--- /dev/null
+#![allow(clippy::wildcard_imports, clippy::enum_glob_use)]
+
+use crate::utils::ast_utils::{eq_field_pat, eq_id, eq_pat, eq_path};
+use crate::utils::{over, span_lint_and_then};
+use rustc_ast::mut_visit::*;
+use rustc_ast::ptr::P;
+use rustc_ast::{self as ast, Pat, PatKind, PatKind::*, DUMMY_NODE_ID};
+use rustc_ast_pretty::pprust;
+use rustc_errors::Applicability;
+use rustc_lint::{EarlyContext, EarlyLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::DUMMY_SP;
+
+use std::cell::Cell;
+use std::mem;
+
+declare_clippy_lint! {
+ /// **What it does:**
+ ///
+ /// Checks for unnested or-patterns, e.g., `Some(0) | Some(2)` and
+ /// suggests replacing the pattern with a nested one, `Some(0 | 2)`.
+ ///
+ /// Another way to think of this is that it rewrites patterns in
+ /// *disjunctive normal form (DNF)* into *conjunctive normal form (CNF)*.
+ ///
+ /// **Why is this bad?**
+ ///
+ /// In the example above, `Some` is repeated, which unncessarily complicates the pattern.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ ///
+ /// ```rust
+ /// fn main() {
+ /// if let Some(0) | Some(2) = Some(0) {}
+ /// }
+ /// ```
+ /// Use instead:
+ /// ```rust
+ /// #![feature(or_patterns)]
+ ///
+ /// fn main() {
+ /// if let Some(0 | 2) = Some(0) {}
+ /// }
+ /// ```
+ pub UNNESTED_OR_PATTERNS,
+ pedantic,
+ "unnested or-patterns, e.g., `Foo(Bar) | Foo(Baz) instead of `Foo(Bar | Baz)`"
+}
+
+declare_lint_pass!(UnnestedOrPatterns => [UNNESTED_OR_PATTERNS]);
+
+impl EarlyLintPass for UnnestedOrPatterns {
+ fn check_arm(&mut self, cx: &EarlyContext<'_>, a: &ast::Arm) {
+ lint_unnested_or_patterns(cx, &a.pat);
+ }
+
+ fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
+ if let ast::ExprKind::Let(pat, _) = &e.kind {
+ lint_unnested_or_patterns(cx, pat);
+ }
+ }
+
+ fn check_param(&mut self, cx: &EarlyContext<'_>, p: &ast::Param) {
+ lint_unnested_or_patterns(cx, &p.pat);
+ }
+
+ fn check_local(&mut self, cx: &EarlyContext<'_>, l: &ast::Local) {
+ lint_unnested_or_patterns(cx, &l.pat);
+ }
+}
+
+fn lint_unnested_or_patterns(cx: &EarlyContext<'_>, pat: &Pat) {
+ if !cx.sess.features_untracked().or_patterns {
+ // Do not suggest nesting the patterns if the feature `or_patterns` is not enabled.
+ return;
+ }
+
+ if let Ident(.., None) | Lit(_) | Wild | Path(..) | Range(..) | Rest | MacCall(_) = pat.kind {
+ // This is a leaf pattern, so cloning is unprofitable.
+ return;
+ }
+
+ let mut pat = P(pat.clone());
+
+ // Nix all the paren patterns everywhere so that they aren't in our way.
+ remove_all_parens(&mut pat);
+
+ // Transform all unnested or-patterns into nested ones, and if there were none, quit.
+ if !unnest_or_patterns(&mut pat) {
+ return;
+ }
+
+ span_lint_and_then(cx, UNNESTED_OR_PATTERNS, pat.span, "unnested or-patterns", |db| {
+ insert_necessary_parens(&mut pat);
+ db.span_suggestion_verbose(
+ pat.span,
+ "nest the patterns",
+ pprust::pat_to_string(&pat),
+ Applicability::MachineApplicable,
+ );
+ });
+}
+
+/// Remove all `(p)` patterns in `pat`.
+fn remove_all_parens(pat: &mut P<Pat>) {
+ struct Visitor;
+ impl MutVisitor for Visitor {
+ fn visit_pat(&mut self, pat: &mut P<Pat>) {
+ noop_visit_pat(pat, self);
+ let inner = match &mut pat.kind {
+ Paren(i) => mem::replace(&mut i.kind, Wild),
+ _ => return,
+ };
+ pat.kind = inner;
+ }
+ }
+ Visitor.visit_pat(pat);
+}
+
+/// Insert parens where necessary according to Rust's precedence rules for patterns.
