1 #![allow(clippy::wildcard_imports, clippy::enum_glob_use)]
3 use clippy_utils::ast_utils::{eq_field_pat, eq_id, eq_pat, eq_path};
4 use clippy_utils::diagnostics::span_lint_and_then;
5 use clippy_utils::over;
6 use rustc_ast::mut_visit::*;
8 use rustc_ast::{self as ast, Pat, PatKind, PatKind::*, DUMMY_NODE_ID};
9 use rustc_ast_pretty::pprust;
10 use rustc_errors::Applicability;
11 use rustc_lint::{EarlyContext, EarlyLintPass};
12 use rustc_session::{declare_lint_pass, declare_tool_lint};
13 use rustc_span::DUMMY_SP;
18 declare_clippy_lint! {
21 /// Checks for unnested or-patterns, e.g., `Some(0) | Some(2)` and
22 /// suggests replacing the pattern with a nested one, `Some(0 | 2)`.
24 /// Another way to think of this is that it rewrites patterns in
25 /// *disjunctive normal form (DNF)* into *conjunctive normal form (CNF)*.
27 /// **Why is this bad?**
29 /// In the example above, `Some` is repeated, which unncessarily complicates the pattern.
31 /// **Known problems:** None.
37 /// if let Some(0) | Some(2) = Some(0) {}
42 /// #![feature(or_patterns)]
45 /// if let Some(0 | 2) = Some(0) {}
48 pub UNNESTED_OR_PATTERNS,
50 "unnested or-patterns, e.g., `Foo(Bar) | Foo(Baz) instead of `Foo(Bar | Baz)`"
53 declare_lint_pass!(UnnestedOrPatterns => [UNNESTED_OR_PATTERNS]);
55 impl EarlyLintPass for UnnestedOrPatterns {
56 fn check_arm(&mut self, cx: &EarlyContext<'_>, a: &ast::Arm) {
57 lint_unnested_or_patterns(cx, &a.pat);
60 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
61 if let ast::ExprKind::Let(pat, _) = &e.kind {
62 lint_unnested_or_patterns(cx, pat);
66 fn check_param(&mut self, cx: &EarlyContext<'_>, p: &ast::Param) {
67 lint_unnested_or_patterns(cx, &p.pat);
70 fn check_local(&mut self, cx: &EarlyContext<'_>, l: &ast::Local) {
71 lint_unnested_or_patterns(cx, &l.pat);
75 fn lint_unnested_or_patterns(cx: &EarlyContext<'_>, pat: &Pat) {
76 if !cx.sess.features_untracked().or_patterns {
77 // Do not suggest nesting the patterns if the feature `or_patterns` is not enabled.
81 if let Ident(.., None) | Lit(_) | Wild | Path(..) | Range(..) | Rest | MacCall(_) = pat.kind {
82 // This is a leaf pattern, so cloning is unprofitable.
86 let mut pat = P(pat.clone());
88 // Nix all the paren patterns everywhere so that they aren't in our way.
89 remove_all_parens(&mut pat);
91 // Transform all unnested or-patterns into nested ones, and if there were none, quit.
92 if !unnest_or_patterns(&mut pat) {
96 span_lint_and_then(cx, UNNESTED_OR_PATTERNS, pat.span, "unnested or-patterns", |db| {
97 insert_necessary_parens(&mut pat);
98 db.span_suggestion_verbose(
101 pprust::pat_to_string(&pat),
102 Applicability::MachineApplicable,
107 /// Remove all `(p)` patterns in `pat`.
108 fn remove_all_parens(pat: &mut P<Pat>) {
110 impl MutVisitor for Visitor {
111 fn visit_pat(&mut self, pat: &mut P<Pat>) {
112 noop_visit_pat(pat, self);
113 let inner = match &mut pat.kind {
114 Paren(i) => mem::replace(&mut i.kind, Wild),
120 Visitor.visit_pat(pat);
123 /// Insert parens where necessary according to Rust's precedence rules for patterns.
124 fn insert_necessary_parens(pat: &mut P<Pat>) {
126 impl MutVisitor for Visitor {
127 fn visit_pat(&mut self, pat: &mut P<Pat>) {
128 use ast::{BindingMode::*, Mutability::*};
129 noop_visit_pat(pat, self);
130 let target = match &mut pat.kind {
131 // `i @ a | b`, `box a | b`, and `& mut? a | b`.
132 Ident(.., Some(p)) | Box(p) | Ref(p, _) if matches!(&p.kind, Or(ps) if ps.len() > 1) => p,
133 Ref(p, Not) if matches!(p.kind, Ident(ByValue(Mut), ..)) => p, // `&(mut x)`
136 target.kind = Paren(P(take_pat(target)));
139 Visitor.visit_pat(pat);
142 /// Unnest or-patterns `p0 | ... | p1` in the pattern `pat`.
143 /// For example, this would transform `Some(0) | FOO | Some(2)` into `Some(0 | 2) | FOO`.
144 fn unnest_or_patterns(pat: &mut P<Pat>) -> bool {
148 impl MutVisitor for Visitor {
149 fn visit_pat(&mut self, p: &mut P<Pat>) {
150 // This is a bottom up transformation, so recurse first.
