1 #![allow(clippy::wildcard_imports, clippy::enum_glob_use)]
3 use crate::utils::ast_utils::{eq_field_pat, eq_id, eq_pat, eq_path};
4 use crate::utils::{over, span_lint_and_then};
5 use rustc_ast::ast::{self, Pat, PatKind, PatKind::*, DUMMY_NODE_ID};
6 use rustc_ast::mut_visit::*;
8 use rustc_ast_pretty::pprust;
9 use rustc_errors::Applicability;
10 use rustc_lint::{EarlyContext, EarlyLintPass};
11 use rustc_session::{declare_lint_pass, declare_tool_lint};
12 use rustc_span::DUMMY_SP;
17 declare_clippy_lint! {
20 /// Checks for unnested or-patterns, e.g., `Some(0) | Some(2)` and
21 /// suggests replacing the pattern with a nested one, `Some(0 | 2)`.
23 /// Another way to think of this is that it rewrites patterns in
24 /// *disjunctive normal form (DNF)* into *conjunctive normal form (CNF)*.
26 /// **Why is this bad?**
28 /// In the example above, `Some` is repeated, which unncessarily complicates the pattern.
30 /// **Known problems:** None.
36 /// if let Some(0) | Some(2) = Some(0) {}
41 /// #![feature(or_patterns)]
44 /// if let Some(0 | 2) = Some(0) {}
47 pub UNNESTED_OR_PATTERNS,
49 "unnested or-patterns, e.g., `Foo(Bar) | Foo(Baz) instead of `Foo(Bar | Baz)`"
52 declare_lint_pass!(UnnestedOrPatterns => [UNNESTED_OR_PATTERNS]);
54 impl EarlyLintPass for UnnestedOrPatterns {
55 fn check_arm(&mut self, cx: &EarlyContext<'_>, a: &ast::Arm) {
56 lint_unnested_or_patterns(cx, &a.pat);
59 fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
60 if let ast::ExprKind::Let(pat, _) = &e.kind {
61 lint_unnested_or_patterns(cx, pat);
65 fn check_param(&mut self, cx: &EarlyContext<'_>, p: &ast::Param) {
66 lint_unnested_or_patterns(cx, &p.pat);
69 fn check_local(&mut self, cx: &EarlyContext<'_>, l: &ast::Local) {
70 lint_unnested_or_patterns(cx, &l.pat);
74 fn lint_unnested_or_patterns(cx: &EarlyContext<'_>, pat: &Pat) {
75 if !cx.sess.features_untracked().or_patterns {
76 // Do not suggest nesting the patterns if the feature `or_patterns` is not enabled.
80 if let Ident(.., None) | Lit(_) | Wild | Path(..) | Range(..) | Rest | MacCall(_) = pat.kind {
81 // This is a leaf pattern, so cloning is unprofitable.
85 let mut pat = P(pat.clone());
87 // Nix all the paren patterns everywhere so that they aren't in our way.
88 remove_all_parens(&mut pat);
90 // Transform all unnested or-patterns into nested ones, and if there were none, quit.
91 if !unnest_or_patterns(&mut pat) {
95 span_lint_and_then(cx, UNNESTED_OR_PATTERNS, pat.span, "unnested or-patterns", |db| {
96 insert_necessary_parens(&mut pat);
97 db.span_suggestion_verbose(
100 pprust::pat_to_string(&pat),
101 Applicability::MachineApplicable,
106 /// Remove all `(p)` patterns in `pat`.
107 fn remove_all_parens(pat: &mut P<Pat>) {
109 impl MutVisitor for Visitor {
110 fn visit_pat(&mut self, pat: &mut P<Pat>) {
111 noop_visit_pat(pat, self);
112 let inner = match &mut pat.kind {
113 Paren(i) => mem::replace(&mut i.kind, Wild),
119 Visitor.visit_pat(pat);
122 /// Insert parens where necessary according to Rust's precedence rules for patterns.
123 fn insert_necessary_parens(pat: &mut P<Pat>) {
125 impl MutVisitor for Visitor {
126 fn visit_pat(&mut self, pat: &mut P<Pat>) {
127 use ast::{BindingMode::*, Mutability::*};
128 noop_visit_pat(pat, self);
129 let target = match &mut pat.kind {
130 // `i @ a | b`, `box a | b`, and `& mut? a | b`.
131 Ident(.., Some(p)) | Box(p) | Ref(p, _) if matches!(&p.kind, Or(ps) if ps.len() > 1) => p,
132 Ref(p, Not) if matches!(p.kind, Ident(ByValue(Mut), ..)) => p, // `&(mut x)`
135 target.kind = Paren(P(take_pat(target)));
138 Visitor.visit_pat(pat);
141 /// Unnest or-patterns `p0 | ... | p1` in the pattern `pat`.
142 /// For example, this would transform `Some(0) | FOO | Some(2)` into `Some(0 | 2) | FOO`.
143 fn unnest_or_patterns(pat: &mut P<Pat>) -> bool {
147 impl MutVisitor for Visitor {
148 fn visit_pat(&mut self, p: &mut P<Pat>) {
149 // This is a bottom up transformation, so recurse first.
