2016-03-01 03:13:54 -06:00
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use rustc::lint::*;
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use syntax::codemap::Span;
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use syntax::parse::token::InternedString;
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use syntax::ast::*;
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use syntax::visit::{self, FnKind};
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2016-03-01 06:05:39 -06:00
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use utils::{span_lint_and_then, in_macro, span_lint};
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2016-03-01 03:13:54 -06:00
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use strsim::levenshtein;
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/// **What it does:** This lint warns about names that are very similar and thus confusing
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///
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/// **Why is this bad?** It's hard to distinguish between names that differ only by a single character
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///
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/// **Known problems:** None?
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///
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/// **Example:** `checked_exp` and `checked_expr`
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declare_lint! {
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pub SIMILAR_NAMES,
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Warn,
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"similarly named items and bindings"
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}
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2016-03-01 06:05:39 -06:00
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/// **What it does:** This lint warns about having too many variables whose name consists of a single character
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///
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/// **Why is this bad?** It's hard to memorize what a variable means without a descriptive name.
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///
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/// **Known problems:** None?
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///
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/// **Example:** let (a, b, c, d, e, f, g) = (...);
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declare_lint! {
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pub MANY_SINGLE_CHAR_NAMES,
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Warn,
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"too many single character bindings"
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}
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pub struct NonExpressiveNames {
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pub similarity_threshold: usize,
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pub max_single_char_names: usize,
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}
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2016-03-01 03:13:54 -06:00
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2016-03-01 06:05:39 -06:00
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impl LintPass for NonExpressiveNames {
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2016-03-01 03:13:54 -06:00
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fn get_lints(&self) -> LintArray {
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2016-03-01 06:05:39 -06:00
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lint_array!(SIMILAR_NAMES, MANY_SINGLE_CHAR_NAMES)
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2016-03-01 03:13:54 -06:00
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}
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}
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struct SimilarNamesLocalVisitor<'a, 'b: 'a> {
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names: Vec<(InternedString, Span)>,
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cx: &'a EarlyContext<'b>,
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2016-03-01 06:05:39 -06:00
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lint: &'a NonExpressiveNames,
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single_char_names: Vec<char>,
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2016-03-01 03:13:54 -06:00
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}
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const WHITELIST: &'static [&'static str] = &[
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"lhs", "rhs",
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];
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struct SimilarNamesNameVisitor<'a, 'b: 'a, 'c: 'b>(&'a mut SimilarNamesLocalVisitor<'b, 'c>);
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impl<'v, 'a, 'b, 'c> visit::Visitor<'v> for SimilarNamesNameVisitor<'a, 'b, 'c> {
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fn visit_pat(&mut self, pat: &'v Pat) {
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if let PatKind::Ident(_, id, _) = pat.node {
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self.check_name(id.span, id.node.name);
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}
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visit::walk_pat(self, pat);
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}
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}
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impl<'a, 'b, 'c> SimilarNamesNameVisitor<'a, 'b, 'c> {
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fn check_name(&mut self, span: Span, name: Name) {
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if in_macro(self.0.cx, span) {
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return;
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}
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let interned_name = name.as_str();
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if interned_name.chars().any(char::is_uppercase) {
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return;
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}
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2016-03-01 06:05:39 -06:00
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let count = interned_name.chars().count();
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if count < 3 {
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2016-03-08 07:36:21 -06:00
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if count != 1 {
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return;
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}
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let c = interned_name.chars().next().expect("already checked");
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// make sure we ignore shadowing
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if self.0.single_char_names.contains(&c) {
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return;
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}
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self.0.single_char_names.push(c);
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if self.0.single_char_names.len() < self.0.lint.max_single_char_names {
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return;
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2016-03-01 06:05:39 -06:00
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}
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2016-03-08 07:36:21 -06:00
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span_lint(self.0.cx,
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MANY_SINGLE_CHAR_NAMES,
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span,
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&format!("{}th binding whose name is just one char",
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self.0.single_char_names.len()));
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2016-03-01 03:13:54 -06:00
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return;
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}
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for &allow in WHITELIST {
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if interned_name == allow {
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return;
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}
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if interned_name.len() <= allow.len() {
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continue;
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}
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// allow_*
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let allow_start = allow.chars().chain(Some('_'));
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if interned_name.chars().zip(allow_start).all(|(l, r)| l == r) {
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return;
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}
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// *_allow
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let allow_end = Some('_').into_iter().chain(allow.chars());
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if interned_name.chars().rev().zip(allow_end.rev()).all(|(l, r)| l == r) {
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return;
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}
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}
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for &(ref existing_name, sp) in &self.0.names {
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let dist = levenshtein(&interned_name, &existing_name);
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// equality is caught by shadow lints
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if dist == 0 {
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continue;
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}
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// if they differ enough it's all good
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2016-03-01 06:05:39 -06:00
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if dist > self.0.lint.similarity_threshold {
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continue;
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}
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// are we doing stuff like `for item in items`?
