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 /// ### Why is this bad?
19 /// It's hard to distinguish between names that differ only
20 /// by a single character.
24 /// let checked_exp = something;
25 /// let checked_expr = something_else;
27 #[clippy::version = "pre 1.29.0"]
30 "similarly named items and bindings"
33 declare_clippy_lint! {
35 /// Checks for too many variables whose name consists of a
38 /// ### Why is this bad?
39 /// It's hard to memorize what a variable means without a
44 /// let (a, b, c, d, e, f, g) = (...);
46 #[clippy::version = "pre 1.29.0"]
47 pub MANY_SINGLE_CHAR_NAMES,
49 "too many single character bindings"
52 declare_clippy_lint! {
54 /// Checks if you have variables whose name consists of just
55 /// underscores and digits.
57 /// ### Why is this bad?
58 /// It's hard to memorize what a variable means without a
67 #[clippy::version = "pre 1.29.0"]
68 pub JUST_UNDERSCORES_AND_DIGITS,
73 #[derive(Copy, Clone)]
74 pub struct NonExpressiveNames {
75 pub single_char_binding_names_threshold: u64,
78 impl_lint_pass!(NonExpressiveNames => [SIMILAR_NAMES, MANY_SINGLE_CHAR_NAMES, JUST_UNDERSCORES_AND_DIGITS]);
84 exemptions: &'static [&'static str],
87 struct SimilarNamesLocalVisitor<'a, 'tcx> {
88 names: Vec<ExistingName>,
89 cx: &'a EarlyContext<'tcx>,
90 lint: &'a NonExpressiveNames,
92 /// A stack of scopes containing the single-character bindings in each scope.
93 single_char_names: Vec<Vec<Ident>>,
96 impl<'a, 'tcx> SimilarNamesLocalVisitor<'a, 'tcx> {
97 fn check_single_char_names(&self) {
98 let num_single_char_names = self.single_char_names.iter().flatten().count();
99 let threshold = self.lint.single_char_binding_names_threshold;
100 if num_single_char_names as u64 > threshold {
105 .map(|ident| ident.span)
106 .collect::<Vec<_>>();
109 MANY_SINGLE_CHAR_NAMES,
111 &format!("{num_single_char_names} bindings with single-character names in scope"),
117 // this list contains lists of names that are allowed to be similar
118 // the assumption is that no name is ever contained in multiple lists.
120 const ALLOWED_TO_BE_SIMILAR: &[&[&str]] = &[
121 &["parsed", "parser"],
128 &["wparam", "lparam"],
132 struct SimilarNamesNameVisitor<'a, 'tcx, 'b>(&'b mut SimilarNamesLocalVisitor<'a, 'tcx>);
134 impl<'a, 'tcx, 'b> Visitor<'tcx> for SimilarNamesNameVisitor<'a, 'tcx, 'b> {
135 fn visit_pat(&mut self, pat: &'tcx Pat) {
137 PatKind::Ident(_, ident, _) => {
138 if !pat.span.from_expansion() {
139 self.check_ident(ident);
142 PatKind::Struct(_, _, ref fields, _) => {
143 for field in fields {
144 if !field.is_shorthand {
145 self.visit_pat(&field.pat);
149 // just go through the first pattern, as either all patterns
150 // bind the same bindings or rustc would have errored much earlier
151 PatKind::Or(ref pats) => self.visit_pat(&pats[0]),
152 _ => walk_pat(self, pat),
158 fn get_exemptions(interned_name: &str) -> Option<&'static [&'static str]> {
159 ALLOWED_TO_BE_SIMILAR
161 .find(|&&list| allowed_to_be_similar(interned_name, list))
166 fn allowed_to_be_similar(interned_name: &str, list: &[&str]) -> bool {
168 .any(|&name| interned_name.starts_with(name) || interned_name.ends_with(name))
171 impl<'a, 'tcx, 'b> SimilarNamesNameVisitor<'a, 'tcx, 'b> {
172 fn check_short_ident(&mut self, ident: Ident) {
179 .any(|id| id.name == ident.name)
184 if let Some(scope) = &mut self.0.single_char_names.last_mut() {
189 #[expect(clippy::too_many_lines)]
190 fn check_ident(&mut self, ident: Ident) {
191 let interned_name = ident.name.as_str();
192 if interned_name.chars().any(char::is_uppercase) {
195 if interned_name.chars().all(|c| c.is_ascii_digit() || c == '_') {
198 JUST_UNDERSCORES_AND_DIGITS,
200 "consider choosing a more descriptive name",
204 if interned_name.starts_with('_') {
205 // these bindings are typically unused or represent an ignored portion of a destructuring pattern
208 let count = interned_name.chars().count();
211 self.check_short_ident(ident);
215 for existing_name in &self.0.names {
216 if allowed_to_be_similar(interned_name, existing_name.exemptions) {
219 match existing_name.len.cmp(&count) {
220 Ordering::Greater => {
221 if existing_name.len - count != 1
222 || levenstein_not_1(interned_name, existing_name.interned.as_str())
228 if count - existing_name.len != 1
229 || levenstein_not_1(existing_name.interned.as_str(), interned_name)
235 let mut interned_chars = interned_name.chars();
236 let interned_str = existing_name.interned.as_str();
