| use rustc::hir::def::{Res, DefKind}; |
| use rustc::hir::def_id::DefId; |
| use rustc::lint; |
| use rustc::ty::{self, Ty}; |
| use rustc::ty::adjustment; |
| use rustc_data_structures::fx::FxHashMap; |
| use lint::{LateContext, EarlyContext, LintContext, LintArray}; |
| use lint::{LintPass, EarlyLintPass, LateLintPass}; |
| |
| use syntax::ast; |
| use syntax::attr; |
| use syntax::errors::Applicability; |
| use syntax::feature_gate::{AttributeType, BuiltinAttribute, BUILTIN_ATTRIBUTE_MAP}; |
| use syntax::print::pprust; |
| use syntax::symbol::{kw, sym}; |
| use syntax::symbol::Symbol; |
| use syntax::util::parser; |
| use syntax_pos::Span; |
| |
| use rustc::hir; |
| |
| use log::debug; |
| |
| declare_lint! { |
| pub UNUSED_MUST_USE, |
| Warn, |
| "unused result of a type flagged as #[must_use]", |
| report_in_external_macro: true |
| } |
| |
| declare_lint! { |
| pub UNUSED_RESULTS, |
| Allow, |
| "unused result of an expression in a statement" |
| } |
| |
| declare_lint_pass!(UnusedResults => [UNUSED_MUST_USE, UNUSED_RESULTS]); |
| |
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedResults { |
| fn check_stmt(&mut self, cx: &LateContext<'_, '_>, s: &hir::Stmt) { |
| let expr = match s.node { |
| hir::StmtKind::Semi(ref expr) => &**expr, |
| _ => return, |
| }; |
| |
| if let hir::ExprKind::Ret(..) = expr.node { |
| return; |
| } |
| |
| let ty = cx.tables.expr_ty(&expr); |
| let type_permits_lack_of_use = check_must_use_ty(cx, ty, &expr, s.span, ""); |
| |
| let mut fn_warned = false; |
| let mut op_warned = false; |
| let maybe_def_id = match expr.node { |
| hir::ExprKind::Call(ref callee, _) => { |
| match callee.node { |
| hir::ExprKind::Path(ref qpath) => { |
| match cx.tables.qpath_res(qpath, callee.hir_id) { |
| Res::Def(DefKind::Fn, def_id) |
| | Res::Def(DefKind::Method, def_id) => Some(def_id), |
| // `Res::Local` if it was a closure, for which we |
| // do not currently support must-use linting |
| _ => None |
| } |
| }, |
| _ => None |
| } |
| }, |
| hir::ExprKind::MethodCall(..) => { |
| cx.tables.type_dependent_def_id(expr.hir_id) |
| }, |
| _ => None |
| }; |
| if let Some(def_id) = maybe_def_id { |
| fn_warned = check_must_use_def(cx, def_id, s.span, "return value of ", ""); |
| } else if type_permits_lack_of_use { |
| // We don't warn about unused unit or uninhabited types. |
| // (See https://github.com/rust-lang/rust/issues/43806 for details.) |
| return; |
| } |
| |
| let must_use_op = match expr.node { |
| // Hardcoding operators here seemed more expedient than the |
| // refactoring that would be needed to look up the `#[must_use]` |
| // attribute which does exist on the comparison trait methods |
| hir::ExprKind::Binary(bin_op, ..) => { |
| match bin_op.node { |
| hir::BinOpKind::Eq | |
| hir::BinOpKind::Lt | |
| hir::BinOpKind::Le | |
| hir::BinOpKind::Ne | |
| hir::BinOpKind::Ge | |
| hir::BinOpKind::Gt => { |
| Some("comparison") |
| }, |
| hir::BinOpKind::Add | |
| hir::BinOpKind::Sub | |
| hir::BinOpKind::Div | |
| hir::BinOpKind::Mul | |
| hir::BinOpKind::Rem => { |
| Some("arithmetic operation") |
| }, |
| hir::BinOpKind::And | hir::BinOpKind::Or => { |
| Some("logical operation") |
| }, |
| hir::BinOpKind::BitXor | |
| hir::BinOpKind::BitAnd | |
| hir::BinOpKind::BitOr | |
| hir::BinOpKind::Shl | |
