1 use crate::utils::{span_lint, span_lint_and_then};
3 Arm, AssocItem, AssocItemKind, Attribute, Block, FnDecl, Item, ItemKind, Local, MacCall, 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;
10 use rustc_span::symbol::{Ident, Symbol};
11 use std::cmp::Ordering;
13 declare_clippy_lint! {
14 /// **What it does:** Checks for names that are very similar and thus confusing.
16 /// **Why is this bad?** It's hard to distinguish between names that differ only
17 /// by a single character.
19 /// **Known problems:** None?
23 /// let checked_exp = something;
24 /// let checked_expr = something_else;
28 "similarly named items and bindings"
31 declare_clippy_lint! {
32 /// **What it does:** Checks for too many variables whose name consists of a
35 /// **Why is this bad?** It's hard to memorize what a variable means without a
38 /// **Known problems:** None?
42 /// let (a, b, c, d, e, f, g) = (...);
44 pub MANY_SINGLE_CHAR_NAMES,
46 "too many single character bindings"
49 declare_clippy_lint! {
50 /// **What it does:** Checks if you have variables whose name consists of just
51 /// underscores and digits.
53 /// **Why is this bad?** It's hard to memorize what a variable means without a
56 /// **Known problems:** None?
64 pub JUST_UNDERSCORES_AND_DIGITS,
69 #[derive(Copy, Clone)]
70 pub struct NonExpressiveNames {
71 pub single_char_binding_names_threshold: u64,
74 impl_lint_pass!(NonExpressiveNames => [SIMILAR_NAMES, MANY_SINGLE_CHAR_NAMES, JUST_UNDERSCORES_AND_DIGITS]);
80 exemptions: &'static [&'static str],
83 struct SimilarNamesLocalVisitor<'a, 'tcx> {
84 names: Vec<ExistingName>,
85 cx: &'a EarlyContext<'tcx>,
86 lint: &'a NonExpressiveNames,
88 /// A stack of scopes containing the single-character bindings in each scope.
89 single_char_names: Vec<Vec<Ident>>,
92 impl<'a, 'tcx> SimilarNamesLocalVisitor<'a, 'tcx> {
93 fn check_single_char_names(&self) {
94 let num_single_char_names = self.single_char_names.iter().flatten().count();
95 let threshold = self.lint.single_char_binding_names_threshold;
96 if num_single_char_names as u64 > threshold {
101 .map(|ident| ident.span)
102 .collect::<Vec<_>>();
105 MANY_SINGLE_CHAR_NAMES,
108 "{} bindings with single-character names in scope",
109 num_single_char_names
116 // this list contains lists of names that are allowed to be similar
117 // the assumption is that no name is ever contained in multiple lists.
119 const ALLOWED_TO_BE_SIMILAR: &[&[&str]] = &[
120 &["parsed", "parser"],
129 struct SimilarNamesNameVisitor<'a, 'tcx, 'b>(&'b mut SimilarNamesLocalVisitor<'a, 'tcx>);
131 impl<'a, 'tcx, 'b> Visitor<'tcx> for SimilarNamesNameVisitor<'a, 'tcx, 'b> {
132 fn visit_pat(&mut self, pat: &'tcx Pat) {
134 PatKind::Ident(_, ident, _) => {
135 if !pat.span.from_expansion() {
136 self.check_ident(ident);
139 PatKind::Struct(_, ref fields, _) => {
140 for field in fields {
141 if !field.is_shorthand {
142 self.visit_pat(&field.pat);
146 // just go through the first pattern, as either all patterns
147 // bind the same bindings or rustc would have errored much earlier
148 PatKind::Or(ref pats) => self.visit_pat(&pats[0]),
149 _ => walk_pat(self, pat),
152 fn visit_mac(&mut self, _mac: &MacCall) {
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 let count = interned_name.chars().count();
209 self.check_short_ident(ident);
213 for existing_name in &self.0.names {
214 if allowed_to_be_similar(&interned_name, existing_name.exemptions) {
217 let mut split_at = None;
218 match existing_name.len.cmp(&count) {
219 Ordering::Greater => {
220 if existing_name.len - count != 1
221 || levenstein_not_1(&interned_name, &existing_name.interned.as_str())
227 if count - existing_name.len != 1
228 || levenstein_not_1(&existing_name.interned.as_str(), &interned_name)
234 let mut interned_chars = interned_name.chars();
235 let interned_str = existing_name.interned.as_str();
236 let mut existing_chars = interned_str.chars();
237 let first_i = interned_chars.next().expect("we know we have at least one char");
238 let first_e = existing_chars.next().expect("we know we have at least one char");
239 let eq_or_numeric = |(a, b): (char, char)| a == b || a.is_numeric() && b.is_numeric();
241 if eq_or_numeric((first_i, first_e)) {
242 let last_i = interned_chars.next_back().expect("we know we have at least two chars");
243 let last_e = existing_chars.next_back().expect("we know we have at least two chars");
244 if eq_or_numeric((last_i, last_e)) {
247 .filter(|&ie| !eq_or_numeric(ie))
254 let second_last_i = interned_chars
256 .expect("we know we have at least three chars");
257 let second_last_e = existing_chars
259 .expect("we know we have at least three chars");
260 if !eq_or_numeric((second_last_i, second_last_e))
261 || second_last_i == '_'
262 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
264 // allowed similarity foo_x, foo_y
265 // or too many chars differ (foo_x, boo_y) or (foox, booy)
268 split_at = interned_name.char_indices().rev().next().map(|(i, _)| i);
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)
281 split_at = interned_name.chars().next().map(char::len_utf8);
289 "binding's name is too similar to existing binding",
291 diag.span_note(existing_name.span, "existing binding defined here");
292 if let Some(split) = split_at {
296 "separate the discriminating character by an \
297 underscore like: `{}_{}`",
298 &interned_name[..split],
299 &interned_name[split..]
