1 use crate::utils::{span_lint, span_lint_and_then};
2 use rustc::lint::{EarlyContext, EarlyLintPass, LintArray, LintPass};
3 use rustc::{declare_tool_lint, lint_array};
6 use syntax::source_map::Span;
7 use syntax::symbol::LocalInternedString;
8 use syntax::visit::{walk_block, walk_expr, walk_pat, Visitor};
10 /// **What it does:** Checks for names that are very similar and thus confusing.
12 /// **Why is this bad?** It's hard to distinguish between names that differ only
13 /// by a single character.
15 /// **Known problems:** None?
19 /// let checked_exp = something;
20 /// let checked_expr = something_else;
22 declare_clippy_lint! {
25 "similarly named items and bindings"
28 /// **What it does:** Checks for too many variables whose name consists of a
31 /// **Why is this bad?** It's hard to memorize what a variable means without a
34 /// **Known problems:** None?
38 /// let (a, b, c, d, e, f, g) = (...);
40 declare_clippy_lint! {
41 pub MANY_SINGLE_CHAR_NAMES,
43 "too many single character bindings"
46 /// **What it does:** Checks if you have variables whose name consists of just
47 /// underscores and digits.
49 /// **Why is this bad?** It's hard to memorize what a variable means without a
52 /// **Known problems:** None?
60 declare_clippy_lint! {
61 pub JUST_UNDERSCORES_AND_DIGITS,
66 pub struct NonExpressiveNames {
67 pub single_char_binding_names_threshold: u64,
70 impl LintPass for NonExpressiveNames {
71 fn get_lints(&self) -> LintArray {
72 lint_array!(SIMILAR_NAMES, MANY_SINGLE_CHAR_NAMES, JUST_UNDERSCORES_AND_DIGITS)
77 interned: LocalInternedString,
80 whitelist: &'static [&'static str],
83 struct SimilarNamesLocalVisitor<'a, 'tcx: 'a> {
84 names: Vec<ExistingName>,
85 cx: &'a EarlyContext<'tcx>,
86 lint: &'a NonExpressiveNames,
87 single_char_names: Vec<char>,
90 // this list contains lists of names that are allowed to be similar
91 // the assumption is that no name is ever contained in multiple lists.
93 const WHITELIST: &[&[&str]] = &[
94 &["parsed", "parser"],
103 struct SimilarNamesNameVisitor<'a: 'b, 'tcx: 'a, 'b>(&'b mut SimilarNamesLocalVisitor<'a, 'tcx>);
105 impl<'a, 'tcx: 'a, 'b> Visitor<'tcx> for SimilarNamesNameVisitor<'a, 'tcx, 'b> {
106 fn visit_pat(&mut self, pat: &'tcx Pat) {
108 PatKind::Ident(_, ident, _) => self.check_name(ident.span, ident.name),
109 PatKind::Struct(_, ref fields, _) => {
110 for field in fields {
111 if !field.node.is_shorthand {
112 self.visit_pat(&field.node.pat);
116 _ => walk_pat(self, pat),
119 fn visit_mac(&mut self, _mac: &Mac) {
124 fn get_whitelist(interned_name: &str) -> Option<&'static [&'static str]> {
125 for &allow in WHITELIST {
126 if whitelisted(interned_name, allow) {
133 fn whitelisted(interned_name: &str, list: &[&str]) -> bool {
135 .any(|&name| interned_name.starts_with(name) || interned_name.ends_with(name))
138 impl<'a, 'tcx, 'b> SimilarNamesNameVisitor<'a, 'tcx, 'b> {
139 fn check_short_name(&mut self, c: char, span: Span) {
140 // make sure we ignore shadowing
141 if self.0.single_char_names.contains(&c) {
144 self.0.single_char_names.push(c);
145 if self.0.single_char_names.len() as u64 >= self.0.lint.single_char_binding_names_threshold {
148 MANY_SINGLE_CHAR_NAMES,
151 "{}th binding whose name is just one char",
152 self.0.single_char_names.len()
157 fn check_name(&mut self, span: Span, name: Name) {
158 let interned_name = name.as_str();
159 if interned_name.chars().any(char::is_uppercase) {
162 if interned_name.chars().all(|c| c.is_digit(10) || c == '_') {
165 JUST_UNDERSCORES_AND_DIGITS,
167 "consider choosing a more descriptive name",
171 let count = interned_name.chars().count();
174 let c = interned_name.chars().next().expect("already checked");
175 self.check_short_name(c, span);
179 for existing_name in &self.0.names {
180 if whitelisted(&interned_name, existing_name.whitelist) {
183 let mut split_at = None;
184 if existing_name.len > count {
185 if existing_name.len - count != 1 || levenstein_not_1(&interned_name, &existing_name.interned) {
188 } else if existing_name.len < count {
