1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 use rustc::hir::pat_util;
13 use rustc::ty::adjustment;
14 use util::nodemap::FnvHashMap;
15 use lint::{LateContext, EarlyContext, LintContext, LintArray};
16 use lint::{LintPass, EarlyLintPass, LateLintPass};
18 use std::collections::hash_map::Entry::{Occupied, Vacant};
21 use syntax::attr::{self, AttrMetaMethods};
22 use syntax::feature_gate::{KNOWN_ATTRIBUTES, AttributeType};
26 use rustc_back::slice;
28 use rustc::hir::intravisit::FnKind;
33 "detect mut variables which don't need to be mutable"
36 #[derive(Copy, Clone)]
40 fn check_unused_mut_pat(&self, cx: &LateContext, pats: &[P<hir::Pat>]) {
41 // collect all mutable pattern and group their NodeIDs by their Identifier to
42 // avoid false warnings in match arms with multiple patterns
44 let mut mutables = FnvHashMap();
46 pat_util::pat_bindings(p, |mode, id, _, path1| {
47 let name = path1.node;
48 if let hir::BindByValue(hir::MutMutable) = mode {
49 if !name.as_str().starts_with("_") {
50 match mutables.entry(name.0 as usize) {
51 Vacant(entry) => { entry.insert(vec![id]); },
52 Occupied(mut entry) => { entry.get_mut().push(id); },
59 let used_mutables = cx.tcx.used_mut_nodes.borrow();
60 for (_, v) in &mutables {
61 if !v.iter().any(|e| used_mutables.contains(e)) {
62 cx.span_lint(UNUSED_MUT, cx.tcx.map.span(v[0]),
63 "variable does not need to be mutable");
69 impl LintPass for UnusedMut {
70 fn get_lints(&self) -> LintArray {
71 lint_array!(UNUSED_MUT)
75 impl LateLintPass for UnusedMut {
76 fn check_expr(&mut self, cx: &LateContext, e: &hir::Expr) {
77 if let hir::ExprMatch(_, ref arms, _) = e.node {
79 self.check_unused_mut_pat(cx, &a.pats)
84 fn check_stmt(&mut self, cx: &LateContext, s: &hir::Stmt) {
85 if let hir::StmtDecl(ref d, _) = s.node {
86 if let hir::DeclLocal(ref l) = d.node {
87 self.check_unused_mut_pat(cx, slice::ref_slice(&l.pat));
92 fn check_fn(&mut self, cx: &LateContext,
93 _: FnKind, decl: &hir::FnDecl,
94 _: &hir::Block, _: Span, _: ast::NodeId) {
95 for a in &decl.inputs {
96 self.check_unused_mut_pat(cx, slice::ref_slice(&a.pat));
104 "unused result of a type flagged as #[must_use]"
110 "unused result of an expression in a statement"
113 #[derive(Copy, Clone)]
114 pub struct UnusedResults;
116 impl LintPass for UnusedResults {
117 fn get_lints(&self) -> LintArray {
118 lint_array!(UNUSED_MUST_USE, UNUSED_RESULTS)
122 impl LateLintPass for UnusedResults {
123 fn check_stmt(&mut self, cx: &LateContext, s: &hir::Stmt) {
124 let expr = match s.node {
125 hir::StmtSemi(ref expr, _) => &**expr,
129 if let hir::ExprRet(..) = expr.node {
133 let t = cx.tcx.expr_ty(&expr);
134 let warned = match t.sty {
135 ty::TyTuple(ref tys) if tys.is_empty() => return,
136 ty::TyBool => return,
137 ty::TyStruct(def, _) |
138 ty::TyEnum(def, _) => {
139 let attrs = cx.tcx.get_attrs(def.did);
140 check_must_use(cx, &attrs[..], s.span)
145 cx.span_lint(UNUSED_RESULTS, s.span, "unused result");
148 fn check_must_use(cx: &LateContext, attrs: &[ast::Attribute], sp: Span) -> bool {
150 if attr.check_name("must_use") {
151 let mut msg = "unused result which must be used".to_string();
152 // check for #[must_use="..."]
