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Commit | Line | Data |
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cdc7bbd5 XL |
1 | use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg, span_lint_and_then}; |
2 | use clippy_utils::source::snippet_with_applicability; | |
136023e0 | 3 | use clippy_utils::{get_item_name, get_parent_as_impl, is_lint_allowed}; |
f20569fa XL |
4 | use if_chain::if_chain; |
5 | use rustc_ast::ast::LitKind; | |
f20569fa | 6 | use rustc_errors::Applicability; |
cdc7bbd5 | 7 | use rustc_hir::def_id::DefIdSet; |
f20569fa XL |
8 | use rustc_hir::{ |
9 | def_id::DefId, AssocItemKind, BinOpKind, Expr, ExprKind, FnRetTy, ImplItem, ImplItemKind, ImplicitSelfKind, Item, | |
10 | ItemKind, Mutability, Node, TraitItemRef, TyKind, | |
11 | }; | |
12 | use rustc_lint::{LateContext, LateLintPass}; | |
5099ac24 | 13 | use rustc_middle::ty::{self, AssocKind, FnSig, Ty}; |
f20569fa | 14 | use rustc_session::{declare_lint_pass, declare_tool_lint}; |
cdc7bbd5 XL |
15 | use rustc_span::{ |
16 | source_map::{Span, Spanned, Symbol}, | |
17 | symbol::sym, | |
18 | }; | |
f20569fa XL |
19 | |
20 | declare_clippy_lint! { | |
94222f64 XL |
21 | /// ### What it does |
22 | /// Checks for getting the length of something via `.len()` | |
f20569fa XL |
23 | /// just to compare to zero, and suggests using `.is_empty()` where applicable. |
24 | /// | |
94222f64 XL |
25 | /// ### Why is this bad? |
26 | /// Some structures can answer `.is_empty()` much faster | |
f20569fa XL |
27 | /// than calculating their length. So it is good to get into the habit of using |
28 | /// `.is_empty()`, and having it is cheap. | |
29 | /// Besides, it makes the intent clearer than a manual comparison in some contexts. | |
30 | /// | |
94222f64 | 31 | /// ### Example |
f20569fa XL |
32 | /// ```ignore |
33 | /// if x.len() == 0 { | |
34 | /// .. | |
35 | /// } | |
36 | /// if y.len() != 0 { | |
37 | /// .. | |
38 | /// } | |
39 | /// ``` | |
40 | /// instead use | |
41 | /// ```ignore | |
42 | /// if x.is_empty() { | |
43 | /// .. | |
44 | /// } | |
45 | /// if !y.is_empty() { | |
46 | /// .. | |
47 | /// } | |
48 | /// ``` | |
a2a8927a | 49 | #[clippy::version = "pre 1.29.0"] |
f20569fa XL |
50 | pub LEN_ZERO, |
51 | style, | |
52 | "checking `.len() == 0` or `.len() > 0` (or similar) when `.is_empty()` could be used instead" | |
53 | } | |
54 | ||
55 | declare_clippy_lint! { | |
94222f64 XL |
56 | /// ### What it does |
57 | /// Checks for items that implement `.len()` but not | |
f20569fa XL |
58 | /// `.is_empty()`. |
59 | /// | |
94222f64 XL |
60 | /// ### Why is this bad? |
61 | /// It is good custom to have both methods, because for | |
f20569fa XL |
62 | /// some data structures, asking about the length will be a costly operation, |
63 | /// whereas `.is_empty()` can usually answer in constant time. Also it used to | |
64 | /// lead to false positives on the [`len_zero`](#len_zero) lint – currently that | |