189 if count - existing_name.len != 1 || levenstein_not_1(&existing_name.interned, &interned_name) {
193 let mut interned_chars = interned_name.chars();
194 let mut existing_chars = existing_name.interned.chars();
195 let first_i = interned_chars.next().expect("we know we have at least one char");
196 let first_e = existing_chars.next().expect("we know we have at least one char");
197 let eq_or_numeric = |(a, b): (char, char)| a == b || a.is_numeric() && b.is_numeric();
199 if eq_or_numeric((first_i, first_e)) {
200 let last_i = interned_chars.next_back().expect("we know we have at least two chars");
201 let last_e = existing_chars.next_back().expect("we know we have at least two chars");
202 if eq_or_numeric((last_i, last_e)) {
205 .filter(|&ie| !eq_or_numeric(ie))
212 let second_last_i = interned_chars
214 .expect("we know we have at least three chars");
215 let second_last_e = existing_chars
217 .expect("we know we have at least three chars");
218 if !eq_or_numeric((second_last_i, second_last_e))
219 || 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.next().expect("we know we have at least two chars");
230 let second_e = existing_chars.next().expect("we know we have at least two chars");
231 if !eq_or_numeric((second_i, second_e))
233 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
235 // allowed similarity x_foo, y_foo
236 // or too many chars differ (x_foo, y_boo) or (xfoo, yboo)
239 split_at = interned_name.chars().next().map(|c| c.len_utf8());
246 "binding's name is too similar to existing binding",
248 diag.span_note(existing_name.span, "existing binding defined here");
249 if let Some(split) = split_at {
253 "separate the discriminating character by an \
254 underscore like: `{}_{}`",
255 &interned_name[..split],
256 &interned_name[split..]
264 self.0.names.push(ExistingName {
265 whitelist: get_whitelist(&interned_name).unwrap_or(&[]),
266 interned: interned_name,
273 impl<'a, 'b> SimilarNamesLocalVisitor<'a, 'b> {
274 /// ensure scoping rules work
275 fn apply<F: for<'c> Fn(&'c mut Self)>(&mut self, f: F) {
276 let n = self.names.len();
277 let single_char_count = self.single_char_names.len();
279 self.names.truncate(n);
280 self.single_char_names.truncate(single_char_count);
284 impl<'a, 'tcx> Visitor<'tcx> for SimilarNamesLocalVisitor<'a, 'tcx> {
285 fn visit_local(&mut self, local: &'tcx Local) {
286 if let Some(ref init) = local.init {
287 self.apply(|this| walk_expr(this, &**init));
289 // add the pattern after the expression because the bindings aren't available
292 SimilarNamesNameVisitor(self).visit_pat(&*local.pat);
294 fn visit_block(&mut self, blk: &'tcx Block) {
295 self.apply(|this| walk_block(this, blk));
297 fn visit_arm(&mut self, arm: &'tcx Arm) {
299 // just go through the first pattern, as either all patterns
300 // bind the same bindings or rustc would have errored much earlier
301 SimilarNamesNameVisitor(this).visit_pat(&arm.pats[0]);
302 this.apply(|this| walk_expr(this, &arm.body));
305 fn visit_item(&mut self, _: &Item) {
306 // do not recurse into inner items
308 fn visit_mac(&mut self, _mac: &Mac) {
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);
327 fn do_check(lint: &mut NonExpressiveNames, cx: &EarlyContext<'_>, attrs: &[Attribute], decl: &FnDecl, blk: &Block) {
328 if !attr::contains_name(attrs, "test") {
329 let mut visitor = SimilarNamesLocalVisitor {
333 single_char_names: Vec::new(),
335 // initialize with function arguments
336 for arg in &decl.inputs {
337 SimilarNamesNameVisitor(&mut visitor).visit_pat(&arg.pat);
339 // walk all other bindings
340 walk_block(&mut visitor, blk);
344 /// Precondition: `a_name.chars().count() < b_name.chars().count()`.
345 fn levenstein_not_1(a_name: &str, b_name: &str) -> bool {
346 debug_assert!(a_name.chars().count() < b_name.chars().count());
347 let mut a_chars = a_name.chars();
348 let mut b_chars = b_name.chars();
349 while let (Some(a), Some(b)) = (a_chars.next(), b_chars.next()) {
353 if let Some(b2) = b_chars.next() {
354 // check if there's just one character inserted
355 return a != b2 || a_chars.ne(b_chars);