1 use clippy_utils::diagnostics::{span_lint, span_lint_and_then};
3 self, Arm, AssocItem, AssocItemKind, Attribute, Block, FnDecl, Item, ItemKind, Local, Pat, PatKind,
5 use rustc_ast::visit::{walk_block, walk_expr, walk_pat, Visitor};
6 use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
7 use rustc_middle::lint::in_external_macro;
8 use rustc_session::{declare_tool_lint, impl_lint_pass};
9 use rustc_span::source_map::Span;
11 use rustc_span::symbol::{Ident, Symbol};
12 use std::cmp::Ordering;
14 declare_clippy_lint! {
16 /// Checks for names that are very similar and thus confusing.
18 /// Note: this lint looks for similar names throughout each
19 /// scope. To allow it, you need to allow it on the scope
20 /// level, not on the name that is reported.
22 /// ### Why is this bad?
23 /// It's hard to distinguish between names that differ only
24 /// by a single character.
28 /// let checked_exp = something;
29 /// let checked_expr = something_else;
31 #[clippy::version = "pre 1.29.0"]
34 "similarly named items and bindings"
37 declare_clippy_lint! {
39 /// Checks for too many variables whose name consists of a
42 /// ### Why is this bad?
43 /// It's hard to memorize what a variable means without a
48 /// let (a, b, c, d, e, f, g) = (...);
50 #[clippy::version = "pre 1.29.0"]
51 pub MANY_SINGLE_CHAR_NAMES,
53 "too many single character bindings"
56 declare_clippy_lint! {
58 /// Checks if you have variables whose name consists of just
59 /// underscores and digits.
61 /// ### Why is this bad?
62 /// It's hard to memorize what a variable means without a
71 #[clippy::version = "pre 1.29.0"]
72 pub JUST_UNDERSCORES_AND_DIGITS,
77 #[derive(Copy, Clone)]
78 pub struct NonExpressiveNames {
79 pub single_char_binding_names_threshold: u64,
82 impl_lint_pass!(NonExpressiveNames => [SIMILAR_NAMES, MANY_SINGLE_CHAR_NAMES, JUST_UNDERSCORES_AND_DIGITS]);
88 exemptions: &'static [&'static str],
91 struct SimilarNamesLocalVisitor<'a, 'tcx> {
92 names: Vec<ExistingName>,
93 cx: &'a EarlyContext<'tcx>,
94 lint: &'a NonExpressiveNames,
96 /// A stack of scopes containing the single-character bindings in each scope.
97 single_char_names: Vec<Vec<Ident>>,
100 impl<'a, 'tcx> SimilarNamesLocalVisitor<'a, 'tcx> {
101 fn check_single_char_names(&self) {
102 let num_single_char_names = self.single_char_names.iter().flatten().count();
103 let threshold = self.lint.single_char_binding_names_threshold;
104 if num_single_char_names as u64 > threshold {
109 .map(|ident| ident.span)
110 .collect::<Vec<_>>();
113 MANY_SINGLE_CHAR_NAMES,
115 &format!("{num_single_char_names} bindings with single-character names in scope"),
121 // this list contains lists of names that are allowed to be similar
122 // the assumption is that no name is ever contained in multiple lists.
124 const ALLOWED_TO_BE_SIMILAR: &[&[&str]] = &[
125 &["parsed", "parser"],
132 &["wparam", "lparam"],
136 struct SimilarNamesNameVisitor<'a, 'tcx, 'b>(&'b mut SimilarNamesLocalVisitor<'a, 'tcx>);
138 impl<'a, 'tcx, 'b> Visitor<'tcx> for SimilarNamesNameVisitor<'a, 'tcx, 'b> {
139 fn visit_pat(&mut self, pat: &'tcx Pat) {
141 PatKind::Ident(_, ident, _) => {
142 if !pat.span.from_expansion() {
143 self.check_ident(ident);
146 PatKind::Struct(_, _, ref fields, _) => {
147 for field in fields {
148 if !field.is_shorthand {
149 self.visit_pat(&field.pat);
153 // just go through the first pattern, as either all patterns
154 // bind the same bindings or rustc would have errored much earlier
155 PatKind::Or(ref pats) => self.visit_pat(&pats[0]),
156 _ => walk_pat(self, pat),
162 fn get_exemptions(interned_name: &str) -> Option<&'static [&'static str]> {
163 ALLOWED_TO_BE_SIMILAR
165 .find(|&&list| allowed_to_be_similar(interned_name, list))
170 fn allowed_to_be_similar(interned_name: &str, list: &[&str]) -> bool {
172 .any(|&name| interned_name.starts_with(name) || interned_name.ends_with(name))
175 impl<'a, 'tcx, 'b> SimilarNamesNameVisitor<'a, 'tcx, 'b> {
176 fn check_short_ident(&mut self, ident: Ident) {
183 .any(|id| id.name == ident.name)
188 if let Some(scope) = &mut self.0.single_char_names.last_mut() {
193 #[expect(clippy::too_many_lines)]
194 fn check_ident(&mut self, ident: Ident) {
195 let interned_name = ident.name.as_str();
196 if interned_name.chars().any(char::is_uppercase) {
199 if interned_name.chars().all(|c| c.is_ascii_digit() || c == '_') {
202 JUST_UNDERSCORES_AND_DIGITS,
204 "consider choosing a more descriptive name",
208 if interned_name.starts_with('_') {
209 // these bindings are typically unused or represent an ignored portion of a destructuring pattern
212 let count = interned_name.chars().count();
215 self.check_short_ident(ident);
219 for existing_name in &self.0.names {
220 if allowed_to_be_similar(interned_name, existing_name.exemptions) {
223 match existing_name.len.cmp(&count) {
