1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution.
4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7 // option. This file may not be copied, modified, or distributed
8 // except according to those terms.
11 use crate::rustc::lint::{LintArray, LintPass, EarlyContext, EarlyLintPass};
12 use crate::rustc::{declare_tool_lint, lint_array};
13 use crate::syntax::source_map::Span;
14 use crate::syntax::symbol::LocalInternedString;
15 use crate::syntax::ast::*;
16 use crate::syntax::attr;
17 use crate::syntax::visit::{walk_block, walk_expr, walk_pat, Visitor};
18 use crate::utils::{span_lint, span_lint_and_then};
20 /// **What it does:** Checks for names that are very similar and thus confusing.
22 /// **Why is this bad?** It's hard to distinguish between names that differ only
23 /// by a single character.
25 /// **Known problems:** None?
29 /// let checked_exp = something;
30 /// let checked_expr = something_else;
32 declare_clippy_lint! {
35 "similarly named items and bindings"
38 /// **What it does:** Checks for too many variables whose name consists of a
41 /// **Why is this bad?** It's hard to memorize what a variable means without a
44 /// **Known problems:** None?
48 /// let (a, b, c, d, e, f, g) = (...);
50 declare_clippy_lint! {
51 pub MANY_SINGLE_CHAR_NAMES,
53 "too many single character bindings"
56 /// **What it does:** Checks if you have variables whose name consists of just
57 /// underscores and digits.
59 /// **Why is this bad?** It's hard to memorize what a variable means without a
62 /// **Known problems:** None?
70 declare_clippy_lint! {
71 pub JUST_UNDERSCORES_AND_DIGITS,
76 pub struct NonExpressiveNames {
77 pub single_char_binding_names_threshold: u64,
80 impl LintPass for NonExpressiveNames {
81 fn get_lints(&self) -> LintArray {
82 lint_array!(SIMILAR_NAMES, MANY_SINGLE_CHAR_NAMES, JUST_UNDERSCORES_AND_DIGITS)
87 interned: LocalInternedString,
90 whitelist: &'static [&'static str],
93 struct SimilarNamesLocalVisitor<'a, 'tcx: 'a> {
94 names: Vec<ExistingName>,
95 cx: &'a EarlyContext<'tcx>,
96 lint: &'a NonExpressiveNames,
97 single_char_names: Vec<char>,
100 // this list contains lists of names that are allowed to be similar
101 // the assumption is that no name is ever contained in multiple lists.
103 const WHITELIST: &[&[&str]] = &[
104 &["parsed", "parser"],
113 struct SimilarNamesNameVisitor<'a: 'b, 'tcx: 'a, 'b>(&'b mut SimilarNamesLocalVisitor<'a, 'tcx>);
115 impl<'a, 'tcx: 'a, 'b> Visitor<'tcx> for SimilarNamesNameVisitor<'a, 'tcx, 'b> {
116 fn visit_pat(&mut self, pat: &'tcx Pat) {
118 PatKind::Ident(_, ident, _) => self.check_name(ident.span, ident.name),
119 PatKind::Struct(_, ref fields, _) => for field in fields {
120 if !field.node.is_shorthand {
121 self.visit_pat(&field.node.pat);
124 _ => walk_pat(self, pat),
127 fn visit_mac(&mut self, _mac: &Mac) {
132 fn get_whitelist(interned_name: &str) -> Option<&'static [&'static str]> {
133 for &allow in WHITELIST {
134 if whitelisted(interned_name, allow) {
141 fn whitelisted(interned_name: &str, list: &[&str]) -> bool {
143 .any(|&name| interned_name.starts_with(name) || interned_name.ends_with(name))
146 impl<'a, 'tcx, 'b> SimilarNamesNameVisitor<'a, 'tcx, 'b> {
147 fn check_short_name(&mut self, c: char, span: Span) {
148 // make sure we ignore shadowing
149 if self.0.single_char_names.contains(&c) {
152 self.0.single_char_names.push(c);
153 if self.0.single_char_names.len() as u64 >= self.0.lint.single_char_binding_names_threshold {
156 MANY_SINGLE_CHAR_NAMES,
158 &format!("{}th binding whose name is just one char", self.0.single_char_names.len()),
162 fn check_name(&mut self, span: Span, name: Name) {
163 let interned_name = name.as_str();
164 if interned_name.chars().any(char::is_uppercase) {
167 if interned_name.chars().all(|c| c.is_digit(10) || c == '_') {
170 JUST_UNDERSCORES_AND_DIGITS,
172 "consider choosing a more descriptive name",
176 let count = interned_name.chars().count();
179 let c = interned_name.chars().next().expect("already checked");
180 self.check_short_name(c, span);
184 for existing_name in &self.0.names {
185 if whitelisted(&interned_name, existing_name.whitelist) {
188 let mut split_at = None;
189 if existing_name.len > count {
190 if existing_name.len - count != 1 || levenstein_not_1(&interned_name, &existing_name.interned) {
193 } else if existing_name.len < count {
194 if count - existing_name.len != 1 || levenstein_not_1(&existing_name.interned, &interned_name) {
198 let mut interned_chars = interned_name.chars();
