1 use crate::utils::{span_lint, span_lint_and_then};
2 use rustc_ast::ast::{Arm, AssocItem, AssocItemKind, Attribute, Block, FnDecl, Item, ItemKind, Local, Pat, PatKind};
3 use rustc_ast::visit::{walk_block, walk_expr, walk_pat, Visitor};
4 use rustc_lint::{EarlyContext, EarlyLintPass};
5 use rustc_middle::lint::in_external_macro;
6 use rustc_session::{declare_tool_lint, impl_lint_pass};
7 use rustc_span::source_map::Span;
9 use rustc_span::symbol::{Ident, Symbol};
10 use std::cmp::Ordering;
12 declare_clippy_lint! {
13 /// **What it does:** Checks for names that are very similar and thus confusing.
15 /// **Why is this bad?** It's hard to distinguish between names that differ only
16 /// by a single character.
18 /// **Known problems:** None?
22 /// let checked_exp = something;
23 /// let checked_expr = something_else;
27 "similarly named items and bindings"
30 declare_clippy_lint! {
31 /// **What it does:** Checks for too many variables whose name consists of a
34 /// **Why is this bad?** It's hard to memorize what a variable means without a
37 /// **Known problems:** None?
41 /// let (a, b, c, d, e, f, g) = (...);
43 pub MANY_SINGLE_CHAR_NAMES,
45 "too many single character bindings"
48 declare_clippy_lint! {
49 /// **What it does:** Checks if you have variables whose name consists of just
50 /// underscores and digits.
52 /// **Why is this bad?** It's hard to memorize what a variable means without a
55 /// **Known problems:** None?
63 pub JUST_UNDERSCORES_AND_DIGITS,
68 #[derive(Copy, Clone)]
69 pub struct NonExpressiveNames {
70 pub single_char_binding_names_threshold: u64,
73 impl_lint_pass!(NonExpressiveNames => [SIMILAR_NAMES, MANY_SINGLE_CHAR_NAMES, JUST_UNDERSCORES_AND_DIGITS]);
79 exemptions: &'static [&'static str],
82 struct SimilarNamesLocalVisitor<'a, 'tcx> {
83 names: Vec<ExistingName>,
84 cx: &'a EarlyContext<'tcx>,
85 lint: &'a NonExpressiveNames,
87 /// A stack of scopes containing the single-character bindings in each scope.
88 single_char_names: Vec<Vec<Ident>>,
91 impl<'a, 'tcx> SimilarNamesLocalVisitor<'a, 'tcx> {
92 fn check_single_char_names(&self) {
93 let num_single_char_names = self.single_char_names.iter().flatten().count();
94 let threshold = self.lint.single_char_binding_names_threshold;
95 if num_single_char_names as u64 > threshold {
100 .map(|ident| ident.span)
101 .collect::<Vec<_>>();
104 MANY_SINGLE_CHAR_NAMES,
107 "{} bindings with single-character names in scope",
108 num_single_char_names
115 // this list contains lists of names that are allowed to be similar
116 // the assumption is that no name is ever contained in multiple lists.
118 const ALLOWED_TO_BE_SIMILAR: &[&[&str]] = &[
119 &["parsed", "parser"],
128 struct SimilarNamesNameVisitor<'a, 'tcx, 'b>(&'b mut SimilarNamesLocalVisitor<'a, 'tcx>);
130 impl<'a, 'tcx, 'b> Visitor<'tcx> for SimilarNamesNameVisitor<'a, 'tcx, 'b> {
131 fn visit_pat(&mut self, pat: &'tcx Pat) {
133 PatKind::Ident(_, ident, _) => {
134 if !pat.span.from_expansion() {
135 self.check_ident(ident);
138 PatKind::Struct(_, ref fields, _) => {
139 for field in fields {
140 if !field.is_shorthand {
141 self.visit_pat(&field.pat);
145 // just go through the first pattern, as either all patterns
146 // bind the same bindings or rustc would have errored much earlier
147 PatKind::Or(ref pats) => self.visit_pat(&pats[0]),
148 _ => walk_pat(self, pat),
154 fn get_exemptions(interned_name: &str) -> Option<&'static [&'static str]> {
155 for &list in ALLOWED_TO_BE_SIMILAR {
156 if allowed_to_be_similar(interned_name, list) {
164 fn allowed_to_be_similar(interned_name: &str, list: &[&str]) -> bool {
166 .any(|&name| interned_name.starts_with(name) || interned_name.ends_with(name))
169 impl<'a, 'tcx, 'b> SimilarNamesNameVisitor<'a, 'tcx, 'b> {
170 fn check_short_ident(&mut self, ident: Ident) {
177 .any(|id| id.name == ident.name)
182 if let Some(scope) = &mut self.0.single_char_names.last_mut() {
187 #[allow(clippy::too_many_lines)]
188 fn check_ident(&mut self, ident: Ident) {
189 let interned_name = ident.name.as_str();
190 if interned_name.chars().any(char::is_uppercase) {
193 if interned_name.chars().all(|c| c.is_digit(10) || c == '_') {
196 JUST_UNDERSCORES_AND_DIGITS,
198 "consider choosing a more descriptive name",
202 let count = interned_name.chars().count();
205 self.check_short_ident(ident);
209 for existing_name in &self.0.names {
210 if allowed_to_be_similar(&interned_name, existing_name.exemptions) {
213 let mut split_at = None;
214 match existing_name.len.cmp(&count) {
215 Ordering::Greater => {
216 if existing_name.len - count != 1
217 || levenstein_not_1(&interned_name, &existing_name.interned.as_str())
223 if count - existing_name.len != 1
