2 use syntax::codemap::Span;
3 use syntax::parse::token::InternedString;
6 use syntax::visit::{Visitor, walk_block, walk_pat, walk_expr};
7 use utils::{span_lint_and_then, in_macro, span_lint};
9 /// **What it does:** This lint warns about names that are very similar and thus confusing
11 /// **Why is this bad?** It's hard to distinguish between names that differ only by a single character
13 /// **Known problems:** None?
15 /// **Example:** `checked_exp` and `checked_expr`
19 "similarly named items and bindings"
22 /// **What it does:** This lint warns about having too many variables whose name consists of a single character
24 /// **Why is this bad?** It's hard to memorize what a variable means without a descriptive name.
26 /// **Known problems:** None?
28 /// **Example:** let (a, b, c, d, e, f, g) = (...);
30 pub MANY_SINGLE_CHAR_NAMES,
32 "too many single character bindings"
35 pub struct NonExpressiveNames {
36 pub max_single_char_names: u64,
39 impl LintPass for NonExpressiveNames {
40 fn get_lints(&self) -> LintArray {
41 lint_array!(SIMILAR_NAMES, MANY_SINGLE_CHAR_NAMES)
46 interned: InternedString,
49 whitelist: &'static [&'static str],
52 struct SimilarNamesLocalVisitor<'a, 'b: 'a> {
53 names: Vec<ExistingName>,
54 cx: &'a EarlyContext<'b>,
55 lint: &'a NonExpressiveNames,
56 single_char_names: Vec<char>,
59 // this list contains lists of names that are allowed to be similar
60 // the assumption is that no name is ever contained in multiple lists.
61 #[cfg_attr(rustfmt, rustfmt_skip)]
62 const WHITELIST: &'static [&'static [&'static str]] = &[
63 &["parsed", "parser"],
69 struct SimilarNamesNameVisitor<'a, 'b: 'a, 'c: 'b>(&'a mut SimilarNamesLocalVisitor<'b, 'c>);
71 impl<'v, 'a, 'b, 'c> Visitor<'v> for SimilarNamesNameVisitor<'a, 'b, 'c> {
72 fn visit_pat(&mut self, pat: &'v Pat) {
74 PatKind::Ident(_, id, _) => self.check_name(id.span, id.node.name),
75 PatKind::Struct(_, ref fields, _) => for field in fields {
76 if !field.node.is_shorthand {
77 self.visit_pat(&field.node.pat);
80 _ => walk_pat(self, pat),
85 fn get_whitelist(interned_name: &str) -> Option<&'static [&'static str]> {
86 for &allow in WHITELIST {
87 if whitelisted(interned_name, allow) {
94 fn whitelisted(interned_name: &str, list: &[&str]) -> bool {
95 if list.iter().any(|&name| interned_name == name) {
100 if interned_name.chars().zip(name.chars()).all(|(l, r)| l == r) {
104 if interned_name.chars().rev().zip(name.chars().rev()).all(|(l, r)| l == r) {
111 impl<'a, 'b, 'c> SimilarNamesNameVisitor<'a, 'b, 'c> {
112 fn check_short_name(&mut self, c: char, span: Span) {
113 // make sure we ignore shadowing
114 if self.0.single_char_names.contains(&c) {
117 self.0.single_char_names.push(c);
118 if self.0.single_char_names.len() as u64 >= self.0.lint.max_single_char_names {
120 MANY_SINGLE_CHAR_NAMES,
122 &format!("{}th binding whose name is just one char", self.0.single_char_names.len()));
125 fn check_name(&mut self, span: Span, name: Name) {
126 if in_macro(self.0.cx, span) {
129 let interned_name = name.as_str();
130 if interned_name.chars().any(char::is_uppercase) {
133 let count = interned_name.chars().count();
136 let c = interned_name.chars().next().expect("already checked");
137 self.check_short_name(c, span);
141 for existing_name in &self.0.names {
142 if whitelisted(&interned_name, existing_name.whitelist) {
145 let mut split_at = None;
146 if existing_name.len > count {
147 if existing_name.len - count != 1 || levenstein_not_1(&interned_name, &existing_name.interned) {
150 } else if existing_name.len < count {
151 if count - existing_name.len != 1 || levenstein_not_1(&existing_name.interned, &interned_name) {
155 let mut interned_chars = interned_name.chars();
156 let mut existing_chars = existing_name.interned.chars();
157 let first_i = interned_chars.next().expect("we know we have at least one char");
158 let first_e = existing_chars.next().expect("we know we have at least one char");
159 let eq_or_numeric = |a: char, b: char| a == b || a.is_numeric() && b.is_numeric();
