2 use syntax::codemap::Span;
3 use syntax::symbol::InternedString;
6 use syntax::visit::{walk_block, walk_expr, walk_pat, Visitor};
7 use utils::{in_macro, span_lint, span_lint_and_then};
9 /// **What it does:** Checks for names that are very similar and thus confusing.
11 /// **Why is this bad?** It's hard to distinguish between names that differ only
12 /// by a single character.
14 /// **Known problems:** None?
18 /// let checked_exp = something;
19 /// let checked_expr = something_else;
24 "similarly named items and bindings"
27 /// **What it does:** Checks for too many variables whose name consists of a
30 /// **Why is this bad?** It's hard to memorize what a variable means without a
33 /// **Known problems:** None?
37 /// let (a, b, c, d, e, f, g) = (...);
40 pub MANY_SINGLE_CHAR_NAMES,
42 "too many single character bindings"
45 pub struct NonExpressiveNames {
46 pub single_char_binding_names_threshold: u64,
49 impl LintPass for NonExpressiveNames {
50 fn get_lints(&self) -> LintArray {
51 lint_array!(SIMILAR_NAMES, MANY_SINGLE_CHAR_NAMES)
56 interned: InternedString,
59 whitelist: &'static [&'static str],
62 struct SimilarNamesLocalVisitor<'a, 'tcx: 'a> {
63 names: Vec<ExistingName>,
64 cx: &'a EarlyContext<'tcx>,
65 lint: &'a NonExpressiveNames,
66 single_char_names: Vec<char>,
69 // this list contains lists of names that are allowed to be similar
70 // the assumption is that no name is ever contained in multiple lists.
71 #[cfg_attr(rustfmt, rustfmt_skip)]
72 const WHITELIST: &[&[&str]] = &[
73 &["parsed", "parser"],
79 struct SimilarNamesNameVisitor<'a: 'b, 'tcx: 'a, 'b>(&'b mut SimilarNamesLocalVisitor<'a, 'tcx>);
81 impl<'a, 'tcx: 'a, 'b> Visitor<'tcx> for SimilarNamesNameVisitor<'a, 'tcx, 'b> {
82 fn visit_pat(&mut self, pat: &'tcx Pat) {
84 PatKind::Ident(_, id, _) => self.check_name(id.span, id.node.name),
85 PatKind::Struct(_, ref fields, _) => for field in fields {
86 if !field.node.is_shorthand {
87 self.visit_pat(&field.node.pat);
90 _ => walk_pat(self, pat),
95 fn get_whitelist(interned_name: &str) -> Option<&'static [&'static str]> {
96 for &allow in WHITELIST {
97 if whitelisted(interned_name, allow) {
104 fn whitelisted(interned_name: &str, list: &[&str]) -> bool {
106 .any(|&name| interned_name.starts_with(name) || interned_name.ends_with(name))
109 impl<'a, 'tcx, 'b> SimilarNamesNameVisitor<'a, 'tcx, 'b> {
110 fn check_short_name(&mut self, c: char, span: Span) {
111 // make sure we ignore shadowing
112 if self.0.single_char_names.contains(&c) {
115 self.0.single_char_names.push(c);
116 if self.0.single_char_names.len() as u64 >= self.0.lint.single_char_binding_names_threshold {
119 MANY_SINGLE_CHAR_NAMES,
121 &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) {
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
159 .expect("we know we have at least one char");
160 let first_e = existing_chars
162 .expect("we know we have at least one char");
163 let eq_or_numeric = |(a, b): (char, char)| a == b || a.is_numeric() && b.is_numeric();
165 if eq_or_numeric((first_i, first_e)) {
166 let last_i = interned_chars
168 .expect("we know we have at least two chars");
169 let last_e = existing_chars
171 .expect("we know we have at least two chars");
172 if eq_or_numeric((last_i, last_e)) {
175 .filter(|&ie| !eq_or_numeric(ie))
181 let second_last_i = interned_chars
183 .expect("we know we have at least three chars");
184 let second_last_e = existing_chars