65 | /// lint will ignore such entities. | |
66 | /// | |
94222f64 | 67 | /// ### Example |
f20569fa XL |
68 | /// ```ignore |
69 | /// impl X { | |
70 | /// pub fn len(&self) -> usize { | |
71 | /// .. | |
72 | /// } | |
73 | /// } | |
74 | /// ``` | |
a2a8927a | 75 | #[clippy::version = "pre 1.29.0"] |
f20569fa XL |
76 | pub LEN_WITHOUT_IS_EMPTY, |
77 | style, | |
78 | "traits or impls with a public `len` method but no corresponding `is_empty` method" | |
79 | } | |
80 | ||
81 | declare_clippy_lint! { | |
94222f64 XL |
82 | /// ### What it does |
83 | /// Checks for comparing to an empty slice such as `""` or `[]`, | |
f20569fa XL |
84 | /// and suggests using `.is_empty()` where applicable. |
85 | /// | |
94222f64 XL |
86 | /// ### Why is this bad? |
87 | /// Some structures can answer `.is_empty()` much faster | |
f20569fa XL |
88 | /// than checking for equality. So it is good to get into the habit of using |
89 | /// `.is_empty()`, and having it is cheap. | |
90 | /// Besides, it makes the intent clearer than a manual comparison in some contexts. | |
91 | /// | |
94222f64 | 92 | /// ### Example |
f20569fa XL |
93 | /// |
94 | /// ```ignore | |
95 | /// if s == "" { | |
96 | /// .. | |
97 | /// } | |
98 | /// | |
99 | /// if arr == [] { | |
100 | /// .. | |
101 | /// } | |
102 | /// ``` | |
103 | /// Use instead: | |
104 | /// ```ignore | |
105 | /// if s.is_empty() { | |
106 | /// .. | |
107 | /// } | |
108 | /// | |
109 | /// if arr.is_empty() { | |
110 | /// .. | |
111 | /// } | |
112 | /// ``` | |
a2a8927a | 113 | #[clippy::version = "1.49.0"] |
f20569fa XL |
114 | pub COMPARISON_TO_EMPTY, |
115 | style, | |
116 | "checking `x == \"\"` or `x == []` (or similar) when `.is_empty()` could be used instead" | |
117 | } | |
118 | ||
119 | declare_lint_pass!(LenZero => [LEN_ZERO, LEN_WITHOUT_IS_EMPTY, COMPARISON_TO_EMPTY]); | |
120 | ||
121 | impl<'tcx> LateLintPass<'tcx> for LenZero { | |
122 | fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) { | |
123 | if item.span.from_expansion() { | |
124 | return; | |
125 | } | |
126 | ||
cdc7bbd5 | 127 | if let ItemKind::Trait(_, _, _, _, trait_items) = item.kind { |
f20569fa XL |
128 | check_trait_items(cx, item, trait_items); |
129 | } | |
130 | } | |
131 | ||
132 | fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx ImplItem<'_>) { | |
133 | if_chain! { | |
136023e0 | 134 | if item.ident.name == sym::len; |
f20569fa XL |
135 | if let ImplItemKind::Fn(sig, _) = &item.kind; |
136 | if sig.decl.implicit_self.has_implicit_self(); | |
2b03887a | 137 | if cx.effective_visibilities.is_exported(item.owner_id.def_id); |
f20569fa XL |
138 | if matches!(sig.decl.output, FnRetTy::Return(_)); |
139 | if let Some(imp) = get_parent_as_impl(cx.tcx, item.hir_id()); | |
140 | if imp.of_trait.is_none(); | |
141 | if let TyKind::Path(ty_path) = &imp.self_ty.kind; | |