150 noop_visit_pat(p, self);
152 // Don't have an or-pattern? Just quit early on.
153 let alternatives = match &mut p.kind {
158 // Collapse or-patterns directly nested in or-patterns.
160 let mut this_level_changed = false;
161 while idx < alternatives.len() {
162 let inner = if let Or(ps) = &mut alternatives[idx].kind {
168 this_level_changed = true;
169 alternatives.splice(idx..=idx, inner);
172 // Focus on `p_n` and then try to transform all `p_i` where `i > n`.
173 let mut focus_idx = 0;
174 while focus_idx < alternatives.len() {
175 this_level_changed |= transform_with_focus_on_idx(alternatives, focus_idx);
178 self.changed |= this_level_changed;
180 // Deal with `Some(Some(0)) | Some(Some(1))`.
181 if this_level_changed {
182 noop_visit_pat(p, self);
187 let mut visitor = Visitor { changed: false };
188 visitor.visit_pat(pat);
192 /// Match `$scrutinee` against `$pat` and extract `$then` from it.
193 /// Panics if there is no match.
194 macro_rules! always_pat {
195 ($scrutinee:expr, $pat:pat => $then:expr) => {
203 /// Focus on `focus_idx` in `alternatives`,
204 /// attempting to extend it with elements of the same constructor `C`
205 /// in `alternatives[focus_idx + 1..]`.
206 fn transform_with_focus_on_idx(alternatives: &mut Vec<P<Pat>>, focus_idx: usize) -> bool {
207 // Extract the kind; we'll need to make some changes in it.
208 let mut focus_kind = mem::replace(&mut alternatives[focus_idx].kind, PatKind::Wild);
209 // We'll focus on `alternatives[focus_idx]`,
210 // so we're draining from `alternatives[focus_idx + 1..]`.
211 let start = focus_idx + 1;
213 // We're trying to find whatever kind (~"constructor") we found in `alternatives[start..]`.
214 let changed = match &mut focus_kind {
215 // These pattern forms are "leafs" and do not have sub-patterns.
216 // Therefore they are not some form of constructor `C`,
217 // with which a pattern `C(p_0)` may be formed,
218 // which we would want to join with other `C(p_j)`s.
219 Ident(.., None) | Lit(_) | Wild | Path(..) | Range(..) | Rest | MacCall(_)
220 // Dealt with elsewhere.
221 | Or(_) | Paren(_) => false,
222 // Transform `box x | ... | box y` into `box (x | y)`.
224 // The cases below until `Slice(...)` deal with *singleton* products.
225 // These patterns have the shape `C(p)`, and not e.g., `C(p0, ..., pn)`.
226 Box(target) => extend_with_matching(
227 target, start, alternatives,
228 |k| matches!(k, Box(_)),
229 |k| always_pat!(k, Box(p) => p),
231 // Transform `&m x | ... | &m y` into `&m (x | y)`.
232 Ref(target, m1) => extend_with_matching(
233 target, start, alternatives,
234 |k| matches!(k, Ref(_, m2) if m1 == m2), // Mutabilities must match.
235 |k| always_pat!(k, Ref(p, _) => p),
237 // Transform `b @ p0 | ... b @ p1` into `b @ (p0 | p1)`.
238 Ident(b1, i1, Some(target)) => extend_with_matching(
239 target, start, alternatives,
240 // Binding names must match.
241 |k| matches!(k, Ident(b2, i2, Some(_)) if b1 == b2 && eq_id(*i1, *i2)),
242 |k| always_pat!(k, Ident(_, _, Some(p)) => p),
244 // Transform `[pre, x, post] | ... | [pre, y, post]` into `[pre, x | y, post]`.
245 Slice(ps1) => extend_with_matching_product(
246 ps1, start, alternatives,
247 |k, ps1, idx| matches!(k, Slice(ps2) if eq_pre_post(ps1, ps2, idx)),
248 |k| always_pat!(k, Slice(ps) => ps),
250 // Transform `(pre, x, post) | ... | (pre, y, post)` into `(pre, x | y, post)`.
251 Tuple(ps1) => extend_with_matching_product(
252 ps1, start, alternatives,
253 |k, ps1, idx| matches!(k, Tuple(ps2) if eq_pre_post(ps1, ps2, idx)),
254 |k| always_pat!(k, Tuple(ps) => ps),
256 // Transform `S(pre, x, post) | ... | S(pre, y, post)` into `S(pre, x | y, post)`.
257 TupleStruct(path1, ps1) => extend_with_matching_product(
258 ps1, start, alternatives,
259 |k, ps1, idx| matches!(
261 TupleStruct(path2, ps2) if eq_path(path1, path2) && eq_pre_post(ps1, ps2, idx)
263 |k| always_pat!(k, TupleStruct(_, ps) => ps),
265 // Transform a record pattern `S { fp_0, ..., fp_n }`.
266 Struct(path1, fps1, rest1) => extend_with_struct_pat(path1, fps1, *rest1, start, alternatives),
269 alternatives[focus_idx].kind = focus_kind;
273 /// Here we focusing on a record pattern `S { fp_0, ..., fp_n }`.