307 self.0.names.push(ExistingName {
308 exemptions: get_exemptions(&interned_name).unwrap_or(&[]),
309 interned: ident.name,
316 impl<'a, 'b> SimilarNamesLocalVisitor<'a, 'b> {
317 /// ensure scoping rules work
318 fn apply<F: for<'c> Fn(&'c mut Self)>(&mut self, f: F) {
319 let n = self.names.len();
320 let single_char_count = self.single_char_names.len();
322 self.names.truncate(n);
323 self.single_char_names.truncate(single_char_count);
327 impl<'a, 'tcx> Visitor<'tcx> for SimilarNamesLocalVisitor<'a, 'tcx> {
328 fn visit_local(&mut self, local: &'tcx Local) {
329 if let Some(ref init) = local.init {
330 self.apply(|this| walk_expr(this, &**init));
332 // add the pattern after the expression because the bindings aren't available
335 SimilarNamesNameVisitor(self).visit_pat(&*local.pat);
337 fn visit_block(&mut self, blk: &'tcx Block) {
338 self.single_char_names.push(vec![]);
340 self.apply(|this| walk_block(this, blk));
342 self.check_single_char_names();
343 self.single_char_names.pop();
345 fn visit_arm(&mut self, arm: &'tcx Arm) {
346 self.single_char_names.push(vec![]);
349 SimilarNamesNameVisitor(this).visit_pat(&arm.pat);
350 this.apply(|this| walk_expr(this, &arm.body));
353 self.check_single_char_names();
354 self.single_char_names.pop();
356 fn visit_item(&mut self, _: &Item) {
357 // do not recurse into inner items
359 fn visit_mac(&mut self, _mac: &MacCall) {
364 impl EarlyLintPass for NonExpressiveNames {
365 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
366 if in_external_macro(cx.sess, item.span) {
370 if let ItemKind::Fn(_, ref sig, _, Some(ref blk)) = item.kind {
371 do_check(self, cx, &item.attrs, &sig.decl, blk);
375 fn check_impl_item(&mut self, cx: &EarlyContext<'_>, item: &AssocItem) {
376 if in_external_macro(cx.sess, item.span) {
380 if let AssocItemKind::Fn(_, ref sig, _, Some(ref blk)) = item.kind {
381 do_check(self, cx, &item.attrs, &sig.decl, blk);
386 fn do_check(lint: &mut NonExpressiveNames, cx: &EarlyContext<'_>, attrs: &[Attribute], decl: &FnDecl, blk: &Block) {
387 if !attrs.iter().any(|attr| attr.has_name(sym!(test))) {
388 let mut visitor = SimilarNamesLocalVisitor {
392 single_char_names: vec![vec![]],
395 // initialize with function arguments
396 for arg in &decl.inputs {
397 SimilarNamesNameVisitor(&mut visitor).visit_pat(&arg.pat);
399 // walk all other bindings
400 walk_block(&mut visitor, blk);
402 visitor.check_single_char_names();
406 /// Precondition: `a_name.chars().count() < b_name.chars().count()`.
408 fn levenstein_not_1(a_name: &str, b_name: &str) -> bool {
409 debug_assert!(a_name.chars().count() < b_name.chars().count());
410 let mut a_chars = a_name.chars();
411 let mut b_chars = b_name.chars();
412 while let (Some(a), Some(b)) = (a_chars.next(), b_chars.next()) {
416 if let Some(b2) = b_chars.next() {
417 // check if there's just one character inserted
418 return a != b2 || a_chars.ne(b_chars);