142 | if let Some(ty_id) = cx.qpath_res(ty_path, imp.self_ty.hir_id).opt_def_id(); | |
143 | if let Some(local_id) = ty_id.as_local(); | |
144 | let ty_hir_id = cx.tcx.hir().local_def_id_to_hir_id(local_id); | |
136023e0 | 145 | if !is_lint_allowed(cx, LEN_WITHOUT_IS_EMPTY, ty_hir_id); |
2b03887a | 146 | if let Some(output) = parse_len_output(cx, cx.tcx.fn_sig(item.owner_id).skip_binder()); |
f20569fa XL |
147 | then { |
148 | let (name, kind) = match cx.tcx.hir().find(ty_hir_id) { | |
149 | Some(Node::ForeignItem(x)) => (x.ident.name, "extern type"), | |
150 | Some(Node::Item(x)) => match x.kind { | |
151 | ItemKind::Struct(..) => (x.ident.name, "struct"), | |
152 | ItemKind::Enum(..) => (x.ident.name, "enum"), | |
153 | ItemKind::Union(..) => (x.ident.name, "union"), | |
154 | _ => (x.ident.name, "type"), | |
155 | } | |
156 | _ => return, | |
157 | }; | |
cdc7bbd5 | 158 | check_for_is_empty(cx, sig.span, sig.decl.implicit_self, output, ty_id, name, kind) |
f20569fa XL |
159 | } |
160 | } | |
161 | } | |
162 | ||
163 | fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { | |
164 | if expr.span.from_expansion() { | |
165 | return; | |
166 | } | |
167 | ||
cdc7bbd5 | 168 | if let ExprKind::Binary(Spanned { node: cmp, .. }, left, right) = expr.kind { |
f20569fa XL |
169 | match cmp { |
170 | BinOpKind::Eq => { | |
171 | check_cmp(cx, expr.span, left, right, "", 0); // len == 0 | |
172 | check_cmp(cx, expr.span, right, left, "", 0); // 0 == len | |
173 | }, | |
174 | BinOpKind::Ne => { | |
175 | check_cmp(cx, expr.span, left, right, "!", 0); // len != 0 | |
176 | check_cmp(cx, expr.span, right, left, "!", 0); // 0 != len | |
177 | }, | |
178 | BinOpKind::Gt => { | |
179 | check_cmp(cx, expr.span, left, right, "!", 0); // len > 0 | |
180 | check_cmp(cx, expr.span, right, left, "", 1); // 1 > len | |
181 | }, | |
182 | BinOpKind::Lt => { | |
183 | check_cmp(cx, expr.span, left, right, "", 1); // len < 1 | |
184 | check_cmp(cx, expr.span, right, left, "!", 0); // 0 < len | |
185 | }, | |
186 | BinOpKind::Ge => check_cmp(cx, expr.span, left, right, "!", 1), // len >= 1 | |
187 | BinOpKind::Le => check_cmp(cx, expr.span, right, left, "!", 1), // 1 <= len | |
188 | _ => (), | |
189 | } | |
190 | } | |
191 | } | |
192 | } | |
193 | ||
194 | fn check_trait_items(cx: &LateContext<'_>, visited_trait: &Item<'_>, trait_items: &[TraitItemRef]) { | |
136023e0 XL |
195 | fn is_named_self(cx: &LateContext<'_>, item: &TraitItemRef, name: Symbol) -> bool { |
196 | item.ident.name == name | |
f20569fa | 197 | && if let AssocItemKind::Fn { has_self } = item.kind { |
2b03887a | 198 | has_self && { cx.tcx.fn_sig(item.id.owner_id).inputs().skip_binder().len() == 1 } |
f20569fa XL |
199 | } else { |
200 | false | |
201 | } | |
202 | } | |
203 | ||
204 | // fill the set with current and super traits | |
cdc7bbd5 | 205 | fn fill_trait_set(traitt: DefId, set: &mut DefIdSet, cx: &LateContext<'_>) { |
f20569fa XL |
206 | if set.insert(traitt) { |
