1 use clippy_utils::diagnostics::{span_lint, span_lint_and_then};
3 Arm, AssocItem, AssocItemKind, Attribute, Block, FnDecl, FnKind, Item, ItemKind, Local, Pat, PatKind,
5 use rustc_ast::visit::{walk_block, walk_expr, walk_pat, Visitor};
6 use rustc_lint::{EarlyContext, EarlyLintPass};
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;
29 "similarly named items and bindings"
32 declare_clippy_lint! {
34 /// Checks for too many variables whose name consists of a
37 /// ### Why is this bad?
38 /// It's hard to memorize what a variable means without a
43 /// let (a, b, c, d, e, f, g) = (...);
45 pub MANY_SINGLE_CHAR_NAMES,
47 "too many single character bindings"
50 declare_clippy_lint! {
52 /// Checks if you have variables whose name consists of just
53 /// underscores and digits.
55 /// ### Why is this bad?
56 /// It's hard to memorize what a variable means without a
65 pub JUST_UNDERSCORES_AND_DIGITS,
70 #[derive(Copy, Clone)]
71 pub struct NonExpressiveNames {
72 pub single_char_binding_names_threshold: u64,
75 impl_lint_pass!(NonExpressiveNames => [SIMILAR_NAMES, MANY_SINGLE_CHAR_NAMES, JUST_UNDERSCORES_AND_DIGITS]);
81 exemptions: &'static [&'static str],
84 struct SimilarNamesLocalVisitor<'a, 'tcx> {
85 names: Vec<ExistingName>,
86 cx: &'a EarlyContext<'tcx>,
87 lint: &'a NonExpressiveNames,
89 /// A stack of scopes containing the single-character bindings in each scope.
90 single_char_names: Vec<Vec<Ident>>,
93 impl<'a, 'tcx> SimilarNamesLocalVisitor<'a, 'tcx> {
94 fn check_single_char_names(&self) {
95 let num_single_char_names = self.single_char_names.iter().flatten().count();
96 let threshold = self.lint.single_char_binding_names_threshold;
97 if num_single_char_names as u64 > threshold {
102 .map(|ident| ident.span)
103 .collect::<Vec<_>>();
106 MANY_SINGLE_CHAR_NAMES,
109 "{} bindings with single-character names in scope",
110 num_single_char_names
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 for &list in ALLOWED_TO_BE_SIMILAR {
160 if allowed_to_be_similar(interned_name, list) {
168 fn allowed_to_be_similar(interned_name: &str, list: &[&str]) -> bool {
170 .any(|&name| interned_name.starts_with(name) || interned_name.ends_with(name))
173 impl<'a, 'tcx, 'b> SimilarNamesNameVisitor<'a, 'tcx, 'b> {
174 fn check_short_ident(&mut self, ident: Ident) {
181 .any(|id| id.name == ident.name)
186 if let Some(scope) = &mut self.0.single_char_names.last_mut() {
191 #[allow(clippy::too_many_lines)]
192 fn check_ident(&mut self, ident: Ident) {
193 let interned_name = ident.name.as_str();
194 if interned_name.chars().any(char::is_uppercase) {
197 if interned_name.chars().all(|c| c.is_digit(10) || c == '_') {
200 JUST_UNDERSCORES_AND_DIGITS,
202 "consider choosing a more descriptive name",
206 if interned_name.starts_with('_') {
207 // these bindings are typically unused or represent an ignored portion of a destructuring pattern
210 let count = interned_name.chars().count();
213 self.check_short_ident(ident);
217 for existing_name in &self.0.names {
218 if allowed_to_be_similar(&interned_name, existing_name.exemptions) {
221 match existing_name.len.cmp(&count) {
222 Ordering::Greater => {
223 if existing_name.len - count != 1
224 || levenstein_not_1(&interned_name, &existing_name.interned.as_str())
230 if count - existing_name.len != 1
231 || levenstein_not_1(&existing_name.interned.as_str(), &interned_name)
237 let mut interned_chars = interned_name.chars();
238 let interned_str = existing_name.interned.as_str();
239 let mut existing_chars = interned_str.chars();
240 let first_i = interned_chars.next().expect("we know we have at least one char");
241 let first_e = existing_chars.next().expect("we know we have at least one char");
242 let eq_or_numeric = |(a, b): (char, char)| a == b || a.is_numeric() && b.is_numeric();
244 if eq_or_numeric((first_i, first_e)) {
245 let last_i = interned_chars.next_back().expect("we know we have at least two chars");
