1 #![allow(clippy::wildcard_imports, clippy::enum_glob_use)]
3 use clippy_utils::ast_utils::{eq_field_pat, eq_id, eq_maybe_qself, eq_pat, eq_path};
4 use clippy_utils::diagnostics::span_lint_and_then;
5 use clippy_utils::{meets_msrv, msrvs, 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_semver::RustcVersion;
13 use rustc_session::{declare_tool_lint, impl_lint_pass};
14 use rustc_span::DUMMY_SP;
19 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?
28 /// In the example above, `Some` is repeated, which unncessarily complicates the pattern.
33 /// if let Some(0) | Some(2) = Some(0) {}
39 /// if let Some(0 | 2) = Some(0) {}
42 pub UNNESTED_OR_PATTERNS,
44 "unnested or-patterns, e.g., `Foo(Bar) | Foo(Baz) instead of `Foo(Bar | Baz)`"
47 #[derive(Clone, Copy)]
48 pub struct UnnestedOrPatterns {
49 msrv: Option<RustcVersion>,
52 impl UnnestedOrPatterns {
54 pub fn new(msrv: Option<RustcVersion>) -> Self {
59 impl_lint_pass!(UnnestedOrPatterns => [UNNESTED_OR_PATTERNS]);
61 impl EarlyLintPass for UnnestedOrPatterns {
62 fn check_arm(&mut self, cx: &EarlyContext<'_>, a: &ast::Arm) {
63 if meets_msrv(self.msrv.as_ref(), &msrvs::OR_PATTERNS) {
64 lint_unnested_or_patterns(cx, &a.pat);
68 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
69 if meets_msrv(self.msrv.as_ref(), &msrvs::OR_PATTERNS) {
70 if let ast::ExprKind::Let(pat, _, _) = &e.kind {
71 lint_unnested_or_patterns(cx, pat);
76 fn check_param(&mut self, cx: &EarlyContext<'_>, p: &ast::Param) {
77 if meets_msrv(self.msrv.as_ref(), &msrvs::OR_PATTERNS) {
78 lint_unnested_or_patterns(cx, &p.pat);
82 fn check_local(&mut self, cx: &EarlyContext<'_>, l: &ast::Local) {
83 if meets_msrv(self.msrv.as_ref(), &msrvs::OR_PATTERNS) {
84 lint_unnested_or_patterns(cx, &l.pat);
88 extract_msrv_attr!(EarlyContext);
91 fn lint_unnested_or_patterns(cx: &EarlyContext<'_>, pat: &Pat) {
92 if let Ident(.., None) | Lit(_) | Wild | Path(..) | Range(..) | Rest | MacCall(_) = pat.kind {
93 // This is a leaf pattern, so cloning is unprofitable.
97 let mut pat = P(pat.clone());
99 // Nix all the paren patterns everywhere so that they aren't in our way.
100 remove_all_parens(&mut pat);
102 // Transform all unnested or-patterns into nested ones, and if there were none, quit.
103 if !unnest_or_patterns(&mut pat) {
107 span_lint_and_then(cx, UNNESTED_OR_PATTERNS, pat.span, "unnested or-patterns", |db| {
108 insert_necessary_parens(&mut pat);
109 db.span_suggestion_verbose(
112 pprust::pat_to_string(&pat),
113 Applicability::MachineApplicable,
118 /// Remove all `(p)` patterns in `pat`.
119 fn remove_all_parens(pat: &mut P<Pat>) {
121 impl MutVisitor for Visitor {
122 fn visit_pat(&mut self, pat: &mut P<Pat>) {
123 noop_visit_pat(pat, self);
124 let inner = match &mut pat.kind {
125 Paren(i) => mem::replace(&mut i.kind, Wild),
131 Visitor.visit_pat(pat);
134 /// Insert parens where necessary according to Rust's precedence rules for patterns.
135 fn insert_necessary_parens(pat: &mut P<Pat>) {
137 impl MutVisitor for Visitor {
138 fn visit_pat(&mut self, pat: &mut P<Pat>) {
139 use ast::{BindingMode::*, Mutability::*};
140 noop_visit_pat(pat, self);
141 let target = match &mut pat.kind {
142 // `i @ a | b`, `box a | b`, and `& mut? a | b`.
143 Ident(.., Some(p)) | Box(p) | Ref(p, _) if matches!(&p.kind, Or(ps) if ps.len() > 1) => p,
144 Ref(p, Not) if matches!(p.kind, Ident(ByValue(Mut), ..)) => p, // `&(mut x)`
147 target.kind = Paren(P(take_pat(target)));
150 Visitor.visit_pat(pat);
153 /// Unnest or-patterns `p0 | ... | p1` in the pattern `pat`.
154 /// For example, this would transform `Some(0) | FOO | Some(2)` into `Some(0 | 2) | FOO`.
155 fn unnest_or_patterns(pat: &mut P<Pat>) -> bool {
159 impl MutVisitor for Visitor {
160 fn visit_pat(&mut self, p: &mut P<Pat>) {
161 // This is a bottom up transformation, so recurse first.
162 noop_visit_pat(p, self);
164 // Don't have an or-pattern? Just quit early on.