151 noop_visit_pat(p, self);
153 // Don't have an or-pattern? Just quit early on.
154 let alternatives = match &mut p.kind {
159 // Collapse or-patterns directly nested in or-patterns.
161 let mut this_level_changed = false;
162 while idx < alternatives.len() {
163 let inner = if let Or(ps) = &mut alternatives[idx].kind {
169 this_level_changed = true;
170 alternatives.splice(idx..=idx, inner);
173 // Focus on `p_n` and then try to transform all `p_i` where `i > n`.
174 let mut focus_idx = 0;
175 while focus_idx < alternatives.len() {
176 this_level_changed |= transform_with_focus_on_idx(alternatives, focus_idx);
179 self.changed |= this_level_changed;
181 // Deal with `Some(Some(0)) | Some(Some(1))`.
182 if this_level_changed {
183 noop_visit_pat(p, self);
188 let mut visitor = Visitor { changed: false };
189 visitor.visit_pat(pat);
193 /// Match `$scrutinee` against `$pat` and extract `$then` from it.
194 /// Panics if there is no match.
195 macro_rules! always_pat {
196 ($scrutinee:expr, $pat:pat => $then:expr) => {
204 /// Focus on `focus_idx` in `alternatives`,
205 /// attempting to extend it with elements of the same constructor `C`
206 /// in `alternatives[focus_idx + 1..]`.
207 fn transform_with_focus_on_idx(alternatives: &mut Vec<P<Pat>>, focus_idx: usize) -> bool {
208 // Extract the kind; we'll need to make some changes in it.
209 let mut focus_kind = mem::replace(&mut alternatives[focus_idx].kind, PatKind::Wild);
210 // We'll focus on `alternatives[focus_idx]`,
211 // so we're draining from `alternatives[focus_idx + 1..]`.
212 let start = focus_idx + 1;
214 // We're trying to find whatever kind (~"constructor") we found in `alternatives[start..]`.
215 let changed = match &mut focus_kind {
216 // These pattern forms are "leafs" and do not have sub-patterns.
217 // Therefore they are not some form of constructor `C`,
218 // with which a pattern `C(p_0)` may be formed,
219 // which we would want to join with other `C(p_j)`s.
220 Ident(.., None) | Lit(_) | Wild | Path(..) | Range(..) | Rest | MacCall(_)
221 // Dealt with elsewhere.
222 | Or(_) | Paren(_) => false,
223 // Transform `box x | ... | box y` into `box (x | y)`.
225 // The cases below until `Slice(...)` deal with *singleton* products.
226 // These patterns have the shape `C(p)`, and not e.g., `C(p0, ..., pn)`.
227 Box(target) => extend_with_matching(
228 target, start, alternatives,
229 |k| matches!(k, Box(_)),
230 |k| always_pat!(k, Box(p) => p),
232 // Transform `&m x | ... | &m y` into `&m (x | y)`.
233 Ref(target, m1) => extend_with_matching(
234 target, start, alternatives,
235 |k| matches!(k, Ref(_, m2) if m1 == m2), // Mutabilities must match.
236 |k| always_pat!(k, Ref(p, _) => p),
238 // Transform `b @ p0 | ... b @ p1` into `b @ (p0 | p1)`.
239 Ident(b1, i1, Some(target)) => extend_with_matching(
240 target, start, alternatives,
241 // Binding names must match.
242 |k| matches!(k, Ident(b2, i2, Some(_)) if b1 == b2 && eq_id(*i1, *i2)),
243 |k| always_pat!(k, Ident(_, _, Some(p)) => p),
245 // Transform `[pre, x, post] | ... | [pre, y, post]` into `[pre, x | y, post]`.
246 Slice(ps1) => extend_with_matching_product(
247 ps1, start, alternatives,
248 |k, ps1, idx| matches!(k, Slice(ps2) if eq_pre_post(ps1, ps2, idx)),
249 |k| always_pat!(k, Slice(ps) => ps),
251 // Transform `(pre, x, post) | ... | (pre, y, post)` into `(pre, x | y, post)`.
252 Tuple(ps1) => extend_with_matching_product(
253 ps1, start, alternatives,
254 |k, ps1, idx| matches!(k, Tuple(ps2) if eq_pre_post(ps1, ps2, idx)),
255 |k| always_pat!(k, Tuple(ps) => ps),
257 // Transform `S(pre, x, post) | ... | S(pre, y, post)` into `S(pre, x | y, post)`.
258 TupleStruct(path1, ps1) => extend_with_matching_product(
259 ps1, start, alternatives,
260 |k, ps1, idx| matches!(
262 TupleStruct(path2, ps2) if eq_path(path1, path2) && eq_pre_post(ps1, ps2, idx)
264 |k| always_pat!(k, TupleStruct(_, ps) => ps),
266 // Transform a record pattern `S { fp_0, ..., fp_n }`.
267 Struct(path1, fps1, rest1) => extend_with_struct_pat(path1, fps1, *rest1, start, alternatives),
270 alternatives[focus_idx].kind = focus_kind;
274 /// Here we focusing on a record pattern `S { fp_0, ..., fp_n }`.