153 if let Some(s) = attr.value_str() {
157 cx.span_lint(UNUSED_MUST_USE, sp, &msg);
169 "unnecessary use of an `unsafe` block"
172 #[derive(Copy, Clone)]
173 pub struct UnusedUnsafe;
175 impl LintPass for UnusedUnsafe {
176 fn get_lints(&self) -> LintArray {
177 lint_array!(UNUSED_UNSAFE)
181 impl LateLintPass for UnusedUnsafe {
182 fn check_expr(&mut self, cx: &LateContext, e: &hir::Expr) {
183 if let hir::ExprBlock(ref blk) = e.node {
184 // Don't warn about generated blocks, that'll just pollute the output.
185 if blk.rules == hir::UnsafeBlock(hir::UserProvided) &&
186 !cx.tcx.used_unsafe.borrow().contains(&blk.id) {
187 cx.span_lint(UNUSED_UNSAFE, blk.span, "unnecessary `unsafe` block");
196 "path statements with no effect"
199 #[derive(Copy, Clone)]
200 pub struct PathStatements;
202 impl LintPass for PathStatements {
203 fn get_lints(&self) -> LintArray {
204 lint_array!(PATH_STATEMENTS)
208 impl LateLintPass for PathStatements {
209 fn check_stmt(&mut self, cx: &LateContext, s: &hir::Stmt) {
210 if let hir::StmtSemi(ref expr, _) = s.node {
211 if let hir::ExprPath(..) = expr.node {
212 cx.span_lint(PATH_STATEMENTS, s.span,
213 "path statement with no effect");
220 pub UNUSED_ATTRIBUTES,
222 "detects attributes that were not used by the compiler"
225 #[derive(Copy, Clone)]
226 pub struct UnusedAttributes;
228 impl LintPass for UnusedAttributes {
229 fn get_lints(&self) -> LintArray {
230 lint_array!(UNUSED_ATTRIBUTES)
234 impl LateLintPass for UnusedAttributes {
235 fn check_attribute(&mut self, cx: &LateContext, attr: &ast::Attribute) {
236 // Note that check_name() marks the attribute as used if it matches.
237 for &(ref name, ty, _) in KNOWN_ATTRIBUTES {
239 AttributeType::Whitelisted if attr.check_name(name) => {
246 let plugin_attributes = cx.sess().plugin_attributes.borrow_mut();
247 for &(ref name, ty) in plugin_attributes.iter() {
248 if ty == AttributeType::Whitelisted && attr.check_name(&name) {
253 if !attr::is_used(attr) {
254 cx.span_lint(UNUSED_ATTRIBUTES, attr.span, "unused attribute");
255 // Is it a builtin attribute that must be used at the crate level?
256 let known_crate = KNOWN_ATTRIBUTES.iter().find(|&&(name, ty, _)| {
257 attr.name() == name &&
258 ty == AttributeType::CrateLevel
261 // Has a plugin registered this attribute as one which must be used at
263 let plugin_crate = plugin_attributes.iter()
264 .find(|&&(ref x, t)| {
265 &*attr.name() == x &&
266 AttributeType::CrateLevel == t
268 if known_crate || plugin_crate {
269 let msg = match attr.node.style {
270 ast::AttrStyle::Outer => "crate-level attribute should be an inner \
271 attribute: add an exclamation mark: #![foo]",
272 ast::AttrStyle::Inner => "crate-level attribute should be in the \
275 cx.span_lint(UNUSED_ATTRIBUTES, attr.span, msg);
284 "`if`, `match`, `while` and `return` do not need parentheses"
287 #[derive(Copy, Clone)]
288 pub struct UnusedParens;
291 fn check_unused_parens_core(&self, cx: &EarlyContext, value: &ast::Expr, msg: &str,
292 struct_lit_needs_parens: bool) {
293 if let ast::ExprKind::Paren(ref inner) = value.node {
294 let necessary = struct_lit_needs_parens && contains_exterior_struct_lit(&inner);
296 cx.span_lint(UNUSED_PARENS, value.span,
297 &format!("unnecessary parentheses around {}", msg))
301 /// Expressions that syntactically contain an "exterior" struct
302 /// literal i.e. not surrounded by any parens or other
303 /// delimiters, e.g. `X { y: 1 }`, `X { y: 1 }.method()`, `foo
304 /// == X { y: 1 }` and `X { y: 1 } == foo` all do, but `(X {
305 /// y: 1 }) == foo` does not.