| hir::BinOpKind::Shr => { |
| Some("bitwise operation") |
| }, |
| } |
| }, |
| hir::ExprKind::Unary(..) => Some("unary operation"), |
| _ => None |
| }; |
| |
| if let Some(must_use_op) = must_use_op { |
| cx.span_lint(UNUSED_MUST_USE, expr.span, |
| &format!("unused {} that must be used", must_use_op)); |
| op_warned = true; |
| } |
| |
| if !(type_permits_lack_of_use || fn_warned || op_warned) { |
| cx.span_lint(UNUSED_RESULTS, s.span, "unused result"); |
| } |
| |
| // Returns whether an error has been emitted (and thus another does not need to be later). |
| fn check_must_use_ty<'tcx>( |
| cx: &LateContext<'_, 'tcx>, |
| ty: Ty<'tcx>, |
| expr: &hir::Expr, |
| span: Span, |
| descr_post_path: &str, |
| ) -> bool { |
| if ty.is_unit() || cx.tcx.is_ty_uninhabited_from( |
| cx.tcx.hir().get_module_parent(expr.hir_id), ty) |
| { |
| return true; |
| } |
| |
| match ty.sty { |
| ty::Adt(def, _) => check_must_use_def(cx, def.did, span, "", descr_post_path), |
| ty::Opaque(def, _) => { |
| let mut has_emitted = false; |
| for (predicate, _) in &cx.tcx.predicates_of(def).predicates { |
| if let ty::Predicate::Trait(ref poly_trait_predicate) = predicate { |
| let trait_ref = poly_trait_predicate.skip_binder().trait_ref; |
| let def_id = trait_ref.def_id; |
| if check_must_use_def(cx, def_id, span, "implementer of ", "") { |
| has_emitted = true; |
| break; |
| } |
| } |
| } |
| has_emitted |
| } |
| ty::Dynamic(binder, _) => { |
| let mut has_emitted = false; |
| for predicate in binder.skip_binder().iter() { |
| if let ty::ExistentialPredicate::Trait(ref trait_ref) = predicate { |
| let def_id = trait_ref.def_id; |
| if check_must_use_def(cx, def_id, span, "", " trait object") { |
| has_emitted = true; |
| break; |
| } |
| } |
| } |
| has_emitted |
| } |
| ty::Tuple(ref tys) => { |
| let mut has_emitted = false; |
| let spans = if let hir::ExprKind::Tup(comps) = &expr.node { |
| debug_assert_eq!(comps.len(), tys.len()); |
| comps.iter().map(|e| e.span).collect() |
| } else { |
| vec![] |
| }; |
| for (i, ty) in tys.iter().map(|k| k.expect_ty()).enumerate() { |
| let descr_post_path = &format!(" in tuple element {}", i); |
| let span = *spans.get(i).unwrap_or(&span); |
| if check_must_use_ty(cx, ty, expr, span, descr_post_path) { |
| has_emitted = true; |
| } |
| } |
| has_emitted |
| } |
| _ => false, |
| } |
| } |
| |
| // Returns whether an error has been emitted (and thus another does not need to be later). |
| fn check_must_use_def( |
| cx: &LateContext<'_, '_>, |
| def_id: DefId, |
| span: Span, |
| descr_pre_path: &str, |
| descr_post_path: &str, |
| ) -> bool { |
| for attr in cx.tcx.get_attrs(def_id).iter() { |
| if attr.check_name(sym::must_use) { |
| let msg = format!("unused {}`{}`{} that must be used", |
| descr_pre_path, cx.tcx.def_path_str(def_id), descr_post_path); |
| let mut err = cx.struct_span_lint(UNUSED_MUST_USE, span, &msg); |
| // check for #[must_use = "..."] |
| if let Some(note) = attr.value_str() { |
| err.note(¬e.as_str()); |
| } |
| err.emit(); |
| return true; |
| } |
| } |
| false |
| } |
| } |
| } |
| |
| declare_lint! { |
| pub PATH_STATEMENTS, |
| Warn, |
| "path statements with no effect" |
| } |
| |
| declare_lint_pass!(PathStatements => [PATH_STATEMENTS]); |
| |
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for PathStatements { |