275 /// In particular, for a record pattern, the order in which the field patterns is irrelevant.
276 /// So when we fixate on some `ident_k: pat_k`, we try to find `ident_k` in the other pattern
277 /// and check that all `fp_i` where `i ∈ ((0...n) \ k)` between two patterns are equal.
278 fn extend_with_struct_pat(
280 fps1: &mut Vec<ast::FieldPat>,
283 alternatives: &mut Vec<P<Pat>>,
285 (0..fps1.len()).any(|idx| {
286 let pos_in_2 = Cell::new(None); // The element `k`.
287 let tail_or = drain_matching(
291 matches!(k, Struct(path2, fps2, rest2)
292 if rest1 == *rest2 // If one struct pattern has `..` so must the other.
293 && eq_path(path1, path2)
294 && fps1.len() == fps2.len()
295 && fps1.iter().enumerate().all(|(idx_1, fp1)| {
297 // In the case of `k`, we merely require identical field names
298 // so that we will transform into `ident_k: p1_k | p2_k`.
299 let pos = fps2.iter().position(|fp2| eq_id(fp1.ident, fp2.ident));
303 fps2.iter().any(|fp2| eq_field_pat(fp1, fp2))
308 |k| always_pat!(k, Struct(_, mut fps, _) => fps.swap_remove(pos_in_2.take().unwrap()).pat),
310 extend_with_tail_or(&mut fps1[idx].pat, tail_or)
314 /// Like `extend_with_matching` but for products with > 1 factor, e.g., `C(p_0, ..., p_n)`.
315 /// Here, the idea is that we fixate on some `p_k` in `C`,
316 /// allowing it to vary between two `targets` and `ps2` (returned by `extract`),
317 /// while also requiring `ps1[..n] ~ ps2[..n]` (pre) and `ps1[n + 1..] ~ ps2[n + 1..]` (post),
318 /// where `~` denotes semantic equality.
319 fn extend_with_matching_product(
320 targets: &mut Vec<P<Pat>>,
322 alternatives: &mut Vec<P<Pat>>,
323 predicate: impl Fn(&PatKind, &[P<Pat>], usize) -> bool,
324 extract: impl Fn(PatKind) -> Vec<P<Pat>>,
326 (0..targets.len()).any(|idx| {
327 let tail_or = drain_matching(
330 |k| predicate(k, targets, idx),
331 |k| extract(k).swap_remove(idx),
333 extend_with_tail_or(&mut targets[idx], tail_or)
337 /// Extract the pattern from the given one and replace it with `Wild`.
338 /// This is meant for temporarily swapping out the pattern for manipulation.
339 fn take_pat(from: &mut Pat) -> Pat {
346 mem::replace(from, dummy)
349 /// Extend `target` as an or-pattern with the alternatives
350 /// in `tail_or` if there are any and return if there were.
351 fn extend_with_tail_or(target: &mut Pat, tail_or: Vec<P<Pat>>) -> bool {
352 fn extend(target: &mut Pat, mut tail_or: Vec<P<Pat>>) {
354 // On an existing or-pattern in the target, append to it.
355 Pat { kind: Or(ps), .. } => ps.append(&mut tail_or),
356 // Otherwise convert the target to an or-pattern.
358 let mut init_or = vec![P(take_pat(target))];
359 init_or.append(&mut tail_or);
360 target.kind = Or(init_or);
365 let changed = !tail_or.is_empty();
367 // Extend the target.
368 extend(target, tail_or);
373 // Extract all inner patterns in `alternatives` matching our `predicate`.
374 // Only elements beginning with `start` are considered for extraction.
377 alternatives: &mut Vec<P<Pat>>,
378 predicate: impl Fn(&PatKind) -> bool,
379 extract: impl Fn(PatKind) -> P<Pat>,
381 let mut tail_or = vec![];
383 for pat in alternatives.drain_filter(|p| {
384 // Check if we should extract, but only if `idx >= start`.
386 idx > start && predicate(&p.kind)
388 tail_or.push(extract(pat.into_inner().kind));
393 fn extend_with_matching(
396 alternatives: &mut Vec<P<Pat>>,
397 predicate: impl Fn(&PatKind) -> bool,
398 extract: impl Fn(PatKind) -> P<Pat>,
400 extend_with_tail_or(target, drain_matching(start, alternatives, predicate, extract))
403 /// Are the patterns in `ps1` and `ps2` equal save for `ps1[idx]` compared to `ps2[idx]`?
404 fn eq_pre_post(ps1: &[P<Pat>], ps2: &[P<Pat>], idx: usize) -> bool {
405 ps1.len() == ps2.len()
406 && ps1[idx].is_rest() == ps2[idx].is_rest() // Avoid `[x, ..] | [x, 0]` => `[x, .. | 0]`.
407 && over(&ps1[..idx], &ps2[..idx], |l, r| eq_pat(l, r))
408 && over(&ps1[idx + 1..], &ps2[idx + 1..], |l, r| eq_pat(l, r))