199 let mut existing_chars = existing_name.interned.chars();
200 let first_i = interned_chars
202 .expect("we know we have at least one char");
203 let first_e = existing_chars
205 .expect("we know we have at least one char");
206 let eq_or_numeric = |(a, b): (char, char)| a == b || a.is_numeric() && b.is_numeric();
208 if eq_or_numeric((first_i, first_e)) {
209 let last_i = interned_chars
211 .expect("we know we have at least two chars");
212 let last_e = existing_chars
214 .expect("we know we have at least two chars");
215 if eq_or_numeric((last_i, last_e)) {
218 .filter(|&ie| !eq_or_numeric(ie))
224 let second_last_i = interned_chars
226 .expect("we know we have at least three chars");
227 let second_last_e = existing_chars
229 .expect("we know we have at least three chars");
230 if !eq_or_numeric((second_last_i, second_last_e)) || second_last_i == '_'
231 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
233 // allowed similarity foo_x, foo_y
234 // or too many chars differ (foo_x, boo_y) or (foox, booy)
237 split_at = interned_name.char_indices().rev().next().map(|(i, _)| i);
240 let second_i = interned_chars
242 .expect("we know we have at least two chars");
243 let second_e = existing_chars
245 .expect("we know we have at least two chars");
246 if !eq_or_numeric((second_i, second_e)) || second_i == '_'
247 || !interned_chars.zip(existing_chars).all(eq_or_numeric)
249 // allowed similarity x_foo, y_foo
250 // or too many chars differ (x_foo, y_boo) or (xfoo, yboo)
253 split_at = interned_name.chars().next().map(|c| c.len_utf8());
260 "binding's name is too similar to existing binding",
262 diag.span_note(existing_name.span, "existing binding defined here");
263 if let Some(split) = split_at {
267 "separate the discriminating character by an \
268 underscore like: `{}_{}`",
269 &interned_name[..split],
270 &interned_name[split..]
278 self.0.names.push(ExistingName {
279 whitelist: get_whitelist(&interned_name).unwrap_or(&[]),
280 interned: interned_name,
287 impl<'a, 'b> SimilarNamesLocalVisitor<'a, 'b> {
288 /// ensure scoping rules work
289 fn apply<F: for<'c> Fn(&'c mut Self)>(&mut self, f: F) {
290 let n = self.names.len();
291 let single_char_count = self.single_char_names.len();
293 self.names.truncate(n);
294 self.single_char_names.truncate(single_char_count);
298 impl<'a, 'tcx> Visitor<'tcx> for SimilarNamesLocalVisitor<'a, 'tcx> {
299 fn visit_local(&mut self, local: &'tcx Local) {
300 if let Some(ref init) = local.init {
301 self.apply(|this| walk_expr(this, &**init));
303 // add the pattern after the expression because the bindings aren't available
306 SimilarNamesNameVisitor(self).visit_pat(&*local.pat);
308 fn visit_block(&mut self, blk: &'tcx Block) {
309 self.apply(|this| walk_block(this, blk));
311 fn visit_arm(&mut self, arm: &'tcx Arm) {
313 // just go through the first pattern, as either all patterns
314 // bind the same bindings or rustc would have errored much earlier
315 SimilarNamesNameVisitor(this).visit_pat(&arm.pats[0]);
316 this.apply(|this| walk_expr(this, &arm.body));
319 fn visit_item(&mut self, _: &Item) {
320 // do not recurse into inner items
322 fn visit_mac(&mut self, _mac: &Mac) {
327 impl EarlyLintPass for NonExpressiveNames {
328 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
329 if let ItemKind::Fn(ref decl, _, _, ref blk) = item.node {
330 do_check(self, cx, &item.attrs, decl, blk);
334 fn check_impl_item(&mut self, cx: &EarlyContext<'_>, item: &ImplItem) {
335 if let ImplItemKind::Method(ref sig, ref blk) = item.node {
336 do_check(self, cx, &item.attrs, &sig.decl, blk);
341 fn do_check(lint: &mut NonExpressiveNames, cx: &EarlyContext<'_>, attrs: &[Attribute], decl: &FnDecl, blk: &Block) {
342 if !attr::contains_name(attrs, "test") {
343 let mut visitor = SimilarNamesLocalVisitor {
347 single_char_names: Vec::new(),
349 // initialize with function arguments
350 for arg in &decl.inputs {
351 SimilarNamesNameVisitor(&mut visitor).visit_pat(&arg.pat);
353 // walk all other bindings
354 walk_block(&mut visitor, blk);
358 /// Precondition: `a_name.chars().count() < b_name.chars().count()`.
359 fn levenstein_not_1(a_name: &str, b_name: &str) -> bool {
360 debug_assert!(a_name.chars().count() < b_name.chars().count());
361 let mut a_chars = a_name.chars();
362 let mut b_chars = b_name.chars();
363 while let (Some(a), Some(b)) = (a_chars.next(), b_chars.next()) {
367 if let Some(b2) = b_chars.next() {
368 // check if there's just one character inserted
369 return a != b2 || a_chars.ne(b_chars);