207 | for supertrait in rustc_trait_selection::traits::supertrait_def_ids(cx.tcx, traitt) { | |
208 | fill_trait_set(supertrait, set, cx); | |
209 | } | |
210 | } | |
211 | } | |
212 | ||
2b03887a FG |
213 | if cx.effective_visibilities.is_exported(visited_trait.owner_id.def_id) |
214 | && trait_items.iter().any(|i| is_named_self(cx, i, sym::len)) | |
136023e0 | 215 | { |
cdc7bbd5 | 216 | let mut current_and_super_traits = DefIdSet::default(); |
2b03887a | 217 | fill_trait_set(visited_trait.owner_id.to_def_id(), &mut current_and_super_traits, cx); |
5099ac24 | 218 | let is_empty = sym!(is_empty); |
f20569fa XL |
219 | |
220 | let is_empty_method_found = current_and_super_traits | |
221 | .iter() | |
5099ac24 | 222 | .flat_map(|&i| cx.tcx.associated_items(i).filter_by_name_unhygienic(is_empty)) |
f20569fa XL |
223 | .any(|i| { |
224 | i.kind == ty::AssocKind::Fn | |
225 | && i.fn_has_self_parameter | |
f20569fa XL |
226 | && cx.tcx.fn_sig(i.def_id).inputs().skip_binder().len() == 1 |
227 | }); | |
228 | ||
229 | if !is_empty_method_found { | |
230 | span_lint( | |
231 | cx, | |
232 | LEN_WITHOUT_IS_EMPTY, | |
233 | visited_trait.span, | |
234 | &format!( | |
235 | "trait `{}` has a `len` method but no (possibly inherited) `is_empty` method", | |
236 | visited_trait.ident.name | |
237 | ), | |
238 | ); | |
239 | } | |
240 | } | |
241 | } | |
242 | ||
cdc7bbd5 XL |
243 | #[derive(Debug, Clone, Copy)] |
244 | enum LenOutput<'tcx> { | |
245 | Integral, | |
246 | Option(DefId), | |
247 | Result(DefId, Ty<'tcx>), | |
248 | } | |
5099ac24 | 249 | fn parse_len_output<'tcx>(cx: &LateContext<'_>, sig: FnSig<'tcx>) -> Option<LenOutput<'tcx>> { |
cdc7bbd5 XL |
250 | match *sig.output().kind() { |
251 | ty::Int(_) | ty::Uint(_) => Some(LenOutput::Integral), | |
5e7ed085 FG |
252 | ty::Adt(adt, subs) if cx.tcx.is_diagnostic_item(sym::Option, adt.did()) => { |
253 | subs.type_at(0).is_integral().then(|| LenOutput::Option(adt.did())) | |
cdc7bbd5 | 254 | }, |
5e7ed085 | 255 | ty::Adt(adt, subs) if cx.tcx.is_diagnostic_item(sym::Result, adt.did()) => subs |
cdc7bbd5 XL |
256 | .type_at(0) |
257 | .is_integral() | |
5e7ed085 | 258 | .then(|| LenOutput::Result(adt.did(), subs.type_at(1))), |
cdc7bbd5 XL |
259 | _ => None, |
260 | } | |
261 | } | |
262 | ||
923072b8 FG |
263 | impl<'tcx> LenOutput<'tcx> { |
264 | fn matches_is_empty_output(self, ty: Ty<'tcx>) -> bool { | |
cdc7bbd5 XL |
265 | match (self, ty.kind()) { |
266 | (_, &ty::Bool) => true, | |
5e7ed085 FG |
267 | (Self::Option(id), &ty::Adt(adt, subs)) if id == adt.did() => subs.type_at(0).is_bool(), |
268 | (Self::Result(id, err_ty), &ty::Adt(adt, subs)) if id == adt.did() => { | |
5099ac24 | 269 | subs.type_at(0).is_bool() && subs.type_at(1) == err_ty |
cdc7bbd5 XL |
270 | }, |
271 | _ => false, | |
272 | } | |
273 | } | |
274 | ||
275 | fn expected_sig(self, self_kind: ImplicitSelfKind) -> String { | |
276 | let self_ref = match self_kind { | |
