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?
31 /// let (a, b, c, d, e, f, g) = (...);
34 pub MANY_SINGLE_CHAR_NAMES,
36 "too many single character bindings"
39 pub struct NonExpressiveNames {
40 pub max_single_char_names: u64,
43 impl LintPass for NonExpressiveNames {
44 fn get_lints(&self) -> LintArray {
45 lint_array!(SIMILAR_NAMES, MANY_SINGLE_CHAR_NAMES)
50 interned: InternedString,
53 whitelist: &'static [&'static str],
56 struct SimilarNamesLocalVisitor<'a, 'b: 'a> {
57 names: Vec<ExistingName>,
58 cx: &'a EarlyContext<'b>,
59 lint: &'a NonExpressiveNames,
60 single_char_names: Vec<char>,
63 // this list contains lists of names that are allowed to be similar
64 // the assumption is that no name is ever contained in multiple lists.
65 #[cfg_attr(rustfmt, rustfmt_skip)]
66 const WHITELIST: &'static [&'static [&'static str]] = &[
67 &["parsed", "parser"],
73 struct SimilarNamesNameVisitor<'a, 'b: 'a, 'c: 'b>(&'a mut SimilarNamesLocalVisitor<'b, 'c>);
75 impl<'a, 'b, 'c> Visitor for SimilarNamesNameVisitor<'a, 'b, 'c> {
76 fn visit_pat(&mut self, pat: &Pat) {
78 PatKind::Ident(_, id, _) => self.check_name(id.span, id.node.name),
79 PatKind::Struct(_, ref fields, _) => {
81 if !field.node.is_shorthand {
82 self.visit_pat(&field.node.pat);
86 _ => walk_pat(self, pat),
91 fn get_whitelist(interned_name: &str) -> Option<&'static [&'static str]> {
92 for &allow in WHITELIST {
93 if whitelisted(interned_name, allow) {
100 fn whitelisted(interned_name: &str, list: &[&str]) -> bool {
101 if list.iter().any(|&name| interned_name == name) {
106 if interned_name.chars().zip(name.chars()).all(|(l, r)| l == r) {
110 if interned_name.chars().rev().zip(name.chars().rev()).all(|(l, r)| l == r) {
117 impl<'a, 'b, 'c> SimilarNamesNameVisitor<'a, 'b, 'c> {
118 fn check_short_name(&mut self, c: char, span: Span) {
119 // make sure we ignore shadowing
120 if self.0.single_char_names.contains(&c) {
123 self.0.single_char_names.push(c);
124 if self.0.single_char_names.len() as u64 >= self.0.lint.max_single_char_names {
126 MANY_SINGLE_CHAR_NAMES,
128 &format!("{}th binding whose name is just one char", self.0.single_char_names.len()));
131 fn check_name(&mut self, span: Span, name: Name) {
132 if in_macro(self.0.cx, span) {
135 let interned_name = name.as_str();
136 if interned_name.chars().any(char::is_uppercase) {
139 let count = interned_name.chars().count();
142 let c = interned_name.chars().next().expect("already checked");
143 self.check_short_name(c, span);
147 for existing_name in &self.0.names {
148 if whitelisted(&interned_name, existing_name.whitelist) {
151 let mut split_at = None;
152 if existing_name.len > count {
153 if existing_name.len - count != 1 || levenstein_not_1(&interned_name, &existing_name.interned) {
156 } else if existing_name.len < count {
157 if count - existing_name.len != 1 || levenstein_not_1(&existing_name.interned, &interned_name) {
161 let mut interned_chars = interned_name.chars();
162 let mut existing_chars = existing_name.interned.chars();
163 let first_i = interned_chars.next().expect("we know we have at least one char");
164 let first_e = existing_chars.next().expect("we know we have at least one char");
165 let eq_or_numeric = |a: char, b: char| a == b || a.is_numeric() && b.is_numeric();
167 if eq_or_numeric(first_i, first_e) {
168 let last_i = interned_chars.next_back().expect("we know we have at least two chars");
169 let last_e = existing_chars.next_back().expect("we know we have at least two chars");
170 if eq_or_numeric(last_i, last_e) {
171 if interned_chars.zip(existing_chars).filter(|&(i, e)| !eq_or_numeric(i, e)).count() != 1 {
