mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-05 02:50:32 +00:00
414 lines
14 KiB
Rust
414 lines
14 KiB
Rust
use clippy_utils::diagnostics::{span_lint, span_lint_and_then};
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use rustc_ast::ast::{
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Arm, AssocItem, AssocItemKind, Attribute, Block, FnDecl, FnKind, Item, ItemKind, Local, Pat,
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PatKind,
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};
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use rustc_ast::visit::{walk_block, walk_expr, walk_pat, Visitor};
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use rustc_lint::{EarlyContext, EarlyLintPass};
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use rustc_middle::lint::in_external_macro;
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use rustc_session::{declare_tool_lint, impl_lint_pass};
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use rustc_span::source_map::Span;
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use rustc_span::sym;
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use rustc_span::symbol::{Ident, Symbol};
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use std::cmp::Ordering;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for names that are very similar and thus confusing.
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///
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/// ### Why is this bad?
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/// It's hard to distinguish between names that differ only
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/// by a single character.
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///
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/// ### Example
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/// ```ignore
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/// let checked_exp = something;
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/// let checked_expr = something_else;
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/// ```
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pub SIMILAR_NAMES,
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pedantic,
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"similarly named items and bindings"
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}
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for too many variables whose name consists of a
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/// single character.
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///
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/// ### Why is this bad?
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/// It's hard to memorize what a variable means without a
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/// descriptive name.
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///
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/// ### Example
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/// ```ignore
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/// let (a, b, c, d, e, f, g) = (...);
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/// ```
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pub MANY_SINGLE_CHAR_NAMES,
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style,
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"too many single character bindings"
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}
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declare_clippy_lint! {
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/// ### What it does
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/// Checks if you have variables whose name consists of just
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/// underscores and digits.
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///
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/// ### Why is this bad?
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/// It's hard to memorize what a variable means without a
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/// descriptive name.
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///
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/// ### Example
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/// ```rust
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/// let _1 = 1;
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/// let ___1 = 1;
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/// let __1___2 = 11;
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/// ```
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pub JUST_UNDERSCORES_AND_DIGITS,
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style,
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"unclear name"
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}
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#[derive(Copy, Clone)]
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pub struct NonExpressiveNames {
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pub single_char_binding_names_threshold: u64,
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}
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impl_lint_pass!(NonExpressiveNames => [SIMILAR_NAMES, MANY_SINGLE_CHAR_NAMES, JUST_UNDERSCORES_AND_DIGITS]);
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struct ExistingName {
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interned: Symbol,
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span: Span,
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len: usize,
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exemptions: &'static [&'static str],
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}
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struct SimilarNamesLocalVisitor<'a, 'tcx> {
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names: Vec<ExistingName>,
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cx: &'a EarlyContext<'tcx>,
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lint: &'a NonExpressiveNames,
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/// A stack of scopes containing the single-character bindings in each scope.
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single_char_names: Vec<Vec<Ident>>,
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}
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impl<'a, 'tcx> SimilarNamesLocalVisitor<'a, 'tcx> {
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fn check_single_char_names(&self) {
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let num_single_char_names = self.single_char_names.iter().flatten().count();
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let threshold = self.lint.single_char_binding_names_threshold;
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if num_single_char_names as u64 > threshold {
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let span = self
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.single_char_names
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.iter()
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.flatten()
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.map(|ident| ident.span)
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.collect::<Vec<_>>();
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span_lint(
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self.cx,
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MANY_SINGLE_CHAR_NAMES,
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span,
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&format!(
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"{} bindings with single-character names in scope",
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num_single_char_names
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),
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);
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}
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}
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}
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// this list contains lists of names that are allowed to be similar
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// the assumption is that no name is ever contained in multiple lists.