277 | ImplicitSelfKind::ImmRef => "&", | |
278 | ImplicitSelfKind::MutRef => "&mut ", | |
279 | _ => "", | |
280 | }; | |
281 | match self { | |
2b03887a FG |
282 | Self::Integral => format!("expected signature: `({self_ref}self) -> bool`"), |
283 | Self::Option(_) => { | |
284 | format!("expected signature: `({self_ref}self) -> bool` or `({self_ref}self) -> Option<bool>") | |
285 | }, | |
286 | Self::Result(..) => { | |
287 | format!("expected signature: `({self_ref}self) -> bool` or `({self_ref}self) -> Result<bool>") | |
288 | }, | |
cdc7bbd5 XL |
289 | } |
290 | } | |
291 | } | |
292 | ||
f20569fa | 293 | /// Checks if the given signature matches the expectations for `is_empty` |
923072b8 | 294 | fn check_is_empty_sig<'tcx>(sig: FnSig<'tcx>, self_kind: ImplicitSelfKind, len_output: LenOutput<'tcx>) -> bool { |
f20569fa | 295 | match &**sig.inputs_and_output { |
5099ac24 | 296 | [arg, res] if len_output.matches_is_empty_output(*res) => { |
f20569fa XL |
297 | matches!( |
298 | (arg.kind(), self_kind), | |
299 | (ty::Ref(_, _, Mutability::Not), ImplicitSelfKind::ImmRef) | |
300 | | (ty::Ref(_, _, Mutability::Mut), ImplicitSelfKind::MutRef) | |
301 | ) || (!arg.is_ref() && matches!(self_kind, ImplicitSelfKind::Imm | ImplicitSelfKind::Mut)) | |
302 | }, | |
303 | _ => false, | |
304 | } | |
305 | } | |
306 | ||
307 | /// Checks if the given type has an `is_empty` method with the appropriate signature. | |
923072b8 FG |
308 | fn check_for_is_empty<'tcx>( |
309 | cx: &LateContext<'tcx>, | |
f20569fa XL |
310 | span: Span, |
311 | self_kind: ImplicitSelfKind, | |
923072b8 | 312 | output: LenOutput<'tcx>, |
f20569fa XL |
313 | impl_ty: DefId, |
314 | item_name: Symbol, | |
315 | item_kind: &str, | |
316 | ) { | |
317 | let is_empty = Symbol::intern("is_empty"); | |
318 | let is_empty = cx | |
319 | .tcx | |
320 | .inherent_impls(impl_ty) | |
321 | .iter() | |
322 | .flat_map(|&id| cx.tcx.associated_items(id).filter_by_name_unhygienic(is_empty)) | |
323 | .find(|item| item.kind == AssocKind::Fn); | |
324 | ||
325 | let (msg, is_empty_span, self_kind) = match is_empty { | |
326 | None => ( | |
327 | format!( | |
2b03887a | 328 | "{item_kind} `{}` has a public `len` method, but no `is_empty` method", |
f20569fa XL |
329 | item_name.as_str(), |
330 | ), | |
331 | None, | |
332 | None, | |
333 | ), | |
2b03887a | 334 | Some(is_empty) if !cx.effective_visibilities.is_exported(is_empty.def_id.expect_local()) => ( |
94222f64 | 335 | format!( |
2b03887a | 336 | "{item_kind} `{}` has a public `len` method, but a private `is_empty` method", |
94222f64 XL |
337 | item_name.as_str(), |
338 | ), | |
339 | Some(cx.tcx.def_span(is_empty.def_id)), | |
340 | None, | |
341 | ), | |
f20569fa XL |
342 | Some(is_empty) |
343 | if !(is_empty.fn_has_self_parameter | |
cdc7bbd5 | 344 | && check_is_empty_sig(cx.tcx.fn_sig(is_empty.def_id).skip_binder(), self_kind, output)) => |
f20569fa XL |
345 | { |