| fn check_stmt(&mut self, cx: &LateContext<'_, '_>, s: &hir::Stmt) { |
| if let hir::StmtKind::Semi(ref expr) = s.node { |
| if let hir::ExprKind::Path(_) = expr.node { |
| cx.span_lint(PATH_STATEMENTS, s.span, "path statement with no effect"); |
| } |
| } |
| } |
| } |
| |
| declare_lint! { |
| pub UNUSED_ATTRIBUTES, |
| Warn, |
| "detects attributes that were not used by the compiler" |
| } |
| |
| #[derive(Copy, Clone)] |
| pub struct UnusedAttributes { |
| builtin_attributes: &'static FxHashMap<Symbol, &'static BuiltinAttribute>, |
| } |
| |
| impl UnusedAttributes { |
| pub fn new() -> Self { |
| UnusedAttributes { |
| builtin_attributes: &*BUILTIN_ATTRIBUTE_MAP, |
| } |
| } |
| } |
| |
| impl_lint_pass!(UnusedAttributes => [UNUSED_ATTRIBUTES]); |
| |
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedAttributes { |
| fn check_attribute(&mut self, cx: &LateContext<'_, '_>, attr: &ast::Attribute) { |
| debug!("checking attribute: {:?}", attr); |
| |
| let attr_info = attr.ident().and_then(|ident| self.builtin_attributes.get(&ident.name)); |
| |
| if let Some(&&(name, ty, ..)) = attr_info { |
| match ty { |
| AttributeType::Whitelisted => { |
| debug!("{:?} is Whitelisted", name); |
| return; |
| } |
| _ => (), |
| } |
| } |
| |
| let plugin_attributes = cx.sess().plugin_attributes.borrow_mut(); |
| for &(name, ty) in plugin_attributes.iter() { |
| if ty == AttributeType::Whitelisted && attr.check_name(name) { |
| debug!("{:?} (plugin attr) is whitelisted with ty {:?}", name, ty); |
| break; |
| } |
| } |
| |
| let name = attr.name_or_empty(); |
| if !attr::is_used(attr) { |
| debug!("Emitting warning for: {:?}", attr); |
| cx.span_lint(UNUSED_ATTRIBUTES, attr.span, "unused attribute"); |
| // Is it a builtin attribute that must be used at the crate level? |
| let known_crate = attr_info.map(|&&(_, ty, ..)| { |
| ty == AttributeType::CrateLevel |
| }).unwrap_or(false); |
| |
| // Has a plugin registered this attribute as one that must be used at |
| // the crate level? |
| let plugin_crate = plugin_attributes.iter() |
| .find(|&&(x, t)| name == x && AttributeType::CrateLevel == t) |
| .is_some(); |
| if known_crate || plugin_crate { |
| let msg = match attr.style { |
| ast::AttrStyle::Outer => { |
| "crate-level attribute should be an inner attribute: add an exclamation \ |
| mark: #![foo]" |
| } |
| ast::AttrStyle::Inner => "crate-level attribute should be in the root module", |
| }; |
| cx.span_lint(UNUSED_ATTRIBUTES, attr.span, msg); |
| } |
| } else { |
| debug!("Attr was used: {:?}", attr); |
| } |
| } |
| } |
| |
| declare_lint! { |
| pub(super) UNUSED_PARENS, |
| Warn, |
| "`if`, `match`, `while` and `return` do not need parentheses" |
| } |
| |
| declare_lint_pass!(UnusedParens => [UNUSED_PARENS]); |
| |
| impl UnusedParens { |
| fn check_unused_parens_expr(&self, |
| cx: &EarlyContext<'_>, |
| value: &ast::Expr, |
| msg: &str, |
| followed_by_block: bool) { |
| match value.node { |
| ast::ExprKind::Paren(ref inner) => { |
| let necessary = followed_by_block && match inner.node { |
| ast::ExprKind::Ret(_) | ast::ExprKind::Break(..) => true, |
| _ => parser::contains_exterior_struct_lit(&inner), |
| }; |
| if !necessary { |
| let expr_text = if let Ok(snippet) = cx.sess().source_map() |