224 || levenstein_not_1(&existing_name.interned.as_str(), &interned_name)
230 let mut interned_chars = interned_name.chars();
231 let interned_str = existing_name.interned.as_str();
232 let mut existing_chars = interned_str.chars();
233 let first_i = interned_chars.next().expect("we know we have at least one char");
234 let first_e = existing_chars.next().expect("we know we have at least one char");
235 let eq_or_numeric = |(a, b): (char, char)| a == b || a.is_numeric() && b.is_numeric();
237 if eq_or_numeric((first_i, first_e)) {
238 let last_i = interned_chars.next_back().expect("we know we have at least two chars");
239 let last_e = existing_chars.next_back().expect("we know we have at least two chars");
240 if eq_or_numeric((last_i, last_e)) {
243 .filter(|&ie| !eq_or_numeric(ie))
250 let second_last_i = interned_chars
252 .expect("we know we have at least three chars");
253 let second_last_e = existing_chars
255 .expect("we know we have at least three chars");
256 if !eq_or_numeric((second_last_i, second_last_e))
257 || second_last_i == '_'
258 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
260 // allowed similarity foo_x, foo_y
261 // or too many chars differ (foo_x, boo_y) or (foox, booy)
264 split_at = interned_name.char_indices().rev().next().map(|(i, _)| i);
267 let second_i = interned_chars.next().expect("we know we have at least two chars");
268 let second_e = existing_chars.next().expect("we know we have at least two chars");
269 if !eq_or_numeric((second_i, second_e))
271 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
273 // allowed similarity x_foo, y_foo
274 // or too many chars differ (x_foo, y_boo) or (xfoo, yboo)
277 split_at = interned_name.chars().next().map(char::len_utf8);
285 "binding's name is too similar to existing binding",
287 diag.span_note(existing_name.span, "existing binding defined here");
288 if let Some(split) = split_at {
292 "separate the discriminating character by an \
293 underscore like: `{}_{}`",
294 &interned_name[..split],
295 &interned_name[split..]
303 self.0.names.push(ExistingName {
304 exemptions: get_exemptions(&interned_name).unwrap_or(&[]),
305 interned: ident.name,
312 impl<'a, 'b> SimilarNamesLocalVisitor<'a, 'b> {
313 /// ensure scoping rules work
314 fn apply<F: for<'c> Fn(&'c mut Self)>(&mut self, f: F) {
315 let n = self.names.len();
316 let single_char_count = self.single_char_names.len();
318 self.names.truncate(n);
319 self.single_char_names.truncate(single_char_count);
323 impl<'a, 'tcx> Visitor<'tcx> for SimilarNamesLocalVisitor<'a, 'tcx> {
324 fn visit_local(&mut self, local: &'tcx Local) {
325 if let Some(ref init) = local.init {
326 self.apply(|this| walk_expr(this, &**init));
328 // add the pattern after the expression because the bindings aren't available
331 SimilarNamesNameVisitor(self).visit_pat(&*local.pat);
333 fn visit_block(&mut self, blk: &'tcx Block) {
334 self.single_char_names.push(vec![]);
336 self.apply(|this| walk_block(this, blk));
338 self.check_single_char_names();
339 self.single_char_names.pop();
341 fn visit_arm(&mut self, arm: &'tcx Arm) {
342 self.single_char_names.push(vec![]);
345 SimilarNamesNameVisitor(this).visit_pat(&arm.pat);
346 this.apply(|this| walk_expr(this, &arm.body));
349 self.check_single_char_names();
350 self.single_char_names.pop();
352 fn visit_item(&mut self, _: &Item) {
353 // do not recurse into inner items
357 impl EarlyLintPass for NonExpressiveNames {
358 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
359 if in_external_macro(cx.sess, item.span) {
363 if let ItemKind::Fn(_, ref sig, _, Some(ref blk)) = item.kind {
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(_, ref sig, _, Some(ref blk)) = item.kind {
374 do_check(self, cx, &item.attrs, &sig.decl, blk);
379 fn do_check(lint: &mut NonExpressiveNames, cx: &EarlyContext<'_>, attrs: &[Attribute], decl: &FnDecl, blk: &Block) {
380 if !attrs.iter().any(|attr| attr.has_name(sym::test)) {
381 let mut visitor = SimilarNamesLocalVisitor {
385 single_char_names: vec![vec![]],
388 // initialize with function arguments
389 for arg in &decl.inputs {
390 SimilarNamesNameVisitor(&mut visitor).visit_pat(&arg.pat);
392 // walk all other bindings
393 walk_block(&mut visitor, blk);
395 visitor.check_single_char_names();
399 /// Precondition: `a_name.chars().count() < b_name.chars().count()`.
401 fn levenstein_not_1(a_name: &str, b_name: &str) -> bool {
402 debug_assert!(a_name.chars().count() < b_name.chars().count());
403 let mut a_chars = a_name.chars();
404 let mut b_chars = b_name.chars();
405 while let (Some(a), Some(b)) = (a_chars.next(), b_chars.next()) {
409 if let Some(b2) = b_chars.next() {
410 // check if there's just one character inserted
411 return a != b2 || a_chars.ne(b_chars);