306 fn contains_exterior_struct_lit(value: &ast::Expr) -> bool {
308 ast::ExprKind::Struct(..) => true,
310 ast::ExprKind::Assign(ref lhs, ref rhs) |
311 ast::ExprKind::AssignOp(_, ref lhs, ref rhs) |
312 ast::ExprKind::Binary(_, ref lhs, ref rhs) => {
313 // X { y: 1 } + X { y: 2 }
314 contains_exterior_struct_lit(&lhs) ||
315 contains_exterior_struct_lit(&rhs)
317 ast::ExprKind::Unary(_, ref x) |
318 ast::ExprKind::Cast(ref x, _) |
319 ast::ExprKind::Type(ref x, _) |
320 ast::ExprKind::Field(ref x, _) |
321 ast::ExprKind::TupField(ref x, _) |
322 ast::ExprKind::Index(ref x, _) => {
323 // &X { y: 1 }, X { y: 1 }.y
324 contains_exterior_struct_lit(&x)
327 ast::ExprKind::MethodCall(_, _, ref exprs) => {
328 // X { y: 1 }.bar(...)
329 contains_exterior_struct_lit(&exprs[0])
338 impl LintPass for UnusedParens {
339 fn get_lints(&self) -> LintArray {
340 lint_array!(UNUSED_PARENS)
344 impl EarlyLintPass for UnusedParens {
345 fn check_expr(&mut self, cx: &EarlyContext, e: &ast::Expr) {
346 use syntax::ast::ExprKind::*;
347 let (value, msg, struct_lit_needs_parens) = match e.node {
348 If(ref cond, _, _) => (cond, "`if` condition", true),
349 While(ref cond, _, _) => (cond, "`while` condition", true),
350 IfLet(_, ref cond, _, _) => (cond, "`if let` head expression", true),
351 WhileLet(_, ref cond, _, _) => (cond, "`while let` head expression", true),
352 ForLoop(_, ref cond, _, _) => (cond, "`for` head expression", true),
353 Match(ref head, _) => (head, "`match` head expression", true),
354 Ret(Some(ref value)) => (value, "`return` value", false),
355 Assign(_, ref value) => (value, "assigned value", false),
356 AssignOp(_, _, ref value) => (value, "assigned value", false),
357 InPlace(_, ref value) => (value, "emplacement value", false),
360 self.check_unused_parens_core(cx, &value, msg, struct_lit_needs_parens);
363 fn check_stmt(&mut self, cx: &EarlyContext, s: &ast::Stmt) {
364 let (value, msg) = match s.node {
365 ast::StmtKind::Local(ref local) => match local.init {
366 Some(ref value) => (value, "assigned value"),
371 self.check_unused_parens_core(cx, &value, msg, false);
376 UNUSED_IMPORT_BRACES,
378 "unnecessary braces around an imported item"
381 #[derive(Copy, Clone)]
382 pub struct UnusedImportBraces;
384 impl LintPass for UnusedImportBraces {
385 fn get_lints(&self) -> LintArray {
386 lint_array!(UNUSED_IMPORT_BRACES)
390 impl LateLintPass for UnusedImportBraces {
391 fn check_item(&mut self, cx: &LateContext, item: &hir::Item) {
392 if let hir::ItemUse(ref view_path) = item.node {
393 if let hir::ViewPathList(_, ref items) = view_path.node {
394 if items.len() == 1 {
395 if let hir::PathListIdent {ref name, ..} = items[0].node {
396 let m = format!("braces around {} is unnecessary",
398 cx.span_lint(UNUSED_IMPORT_BRACES, item.span,
410 "detects unnecessary allocations that can be eliminated"
413 #[derive(Copy, Clone)]
414 pub struct UnusedAllocation;
416 impl LintPass for UnusedAllocation {
417 fn get_lints(&self) -> LintArray {
418 lint_array!(UNUSED_ALLOCATION)
422 impl LateLintPass for UnusedAllocation {
423 fn check_expr(&mut self, cx: &LateContext, e: &hir::Expr) {
425 hir::ExprBox(_) => {}
429 if let Some(adjustment) = cx.tcx.tables.borrow().adjustments.get(&e.id) {
430 if let adjustment::AdjustDerefRef(adjustment::AutoDerefRef {
434 &Some(adjustment::AutoPtr(_, hir::MutImmutable)) => {
435 cx.span_lint(UNUSED_ALLOCATION, e.span,
436 "unnecessary allocation, use & instead");
438 &Some(adjustment::AutoPtr(_, hir::MutMutable)) => {
439 cx.span_lint(UNUSED_ALLOCATION, e.span,
440 "unnecessary allocation, use &mut instead");