| .span_to_snippet(value.span) { |
| snippet |
| } else { |
| pprust::expr_to_string(value) |
| }; |
| Self::remove_outer_parens(cx, value.span, &expr_text, msg); |
| } |
| } |
| ast::ExprKind::Let(_, ref expr) => { |
| // FIXME(#60336): Properly handle `let true = (false && true)` |
| // actually needing the parenthesis. |
| self.check_unused_parens_expr(cx, expr, "`let` head expression", followed_by_block); |
| } |
| _ => {} |
| } |
| } |
| |
| fn check_unused_parens_pat(&self, |
| cx: &EarlyContext<'_>, |
| value: &ast::Pat, |
| msg: &str) { |
| if let ast::PatKind::Paren(_) = value.node { |
| let pattern_text = if let Ok(snippet) = cx.sess().source_map() |
| .span_to_snippet(value.span) { |
| snippet |
| } else { |
| pprust::pat_to_string(value) |
| }; |
| Self::remove_outer_parens(cx, value.span, &pattern_text, msg); |
| } |
| } |
| |
| fn remove_outer_parens(cx: &EarlyContext<'_>, span: Span, pattern: &str, msg: &str) { |
| let span_msg = format!("unnecessary parentheses around {}", msg); |
| let mut err = cx.struct_span_lint(UNUSED_PARENS, span, &span_msg); |
| let mut ate_left_paren = false; |
| let mut ate_right_paren = false; |
| let parens_removed = pattern |
| .trim_matches(|c| { |
| match c { |
| '(' => { |
| if ate_left_paren { |
| false |
| } else { |
| ate_left_paren = true; |
| true |
| } |
| }, |
| ')' => { |
| if ate_right_paren { |
| false |
| } else { |
| ate_right_paren = true; |
| true |
| } |
| }, |
| _ => false, |
| } |
| }).to_owned(); |
| err.span_suggestion_short( |
| span, |
| "remove these parentheses", |
| parens_removed, |
| Applicability::MachineApplicable, |
| ); |
| err.emit(); |
| } |
| } |
| |
| impl EarlyLintPass for UnusedParens { |
| fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) { |
| use syntax::ast::ExprKind::*; |
| let (value, msg, followed_by_block) = match e.node { |
| If(ref cond, ..) => (cond, "`if` condition", true), |
| While(ref cond, ..) => (cond, "`while` condition", true), |
| ForLoop(_, ref cond, ..) => (cond, "`for` head expression", true), |
| Match(ref head, _) => (head, "`match` head expression", true), |
| Ret(Some(ref value)) => (value, "`return` value", false), |
| Assign(_, ref value) => (value, "assigned value", false), |
| AssignOp(.., ref value) => (value, "assigned value", false), |
| // either function/method call, or something this lint doesn't care about |
| ref call_or_other => { |
| let (args_to_check, call_kind) = match *call_or_other { |
| Call(_, ref args) => (&args[..], "function"), |
| // first "argument" is self (which sometimes needs parens) |
| MethodCall(_, ref args) => (&args[1..], "method"), |
| // actual catch-all arm |
| _ => { |
| return; |
| } |
| }; |
| // Don't lint if this is a nested macro expansion: otherwise, the lint could |
| // trigger in situations that macro authors shouldn't have to care about, e.g., |
| // when a parenthesized token tree matched in one macro expansion is matched as |
| // an expression in another and used as a fn/method argument (Issue #47775) |
| if e.span.ctxt().outer_expn_info() |
| .map_or(false, |info| info.call_site.ctxt().outer_expn_info().is_some()) { |
| return; |
| } |
| let msg = format!("{} argument", call_kind); |
| for arg in args_to_check { |
| self.check_unused_parens_expr(cx, arg, &msg, false); |
| } |
| return; |