237 let mut existing_chars = interned_str.chars();
238 let first_i = interned_chars.next().expect("we know we have at least one char");
239 let first_e = existing_chars.next().expect("we know we have at least one char");
240 let eq_or_numeric = |(a, b): (char, char)| a == b || a.is_numeric() && b.is_numeric();
242 if eq_or_numeric((first_i, first_e)) {
243 let last_i = interned_chars.next_back().expect("we know we have at least two chars");
244 let last_e = existing_chars.next_back().expect("we know we have at least two chars");
245 if eq_or_numeric((last_i, last_e)) {
248 .filter(|&ie| !eq_or_numeric(ie))
255 let second_last_i = interned_chars
257 .expect("we know we have at least three chars");
258 let second_last_e = existing_chars
260 .expect("we know we have at least three chars");
261 if !eq_or_numeric((second_last_i, second_last_e))
262 || second_last_i == '_'
263 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
265 // allowed similarity foo_x, foo_y
266 // or too many chars differ (foo_x, boo_y) or (foox, booy)
271 let second_i = interned_chars.next().expect("we know we have at least two chars");
272 let second_e = existing_chars.next().expect("we know we have at least two chars");
273 if !eq_or_numeric((second_i, second_e))
275 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
277 // allowed similarity x_foo, y_foo
278 // or too many chars differ (x_foo, y_boo) or (xfoo, yboo)
288 "binding's name is too similar to existing binding",
290 diag.span_note(existing_name.span, "existing binding defined here");
295 self.0.names.push(ExistingName {
296 exemptions: get_exemptions(interned_name).unwrap_or(&[]),
297 interned: ident.name,
304 impl<'a, 'b> SimilarNamesLocalVisitor<'a, 'b> {
305 /// ensure scoping rules work
306 fn apply<F: for<'c> Fn(&'c mut Self)>(&mut self, f: F) {
307 let n = self.names.len();
308 let single_char_count = self.single_char_names.len();
310 self.names.truncate(n);
311 self.single_char_names.truncate(single_char_count);
315 impl<'a, 'tcx> Visitor<'tcx> for SimilarNamesLocalVisitor<'a, 'tcx> {
316 fn visit_local(&mut self, local: &'tcx Local) {
317 if let Some((init, els)) = &local.kind.init_else_opt() {
318 self.apply(|this| walk_expr(this, init));
319 if let Some(els) = els {
320 self.apply(|this| walk_block(this, els));
323 // add the pattern after the expression because the bindings aren't available
326 SimilarNamesNameVisitor(self).visit_pat(&local.pat);
328 fn visit_block(&mut self, blk: &'tcx Block) {
329 self.single_char_names.push(vec![]);
331 self.apply(|this| walk_block(this, blk));
333 self.check_single_char_names();
334 self.single_char_names.pop();
336 fn visit_arm(&mut self, arm: &'tcx Arm) {
337 self.single_char_names.push(vec![]);
340 SimilarNamesNameVisitor(this).visit_pat(&arm.pat);
341 this.apply(|this| walk_expr(this, &arm.body));
344 self.check_single_char_names();
345 self.single_char_names.pop();
347 fn visit_item(&mut self, _: &Item) {
348 // do not recurse into inner items
352 impl EarlyLintPass for NonExpressiveNames {
353 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
354 if in_external_macro(cx.sess(), item.span) {
358 if let ItemKind::Fn(box ast::Fn {
364 do_check(self, cx, &item.attrs, &sig.decl, blk);
368 fn check_impl_item(&mut self, cx: &EarlyContext<'_>, item: &AssocItem) {
369 if in_external_macro(cx.sess(), item.span) {
373 if let AssocItemKind::Fn(box ast::Fn {
379 do_check(self, cx, &item.attrs, &sig.decl, blk);
384 fn do_check(lint: &mut NonExpressiveNames, cx: &EarlyContext<'_>, attrs: &[Attribute], decl: &FnDecl, blk: &Block) {
385 if !attrs.iter().any(|attr| attr.has_name(sym::test)) {
386 let mut visitor = SimilarNamesLocalVisitor {
390 single_char_names: vec![vec![]],
393 // initialize with function arguments
394 for arg in &decl.inputs {
395 SimilarNamesNameVisitor(&mut visitor).visit_pat(&arg.pat);
397 // walk all other bindings
398 walk_block(&mut visitor, blk);
400 visitor.check_single_char_names();
404 /// Precondition: `a_name.chars().count() < b_name.chars().count()`.
406 fn levenstein_not_1(a_name: &str, b_name: &str) -> bool {
407 debug_assert!(a_name.chars().count() < b_name.chars().count());
408 let mut a_chars = a_name.chars();
409 let mut b_chars = b_name.chars();
410 while let (Some(a), Some(b)) = (a_chars.next(), b_chars.next()) {
414 if let Some(b2) = b_chars.next() {
415 // check if there's just one character inserted
416 return a != b2 || a_chars.ne(b_chars);