224 Ordering::Greater => {
225 if existing_name.len - count != 1
226 || levenstein_not_1(interned_name, existing_name.interned.as_str())
232 if count - existing_name.len != 1
233 || levenstein_not_1(existing_name.interned.as_str(), interned_name)
239 let mut interned_chars = interned_name.chars();
240 let interned_str = existing_name.interned.as_str();
241 let mut existing_chars = interned_str.chars();
242 let first_i = interned_chars.next().expect("we know we have at least one char");
243 let first_e = existing_chars.next().expect("we know we have at least one char");
244 let eq_or_numeric = |(a, b): (char, char)| a == b || a.is_numeric() && b.is_numeric();
246 if eq_or_numeric((first_i, first_e)) {
247 let last_i = interned_chars.next_back().expect("we know we have at least two chars");
248 let last_e = existing_chars.next_back().expect("we know we have at least two chars");
249 if eq_or_numeric((last_i, last_e)) {
252 .filter(|&ie| !eq_or_numeric(ie))
259 let second_last_i = interned_chars
261 .expect("we know we have at least three chars");
262 let second_last_e = existing_chars
264 .expect("we know we have at least three chars");
265 if !eq_or_numeric((second_last_i, second_last_e))
266 || second_last_i == '_'
267 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
269 // allowed similarity foo_x, foo_y
270 // or too many chars differ (foo_x, boo_y) or (foox, booy)
275 let second_i = interned_chars.next().expect("we know we have at least two chars");
276 let second_e = existing_chars.next().expect("we know we have at least two chars");
277 if !eq_or_numeric((second_i, second_e))
279 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
281 // allowed similarity x_foo, y_foo
282 // or too many chars differ (x_foo, y_boo) or (xfoo, yboo)
292 "binding's name is too similar to existing binding",
294 diag.span_note(existing_name.span, "existing binding defined here");
299 self.0.names.push(ExistingName {
300 exemptions: get_exemptions(interned_name).unwrap_or(&[]),
301 interned: ident.name,
308 impl<'a, 'b> SimilarNamesLocalVisitor<'a, 'b> {
309 /// ensure scoping rules work
310 fn apply<F: for<'c> Fn(&'c mut Self)>(&mut self, f: F) {
311 let n = self.names.len();
312 let single_char_count = self.single_char_names.len();
314 self.names.truncate(n);
315 self.single_char_names.truncate(single_char_count);
319 impl<'a, 'tcx> Visitor<'tcx> for SimilarNamesLocalVisitor<'a, 'tcx> {
320 fn visit_local(&mut self, local: &'tcx Local) {
321 if let Some((init, els)) = &local.kind.init_else_opt() {
322 self.apply(|this| walk_expr(this, init));
323 if let Some(els) = els {
324 self.apply(|this| walk_block(this, els));
327 // add the pattern after the expression because the bindings aren't available
330 SimilarNamesNameVisitor(self).visit_pat(&local.pat);
332 fn visit_block(&mut self, blk: &'tcx Block) {
333 self.single_char_names.push(vec![]);
335 self.apply(|this| walk_block(this, blk));
337 self.check_single_char_names();
338 self.single_char_names.pop();
340 fn visit_arm(&mut self, arm: &'tcx Arm) {
341 self.single_char_names.push(vec![]);
344 SimilarNamesNameVisitor(this).visit_pat(&arm.pat);
345 this.apply(|this| walk_expr(this, &arm.body));
348 self.check_single_char_names();
349 self.single_char_names.pop();
351 fn visit_item(&mut self, _: &Item) {
352 // do not recurse into inner items
356 impl EarlyLintPass for NonExpressiveNames {
357 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
358 if in_external_macro(cx.sess(), item.span) {
362 if let ItemKind::Fn(box ast::Fn {
368 do_check(self, cx, &item.attrs, &sig.decl, blk);
372 fn check_impl_item(&mut self, cx: &EarlyContext<'_>, item: &AssocItem) {
373 if in_external_macro(cx.sess(), item.span) {
377 if let AssocItemKind::Fn(box ast::Fn {
383 do_check(self, cx, &item.attrs, &sig.decl, blk);
388 fn do_check(lint: &mut NonExpressiveNames, cx: &EarlyContext<'_>, attrs: &[Attribute], decl: &FnDecl, blk: &Block) {
389 if !attrs.iter().any(|attr| attr.has_name(sym::test)) {
390 let mut visitor = SimilarNamesLocalVisitor {
394 single_char_names: vec![vec![]],
397 // initialize with function arguments
398 for arg in &decl.inputs {
399 SimilarNamesNameVisitor(&mut visitor).visit_pat(&arg.pat);
401 // walk all other bindings
402 walk_block(&mut visitor, blk);
404 visitor.check_single_char_names();
408 /// Precondition: `a_name.chars().count() < b_name.chars().count()`.
410 fn levenstein_not_1(a_name: &str, b_name: &str) -> bool {
411 debug_assert!(a_name.chars().count() < b_name.chars().count());
412 let mut a_chars = a_name.chars();
413 let mut b_chars = b_name.chars();
414 while let (Some(a), Some(b)) = (a_chars.next(), b_chars.next()) {
418 if let Some(b2) = b_chars.next() {
419 // check if there's just one character inserted
420 return a != b2 || a_chars.ne(b_chars);