+fn insert_necessary_parens(pat: &mut P<Pat>) {
+ struct Visitor;
+ impl MutVisitor for Visitor {
+ fn visit_pat(&mut self, pat: &mut P<Pat>) {
+ use ast::{BindingMode::*, Mutability::*};
+ noop_visit_pat(pat, self);
+ let target = match &mut pat.kind {
+ // `i @ a | b`, `box a | b`, and `& mut? a | b`.
+ Ident(.., Some(p)) | Box(p) | Ref(p, _) if matches!(&p.kind, Or(ps) if ps.len() > 1) => p,
+ Ref(p, Not) if matches!(p.kind, Ident(ByValue(Mut), ..)) => p, // `&(mut x)`
+ _ => return,
+ };
+ target.kind = Paren(P(take_pat(target)));
+ }
+ }
+ Visitor.visit_pat(pat);
+}
+
+/// Unnest or-patterns `p0 | ... | p1` in the pattern `pat`.
+/// For example, this would transform `Some(0) | FOO | Some(2)` into `Some(0 | 2) | FOO`.
+fn unnest_or_patterns(pat: &mut P<Pat>) -> bool {
+ struct Visitor {
+ changed: bool,
+ }
+ impl MutVisitor for Visitor {
+ fn visit_pat(&mut self, p: &mut P<Pat>) {
+ // This is a bottom up transformation, so recurse first.
+ noop_visit_pat(p, self);
+
+ // Don't have an or-pattern? Just quit early on.
+ let alternatives = match &mut p.kind {
+ Or(ps) => ps,
+ _ => return,
+ };
+
+ // Collapse or-patterns directly nested in or-patterns.
+ let mut idx = 0;
+ let mut this_level_changed = false;
+ while idx < alternatives.len() {
+ let inner = if let Or(ps) = &mut alternatives[idx].kind {
+ mem::take(ps)
+ } else {
+ idx += 1;
+ continue;
+ };
+ this_level_changed = true;
+ alternatives.splice(idx..=idx, inner);
+ }
+
+ // Focus on `p_n` and then try to transform all `p_i` where `i > n`.
+ let mut focus_idx = 0;
+ while focus_idx < alternatives.len() {
+ this_level_changed |= transform_with_focus_on_idx(alternatives, focus_idx);
+ focus_idx += 1;
+ }
+ self.changed |= this_level_changed;
+
+ // Deal with `Some(Some(0)) | Some(Some(1))`.
+ if this_level_changed {
+ noop_visit_pat(p, self);
+ }
+ }
+ }
+
+ let mut visitor = Visitor { changed: false };
+ visitor.visit_pat(pat);
+ visitor.changed
+}
+
+/// Match `$scrutinee` against `$pat` and extract `$then` from it.
+/// Panics if there is no match.
+macro_rules! always_pat {
+ ($scrutinee:expr, $pat:pat => $then:expr) => {
+ match $scrutinee {
+ $pat => $then,
+ _ => unreachable!(),
+ }
+ };
+}
+
+/// Focus on `focus_idx` in `alternatives`,
+/// attempting to extend it with elements of the same constructor `C`
+/// in `alternatives[focus_idx + 1..]`.
+fn transform_with_focus_on_idx(alternatives: &mut Vec<P<Pat>>, focus_idx: usize) -> bool {
+ // Extract the kind; we'll need to make some changes in it.
+ let mut focus_kind = mem::replace(&mut alternatives[focus_idx].kind, PatKind::Wild);
+ // We'll focus on `alternatives[focus_idx]`,
+ // so we're draining from `alternatives[focus_idx + 1..]`.
+ let start = focus_idx + 1;
+
+ // We're trying to find whatever kind (~"constructor") we found in `alternatives[start..]`.
+ let changed = match &mut focus_kind {
+ // These pattern forms are "leafs" and do not have sub-patterns.
+ // Therefore they are not some form of constructor `C`,
+ // with which a pattern `C(p_0)` may be formed,
+ // which we would want to join with other `C(p_j)`s.
+ Ident(.., None) | Lit(_) | Wild | Path(..) | Range(..) | Rest | MacCall(_)
+ // Dealt with elsewhere.
+ | Or(_) | Paren(_) => false,
+ // Transform `box x | ... | box y` into `box (x | y)`.