274 /// In particular, for a record pattern, the order in which the field patterns is irrelevant.
275 /// So when we fixate on some `ident_k: pat_k`, we try to find `ident_k` in the other pattern
276 /// and check that all `fp_i` where `i ∈ ((0...n) \ k)` between two patterns are equal.
277 fn extend_with_struct_pat(
279 fps1: &mut Vec<ast::FieldPat>,
282 alternatives: &mut Vec<P<Pat>>,
284 (0..fps1.len()).any(|idx| {
285 let pos_in_2 = Cell::new(None); // The element `k`.
286 let tail_or = drain_matching(
290 matches!(k, Struct(path2, fps2, rest2)
291 if rest1 == *rest2 // If one struct pattern has `..` so must the other.
292 && eq_path(path1, path2)
293 && fps1.len() == fps2.len()
294 && fps1.iter().enumerate().all(|(idx_1, fp1)| {
296 // In the case of `k`, we merely require identical field names
297 // so that we will transform into `ident_k: p1_k | p2_k`.
298 let pos = fps2.iter().position(|fp2| eq_id(fp1.ident, fp2.ident));
302 fps2.iter().any(|fp2| eq_field_pat(fp1, fp2))
307 |k| always_pat!(k, Struct(_, mut fps, _) => fps.swap_remove(pos_in_2.take().unwrap()).pat),
309 extend_with_tail_or(&mut fps1[idx].pat, tail_or)
313 /// Like `extend_with_matching` but for products with > 1 factor, e.g., `C(p_0, ..., p_n)`.
314 /// Here, the idea is that we fixate on some `p_k` in `C`,
315 /// allowing it to vary between two `targets` and `ps2` (returned by `extract`),
316 /// while also requiring `ps1[..n] ~ ps2[..n]` (pre) and `ps1[n + 1..] ~ ps2[n + 1..]` (post),
317 /// where `~` denotes semantic equality.
318 fn extend_with_matching_product(
319 targets: &mut Vec<P<Pat>>,
321 alternatives: &mut Vec<P<Pat>>,
322 predicate: impl Fn(&PatKind, &[P<Pat>], usize) -> bool,
323 extract: impl Fn(PatKind) -> Vec<P<Pat>>,
325 (0..targets.len()).any(|idx| {
326 let tail_or = drain_matching(
329 |k| predicate(k, targets, idx),
330 |k| extract(k).swap_remove(idx),
332 extend_with_tail_or(&mut targets[idx], tail_or)
336 /// Extract the pattern from the given one and replace it with `Wild`.
337 /// This is meant for temporarily swapping out the pattern for manipulation.
338 fn take_pat(from: &mut Pat) -> Pat {
344 mem::replace(from, dummy)
347 /// Extend `target` as an or-pattern with the alternatives
348 /// in `tail_or` if there are any and return if there were.
349 fn extend_with_tail_or(target: &mut Pat, tail_or: Vec<P<Pat>>) -> bool {
350 fn extend(target: &mut Pat, mut tail_or: Vec<P<Pat>>) {
352 // On an existing or-pattern in the target, append to it.
353 Pat { kind: Or(ps), .. } => ps.append(&mut tail_or),
354 // Otherwise convert the target to an or-pattern.
356 let mut init_or = vec![P(take_pat(target))];
357 init_or.append(&mut tail_or);
358 target.kind = Or(init_or);
363 let changed = !tail_or.is_empty();
365 // Extend the target.
366 extend(target, tail_or);
371 // Extract all inner patterns in `alternatives` matching our `predicate`.
372 // Only elements beginning with `start` are considered for extraction.
375 alternatives: &mut Vec<P<Pat>>,
376 predicate: impl Fn(&PatKind) -> bool,
377 extract: impl Fn(PatKind) -> P<Pat>,
379 let mut tail_or = vec![];
381 for pat in alternatives.drain_filter(|p| {
382 // Check if we should extract, but only if `idx >= start`.
384 idx > start && predicate(&p.kind)
386 tail_or.push(extract(pat.into_inner().kind));
391 fn extend_with_matching(
394 alternatives: &mut Vec<P<Pat>>,
395 predicate: impl Fn(&PatKind) -> bool,
396 extract: impl Fn(PatKind) -> P<Pat>,
398 extend_with_tail_or(target, drain_matching(start, alternatives, predicate, extract))
401 /// Are the patterns in `ps1` and `ps2` equal save for `ps1[idx]` compared to `ps2[idx]`?
402 fn eq_pre_post(ps1: &[P<Pat>], ps2: &[P<Pat>], idx: usize) -> bool {
403 ps1.len() == ps2.len()
404 && ps1[idx].is_rest() == ps2[idx].is_rest() // Avoid `[x, ..] | [x, 0]` => `[x, .. | 0]`.
405 && over(&ps1[..idx], &ps2[..idx], |l, r| eq_pat(l, r))
406 && over(&ps1[idx + 1..], &ps2[idx + 1..], |l, r| eq_pat(l, r))