246 let last_e = existing_chars.next_back().expect("we know we have at least two chars");
247 if eq_or_numeric((last_i, last_e)) {
250 .filter(|&ie| !eq_or_numeric(ie))
257 let second_last_i = interned_chars
259 .expect("we know we have at least three chars");
260 let second_last_e = existing_chars
262 .expect("we know we have at least three chars");
263 if !eq_or_numeric((second_last_i, second_last_e))
264 || second_last_i == '_'
265 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
267 // allowed similarity foo_x, foo_y
268 // or too many chars differ (foo_x, boo_y) or (foox, booy)
273 let second_i = interned_chars.next().expect("we know we have at least two chars");
274 let second_e = existing_chars.next().expect("we know we have at least two chars");
275 if !eq_or_numeric((second_i, second_e))
277 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
279 // allowed similarity x_foo, y_foo
280 // or too many chars differ (x_foo, y_boo) or (xfoo, yboo)
290 "binding's name is too similar to existing binding",
292 diag.span_note(existing_name.span, "existing binding defined here");
297 self.0.names.push(ExistingName {
298 exemptions: get_exemptions(&interned_name).unwrap_or(&[]),
299 interned: ident.name,
306 impl<'a, 'b> SimilarNamesLocalVisitor<'a, 'b> {
307 /// ensure scoping rules work
308 fn apply<F: for<'c> Fn(&'c mut Self)>(&mut self, f: F) {
309 let n = self.names.len();
310 let single_char_count = self.single_char_names.len();
312 self.names.truncate(n);
313 self.single_char_names.truncate(single_char_count);
317 impl<'a, 'tcx> Visitor<'tcx> for SimilarNamesLocalVisitor<'a, 'tcx> {
318 fn visit_local(&mut self, local: &'tcx Local) {
319 if let Some(ref init) = local.init {
320 self.apply(|this| walk_expr(this, &**init));
322 // add the pattern after the expression because the bindings aren't available
325 SimilarNamesNameVisitor(self).visit_pat(&*local.pat);
327 fn visit_block(&mut self, blk: &'tcx Block) {
328 self.single_char_names.push(vec![]);
330 self.apply(|this| walk_block(this, blk));
332 self.check_single_char_names();
333 self.single_char_names.pop();
335 fn visit_arm(&mut self, arm: &'tcx Arm) {
336 self.single_char_names.push(vec![]);
339 SimilarNamesNameVisitor(this).visit_pat(&arm.pat);
340 this.apply(|this| walk_expr(this, &arm.body));
343 self.check_single_char_names();
344 self.single_char_names.pop();
346 fn visit_item(&mut self, _: &Item) {
347 // do not recurse into inner items
351 impl EarlyLintPass for NonExpressiveNames {
352 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
353 if in_external_macro(cx.sess, item.span) {
357 if let ItemKind::Fn(box FnKind(_, ref sig, _, Some(ref blk))) = item.kind {
358 do_check(self, cx, &item.attrs, &sig.decl, blk);
362 fn check_impl_item(&mut self, cx: &EarlyContext<'_>, item: &AssocItem) {
363 if in_external_macro(cx.sess, item.span) {
367 if let AssocItemKind::Fn(box FnKind(_, ref sig, _, Some(ref blk))) = item.kind {
368 do_check(self, cx, &item.attrs, &sig.decl, blk);
373 fn do_check(lint: &mut NonExpressiveNames, cx: &EarlyContext<'_>, attrs: &[Attribute], decl: &FnDecl, blk: &Block) {
374 if !attrs.iter().any(|attr| attr.has_name(sym::test)) {
375 let mut visitor = SimilarNamesLocalVisitor {
379 single_char_names: vec![vec![]],
382 // initialize with function arguments
383 for arg in &decl.inputs {
384 SimilarNamesNameVisitor(&mut visitor).visit_pat(&arg.pat);
386 // walk all other bindings
387 walk_block(&mut visitor, blk);
389 visitor.check_single_char_names();
393 /// Precondition: `a_name.chars().count() < b_name.chars().count()`.
395 fn levenstein_not_1(a_name: &str, b_name: &str) -> bool {
396 debug_assert!(a_name.chars().count() < b_name.chars().count());
397 let mut a_chars = a_name.chars();
398 let mut b_chars = b_name.chars();
399 while let (Some(a), Some(b)) = (a_chars.next(), b_chars.next()) {
403 if let Some(b2) = b_chars.next() {
404 // check if there's just one character inserted
405 return a != b2 || a_chars.ne(b_chars);