1 use crate::reexport::*;
2 use crate::utils::{contains_name, higher, iter_input_pats, snippet, span_lint_and_then};
3 use rustc::hir::intravisit::FnKind;
5 use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass};
7 use rustc::{declare_tool_lint, lint_array};
8 use syntax::source_map::Span;
10 declare_clippy_lint! {
11 /// **What it does:** Checks for bindings that shadow other bindings already in
12 /// scope, while just changing reference level or mutability.
14 /// **Why is this bad?** Not much, in fact it's a very common pattern in Rust
15 /// code. Still, some may opt to avoid it in their code base, they can set this
18 /// **Known problems:** This lint, as the other shadowing related lints,
19 /// currently only catches very simple patterns.
27 "rebinding a name to itself, e.g., `let mut x = &mut x`"
30 declare_clippy_lint! {
31 /// **What it does:** Checks for bindings that shadow other bindings already in
32 /// scope, while reusing the original value.
34 /// **Why is this bad?** Not too much, in fact it's a common pattern in Rust
35 /// code. Still, some argue that name shadowing like this hurts readability,
36 /// because a value may be bound to different things depending on position in
39 /// **Known problems:** This lint, as the other shadowing related lints,
40 /// currently only catches very simple patterns.
46 /// use different variable name:
52 "rebinding a name to an expression that re-uses the original value, e.g., `let x = x + 1`"
55 declare_clippy_lint! {
56 /// **What it does:** Checks for bindings that shadow other bindings already in
57 /// scope, either without a initialization or with one that does not even use
58 /// the original value.
60 /// **Why is this bad?** Name shadowing can hurt readability, especially in
61 /// large code bases, because it is easy to lose track of the active binding at
62 /// any place in the code. This can be alleviated by either giving more specific
63 /// names to bindings or introducing more scopes to contain the bindings.
65 /// **Known problems:** This lint, as the other shadowing related lints,
66 /// currently only catches very simple patterns.
71 /// let x = z; // shadows the earlier binding
75 "rebinding a name without even using the original value"
78 #[derive(Copy, Clone)]
81 impl LintPass for Pass {
82 fn get_lints(&self) -> LintArray {
83 lint_array!(SHADOW_SAME, SHADOW_REUSE, SHADOW_UNRELATED)
86 fn name(&self) -> &'static str {
91 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
94 cx: &LateContext<'a, 'tcx>,
101 if in_external_macro(cx.sess(), body.value.span) {
104 check_fn(cx, decl, body);
108 fn check_fn<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl, body: &'tcx Body) {
109 let mut bindings = Vec::new();
110 for arg in iter_input_pats(decl, body) {
111 if let PatKind::Binding(.., ident, _) = arg.pat.node {
112 bindings.push((ident.name, ident.span))
115 check_expr(cx, &body.value, &mut bindings);
118 fn check_block<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, block: &'tcx Block, bindings: &mut Vec<(Name, Span)>) {
119 let len = bindings.len();
120 for stmt in &block.stmts {
122 StmtKind::Local(ref local) => check_local(cx, local, bindings),
123 StmtKind::Expr(ref e) | StmtKind::Semi(ref e) => check_expr(cx, e, bindings),
124 StmtKind::Item(..) => {},
127 if let Some(ref o) = block.expr {
128 check_expr(cx, o, bindings);
130 bindings.truncate(len);
133 fn check_local<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, local: &'tcx Local, bindings: &mut Vec<(Name, Span)>) {
134 if in_external_macro(cx.sess(), local.span) {
137 if higher::is_from_for_desugar(local) {
147 if let Some(ref t) = *ty {
148 check_ty(cx, t, bindings)
150 if let Some(ref o) = *init {
151 check_expr(cx, o, bindings);
152 check_pat(cx, pat, Some(o), span, bindings);
154 check_pat(cx, pat, None, span, bindings);
158 fn is_binding(cx: &LateContext<'_, '_>, pat_id: HirId) -> bool {
159 let var_ty = cx.tables.node_type(pat_id);
161 ty::Adt(..) => false,
166 fn check_pat<'a, 'tcx>(
167 cx: &LateContext<'a, 'tcx>,
169 init: Option<&'tcx Expr>,
171 bindings: &mut Vec<(Name, Span)>,
173 // TODO: match more stuff / destructuring
175 PatKind::Binding(.., ident, ref inner) => {
176 let name = ident.name;
177 if is_binding(cx, pat.hir_id) {
178 let mut new_binding = true;
179 for tup in bindings.iter_mut() {
181 lint_shadow(cx, name, span, pat.span, init, tup.1);
188 bindings.push((name, ident.span));
191 if let Some(ref p) = *inner {
192 check_pat(cx, p, init, span, bindings);
195 PatKind::Struct(_, ref pfields, _) => {
196 if let Some(init_struct) = init {
197 if let ExprKind::Struct(_, ref efields, _) = init_struct.node {
198 for field in pfields {
199 let name = field.node.ident.name;
200 let efield = efields.iter().find(|f| f.ident.name == name).map(|f| &*f.expr);
201 check_pat(cx, &field.node.pat, efield, span, bindings);
204 for field in pfields {
205 check_pat(cx, &field.node.pat, init, span, bindings);
209 for field in pfields {
210 check_pat(cx, &field.node.pat, None, span, bindings);
214 PatKind::Tuple(ref inner, _) => {
215 if let Some(init_tup) = init {
216 if let ExprKind::Tup(ref tup) = init_tup.node {
217 for (i, p) in inner.iter().enumerate() {
218 check_pat(cx, p, Some(&tup[i]), p.span, bindings);
222 check_pat(cx, p, init, span, bindings);
227 check_pat(cx, p, None, span, bindings);
231 PatKind::Box(ref inner) => {
232 if let Some(initp) = init {
233 if let ExprKind::Box(ref inner_init) = initp.node {
234 check_pat(cx, inner, Some(&**inner_init), span, bindings);
236 check_pat(cx, inner, init, span, bindings);
239 check_pat(cx, inner, init, span, bindings);
242 PatKind::Ref(ref inner, _) => check_pat(cx, inner, init, span, bindings),
243 // PatVec(Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>),
248 fn lint_shadow<'a, 'tcx: 'a>(
249 cx: &LateContext<'a, 'tcx>,
253 init: Option<&'tcx Expr>,
256 if let Some(expr) = init {
257 if is_self_shadow(name, expr) {
263 "`{}` is shadowed by itself in `{}`",
264 snippet(cx, pattern_span, "_"),
265 snippet(cx, expr.span, "..")