346 | ( | |
347 | format!( | |
2b03887a | 348 | "{item_kind} `{}` has a public `len` method, but the `is_empty` method has an unexpected signature", |
f20569fa XL |
349 | item_name.as_str(), |
350 | ), | |
351 | Some(cx.tcx.def_span(is_empty.def_id)), | |
352 | Some(self_kind), | |
353 | ) | |
354 | }, | |
355 | Some(_) => return, | |
356 | }; | |
357 | ||
358 | span_lint_and_then(cx, LEN_WITHOUT_IS_EMPTY, span, &msg, |db| { | |
359 | if let Some(span) = is_empty_span { | |
360 | db.span_note(span, "`is_empty` defined here"); | |
361 | } | |
362 | if let Some(self_kind) = self_kind { | |
cdc7bbd5 | 363 | db.note(&output.expected_sig(self_kind)); |
f20569fa XL |
364 | } |
365 | }); | |
366 | } | |
367 | ||
368 | fn check_cmp(cx: &LateContext<'_>, span: Span, method: &Expr<'_>, lit: &Expr<'_>, op: &str, compare_to: u32) { | |
f2b60f7d FG |
369 | if let (&ExprKind::MethodCall(method_path, receiver, args, _), &ExprKind::Lit(ref lit)) = (&method.kind, &lit.kind) |
370 | { | |
f20569fa XL |
371 | // check if we are in an is_empty() method |
372 | if let Some(name) = get_item_name(cx, method) { | |
373 | if name.as_str() == "is_empty" { | |
374 | return; | |
375 | } | |
376 | } | |
377 | ||
f2b60f7d FG |
378 | check_len( |
379 | cx, | |
380 | span, | |
381 | method_path.ident.name, | |
382 | receiver, | |
383 | args, | |
384 | &lit.node, | |
385 | op, | |
386 | compare_to, | |
387 | ); | |
f20569fa | 388 | } else { |
17df50a5 | 389 | check_empty_expr(cx, span, method, lit, op); |
f20569fa XL |
390 | } |
391 | } | |
392 | ||
f2b60f7d FG |
393 | // FIXME(flip1995): Figure out how to reduce the number of arguments |
394 | #[allow(clippy::too_many_arguments)] | |
f20569fa XL |
395 | fn check_len( |
396 | cx: &LateContext<'_>, | |
397 | span: Span, | |
398 | method_name: Symbol, | |
f2b60f7d | 399 | receiver: &Expr<'_>, |
f20569fa XL |
400 | args: &[Expr<'_>], |
401 | lit: &LitKind, | |
402 | op: &str, | |
403 | compare_to: u32, | |
404 | ) { | |
405 | if let LitKind::Int(lit, _) = *lit { | |
406 | // check if length is compared to the specified number | |
407 | if lit != u128::from(compare_to) { | |
408 | return; | |
409 | } | |
410 | ||
f2b60f7d | 411 | if method_name == sym::len && args.is_empty() && has_is_empty(cx, receiver) { |
f20569fa XL |
412 | let mut applicability = Applicability::MachineApplicable; |
413 | span_lint_and_sugg( | |
414 | cx, | |
415 | LEN_ZERO, | |
416 | span, | |
417 | &format!("length comparison to {}", if compare_to == 0 { "zero" } else { "one" }), | |
2b03887a | 418 | &format!("using `{op}is_empty` is clearer and more explicit"), |
f20569fa | 419 | format!( |
2b03887a | 420 | "{op}{}.is_empty()", |
f2b60f7d | 421 | snippet_with_applicability(cx, receiver.span, "_", &mut applicability) |
f20569fa XL |
422 | ), |
423 | applicability, | |
424 | ); | |
425 | } | |
426 | } | |
427 | } | |
428 | ||
429 | fn check_empty_expr(cx: &LateContext<'_>, span: Span, lit1: &Expr<'_>, lit2: &Expr<'_>, op: &str) { | |