+ //
+ // The cases below until `Slice(...)` deal with *singleton* products.
+ // These patterns have the shape `C(p)`, and not e.g., `C(p0, ..., pn)`.
+ Box(target) => extend_with_matching(
+ target, start, alternatives,
+ |k| matches!(k, Box(_)),
+ |k| always_pat!(k, Box(p) => p),
+ ),
+ // Transform `&m x | ... | &m y` into `&m (x | y)`.
+ Ref(target, m1) => extend_with_matching(
+ target, start, alternatives,
+ |k| matches!(k, Ref(_, m2) if m1 == m2), // Mutabilities must match.
+ |k| always_pat!(k, Ref(p, _) => p),
+ ),
+ // Transform `b @ p0 | ... b @ p1` into `b @ (p0 | p1)`.
+ Ident(b1, i1, Some(target)) => extend_with_matching(
+ target, start, alternatives,
+ // Binding names must match.
+ |k| matches!(k, Ident(b2, i2, Some(_)) if b1 == b2 && eq_id(*i1, *i2)),
+ |k| always_pat!(k, Ident(_, _, Some(p)) => p),
+ ),
+ // Transform `[pre, x, post] | ... | [pre, y, post]` into `[pre, x | y, post]`.
+ Slice(ps1) => extend_with_matching_product(
+ ps1, start, alternatives,
+ |k, ps1, idx| matches!(k, Slice(ps2) if eq_pre_post(ps1, ps2, idx)),
+ |k| always_pat!(k, Slice(ps) => ps),
+ ),
+ // Transform `(pre, x, post) | ... | (pre, y, post)` into `(pre, x | y, post)`.
+ Tuple(ps1) => extend_with_matching_product(
+ ps1, start, alternatives,
+ |k, ps1, idx| matches!(k, Tuple(ps2) if eq_pre_post(ps1, ps2, idx)),
+ |k| always_pat!(k, Tuple(ps) => ps),
+ ),
+ // Transform `S(pre, x, post) | ... | S(pre, y, post)` into `S(pre, x | y, post)`.
+ TupleStruct(path1, ps1) => extend_with_matching_product(
+ ps1, start, alternatives,
+ |k, ps1, idx| matches!(
+ k,
+ TupleStruct(path2, ps2) if eq_path(path1, path2) && eq_pre_post(ps1, ps2, idx)
+ ),
+ |k| always_pat!(k, TupleStruct(_, ps) => ps),
+ ),
+ // Transform a record pattern `S { fp_0, ..., fp_n }`.
+ Struct(path1, fps1, rest1) => extend_with_struct_pat(path1, fps1, *rest1, start, alternatives),
+ };
+
+ alternatives[focus_idx].kind = focus_kind;
+ changed
+}
+
+/// Here we focusing on a record pattern `S { fp_0, ..., fp_n }`.
+/// In particular, for a record pattern, the order in which the field patterns is irrelevant.
+/// So when we fixate on some `ident_k: pat_k`, we try to find `ident_k` in the other pattern
+/// and check that all `fp_i` where `i ∈ ((0...n) \ k)` between two patterns are equal.
+fn extend_with_struct_pat(
+ path1: &ast::Path,
+ fps1: &mut Vec<ast::PatField>,
+ rest1: bool,
+ start: usize,
+ alternatives: &mut Vec<P<Pat>>,
+) -> bool {
+ (0..fps1.len()).any(|idx| {
+ let pos_in_2 = Cell::new(None); // The element `k`.
+ let tail_or = drain_matching(
+ start,
+ alternatives,
+ |k| {
+ matches!(k, Struct(path2, fps2, rest2)
+ if rest1 == *rest2 // If one struct pattern has `..` so must the other.
+ && eq_path(path1, path2)
+ && fps1.len() == fps2.len()
+ && fps1.iter().enumerate().all(|(idx_1, fp1)| {
+ if idx_1 == idx {
+ // In the case of `k`, we merely require identical field names
+ // so that we will transform into `ident_k: p1_k | p2_k`.
+ let pos = fps2.iter().position(|fp2| eq_id(fp1.ident, fp2.ident));
+ pos_in_2.set(pos);
+ pos.is_some()
+ } else {
+ fps2.iter().any(|fp2| eq_field_pat(fp1, fp2))
+ }
+ }))
+ },
+ // Extract `p2_k`.
