2 use syntax::codemap::Span;
3 use syntax::symbol::LocalInternedString;
6 use syntax::visit::{walk_block, walk_expr, walk_pat, Visitor};
7 use crate::utils::{in_macro, span_lint, span_lint_and_then};
9 /// **What it does:** Checks for names that are very similar and thus confusing.
11 /// **Why is this bad?** It's hard to distinguish between names that differ only
12 /// by a single character.
14 /// **Known problems:** None?
18 /// let checked_exp = something;
19 /// let checked_expr = something_else;
21 declare_clippy_lint! {
24 "similarly named items and bindings"
27 /// **What it does:** Checks for too many variables whose name consists of a
30 /// **Why is this bad?** It's hard to memorize what a variable means without a
33 /// **Known problems:** None?
37 /// let (a, b, c, d, e, f, g) = (...);
39 declare_clippy_lint! {
40 pub MANY_SINGLE_CHAR_NAMES,
42 "too many single character bindings"
45 /// **What it does:** Checks if you have variables whose name consists of just
46 /// underscores and digits.
48 /// **Why is this bad?** It's hard to memorize what a variable means without a
51 /// **Known problems:** None?
59 declare_clippy_lint! {
60 pub JUST_UNDERSCORES_AND_DIGITS,
65 pub struct NonExpressiveNames {
66 pub single_char_binding_names_threshold: u64,
69 impl LintPass for NonExpressiveNames {
70 fn get_lints(&self) -> LintArray {
71 lint_array!(SIMILAR_NAMES, MANY_SINGLE_CHAR_NAMES, JUST_UNDERSCORES_AND_DIGITS)
76 interned: LocalInternedString,
79 whitelist: &'static [&'static str],
82 struct SimilarNamesLocalVisitor<'a, 'tcx: 'a> {
83 names: Vec<ExistingName>,
84 cx: &'a EarlyContext<'tcx>,
85 lint: &'a NonExpressiveNames,
86 single_char_names: Vec<char>,
89 // this list contains lists of names that are allowed to be similar
90 // the assumption is that no name is ever contained in multiple lists.
91 #[cfg_attr(rustfmt, rustfmt_skip)]
92 const WHITELIST: &[&[&str]] = &[
93 &["parsed", "parser"],
102 struct SimilarNamesNameVisitor<'a: 'b, 'tcx: 'a, 'b>(&'b mut SimilarNamesLocalVisitor<'a, 'tcx>);
104 impl<'a, 'tcx: 'a, 'b> Visitor<'tcx> for SimilarNamesNameVisitor<'a, 'tcx, 'b> {
105 fn visit_pat(&mut self, pat: &'tcx Pat) {
107 PatKind::Ident(_, ident, _) => self.check_name(ident.span, ident.name),
108 PatKind::Struct(_, ref fields, _) => for field in fields {
109 if !field.node.is_shorthand {
110 self.visit_pat(&field.node.pat);
113 _ => walk_pat(self, pat),
118 fn get_whitelist(interned_name: &str) -> Option<&'static [&'static str]> {
119 for &allow in WHITELIST {
120 if whitelisted(interned_name, allow) {
127 fn whitelisted(interned_name: &str, list: &[&str]) -> bool {
129 .any(|&name| interned_name.starts_with(name) || interned_name.ends_with(name))
132 impl<'a, 'tcx, 'b> SimilarNamesNameVisitor<'a, 'tcx, 'b> {
133 fn check_short_name(&mut self, c: char, span: Span) {
134 // make sure we ignore shadowing
135 if self.0.single_char_names.contains(&c) {
138 self.0.single_char_names.push(c);
139 if self.0.single_char_names.len() as u64 >= self.0.lint.single_char_binding_names_threshold {
142 MANY_SINGLE_CHAR_NAMES,
144 &format!("{}th binding whose name is just one char", self.0.single_char_names.len()),
148 fn check_name(&mut self, span: Span, name: Name) {
152 let interned_name = name.as_str();
153 if interned_name.chars().any(char::is_uppercase) {
156 if interned_name.chars().all(|c| c.is_digit(10) || c == '_') {
159 JUST_UNDERSCORES_AND_DIGITS,
161 "consider choosing a more descriptive name",
165 let count = interned_name.chars().count();
168 let c = interned_name.chars().next().expect("already checked");
169 self.check_short_name(c, span);
173 for existing_name in &self.0.names {
174 if whitelisted(&interned_name, existing_name.whitelist) {
177 let mut split_at = None;
178 if existing_name.len > count {
179 if existing_name.len - count != 1 || levenstein_not_1(&interned_name, &existing_name.interned) {
182 } else if existing_name.len < count {
183 if count - existing_name.len != 1 || levenstein_not_1(&existing_name.interned, &interned_name) {
187 let mut interned_chars = interned_name.chars();
188 let mut existing_chars = existing_name.interned.chars();
189 let first_i = interned_chars
191 .expect("we know we have at least one char");
192 let first_e = existing_chars