175 let second_last_i = interned_chars.next_back().expect("we know we have at least three chars");
176 let second_last_e = existing_chars.next_back().expect("we know we have at least three chars");
177 if !eq_or_numeric(second_last_i, second_last_e) || second_last_i == '_' ||
178 !interned_chars.zip(existing_chars).all(|(i, e)| eq_or_numeric(i, e)) {
179 // allowed similarity foo_x, foo_y
180 // or too many chars differ (foo_x, boo_y) or (foox, booy)
183 split_at = interned_name.char_indices().rev().next().map(|(i, _)| i);
186 let second_i = interned_chars.next().expect("we know we have at least two chars");
187 let second_e = existing_chars.next().expect("we know we have at least two chars");
188 if !eq_or_numeric(second_i, second_e) || second_i == '_' ||
189 !interned_chars.zip(existing_chars).all(|(i, e)| eq_or_numeric(i, e)) {
190 // allowed similarity x_foo, y_foo
191 // or too many chars differ (x_foo, y_boo) or (xfoo, yboo)
194 split_at = interned_name.chars().next().map(|c| c.len_utf8());
197 span_lint_and_then(self.0.cx,
200 "binding's name is too similar to existing binding",
202 diag.span_note(existing_name.span, "existing binding defined here");
203 if let Some(split) = split_at {
205 &format!("separate the discriminating character by an \
206 underscore like: `{}_{}`",
207 &interned_name[..split],
208 &interned_name[split..]));
213 self.0.names.push(ExistingName {
214 whitelist: get_whitelist(&interned_name).unwrap_or(&[]),
215 interned: interned_name,
222 impl<'a, 'b> SimilarNamesLocalVisitor<'a, 'b> {
223 /// ensure scoping rules work
224 fn apply<F: for<'c> Fn(&'c mut Self)>(&mut self, f: F) {
225 let n = self.names.len();
226 let single_char_count = self.single_char_names.len();
228 self.names.truncate(n);
229 self.single_char_names.truncate(single_char_count);
233 impl<'a, 'b> Visitor for SimilarNamesLocalVisitor<'a, 'b> {
234 fn visit_local(&mut self, local: &Local) {
235 if let Some(ref init) = local.init {
236 self.apply(|this| walk_expr(this, &**init));
238 // add the pattern after the expression because the bindings aren't available yet in the init expression
239 SimilarNamesNameVisitor(self).visit_pat(&*local.pat);
241 fn visit_block(&mut self, blk: &Block) {
242 self.apply(|this| walk_block(this, blk));
244 fn visit_arm(&mut self, arm: &Arm) {
246 // just go through the first pattern, as either all patterns bind the same bindings or rustc would have errored much earlier
247 SimilarNamesNameVisitor(this).visit_pat(&arm.pats[0]);
248 this.apply(|this| walk_expr(this, &arm.body));
251 fn visit_item(&mut self, _: &Item) {
252 // do not recurse into inner items
256 impl EarlyLintPass for NonExpressiveNames {
257 fn check_item(&mut self, cx: &EarlyContext, item: &Item) {
258 if let ItemKind::Fn(ref decl, _, _, _, _, ref blk) = item.node {
259 if !attr::contains_name(&item.attrs, "test") {
260 let mut visitor = SimilarNamesLocalVisitor {
264 single_char_names: Vec::new(),
266 // initialize with function arguments
267 for arg in &decl.inputs {
268 SimilarNamesNameVisitor(&mut visitor).visit_pat(&arg.pat);
270 // walk all other bindings
271 walk_block(&mut visitor, blk);
277 /// Precondition: `a_name.chars().count() < b_name.chars().count()`.
278 fn levenstein_not_1(a_name: &str, b_name: &str) -> bool {
279 debug_assert!(a_name.chars().count() < b_name.chars().count());
280 let mut a_chars = a_name.chars();
281 let mut b_chars = b_name.chars();
282 while let (Some(a), Some(b)) = (a_chars.next(), b_chars.next()) {
286 if let Some(b2) = b_chars.next() {
287 // check if there's just one character inserted
288 return a != b2 || a_chars.ne(b_chars);