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_lint_pass, declare_tool_lint};
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.
28 "rebinding a name to itself, e.g., `let mut x = &mut x`"
31 declare_clippy_lint! {
32 /// **What it does:** Checks for bindings that shadow other bindings already in
33 /// scope, while reusing the original value.
35 /// **Why is this bad?** Not too much, in fact it's a common pattern in Rust
36 /// code. Still, some argue that name shadowing like this hurts readability,
37 /// because a value may be bound to different things depending on position in
40 /// **Known problems:** This lint, as the other shadowing related lints,
41 /// currently only catches very simple patterns.
48 /// use different variable name:
55 "rebinding a name to an expression that re-uses the original value, e.g., `let x = x + 1`"
58 declare_clippy_lint! {
59 /// **What it does:** Checks for bindings that shadow other bindings already in
60 /// scope, either without a initialization or with one that does not even use
61 /// the original value.
63 /// **Why is this bad?** Name shadowing can hurt readability, especially in
64 /// large code bases, because it is easy to lose track of the active binding at
65 /// any place in the code. This can be alleviated by either giving more specific
66 /// names to bindings or introducing more scopes to contain the bindings.
68 /// **Known problems:** This lint, as the other shadowing related lints,
69 /// currently only catches very simple patterns.
76 /// let x = z; // shadows the earlier binding
80 "rebinding a name without even using the original value"
83 declare_lint_pass!(Shadow => [SHADOW_SAME, SHADOW_REUSE, SHADOW_UNRELATED]);
85 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Shadow {
88 cx: &LateContext<'a, 'tcx>,
95 if in_external_macro(cx.sess(), body.value.span) {
98 check_fn(cx, decl, body);
102 fn check_fn<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl, body: &'tcx Body) {
103 let mut bindings = Vec::new();
104 for arg in iter_input_pats(decl, body) {
105 if let PatKind::Binding(.., ident, _) = arg.pat.kind {
106 bindings.push((ident.name, ident.span))
109 check_expr(cx, &body.value, &mut bindings);
112 fn check_block<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, block: &'tcx Block, bindings: &mut Vec<(Name, Span)>) {
113 let len = bindings.len();
114 for stmt in &block.stmts {
116 StmtKind::Local(ref local) => check_local(cx, local, bindings),
117 StmtKind::Expr(ref e) | StmtKind::Semi(ref e) => check_expr(cx, e, bindings),
118 StmtKind::Item(..) => {},
121 if let Some(ref o) = block.expr {
122 check_expr(cx, o, bindings);
124 bindings.truncate(len);
127 fn check_local<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, local: &'tcx Local, bindings: &mut Vec<(Name, Span)>) {
128 if in_external_macro(cx.sess(), local.span) {
131 if higher::is_from_for_desugar(local) {
141 if let Some(ref t) = *ty {
142 check_ty(cx, t, bindings)
144 if let Some(ref o) = *init {
145 check_expr(cx, o, bindings);
146 check_pat(cx, pat, Some(o), span, bindings);
148 check_pat(cx, pat, None, span, bindings);
152 fn is_binding(cx: &LateContext<'_, '_>, pat_id: HirId) -> bool {
153 let var_ty = cx.tables.node_type(pat_id);
155 ty::Adt(..) => false,
160 fn check_pat<'a, 'tcx>(
161 cx: &LateContext<'a, 'tcx>,
163 init: Option<&'tcx Expr>,
165 bindings: &mut Vec<(Name, Span)>,
167 // TODO: match more stuff / destructuring
169 PatKind::Binding(.., ident, ref inner) => {
170 let name = ident.name;
171 if is_binding(cx, pat.hir_id) {
172 let mut new_binding = true;
173 for tup in bindings.iter_mut() {
175 lint_shadow(cx, name, span, pat.span, init, tup.1);
182 bindings.push((name, ident.span));
185 if let Some(ref p) = *inner {
186 check_pat(cx, p, init, span, bindings);
189 PatKind::Struct(_, ref pfields, _) => {
190 if let Some(init_struct) = init {
191 if let ExprKind::Struct(_, ref efields, _) = init_struct.kind {
192 for field in pfields {
193 let name = field.ident.name;
196 .find_map(|f| if f.ident.name == name { Some(&*f.expr) } else { None });
197 check_pat(cx, &field.pat, efield, span, bindings);
200 for field in pfields {
201 check_pat(cx, &field.pat, init, span, bindings);
205 for field in pfields {
206 check_pat(cx, &field.pat, None, span, bindings);
210 PatKind::Tuple(ref inner, _) => {
211 if let Some(init_tup) = init {
212 if let ExprKind::Tup(ref tup) = init_tup.kind {
213 for (i, p) in inner.iter().enumerate() {
214 check_pat(cx, p, Some(&tup[i]), p.span, bindings);
218 check_pat(cx, p, init, span, bindings);
223 check_pat(cx, p, None, span, bindings);
227 PatKind::Box(ref inner) => {
228 if let Some(initp) = init {
229 if let ExprKind::Box(ref inner_init) = initp.kind {
230 check_pat(cx, inner, Some(&**inner_init), span, bindings);
232 check_pat(cx, inner, init, span, bindings);
235 check_pat(cx, inner, init, span, bindings);
238 PatKind::Ref(ref inner, _) => check_pat(cx, inner, init, span, bindings),
239 // PatVec(Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>),
244 fn lint_shadow<'a, 'tcx>(
245 cx: &LateContext<'a, 'tcx>,
249 init: Option<&'tcx Expr>,
252 if let Some(expr) = init {
253 if is_self_shadow(name, expr) {
259 "`{}` is shadowed by itself in `{}`",
260 snippet(cx, pattern_span, "_"),
261 snippet(cx, expr.span, "..")
