1 use crate::utils::{span_lint, span_lint_and_then};
2 use rustc::impl_lint_pass;
3 use rustc::lint::{EarlyContext, EarlyLintPass, LintArray, LintPass};
4 use rustc_session::declare_tool_lint;
5 use rustc_span::source_map::Span;
6 use rustc_span::symbol::SymbolStr;
7 use std::cmp::Ordering;
10 use syntax::visit::{walk_block, walk_expr, walk_pat, Visitor};
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 whitelist: &'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 WHITELIST: &[&[&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, _) => self.check_ident(ident),
134 PatKind::Struct(_, ref fields, _) => {
135 for field in fields {
136 if !field.is_shorthand {
137 self.visit_pat(&field.pat);
141 // just go through the first pattern, as either all patterns
142 // bind the same bindings or rustc would have errored much earlier
143 PatKind::Or(ref pats) => self.visit_pat(&pats[0]),
144 _ => walk_pat(self, pat),
147 fn visit_mac(&mut self, _mac: &Mac) {
153 fn get_whitelist(interned_name: &str) -> Option<&'static [&'static str]> {
154 for &allow in WHITELIST {
155 if whitelisted(interned_name, allow) {
163 fn whitelisted(interned_name: &str, list: &[&str]) -> bool {
165 .any(|&name| interned_name.starts_with(name) || interned_name.ends_with(name))
168 impl<'a, 'tcx, 'b> SimilarNamesNameVisitor<'a, 'tcx, 'b> {
169 fn check_short_ident(&mut self, ident: Ident) {
176 .any(|id| id.name == ident.name)
181 if let Some(scope) = &mut self.0.single_char_names.last_mut() {
186 #[allow(clippy::too_many_lines)]
187 fn check_ident(&mut self, ident: Ident) {
188 let interned_name = ident.name.as_str();
189 if interned_name.chars().any(char::is_uppercase) {
192 if interned_name.chars().all(|c| c.is_digit(10) || c == '_') {
195 JUST_UNDERSCORES_AND_DIGITS,
197 "consider choosing a more descriptive name",
201 let count = interned_name.chars().count();
204 self.check_short_ident(ident);
208 for existing_name in &self.0.names {
209 if whitelisted(&interned_name, existing_name.whitelist) {
212 let mut split_at = None;
213 match existing_name.len.cmp(&count) {
214 Ordering::Greater => {
215 if existing_name.len - count != 1 || levenstein_not_1(&interned_name, &existing_name.interned) {
220 if count - existing_name.len != 1 || levenstein_not_1(&existing_name.interned, &interned_name) {
225 let mut interned_chars = interned_name.chars();
226 let mut existing_chars = existing_name.interned.chars();
227 let first_i = interned_chars.next().expect("we know we have at least one char");
228 let first_e = existing_chars.next().expect("we know we have at least one char");
229 let eq_or_numeric = |(a, b): (char, char)| a == b || a.is_numeric() && b.is_numeric();
231 if eq_or_numeric((first_i, first_e)) {
232 let last_i = interned_chars.next_back().expect("we know we have at least two chars");
233 let last_e = existing_chars.next_back().expect("we know we have at least two chars");
234 if eq_or_numeric((last_i, last_e)) {
237 .filter(|&ie| !eq_or_numeric(ie))
244 let second_last_i = interned_chars
246 .expect("we know we have at least three chars");
247 let second_last_e = existing_chars
249 .expect("we know we have at least three chars");
250 if !eq_or_numeric((second_last_i, second_last_e))
251 || second_last_i == '_'
252 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
254 // allowed similarity foo_x, foo_y
255 // or too many chars differ (foo_x, boo_y) or (foox, booy)
258 split_at = interned_name.char_indices().rev().next().map(|(i, _)| i);
261 let second_i = interned_chars.next().expect("we know we have at least two chars");
262 let second_e = existing_chars.next().expect("we know we have at least two chars");
263 if !eq_or_numeric((second_i, second_e))
265 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
267 // allowed similarity x_foo, y_foo
268 // or too many chars differ (x_foo, y_boo) or (xfoo, yboo)
271 split_at = interned_name.chars().next().map(char::len_utf8);
279 "binding's name is too similar to existing binding",
281 diag.span_note(existing_name.span, "existing binding defined here");
282 if let Some(split) = split_at {
286 "separate the discriminating character by an \
287 underscore like: `{}_{}`",
288 &interned_name[..split],
289 &interned_name[split..]
297 self.0.names.push(ExistingName {
298 whitelist: get_whitelist(&interned_name).unwrap_or(&[]),
299 interned: interned_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
349 fn visit_mac(&mut self, _mac: &Mac) {
354 impl EarlyLintPass for NonExpressiveNames {
355 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
356 if let ItemKind::Fn(ref sig, _, ref blk) = item.kind {
357 do_check(self, cx, &item.attrs, &sig.decl, blk);
361 fn check_impl_item(&mut self, cx: &EarlyContext<'_>, item: &AssocItem) {
362 if let AssocItemKind::Fn(ref sig, Some(ref blk)) = item.kind {
363 do_check(self, cx, &item.attrs, &sig.decl, blk);
368 fn do_check(lint: &mut NonExpressiveNames, cx: &EarlyContext<'_>, attrs: &[Attribute], decl: &FnDecl, blk: &Block) {
369 if !attr::contains_name(attrs, sym!(test)) {
370 let mut visitor = SimilarNamesLocalVisitor {
374 single_char_names: vec![vec![]],
377 // initialize with function arguments
378 for arg in &decl.inputs {
379 SimilarNamesNameVisitor(&mut visitor).visit_pat(&arg.pat);
381 // walk all other bindings
382 walk_block(&mut visitor, blk);
384 visitor.check_single_char_names();
388 /// Precondition: `a_name.chars().count() < b_name.chars().count()`.
390 fn levenstein_not_1(a_name: &str, b_name: &str) -> bool {
391 debug_assert!(a_name.chars().count() < b_name.chars().count());
392 let mut a_chars = a_name.chars();
393 let mut b_chars = b_name.chars();
394 while let (Some(a), Some(b)) = (a_chars.next(), b_chars.next()) {
398 if let Some(b2) = b_chars.next() {
399 // check if there's just one character inserted
400 return a != b2 || a_chars.ne(b_chars);