+ |k| always_pat!(k, Struct(_, mut fps, _) => fps.swap_remove(pos_in_2.take().unwrap()).pat),
+ );
+ extend_with_tail_or(&mut fps1[idx].pat, tail_or)
+ })
+}
+
+/// Like `extend_with_matching` but for products with > 1 factor, e.g., `C(p_0, ..., p_n)`.
+/// Here, the idea is that we fixate on some `p_k` in `C`,
+/// allowing it to vary between two `targets` and `ps2` (returned by `extract`),
+/// while also requiring `ps1[..n] ~ ps2[..n]` (pre) and `ps1[n + 1..] ~ ps2[n + 1..]` (post),
+/// where `~` denotes semantic equality.
+fn extend_with_matching_product(
+ targets: &mut Vec<P<Pat>>,
+ start: usize,
+ alternatives: &mut Vec<P<Pat>>,
+ predicate: impl Fn(&PatKind, &[P<Pat>], usize) -> bool,
+ extract: impl Fn(PatKind) -> Vec<P<Pat>>,
+) -> bool {
+ (0..targets.len()).any(|idx| {
+ let tail_or = drain_matching(
+ start,
+ alternatives,
+ |k| predicate(k, targets, idx),
+ |k| extract(k).swap_remove(idx),
+ );
+ extend_with_tail_or(&mut targets[idx], tail_or)
+ })
+}
+
+/// Extract the pattern from the given one and replace it with `Wild`.
+/// This is meant for temporarily swapping out the pattern for manipulation.
+fn take_pat(from: &mut Pat) -> Pat {
+ let dummy = Pat {
+ id: DUMMY_NODE_ID,
+ kind: Wild,
+ span: DUMMY_SP,
+ tokens: None,
+ };
+ mem::replace(from, dummy)
+}
+
+/// Extend `target` as an or-pattern with the alternatives
+/// in `tail_or` if there are any and return if there were.
+fn extend_with_tail_or(target: &mut Pat, tail_or: Vec<P<Pat>>) -> bool {
+ fn extend(target: &mut Pat, mut tail_or: Vec<P<Pat>>) {
+ match target {
+ // On an existing or-pattern in the target, append to it.
+ Pat { kind: Or(ps), .. } => ps.append(&mut tail_or),
+ // Otherwise convert the target to an or-pattern.
+ target => {
+ let mut init_or = vec![P(take_pat(target))];
+ init_or.append(&mut tail_or);
+ target.kind = Or(init_or);
+ },
+ }
+ }
+
+ let changed = !tail_or.is_empty();
+ if changed {
+ // Extend the target.
+ extend(target, tail_or);
+ }
+ changed
+}
+
+// Extract all inner patterns in `alternatives` matching our `predicate`.
+// Only elements beginning with `start` are considered for extraction.
+fn drain_matching(
+ start: usize,
+ alternatives: &mut Vec<P<Pat>>,
+ predicate: impl Fn(&PatKind) -> bool,
+ extract: impl Fn(PatKind) -> P<Pat>,
+) -> Vec<P<Pat>> {
+ let mut tail_or = vec![];
+ let mut idx = 0;
+ for pat in alternatives.drain_filter(|p| {
+ // Check if we should extract, but only if `idx >= start`.
+ idx += 1;
+ idx > start && predicate(&p.kind)
+ }) {
+ tail_or.push(extract(pat.into_inner().kind));
+ }
+ tail_or
+}
+
+fn extend_with_matching(
+ target: &mut Pat,
+ start: usize,
+ alternatives: &mut Vec<P<Pat>>,
+ predicate: impl Fn(&PatKind) -> bool,
+ extract: impl Fn(PatKind) -> P<Pat>,
+) -> bool {
+ extend_with_tail_or(target, drain_matching(start, alternatives, predicate, extract))
+}
+
+/// Are the patterns in `ps1` and `ps2` equal save for `ps1[idx]` compared to `ps2[idx]`?
+fn eq_pre_post(ps1: &[P<Pat>], ps2: &[P<Pat>], idx: usize) -> bool {
+ ps1.len() == ps2.len()
+ && ps1[idx].is_rest() == ps2[idx].is_rest() // Avoid `[x, ..] | [x, 0]` => `[x, .. | 0]`.
+ && over(&ps1[..idx], &ps2[..idx], |l, r| eq_pat(l, r))
+ && over(&ps1[idx + 1..], &ps2[idx + 1..], |l, r| eq_pat(l, r))
+}
projects / rustc.git / blobdiff