264 db.span_note(prev_span, "previous binding is here");
267 } else if contains_name(name, expr) {
273 "`{}` is shadowed by `{}` which reuses the original value",
274 snippet(cx, pattern_span, "_"),
275 snippet(cx, expr.span, "..")
278 db.span_note(expr.span, "initialization happens here");
279 db.span_note(prev_span, "previous binding is here");
288 "`{}` is shadowed by `{}`",
289 snippet(cx, pattern_span, "_"),
290 snippet(cx, expr.span, "..")
293 db.span_note(expr.span, "initialization happens here");
294 db.span_note(prev_span, "previous binding is here");
303 &format!("`{}` shadows a previous declaration", snippet(cx, pattern_span, "_")),
305 db.span_note(prev_span, "previous binding is here");
311 fn check_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr, bindings: &mut Vec<(Name, Span)>) {
312 if in_external_macro(cx.sess(), expr.span) {
316 ExprKind::Unary(_, ref e)
317 | ExprKind::Field(ref e, _)
318 | ExprKind::AddrOf(_, _, ref e)
319 | ExprKind::Box(ref e) => check_expr(cx, e, bindings),
320 ExprKind::Block(ref block, _) | ExprKind::Loop(ref block, _, _) => check_block(cx, block, bindings),
322 // ExprKind::MethodCall
323 ExprKind::Array(ref v) | ExprKind::Tup(ref v) => {
325 check_expr(cx, e, bindings)
328 ExprKind::Match(ref init, ref arms, _) => {
329 check_expr(cx, init, bindings);
330 let len = bindings.len();
332 check_pat(cx, &arm.pat, Some(&**init), arm.pat.span, bindings);
333 // This is ugly, but needed to get the right type
334 if let Some(ref guard) = arm.guard {
336 Guard::If(if_expr) => check_expr(cx, if_expr, bindings),
339 check_expr(cx, &arm.body, bindings);
340 bindings.truncate(len);
347 fn check_ty<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, ty: &'tcx Ty, bindings: &mut Vec<(Name, Span)>) {
349 TyKind::Slice(ref sty) => check_ty(cx, sty, bindings),
350 TyKind::Array(ref fty, ref anon_const) => {
351 check_ty(cx, fty, bindings);
352 check_expr(cx, &cx.tcx.hir().body(anon_const.body).value, bindings);
354 TyKind::Ptr(MutTy { ty: ref mty, .. }) | TyKind::Rptr(_, MutTy { ty: ref mty, .. }) => {
355 check_ty(cx, mty, bindings)
357 TyKind::Tup(ref tup) => {
359 check_ty(cx, t, bindings)
362 TyKind::Typeof(ref anon_const) => check_expr(cx, &cx.tcx.hir().body(anon_const.body).value, bindings),
367 fn is_self_shadow(name: Name, expr: &Expr) -> bool {
369 ExprKind::Box(ref inner) | ExprKind::AddrOf(_, _, ref inner) => is_self_shadow(name, inner),
370 ExprKind::Block(ref block, _) => {
371 block.stmts.is_empty() && block.expr.as_ref().map_or(false, |e| is_self_shadow(name, e))
373 ExprKind::Unary(op, ref inner) => (UnDeref == op) && is_self_shadow(name, inner),
374 ExprKind::Path(QPath::Resolved(_, ref path)) => path_eq_name(name, path),
379 fn path_eq_name(name: Name, path: &Path) -> bool {
380 !path.is_global() && path.segments.len() == 1 && path.segments[0].ident.as_str() == name.as_str()