161 if eq_or_numeric(first_i, first_e) {
162 let last_i = interned_chars.next_back().expect("we know we have at least two chars");
163 let last_e = existing_chars.next_back().expect("we know we have at least two chars");
164 if eq_or_numeric(last_i, last_e) {
165 if interned_chars.zip(existing_chars).filter(|&(i, e)| !eq_or_numeric(i, e)).count() != 1 {
169 let second_last_i = interned_chars.next_back().expect("we know we have at least three chars");
170 let second_last_e = existing_chars.next_back().expect("we know we have at least three chars");
171 if !eq_or_numeric(second_last_i, second_last_e) || second_last_i == '_' ||
172 !interned_chars.zip(existing_chars).all(|(i, e)| eq_or_numeric(i, e)) {
173 // allowed similarity foo_x, foo_y
174 // or too many chars differ (foo_x, boo_y) or (foox, booy)
177 split_at = interned_name.char_indices().rev().next().map(|(i, _)| i);
180 let second_i = interned_chars.next().expect("we know we have at least two chars");
181 let second_e = existing_chars.next().expect("we know we have at least two chars");
182 if !eq_or_numeric(second_i, second_e) || second_i == '_' ||
183 !interned_chars.zip(existing_chars).all(|(i, e)| eq_or_numeric(i, e)) {
184 // allowed similarity x_foo, y_foo
185 // or too many chars differ (x_foo, y_boo) or (xfoo, yboo)
188 split_at = interned_name.chars().next().map(|c| c.len_utf8());
191 span_lint_and_then(self.0.cx,
194 "binding's name is too similar to existing binding",
196 diag.span_note(existing_name.span, "existing binding defined here");
197 if let Some(split) = split_at {
199 &format!("separate the discriminating character by an \
200 underscore like: `{}_{}`",
201 &interned_name[..split],
202 &interned_name[split..]));
207 self.0.names.push(ExistingName {
208 whitelist: get_whitelist(&interned_name).unwrap_or(&[]),
209 interned: interned_name,
216 impl<'a, 'b> SimilarNamesLocalVisitor<'a, 'b> {
217 /// ensure scoping rules work
218 fn apply<F: for<'c> Fn(&'c mut Self)>(&mut self, f: F) {
219 let n = self.names.len();
220 let single_char_count = self.single_char_names.len();
222 self.names.truncate(n);
223 self.single_char_names.truncate(single_char_count);
227 impl<'v, 'a, 'b> Visitor<'v> for SimilarNamesLocalVisitor<'a, 'b> {
228 fn visit_local(&mut self, local: &'v Local) {
229 if let Some(ref init) = local.init {
230 self.apply(|this| walk_expr(this, &**init));
232 // add the pattern after the expression because the bindings aren't available yet in the init expression
233 SimilarNamesNameVisitor(self).visit_pat(&*local.pat);
235 fn visit_block(&mut self, blk: &'v Block) {
236 self.apply(|this| walk_block(this, blk));
238 fn visit_arm(&mut self, arm: &'v Arm) {
240 // just go through the first pattern, as either all patterns bind the same bindings or rustc would have errored much earlier
241 SimilarNamesNameVisitor(this).visit_pat(&arm.pats[0]);
242 this.apply(|this| walk_expr(this, &arm.body));
245 fn visit_item(&mut self, _: &'v Item) {
246 // do not recurse into inner items
250 impl EarlyLintPass for NonExpressiveNames {
251 fn check_item(&mut self, cx: &EarlyContext, item: &Item) {
252 if let ItemKind::Fn(ref decl, _, _, _, _, ref blk) = item.node {
253 if !attr::contains_name(&item.attrs, "test") {
254 let mut visitor = SimilarNamesLocalVisitor {
258 single_char_names: Vec::new(),
260 // initialize with function arguments
261 for arg in &decl.inputs {
262 SimilarNamesNameVisitor(&mut visitor).visit_pat(&arg.pat);
264 // walk all other bindings
265 walk_block(&mut visitor, blk);
271 /// Precondition: `a_name.chars().count() < b_name.chars().count()`.
272 fn levenstein_not_1(a_name: &str, b_name: &str) -> bool {
273 debug_assert!(a_name.chars().count() < b_name.chars().count());
274 let mut a_chars = a_name.chars();
275 let mut b_chars = b_name.chars();
276 while let (Some(a), Some(b)) = (a_chars.next(), b_chars.next()) {
280 if let Some(b2) = b_chars.next() {
281 // check if there's just one character inserted
282 return a != b2 || a_chars.ne(b_chars);