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#[rustfmt::skip]
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const ALLOWED_TO_BE_SIMILAR: &[&[&str]] = &[
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&["parsed", "parser"],
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&["lhs", "rhs"],
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&["tx", "rx"],
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&["set", "get"],
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&["args", "arms"],
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&["qpath", "path"],
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&["lit", "lint"],
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&["wparam", "lparam"],
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&["iter", "item"],
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];
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struct SimilarNamesNameVisitor<'a, 'tcx, 'b>(&'b mut SimilarNamesLocalVisitor<'a, 'tcx>);
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impl<'a, 'tcx, 'b> Visitor<'tcx> for SimilarNamesNameVisitor<'a, 'tcx, 'b> {
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fn visit_pat(&mut self, pat: &'tcx Pat) {
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match pat.kind {
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PatKind::Ident(_, ident, _) => {
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if !pat.span.from_expansion() {
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self.check_ident(ident);
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}
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},
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PatKind::Struct(_, _, ref fields, _) => {
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for field in fields {
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if !field.is_shorthand {
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self.visit_pat(&field.pat);
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}
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}
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},
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// just go through the first pattern, as either all patterns
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// bind the same bindings or rustc would have errored much earlier
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PatKind::Or(ref pats) => self.visit_pat(&pats[0]),
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_ => walk_pat(self, pat),
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}
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}
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}
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#[must_use]
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fn get_exemptions(interned_name: &str) -> Option<&'static [&'static str]> {
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for &list in ALLOWED_TO_BE_SIMILAR {
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if allowed_to_be_similar(interned_name, list) {
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return Some(list);
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}
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}
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None
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}
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#[must_use]
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fn allowed_to_be_similar(interned_name: &str, list: &[&str]) -> bool {
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list.iter()
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.any(|&name| interned_name.starts_with(name) || interned_name.ends_with(name))
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}
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impl<'a, 'tcx, 'b> SimilarNamesNameVisitor<'a, 'tcx, 'b> {
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fn check_short_ident(&mut self, ident: Ident) {
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// Ignore shadowing
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if self
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.0
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.single_char_names
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.iter()
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.flatten()
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.any(|id| id.name == ident.name)
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{
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return;
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}
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if let Some(scope) = &mut self.0.single_char_names.last_mut() {
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scope.push(ident);
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}
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}
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#[allow(clippy::too_many_lines)]
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fn check_ident(&mut self, ident: Ident) {
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let interned_name = ident.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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if interned_name.chars().all(|c| c.is_digit(10) || c == '_') {
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span_lint(
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self.0.cx,
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JUST_UNDERSCORES_AND_DIGITS,
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ident.span,
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"consider choosing a more descriptive name",
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);
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return;
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}
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if interned_name.starts_with('_') {
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// these bindings are typically unused or represent an ignored portion of a destructuring pattern
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return;
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}
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let count = interned_name.chars().count();
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if count < 3 {
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if count == 1 {
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self.check_short_ident(ident);
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}
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return;
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}
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for existing_name in &self.0.names {
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if allowed_to_be_similar(&interned_name, existing_name.exemptions) {
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continue;
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}
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match existing_name.len.cmp(&count) {
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Ordering::Greater => {
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if existing_name.len - count != 1
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|| levenstein_not_1(&interned_name, &existing_name.interned.as_str())
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{
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continue;
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}
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},
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Ordering::Less => {
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if count - existing_name.len != 1
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|| levenstein_not_1(&existing_name.interned.as_str(), &interned_name)
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{
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continue;
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}
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},
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Ordering::Equal => {
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let mut interned_chars = interned_name.chars();
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let interned_str = existing_name.interned.as_str();
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let mut existing_chars = interned_str.chars();
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let first_i = interned_chars.next().expect("we know we have at least one char");
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let first_e = existing_chars.next().expect("we know we have at least one char");
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let eq_or_numeric = |(a, b): (char, char)| a == b || a.is_numeric() && b.is_numeric();
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if eq_or_numeric((first_i, first_e)) {
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let last_i = interned_chars.next_back().expect("we know we have at least two chars");
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let last_e = existing_chars.next_back().expect("we know we have at least two chars");
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if eq_or_numeric((last_i, last_e)) {
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if interned_chars
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.zip(existing_chars)
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.filter(|&ie| !eq_or_numeric(ie))
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.count()
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!= 1
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{
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continue;
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}
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} else {
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let second_last_i = interned_chars
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.next_back()
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.expect("we know we have at least three chars");
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let second_last_e = existing_chars