194 .expect("we know we have at least one char");
195 let eq_or_numeric = |(a, b): (char, char)| a == b || a.is_numeric() && b.is_numeric();
197 if eq_or_numeric((first_i, first_e)) {
198 let last_i = interned_chars
200 .expect("we know we have at least two chars");
201 let last_e = existing_chars
203 .expect("we know we have at least two chars");
204 if eq_or_numeric((last_i, last_e)) {
207 .filter(|&ie| !eq_or_numeric(ie))
213 let second_last_i = interned_chars
215 .expect("we know we have at least three chars");
216 let second_last_e = existing_chars
218 .expect("we know we have at least three chars");
219 if !eq_or_numeric((second_last_i, second_last_e)) || second_last_i == '_'
220 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
222 // allowed similarity foo_x, foo_y
223 // or too many chars differ (foo_x, boo_y) or (foox, booy)
226 split_at = interned_name.char_indices().rev().next().map(|(i, _)| i);
229 let second_i = interned_chars
231 .expect("we know we have at least two chars");
232 let second_e = existing_chars
234 .expect("we know we have at least two chars");
235 if !eq_or_numeric((second_i, second_e)) || second_i == '_'
236 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
238 // allowed similarity x_foo, y_foo
239 // or too many chars differ (x_foo, y_boo) or (xfoo, yboo)
242 split_at = interned_name.chars().next().map(|c| c.len_utf8());
249 "binding's name is too similar to existing binding",
251 diag.span_note(existing_name.span, "existing binding defined here");
252 if let Some(split) = split_at {
256 "separate the discriminating character by an \
257 underscore like: `{}_{}`",
258 &interned_name[..split],
259 &interned_name[split..]
267 self.0.names.push(ExistingName {
268 whitelist: get_whitelist(&interned_name).unwrap_or(&[]),
269 interned: interned_name,
276 impl<'a, 'b> SimilarNamesLocalVisitor<'a, 'b> {
277 /// ensure scoping rules work
278 fn apply<F: for<'c> Fn(&'c mut Self)>(&mut self, f: F) {
279 let n = self.names.len();
280 let single_char_count = self.single_char_names.len();
282 self.names.truncate(n);
283 self.single_char_names.truncate(single_char_count);
287 impl<'a, 'tcx> Visitor<'tcx> for SimilarNamesLocalVisitor<'a, 'tcx> {
288 fn visit_local(&mut self, local: &'tcx Local) {
289 if let Some(ref init) = local.init {
290 self.apply(|this| walk_expr(this, &**init));
292 // add the pattern after the expression because the bindings aren't available
295 SimilarNamesNameVisitor(self).visit_pat(&*local.pat);
297 fn visit_block(&mut self, blk: &'tcx Block) {
298 self.apply(|this| walk_block(this, blk));
300 fn visit_arm(&mut self, arm: &'tcx Arm) {
302 // just go through the first pattern, as either all patterns
303 // bind the same bindings or rustc would have errored much earlier
304 SimilarNamesNameVisitor(this).visit_pat(&arm.pats[0]);
305 this.apply(|this| walk_expr(this, &arm.body));
308 fn visit_item(&mut self, _: &Item) {
309 // do not recurse into inner items
313 impl EarlyLintPass for NonExpressiveNames {
314 fn check_item(&mut self, cx: &EarlyContext, item: &Item) {
315 if let ItemKind::Fn(ref decl, _, _, _, _, ref blk) = item.node {
316 do_check(self, cx, &item.attrs, decl, blk);
320 fn check_impl_item(&mut self, cx: &EarlyContext, item: &ImplItem) {
321 if let ImplItemKind::Method(ref sig, ref blk) = item.node {
322 do_check(self, cx, &item.attrs, &sig.decl, blk);
328 fn do_check(lint: &mut NonExpressiveNames, cx: &EarlyContext, attrs: &[Attribute], decl: &FnDecl, blk: &Block) {
329 if !attr::contains_name(attrs, "test") {
330 let mut visitor = SimilarNamesLocalVisitor {
334 single_char_names: Vec::new(),
336 // initialize with function arguments
337 for arg in &decl.inputs {
338 SimilarNamesNameVisitor(&mut visitor).visit_pat(&arg.pat);
340 // walk all other bindings
341 walk_block(&mut visitor, blk);
345 /// Precondition: `a_name.chars().count() < b_name.chars().count()`.
346 fn levenstein_not_1(a_name: &str, b_name: &str) -> bool {
347 debug_assert!(a_name.chars().count() < b_name.chars().count());
348 let mut a_chars = a_name.chars();
349 let mut b_chars = b_name.chars();
350 while let (Some(a), Some(b)) = (a_chars.next(), b_chars.next()) {
354 if let Some(b2) = b_chars.next() {
355 // check if there's just one character inserted
356 return a != b2 || a_chars.ne(b_chars);