186 .expect("we know we have at least three chars");
187 if !eq_or_numeric((second_last_i, second_last_e)) || second_last_i == '_' ||
188 !interned_chars.zip(existing_chars).all(eq_or_numeric)
190 // allowed similarity foo_x, foo_y
191 // or too many chars differ (foo_x, boo_y) or (foox, booy)
194 split_at = interned_name.char_indices().rev().next().map(|(i, _)| i);
197 let second_i = interned_chars
199 .expect("we know we have at least two chars");
200 let second_e = existing_chars
202 .expect("we know we have at least two chars");
203 if !eq_or_numeric((second_i, second_e)) || second_i == '_' ||
204 !interned_chars.zip(existing_chars).all(eq_or_numeric)
206 // allowed similarity x_foo, y_foo
207 // or too many chars differ (x_foo, y_boo) or (xfoo, yboo)
210 split_at = interned_name.chars().next().map(|c| c.len_utf8());
217 "binding's name is too similar to existing binding",
219 diag.span_note(existing_name.span, "existing binding defined here");
220 if let Some(split) = split_at {
224 "separate the discriminating character by an \
225 underscore like: `{}_{}`",
226 &interned_name[..split],
227 &interned_name[split..]
235 self.0.names.push(ExistingName {
236 whitelist: get_whitelist(&interned_name).unwrap_or(&[]),
237 interned: interned_name,
244 impl<'a, 'b> SimilarNamesLocalVisitor<'a, 'b> {
245 /// ensure scoping rules work
246 fn apply<F: for<'c> Fn(&'c mut Self)>(&mut self, f: F) {
247 let n = self.names.len();
248 let single_char_count = self.single_char_names.len();
250 self.names.truncate(n);
251 self.single_char_names.truncate(single_char_count);
255 impl<'a, 'tcx> Visitor<'tcx> for SimilarNamesLocalVisitor<'a, 'tcx> {
256 fn visit_local(&mut self, local: &'tcx Local) {
257 if let Some(ref init) = local.init {
258 self.apply(|this| walk_expr(this, &**init));
260 // add the pattern after the expression because the bindings aren't available
263 SimilarNamesNameVisitor(self).visit_pat(&*local.pat);
265 fn visit_block(&mut self, blk: &'tcx Block) {
266 self.apply(|this| walk_block(this, blk));
268 fn visit_arm(&mut self, arm: &'tcx Arm) {
270 // just go through the first pattern, as either all patterns
271 // bind the same bindings or rustc would have errored much earlier
272 SimilarNamesNameVisitor(this).visit_pat(&arm.pats[0]);
273 this.apply(|this| walk_expr(this, &arm.body));
276 fn visit_item(&mut self, _: &Item) {
277 // do not recurse into inner items
281 impl EarlyLintPass for NonExpressiveNames {
282 fn check_item(&mut self, cx: &EarlyContext, item: &Item) {
283 if let ItemKind::Fn(ref decl, _, _, _, _, ref blk) = item.node {
284 if !attr::contains_name(&item.attrs, "test") {
285 let mut visitor = SimilarNamesLocalVisitor {
289 single_char_names: Vec::new(),
291 // initialize with function arguments
292 for arg in &decl.inputs {
293 SimilarNamesNameVisitor(&mut visitor).visit_pat(&arg.pat);
295 // walk all other bindings
296 walk_block(&mut visitor, blk);
302 /// Precondition: `a_name.chars().count() < b_name.chars().count()`.
303 fn levenstein_not_1(a_name: &str, b_name: &str) -> bool {
304 debug_assert!(a_name.chars().count() < b_name.chars().count());
305 let mut a_chars = a_name.chars();
306 let mut b_chars = b_name.chars();
307 while let (Some(a), Some(b)) = (a_chars.next(), b_chars.next()) {
311 if let Some(b2) = b_chars.next() {
312 // check if there's just one character inserted
313 return a != b2 || a_chars.ne(b_chars);