1 use clippy_utils::diagnostics::{span_lint, span_lint_and_then};
3 Arm, AssocItem, AssocItemKind, Attribute, Block, FnDecl, FnKind, Item, ItemKind, Local, Pat,
6 use rustc_ast::visit::{walk_block, walk_expr, walk_pat, Visitor};
7 use rustc_lint::{EarlyContext, EarlyLintPass};
8 use rustc_middle::lint::in_external_macro;
9 use rustc_session::{declare_tool_lint, impl_lint_pass};
10 use rustc_span::source_map::Span;
12 use rustc_span::symbol::{Ident, Symbol};
13 use std::cmp::Ordering;
15 declare_clippy_lint! {
17 /// Checks for names that are very similar and thus confusing.
19 /// ### Why is this bad?
20 /// It's hard to distinguish between names that differ only
21 /// by a single character.
25 /// let checked_exp = something;
26 /// let checked_expr = something_else;
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 pub MANY_SINGLE_CHAR_NAMES,
48 "too many single character bindings"
51 declare_clippy_lint! {
53 /// Checks if you have variables whose name consists of just
54 /// underscores and digits.
56 /// ### Why is this bad?
57 /// It's hard to memorize what a variable means without a
66 pub JUST_UNDERSCORES_AND_DIGITS,
71 #[derive(Copy, Clone)]
72 pub struct NonExpressiveNames {
73 pub single_char_binding_names_threshold: u64,
76 impl_lint_pass!(NonExpressiveNames => [SIMILAR_NAMES, MANY_SINGLE_CHAR_NAMES, JUST_UNDERSCORES_AND_DIGITS]);
82 exemptions: &'static [&'static str],
85 struct SimilarNamesLocalVisitor<'a, 'tcx> {
86 names: Vec<ExistingName>,
87 cx: &'a EarlyContext<'tcx>,
88 lint: &'a NonExpressiveNames,
90 /// A stack of scopes containing the single-character bindings in each scope.
91 single_char_names: Vec<Vec<Ident>>,
94 impl<'a, 'tcx> SimilarNamesLocalVisitor<'a, 'tcx> {
95 fn check_single_char_names(&self) {
96 let num_single_char_names = self.single_char_names.iter().flatten().count();
97 let threshold = self.lint.single_char_binding_names_threshold;
98 if num_single_char_names as u64 > threshold {
103 .map(|ident| ident.span)
104 .collect::<Vec<_>>();
107 MANY_SINGLE_CHAR_NAMES,
110 "{} bindings with single-character names in scope",
111 num_single_char_names
118 // this list contains lists of names that are allowed to be similar
119 // the assumption is that no name is ever contained in multiple lists.
121 const ALLOWED_TO_BE_SIMILAR: &[&[&str]] = &[
122 &["parsed", "parser"],
129 &["wparam", "lparam"],
133 struct SimilarNamesNameVisitor<'a, 'tcx, 'b>(&'b mut SimilarNamesLocalVisitor<'a, 'tcx>);
135 impl<'a, 'tcx, 'b> Visitor<'tcx> for SimilarNamesNameVisitor<'a, 'tcx, 'b> {
136 fn visit_pat(&mut self, pat: &'tcx Pat) {
138 PatKind::Ident(_, ident, _) => {
139 if !pat.span.from_expansion() {
140 self.check_ident(ident);
143 PatKind::Struct(_, _, ref fields, _) => {
144 for field in fields {
145 if !field.is_shorthand {
146 self.visit_pat(&field.pat);
150 // just go through the first pattern, as either all patterns
151 // bind the same bindings or rustc would have errored much earlier
152 PatKind::Or(ref pats) => self.visit_pat(&pats[0]),
153 _ => walk_pat(self, pat),
159 fn get_exemptions(interned_name: &str) -> Option<&'static [&'static str]> {
160 for &list in ALLOWED_TO_BE_SIMILAR {
161 if allowed_to_be_similar(interned_name, list) {
169 fn allowed_to_be_similar(interned_name: &str, list: &[&str]) -> bool {
171 .any(|&name| interned_name.starts_with(name) || interned_name.ends_with(name))
174 impl<'a, 'tcx, 'b> SimilarNamesNameVisitor<'a, 'tcx, 'b> {
175 fn check_short_ident(&mut self, ident: Ident) {
182 .any(|id| id.name == ident.name)
187 if let Some(scope) = &mut self.0.single_char_names.last_mut() {
192 #[allow(clippy::too_many_lines)]
193 fn check_ident(&mut self, ident: Ident) {
194 let interned_name = ident.name.as_str();
195 if interned_name.chars().any(char::is_uppercase) {
198 if interned_name.chars().all(|c| c.is_digit(10) || c == '_') {
201 JUST_UNDERSCORES_AND_DIGITS,
203 "consider choosing a more descriptive name",
207 if interned_name.starts_with('_') {
208 // these bindings are typically unused or represent an ignored portion of a destructuring pattern
211 let count = interned_name.chars().count();
214 self.check_short_ident(ident);