268 db.span_note(prev_span, "previous binding is here");
271 } else if contains_name(name, expr) {
277 "`{}` is shadowed by `{}` which reuses the original value",
278 snippet(cx, pattern_span, "_"),
279 snippet(cx, expr.span, "..")
282 db.span_note(expr.span, "initialization happens here");
283 db.span_note(prev_span, "previous binding is here");
292 "`{}` is shadowed by `{}`",
293 snippet(cx, pattern_span, "_"),
294 snippet(cx, expr.span, "..")
297 db.span_note(expr.span, "initialization happens here");
298 db.span_note(prev_span, "previous binding is here");
307 &format!("`{}` shadows a previous declaration", snippet(cx, pattern_span, "_")),
309 db.span_note(prev_span, "previous binding is here");
315 fn check_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr, bindings: &mut Vec<(Name, Span)>) {
316 if in_external_macro(cx.sess(), expr.span) {
320 ExprKind::Unary(_, ref e) | ExprKind::Field(ref e, _) | ExprKind::AddrOf(_, ref e) | ExprKind::Box(ref e) => {
321 check_expr(cx, e, bindings)
323 ExprKind::Block(ref block, _) | ExprKind::Loop(ref block, _, _) => check_block(cx, block, bindings),
325 // ExprKind::MethodCall
326 ExprKind::Array(ref v) | ExprKind::Tup(ref v) => {
328 check_expr(cx, e, bindings)
331 ExprKind::If(ref cond, ref then, ref otherwise) => {
332 check_expr(cx, cond, bindings);
333 check_expr(cx, &**then, bindings);
334 if let Some(ref o) = *otherwise {
335 check_expr(cx, o, bindings);
338 ExprKind::While(ref cond, ref block, _) => {
339 check_expr(cx, cond, bindings);
340 check_block(cx, block, bindings);
342 ExprKind::Match(ref init, ref arms, _) => {
343 check_expr(cx, init, bindings);
344 let len = bindings.len();
346 for pat in &arm.pats {
347 check_pat(cx, pat, Some(&**init), pat.span, bindings);
348 // This is ugly, but needed to get the right type
349 if let Some(ref guard) = arm.guard {
351 Guard::If(if_expr) => check_expr(cx, if_expr, bindings),
354 check_expr(cx, &arm.body, bindings);
355 bindings.truncate(len);
363 fn check_ty<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, ty: &'tcx Ty, bindings: &mut Vec<(Name, Span)>) {
365 TyKind::Slice(ref sty) => check_ty(cx, sty, bindings),
366 TyKind::Array(ref fty, ref anon_const) => {
367 check_ty(cx, fty, bindings);
368 check_expr(cx, &cx.tcx.hir().body(anon_const.body).value, bindings);
370 TyKind::Ptr(MutTy { ty: ref mty, .. }) | TyKind::Rptr(_, MutTy { ty: ref mty, .. }) => {
371 check_ty(cx, mty, bindings)
373 TyKind::Tup(ref tup) => {
375 check_ty(cx, t, bindings)
378 TyKind::Typeof(ref anon_const) => check_expr(cx, &cx.tcx.hir().body(anon_const.body).value, bindings),
383 fn is_self_shadow(name: Name, expr: &Expr) -> bool {
385 ExprKind::Box(ref inner) | ExprKind::AddrOf(_, ref inner) => is_self_shadow(name, inner),
386 ExprKind::Block(ref block, _) => {
387 block.stmts.is_empty() && block.expr.as_ref().map_or(false, |e| is_self_shadow(name, e))
389 ExprKind::Unary(op, ref inner) => (UnDeref == op) && is_self_shadow(name, inner),
390 ExprKind::Path(QPath::Resolved(_, ref path)) => path_eq_name(name, path),
395 fn path_eq_name(name: Name, path: &Path) -> bool {
396 !path.is_global() && path.segments.len() == 1 && path.segments[0].ident.as_str() == name.as_str()