//! checks for attributes use crate::reexport::*; use rustc::hir::*; use rustc::lint::*; use rustc::ty::{self, TyCtxt}; use semver::Version; use syntax::ast::{AttrStyle, Attribute, Lit, LitKind, MetaItemKind, NestedMetaItem, NestedMetaItemKind}; use syntax::codemap::Span; use crate::utils::{ in_macro, last_line_of_span, match_def_path, opt_def_id, paths, snippet_opt, span_lint, span_lint_and_then, without_block_comments, }; /// **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_clippy_lint! { pub INLINE_ALWAYS, pedantic, "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_clippy_lint! { pub USELESS_ATTRIBUTE, correctness, "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_clippy_lint! { pub DEPRECATED_SEMVER, correctness, "use of `#[deprecated(since = \"x\")]` where x is not semver" } /// **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 /// // Bad /// #[inline(always)] /// /// fn not_quite_good_code(..) { ... } /// /// // Good (as inner attribute) /// #![inline(always)] /// /// fn this_is_fine(..) { ... } /// /// // Good (as outer attribute) /// #[inline(always)] /// fn this_is_fine_too(..) { ... } /// ``` declare_clippy_lint! { pub EMPTY_LINE_AFTER_OUTER_ATTR, nursery, "empty line after outer attribute" } #[derive(Copy, Clone)] pub struct AttrPass; impl LintPass for AttrPass { fn get_lints(&self) -> LintArray { lint_array!( INLINE_ALWAYS, DEPRECATED_SEMVER, USELESS_ATTRIBUTE, EMPTY_LINE_AFTER_OUTER_ATTR ) } } 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() != "deprecated" { return; } for item in items { if_chain! { if let NestedMetaItemKind::MetaItem(ref mi) = item.node; if let MetaItemKind::NameValue(ref lit) = mi.node; if mi.name() == "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.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() { match &*attr.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; } } } let line_span = last_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); }, ); } } }, _ => {}, } } } }, _ => {}, } } 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 { true } } 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 { if let Some(fun_id) = opt_def_id(tables.qpath_def(qpath, path_expr.hir_id)) { !match_def_path(tcx, fun_id, &paths::BEGIN_PANIC) } else { true } } else { true }, _ => true, } } fn check_attrs(cx: &LateContext, span: Span, name: &Name, attrs: &[Attribute]) { if in_macro(span) { return; } for attr in attrs { if attr.is_sugared_doc { return; } if attr.style == AttrStyle::Outer { if attr.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(ref values) = attr.meta_item_list() { if values.len() != 1 || attr.name() != "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 } } // If the snippet is empty, it's an attribute that was inserted during macro // expansion and we want to ignore those, because they could come from external // sources that the user has no control over. // For some reason these attributes don't have any expansion info on them, so // we have to check it this way until there is a better way. fn is_present_in_source(cx: &LateContext, span: Span) -> bool { if let Some(snippet) = snippet_opt(cx, span) { if snippet.is_empty() { return false; } } true }