165 let alternatives = match &mut p.kind {
170 // Collapse or-patterns directly nested in or-patterns.
172 let mut this_level_changed = false;
173 while idx < alternatives.len() {
174 let inner = if let Or(ps) = &mut alternatives[idx].kind {
180 this_level_changed = true;
181 alternatives.splice(idx..=idx, inner);
184 // Focus on `p_n` and then try to transform all `p_i` where `i > n`.
185 let mut focus_idx = 0;
186 while focus_idx < alternatives.len() {
187 this_level_changed |= transform_with_focus_on_idx(alternatives, focus_idx);
190 self.changed |= this_level_changed;
192 // Deal with `Some(Some(0)) | Some(Some(1))`.
193 if this_level_changed {
194 noop_visit_pat(p, self);
199 let mut visitor = Visitor { changed: false };
200 visitor.visit_pat(pat);
204 /// Match `$scrutinee` against `$pat` and extract `$then` from it.
205 /// Panics if there is no match.
206 macro_rules! always_pat {
207 ($scrutinee:expr, $pat:pat => $then:expr) => {
215 /// Focus on `focus_idx` in `alternatives`,
216 /// attempting to extend it with elements of the same constructor `C`
217 /// in `alternatives[focus_idx + 1..]`.
218 fn transform_with_focus_on_idx(alternatives: &mut Vec<P<Pat>>, focus_idx: usize) -> bool {
219 // Extract the kind; we'll need to make some changes in it.
220 let mut focus_kind = mem::replace(&mut alternatives[focus_idx].kind, PatKind::Wild);
221 // We'll focus on `alternatives[focus_idx]`,
222 // so we're draining from `alternatives[focus_idx + 1..]`.
223 let start = focus_idx + 1;
225 // We're trying to find whatever kind (~"constructor") we found in `alternatives[start..]`.
226 let changed = match &mut focus_kind {
227 // These pattern forms are "leafs" and do not have sub-patterns.
228 // Therefore they are not some form of constructor `C`,
229 // with which a pattern `C(p_0)` may be formed,
230 // which we would want to join with other `C(p_j)`s.
231 Ident(.., None) | Lit(_) | Wild | Path(..) | Range(..) | Rest | MacCall(_)
232 // Dealt with elsewhere.
233 | Or(_) | Paren(_) => false,
234 // Transform `box x | ... | box y` into `box (x | y)`.
236 // The cases below until `Slice(...)` deal with *singleton* products.
237 // These patterns have the shape `C(p)`, and not e.g., `C(p0, ..., pn)`.
238 Box(target) => extend_with_matching(
239 target, start, alternatives,
240 |k| matches!(k, Box(_)),
241 |k| always_pat!(k, Box(p) => p),
243 // Transform `&m x | ... | &m y` into `&m (x | y)`.
244 Ref(target, m1) => extend_with_matching(
245 target, start, alternatives,
246 |k| matches!(k, Ref(_, m2) if m1 == m2), // Mutabilities must match.
247 |k| always_pat!(k, Ref(p, _) => p),
249 // Transform `b @ p0 | ... b @ p1` into `b @ (p0 | p1)`.
250 Ident(b1, i1, Some(target)) => extend_with_matching(
251 target, start, alternatives,
252 // Binding names must match.
253 |k| matches!(k, Ident(b2, i2, Some(_)) if b1 == b2 && eq_id(*i1, *i2)),
254 |k| always_pat!(k, Ident(_, _, Some(p)) => p),
256 // Transform `[pre, x, post] | ... | [pre, y, post]` into `[pre, x | y, post]`.
257 Slice(ps1) => extend_with_matching_product(
258 ps1, start, alternatives,
259 |k, ps1, idx| matches!(k, Slice(ps2) if eq_pre_post(ps1, ps2, idx)),
260 |k| always_pat!(k, Slice(ps) => ps),
262 // Transform `(pre, x, post) | ... | (pre, y, post)` into `(pre, x | y, post)`.
263 Tuple(ps1) => extend_with_matching_product(
264 ps1, start, alternatives,
265 |k, ps1, idx| matches!(k, Tuple(ps2) if eq_pre_post(ps1, ps2, idx)),
266 |k| always_pat!(k, Tuple(ps) => ps),
268 // Transform `S(pre, x, post) | ... | S(pre, y, post)` into `S(pre, x | y, post)`.
269 TupleStruct(qself1, path1, ps1) => extend_with_matching_product(
270 ps1, start, alternatives,
271 |k, ps1, idx| matches!(
273 TupleStruct(qself2, path2, ps2)
274 if eq_maybe_qself(qself1, qself2) && eq_path(path1, path2) && eq_pre_post(ps1, ps2, idx)
276 |k| always_pat!(k, TupleStruct(_, _, ps) => ps),
278 // Transform a record pattern `S { fp_0, ..., fp_n }`.
279 Struct(qself1, path1, fps1, rest1) => extend_with_struct_pat(qself1, path1, fps1, *rest1, start, alternatives),
282 alternatives[focus_idx].kind = focus_kind;
286 /// Here we focusing on a record pattern `S { fp_0, ..., fp_n }`.
