, USELESS_ATTRIBUTE) } } impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AttrPass { fn check_attribute(&mut self, cx: &LateContext<'a, 'tcx>, attr: &'tcx Attribute) { if let Some(ref items) = attr.meta_item_list() { if items.is_empty() || attr.name().map_or(true, |n| n != "deprecated") { return; } for item in items { if_let_chain! {[ let NestedMetaItemKind::MetaItem(ref mi) = item.node, let MetaItemKind::NameValue(ref lit) = mi.node, mi.name() == "since", ], { check_semver(cx, item.span, lit); }} } } } fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) { if is_relevant_item(cx.tcx, item) { check_attrs(cx, item.span, &item.name, &item.attrs) } match item.node { ItemExternCrate(_) | ItemUse(_, _) => { for attr in &item.attrs { if let Some(ref lint_list) = attr.meta_item_list() { if let Some(name) = attr.name() { match &*name.as_str() { "allow" | "warn" | "deny" | "forbid" => { // whitelist `unused_imports` and `deprecated` for lint in lint_list { if is_word(lint, "unused_imports") || is_word(lint, "deprecated") { if let ItemUse(_, _) = item.node { return; } } } if let Some(mut sugg) = snippet_opt(cx, attr.span) { if sugg.len() > 1 { span_lint_and_then(cx, USELESS_ATTRIBUTE, attr.span, "useless lint attribute", |db| { sugg.insert(1, '!'); db.span_suggestion(attr.span, "if you just forgot a `!`, use", sugg); }); } } }, _ => {}, } } } } }, _ => {}, } } fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem) { if is_relevant_impl(cx.tcx, item) { check_attrs(cx, item.span, &item.name, &item.attrs) } } fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) { if is_relevant_trait(cx.tcx, item) { check_attrs(cx, item.span, &item.name, &item.attrs) } } } fn is_relevant_item(tcx: TyCtxt, item: &Item) -> bool { if let ItemFn(_, _, _, _, _, eid) = item.node { is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir.body(eid).value) } else { false } } fn is_relevant_impl(tcx: TyCtxt, item: &ImplItem) -> bool { match item.node { ImplItemKind::Method(_, eid) => is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir.body(eid).value), _ => false, } } fn is_relevant_trait(tcx: TyCtxt, item: &TraitItem) -> bool { match item.node { TraitItemKind::Method(_, TraitMethod::Required(_)) => true, TraitItemKind::Method(_, TraitMethod::Provided(eid)) => { is_relevant_expr(tcx, tcx.body_tables(eid), &tcx.hir.body(eid).value) }, _ => false, } } fn is_relevant_block(tcx: TyCtxt, tables: &ty::TypeckTables, block: &Block) -> bool { if let Some(stmt) = block.stmts.first() { match stmt.node { StmtDecl(_, _) => true, StmtExpr(ref expr, _) | StmtSemi(ref expr, _) => is_relevant_expr(tcx, tables, expr), } } else { block.expr.as_ref().map_or(false, |e| is_relevant_expr(tcx, tables, e)) } } fn is_relevant_expr(tcx: TyCtxt, tables: &ty::TypeckTables, expr: &Expr) -> bool { match expr.node { ExprBlock(ref block) => is_relevant_block(tcx, tables, block), ExprRet(Some(ref e)) => is_relevant_expr(tcx, tables, e), ExprRet(None) | ExprBreak(_, None) => false, ExprCall(ref path_expr, _) => { if let ExprPath(ref qpath) = path_expr.node { let fun_id = tables.qpath_def(qpath, path_expr.id).def_id(); !match_def_path(tcx, fun_id, &paths::BEGIN_PANIC) } else { true } }, _ => true, } } fn check_attrs(cx: &LateContext, span: Span, name: &Name, attrs: &[Attribute]) { if in_macro(span) { return; } for attr in attrs { if let Some(ref values) = attr.meta_item_list() { if values.len() != 1 || attr.name().map_or(true, |n| n != "inline") { continue; } if is_word(&values[0], "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(ref is, _) = lit.node { 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: &str) -> bool { if let NestedMetaItemKind::MetaItem(ref mi) = nmi.node { mi.is_word() && mi.name() == expected } else { false } }