| } |
| }; |
| self.check_unused_parens_expr(cx, &value, msg, followed_by_block); |
| } |
| |
| fn check_pat(&mut self, cx: &EarlyContext<'_>, p: &ast::Pat) { |
| use ast::PatKind::{Paren, Range}; |
| // The lint visitor will visit each subpattern of `p`. We do not want to lint any range |
| // pattern no matter where it occurs in the pattern. For something like `&(a..=b)`, there |
| // is a recursive `check_pat` on `a` and `b`, but we will assume that if there are |
| // unnecessary parens they serve a purpose of readability. |
| if let Paren(ref pat) = p.node { |
| match pat.node { |
| Range(..) => {} |
| _ => self.check_unused_parens_pat(cx, &p, "pattern") |
| } |
| } |
| } |
| |
| fn check_stmt(&mut self, cx: &EarlyContext<'_>, s: &ast::Stmt) { |
| if let ast::StmtKind::Local(ref local) = s.node { |
| if let Some(ref value) = local.init { |
| self.check_unused_parens_expr(cx, &value, "assigned value", false); |
| } |
| } |
| } |
| } |
| |
| declare_lint! { |
| UNUSED_IMPORT_BRACES, |
| Allow, |
| "unnecessary braces around an imported item" |
| } |
| |
| declare_lint_pass!(UnusedImportBraces => [UNUSED_IMPORT_BRACES]); |
| |
| impl UnusedImportBraces { |
| fn check_use_tree(&self, cx: &EarlyContext<'_>, use_tree: &ast::UseTree, item: &ast::Item) { |
| if let ast::UseTreeKind::Nested(ref items) = use_tree.kind { |
| // Recursively check nested UseTrees |
| for &(ref tree, _) in items { |
| self.check_use_tree(cx, tree, item); |
| } |
| |
| // Trigger the lint only if there is one nested item |
| if items.len() != 1 { |
| return; |
| } |
| |
| // Trigger the lint if the nested item is a non-self single item |
| let node_ident; |
| match items[0].0.kind { |
| ast::UseTreeKind::Simple(rename, ..) => { |
| let orig_ident = items[0].0.prefix.segments.last().unwrap().ident; |
| if orig_ident.name == kw::SelfLower { |
| return; |
| } |
| node_ident = rename.unwrap_or(orig_ident); |
| } |
| ast::UseTreeKind::Glob => { |
| node_ident = ast::Ident::from_str("*"); |
| } |
| ast::UseTreeKind::Nested(_) => { |
| return; |
| } |
| } |
| |
| let msg = format!("braces around {} is unnecessary", node_ident.name); |
| cx.span_lint(UNUSED_IMPORT_BRACES, item.span, &msg); |
| } |
| } |
| } |
| |
| impl EarlyLintPass for UnusedImportBraces { |
| fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) { |
| if let ast::ItemKind::Use(ref use_tree) = item.node { |
| self.check_use_tree(cx, use_tree, item); |
| } |
| } |
| } |
| |
| declare_lint! { |
| pub(super) UNUSED_ALLOCATION, |
| Warn, |
| "detects unnecessary allocations that can be eliminated" |
| } |
| |
| declare_lint_pass!(UnusedAllocation => [UNUSED_ALLOCATION]); |
| |
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedAllocation { |
| fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr) { |
| match e.node { |
| hir::ExprKind::Box(_) => {} |
| _ => return, |
| } |
| |
| for adj in cx.tables.expr_adjustments(e) { |
| if let adjustment::Adjust::Borrow(adjustment::AutoBorrow::Ref(_, m)) = adj.kind { |
| let msg = match m { |
| adjustment::AutoBorrowMutability::Immutable => |
| "unnecessary allocation, use & instead", |
| adjustment::AutoBorrowMutability::Mutable { .. }=> |
| "unnecessary allocation, use &mut instead" |
| }; |
| cx.span_lint(UNUSED_ALLOCATION, e.span, msg); |
| } |
| } |
| } |
| } |