218 for existing_name in &self.0.names {
219 if allowed_to_be_similar(&interned_name, existing_name.exemptions) {
222 match existing_name.len.cmp(&count) {
223 Ordering::Greater => {
224 if existing_name.len - count != 1
225 || levenstein_not_1(&interned_name, &existing_name.interned.as_str())
231 if count - existing_name.len != 1
232 || levenstein_not_1(&existing_name.interned.as_str(), &interned_name)
238 let mut interned_chars = interned_name.chars();
239 let interned_str = existing_name.interned.as_str();
240 let mut existing_chars = interned_str.chars();
241 let first_i = interned_chars.next().expect("we know we have at least one char");
242 let first_e = existing_chars.next().expect("we know we have at least one char");
243 let eq_or_numeric = |(a, b): (char, char)| a == b || a.is_numeric() && b.is_numeric();
245 if eq_or_numeric((first_i, first_e)) {
246 let last_i = interned_chars.next_back().expect("we know we have at least two chars");
247 let last_e = existing_chars.next_back().expect("we know we have at least two chars");
248 if eq_or_numeric((last_i, last_e)) {
251 .filter(|&ie| !eq_or_numeric(ie))
258 let second_last_i = interned_chars
260 .expect("we know we have at least three chars");
261 let second_last_e = existing_chars
263 .expect("we know we have at least three chars");
264 if !eq_or_numeric((second_last_i, second_last_e))
265 || second_last_i == '_'
266 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
268 // allowed similarity foo_x, foo_y
269 // or too many chars differ (foo_x, boo_y) or (foox, booy)
274 let second_i = interned_chars.next().expect("we know we have at least two chars");
275 let second_e = existing_chars.next().expect("we know we have at least two chars");
276 if !eq_or_numeric((second_i, second_e))
278 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
280 // allowed similarity x_foo, y_foo
281 // or too many chars differ (x_foo, y_boo) or (xfoo, yboo)
291 "binding's name is too similar to existing binding",
293 diag.span_note(existing_name.span, "existing binding defined here");
298 self.0.names.push(ExistingName {
299 exemptions: get_exemptions(&interned_name).unwrap_or(&[]),
300 interned: ident.name,
307 impl<'a, 'b> SimilarNamesLocalVisitor<'a, 'b> {
308 /// ensure scoping rules work
309 fn apply<F: for<'c> Fn(&'c mut Self)>(&mut self, f: F) {
310 let n = self.names.len();
311 let single_char_count = self.single_char_names.len();
313 self.names.truncate(n);
314 self.single_char_names.truncate(single_char_count);
318 impl<'a, 'tcx> Visitor<'tcx> for SimilarNamesLocalVisitor<'a, 'tcx> {
319 fn visit_local(&mut self, local: &'tcx Local) {
320 if let Some(ref init) = local.init {
321 self.apply(|this| walk_expr(this, &**init));
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 FnKind(_, ref sig, _, Some(ref blk))) = item.kind {
359 do_check(self, cx, &item.attrs, &sig.decl, blk);
363 fn check_impl_item(&mut self, cx: &EarlyContext<'_>, item: &AssocItem) {
364 if in_external_macro(cx.sess, item.span) {
368 if let AssocItemKind::Fn(box FnKind(_, ref sig, _, Some(ref blk))) = item.kind {
369 do_check(self, cx, &item.attrs, &sig.decl, blk);
374 fn do_check(lint: &mut NonExpressiveNames, cx: &EarlyContext<'_>, attrs: &[Attribute], decl: &FnDecl, blk: &Block) {
375 if !attrs.iter().any(|attr| attr.has_name(sym::test)) {
376 let mut visitor = SimilarNamesLocalVisitor {
380 single_char_names: vec![vec![]],
383 // initialize with function arguments
384 for arg in &decl.inputs {
385 SimilarNamesNameVisitor(&mut visitor).visit_pat(&arg.pat);
387 // walk all other bindings
388 walk_block(&mut visitor, blk);
390 visitor.check_single_char_names();
394 /// Precondition: `a_name.chars().count() < b_name.chars().count()`.
396 fn levenstein_not_1(a_name: &str, b_name: &str) -> bool {
397 debug_assert!(a_name.chars().count() < b_name.chars().count());
398 let mut a_chars = a_name.chars();
399 let mut b_chars = b_name.chars();
400 while let (Some(a), Some(b)) = (a_chars.next(), b_chars.next()) {
404 if let Some(b2) = b_chars.next() {
405 // check if there's just one character inserted
406 return a != b2 || a_chars.ne(b_chars);