287 /// In particular, for a record pattern, the order in which the field patterns is irrelevant.
288 /// So when we fixate on some `ident_k: pat_k`, we try to find `ident_k` in the other pattern
289 /// and check that all `fp_i` where `i ∈ ((0...n) \ k)` between two patterns are equal.
290 fn extend_with_struct_pat(
291 qself1: &Option<ast::QSelf>,
293 fps1: &mut Vec<ast::PatField>,
296 alternatives: &mut Vec<P<Pat>>,
298 (0..fps1.len()).any(|idx| {
299 let pos_in_2 = Cell::new(None); // The element `k`.
300 let tail_or = drain_matching(
304 matches!(k, Struct(qself2, path2, fps2, rest2)
305 if rest1 == *rest2 // If one struct pattern has `..` so must the other.
306 && eq_maybe_qself(qself1, qself2)
307 && eq_path(path1, path2)
308 && fps1.len() == fps2.len()
309 && fps1.iter().enumerate().all(|(idx_1, fp1)| {
311 // In the case of `k`, we merely require identical field names
312 // so that we will transform into `ident_k: p1_k | p2_k`.
313 let pos = fps2.iter().position(|fp2| eq_id(fp1.ident, fp2.ident));
317 fps2.iter().any(|fp2| eq_field_pat(fp1, fp2))
322 |k| always_pat!(k, Struct(_, _, mut fps, _) => fps.swap_remove(pos_in_2.take().unwrap()).pat),
324 extend_with_tail_or(&mut fps1[idx].pat, tail_or)
328 /// Like `extend_with_matching` but for products with > 1 factor, e.g., `C(p_0, ..., p_n)`.
329 /// Here, the idea is that we fixate on some `p_k` in `C`,
330 /// allowing it to vary between two `targets` and `ps2` (returned by `extract`),
331 /// while also requiring `ps1[..n] ~ ps2[..n]` (pre) and `ps1[n + 1..] ~ ps2[n + 1..]` (post),
332 /// where `~` denotes semantic equality.
333 fn extend_with_matching_product(
334 targets: &mut Vec<P<Pat>>,
336 alternatives: &mut Vec<P<Pat>>,
337 predicate: impl Fn(&PatKind, &[P<Pat>], usize) -> bool,
338 extract: impl Fn(PatKind) -> Vec<P<Pat>>,
340 (0..targets.len()).any(|idx| {
341 let tail_or = drain_matching(
344 |k| predicate(k, targets, idx),
345 |k| extract(k).swap_remove(idx),
347 extend_with_tail_or(&mut targets[idx], tail_or)
351 /// Extract the pattern from the given one and replace it with `Wild`.
352 /// This is meant for temporarily swapping out the pattern for manipulation.
353 fn take_pat(from: &mut Pat) -> Pat {
360 mem::replace(from, dummy)
363 /// Extend `target` as an or-pattern with the alternatives
364 /// in `tail_or` if there are any and return if there were.
365 fn extend_with_tail_or(target: &mut Pat, tail_or: Vec<P<Pat>>) -> bool {
366 fn extend(target: &mut Pat, mut tail_or: Vec<P<Pat>>) {
368 // On an existing or-pattern in the target, append to it.
369 Pat { kind: Or(ps), .. } => ps.append(&mut tail_or),
370 // Otherwise convert the target to an or-pattern.
372 let mut init_or = vec![P(take_pat(target))];
373 init_or.append(&mut tail_or);
374 target.kind = Or(init_or);
379 let changed = !tail_or.is_empty();
381 // Extend the target.
382 extend(target, tail_or);
387 // Extract all inner patterns in `alternatives` matching our `predicate`.
388 // Only elements beginning with `start` are considered for extraction.
391 alternatives: &mut Vec<P<Pat>>,
392 predicate: impl Fn(&PatKind) -> bool,
393 extract: impl Fn(PatKind) -> P<Pat>,
395 let mut tail_or = vec![];
397 for pat in alternatives.drain_filter(|p| {
398 // Check if we should extract, but only if `idx >= start`.
400 idx > start && predicate(&p.kind)
402 tail_or.push(extract(pat.into_inner().kind));
407 fn extend_with_matching(
410 alternatives: &mut Vec<P<Pat>>,
411 predicate: impl Fn(&PatKind) -> bool,
412 extract: impl Fn(PatKind) -> P<Pat>,
414 extend_with_tail_or(target, drain_matching(start, alternatives, predicate, extract))
417 /// Are the patterns in `ps1` and `ps2` equal save for `ps1[idx]` compared to `ps2[idx]`?
418 fn eq_pre_post(ps1: &[P<Pat>], ps2: &[P<Pat>], idx: usize) -> bool {
419 ps1.len() == ps2.len()
420 && ps1[idx].is_rest() == ps2[idx].is_rest() // Avoid `[x, ..] | [x, 0]` => `[x, .. | 0]`.
421 && over(&ps1[..idx], &ps2[..idx], |l, r| eq_pat(l, r))
422 && over(&ps1[idx + 1..], &ps2[idx + 1..], |l, r| eq_pat(l, r))