430 | if (is_empty_array(lit2) || is_empty_string(lit2)) && has_is_empty(cx, lit1) { | |
431 | let mut applicability = Applicability::MachineApplicable; | |
432 | span_lint_and_sugg( | |
433 | cx, | |
434 | COMPARISON_TO_EMPTY, | |
435 | span, | |
436 | "comparison to empty slice", | |
2b03887a | 437 | &format!("using `{op}is_empty` is clearer and more explicit"), |
f20569fa | 438 | format!( |
2b03887a | 439 | "{op}{}.is_empty()", |
f20569fa XL |
440 | snippet_with_applicability(cx, lit1.span, "_", &mut applicability) |
441 | ), | |
442 | applicability, | |
443 | ); | |
444 | } | |
445 | } | |
446 | ||
447 | fn is_empty_string(expr: &Expr<'_>) -> bool { | |
448 | if let ExprKind::Lit(ref lit) = expr.kind { | |
449 | if let LitKind::Str(lit, _) = lit.node { | |
450 | let lit = lit.as_str(); | |
a2a8927a | 451 | return lit.is_empty(); |
f20569fa XL |
452 | } |
453 | } | |
454 | false | |
455 | } | |
456 | ||
457 | fn is_empty_array(expr: &Expr<'_>) -> bool { | |
cdc7bbd5 | 458 | if let ExprKind::Array(arr) = expr.kind { |
f20569fa XL |
459 | return arr.is_empty(); |
460 | } | |
461 | false | |
462 | } | |
463 | ||
464 | /// Checks if this type has an `is_empty` method. | |
465 | fn has_is_empty(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool { | |
466 | /// Gets an `AssocItem` and return true if it matches `is_empty(self)`. | |
467 | fn is_is_empty(cx: &LateContext<'_>, item: &ty::AssocItem) -> bool { | |
5099ac24 | 468 | if item.kind == ty::AssocKind::Fn { |
c295e0f8 XL |
469 | let sig = cx.tcx.fn_sig(item.def_id); |
470 | let ty = sig.skip_binder(); | |
471 | ty.inputs().len() == 1 | |
f20569fa XL |
472 | } else { |
473 | false | |
474 | } | |
475 | } | |
476 | ||
477 | /// Checks the inherent impl's items for an `is_empty(self)` method. | |
478 | fn has_is_empty_impl(cx: &LateContext<'_>, id: DefId) -> bool { | |
5099ac24 | 479 | let is_empty = sym!(is_empty); |
f20569fa XL |
480 | cx.tcx.inherent_impls(id).iter().any(|imp| { |
481 | cx.tcx | |
482 | .associated_items(*imp) | |
5099ac24 | 483 | .filter_by_name_unhygienic(is_empty) |
cdc7bbd5 | 484 | .any(|item| is_is_empty(cx, item)) |
f20569fa XL |
485 | }) |
486 | } | |
487 | ||
488 | let ty = &cx.typeck_results().expr_ty(expr).peel_refs(); | |
489 | match ty.kind() { | |
cdc7bbd5 | 490 | ty::Dynamic(tt, ..) => tt.principal().map_or(false, |principal| { |
5099ac24 | 491 | let is_empty = sym!(is_empty); |
f20569fa XL |
492 | cx.tcx |
493 | .associated_items(principal.def_id()) | |
5099ac24 | 494 | .filter_by_name_unhygienic(is_empty) |
cdc7bbd5 | 495 | .any(|item| is_is_empty(cx, item)) |
f20569fa XL |
496 | }), |
497 | ty::Projection(ref proj) => has_is_empty_impl(cx, proj.item_def_id), | |
5e7ed085 | 498 | ty::Adt(id, _) => has_is_empty_impl(cx, id.did()), |
f20569fa XL |
499 | ty::Array(..) | ty::Slice(..) | ty::Str => true, |
500 | _ => false, | |
501 | } | |
502 | } |