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.next_back()
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.expect("we know we have at least three chars");
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if !eq_or_numeric((second_last_i, second_last_e))
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|| second_last_i == '_'
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|| !interned_chars.zip(existing_chars).all(eq_or_numeric)
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{
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// allowed similarity foo_x, foo_y
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// or too many chars differ (foo_x, boo_y) or (foox, booy)
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continue;
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}
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}
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} else {
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let second_i = interned_chars.next().expect("we know we have at least two chars");
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let second_e = existing_chars.next().expect("we know we have at least two chars");
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if !eq_or_numeric((second_i, second_e))
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|| second_i == '_'
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|| !interned_chars.zip(existing_chars).all(eq_or_numeric)
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{
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// allowed similarity x_foo, y_foo
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// or too many chars differ (x_foo, y_boo) or (xfoo, yboo)
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continue;
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}
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}
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},
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}
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span_lint_and_then(
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self.0.cx,
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SIMILAR_NAMES,
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ident.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(existing_name.span, "existing binding defined here");
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},
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);
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return;
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}
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self.0.names.push(ExistingName {
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exemptions: get_exemptions(&interned_name).unwrap_or(&[]),
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interned: ident.name,
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span: ident.span,
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len: count,
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});
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}
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}
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impl<'a, 'b> SimilarNamesLocalVisitor<'a, 'b> {
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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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}
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}
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impl<'a, 'tcx> Visitor<'tcx> for SimilarNamesLocalVisitor<'a, 'tcx> {
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fn visit_local(&mut self, local: &'tcx Local) {
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if let Some(ref init) = local.init {
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self.apply(|this| walk_expr(this, &**init));
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}
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// add the pattern after the expression because the bindings aren't available
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// yet in the init
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// expression
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SimilarNamesNameVisitor(self).visit_pat(&*local.pat);
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}
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fn visit_block(&mut self, blk: &'tcx Block) {
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self.single_char_names.push(vec![]);
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self.apply(|this| walk_block(this, blk));
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self.check_single_char_names();
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self.single_char_names.pop();
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}
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fn visit_arm(&mut self, arm: &'tcx Arm) {
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self.single_char_names.push(vec![]);
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self.apply(|this| {
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SimilarNamesNameVisitor(this).visit_pat(&arm.pat);
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this.apply(|this| walk_expr(this, &arm.body));
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});
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self.check_single_char_names();
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self.single_char_names.pop();
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}
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fn visit_item(&mut self, _: &Item) {
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// do not recurse into inner items
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}
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}
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impl EarlyLintPass for NonExpressiveNames {
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fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
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if in_external_macro(cx.sess, item.span) {
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return;
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}
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if let ItemKind::Fn(box FnKind(_, ref sig, _, Some(ref blk))) = item.kind {
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do_check(self, cx, &item.attrs, &sig.decl, blk);
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}
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}
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fn check_impl_item(&mut self, cx: &EarlyContext<'_>, item: &AssocItem) {
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if in_external_macro(cx.sess, item.span) {
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return;
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}
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if let AssocItemKind::Fn(box FnKind(_, ref sig, _, Some(ref blk))) = item.kind {
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do_check(self, cx, &item.attrs, &sig.decl, blk);
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}
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}
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}
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fn do_check(lint: &mut NonExpressiveNames, cx: &EarlyContext<'_>, attrs: &[Attribute], decl: &FnDecl, blk: &Block) {
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if !attrs.iter().any(|attr| attr.has_name(sym::test)) {
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let mut visitor = SimilarNamesLocalVisitor {
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names: Vec::new(),
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cx,
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lint,
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single_char_names: vec![vec![]],
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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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SimilarNamesNameVisitor(&mut visitor).visit_pat(&arg.pat);
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}
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// walk all other bindings
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walk_block(&mut visitor, blk);
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visitor.check_single_char_names();
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}
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}
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/// Precondition: `a_name.chars().count() < b_name.chars().count()`.
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#[must_use]
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fn levenstein_not_1(a_name: &str, b_name: &str) -> bool {
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debug_assert!(a_name.chars().count() < b_name.chars().count());
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let mut a_chars = a_name.chars();
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let mut b_chars = b_name.chars();
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while let (Some(a), Some(b)) = (a_chars.next(), b_chars.next()) {
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if a == b {
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continue;
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}
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if let Some(b2) = b_chars.next() {
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// check if there's just one character inserted
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return a != b2 || a_chars.ne(b_chars);
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}
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// tuple
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// ntuple
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return true;
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}
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// for item in items
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true
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}
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