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if interned_name.starts_with(&**existing_name) ||
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existing_name.starts_with(&*interned_name) ||
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interned_name.ends_with(&**existing_name) ||
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existing_name.ends_with(&*interned_name) {
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continue;
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}
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2016-03-01 03:34:45 -06:00
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let mut split_at = None;
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2016-03-01 03:13:54 -06:00
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if dist == 1 {
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// are we doing stuff like a_bar, b_bar, c_bar?
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2016-03-01 03:34:45 -06:00
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if interned_name.chars().next() != existing_name.chars().next() {
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if interned_name.chars().nth(1) == Some('_') {
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continue;
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}
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split_at = interned_name.chars().next().map(|c| c.len_utf8());
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}
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// are we doing stuff like foo_x, foo_y, foo_z?
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2016-03-01 03:34:45 -06:00
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if interned_name.chars().rev().next() != existing_name.chars().rev().next() {
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if interned_name.chars().rev().nth(1) == Some('_') {
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continue;
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}
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split_at = interned_name.char_indices().rev().next().map(|(i, _)| i);
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2016-03-01 03:13:54 -06:00
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}
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}
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2016-03-01 03:34:45 -06:00
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span_lint_and_then(self.0.cx,
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SIMILAR_NAMES,
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span,
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"binding's name is too similar to existing binding",
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|diag| {
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diag.span_note(sp, "existing binding defined here");
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if let Some(split) = split_at {
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diag.span_help(span, &format!("separate the discriminating character \
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by an underscore like: `{}_{}`",
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&interned_name[..split],
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&interned_name[split..]));
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}
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});
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2016-03-01 03:13:54 -06:00
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return;
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}
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self.0.names.push((interned_name, span));
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}
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}
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2016-03-01 06:05:39 -06:00
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impl<'a, 'b> SimilarNamesLocalVisitor<'a, 'b> {
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2016-03-08 07:36:21 -06:00
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/// ensure scoping rules work
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fn apply<F: for<'c> Fn(&'c mut Self)>(&mut self, f: F) {
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let n = self.names.len();
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let single_char_count = self.single_char_names.len();
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f(self);
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self.names.truncate(n);
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self.single_char_names.truncate(single_char_count);
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2016-03-01 06:05:39 -06:00
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}
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}
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2016-03-01 03:13:54 -06:00
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impl<'v, 'a, 'b> visit::Visitor<'v> for SimilarNamesLocalVisitor<'a, 'b> {
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fn visit_local(&mut self, local: &'v Local) {
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2016-03-08 07:36:21 -06:00
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if let Some(ref init) = local.init {
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self.apply(|this| visit::walk_expr(this, &**init));
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}
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// add the pattern after the expression because the bindings aren't available yet in the init expression
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SimilarNamesNameVisitor(self).visit_pat(&*local.pat);
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2016-03-01 03:13:54 -06:00
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}
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fn visit_block(&mut self, blk: &'v Block) {
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2016-03-08 07:36:21 -06:00
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self.apply(|this| visit::walk_block(this, blk));
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}
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fn visit_arm(&mut self, arm: &'v Arm) {
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2016-03-08 07:36:21 -06:00
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self.apply(|this| {
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// just go through the first pattern, as either all patterns bind the same bindings or rustc would have errored much earlier
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SimilarNamesNameVisitor(this).visit_pat(&arm.pats[0]);
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this.apply(|this| visit::walk_expr(this, &arm.body));
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});
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2016-03-01 03:13:54 -06:00
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}
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fn visit_item(&mut self, _: &'v Item) {
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// do nothing
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}
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}
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2016-03-01 06:05:39 -06:00
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impl EarlyLintPass for NonExpressiveNames {
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2016-03-01 03:13:54 -06:00
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fn check_fn(&mut self, cx: &EarlyContext, _: FnKind, decl: &FnDecl, blk: &Block, _: Span, _: NodeId) {
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let mut visitor = SimilarNamesLocalVisitor {
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names: Vec::new(),
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cx: cx,
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2016-03-01 06:05:39 -06:00
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lint: &self,
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single_char_names: Vec::new(),
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2016-03-01 03:13:54 -06:00
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};
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// initialize with function arguments
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for arg in &decl.inputs {
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visit::walk_pat(&mut SimilarNamesNameVisitor(&mut visitor), &arg.pat);
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}
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// walk all other bindings
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visit::walk_block(&mut visitor, blk);
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}
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}
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