mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-23 03:23:33 +00:00
0930ac91b9
changelog: none
414 lines
18 KiB
Rust
414 lines
18 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_then;
|
||
use clippy_utils::source::snippet;
|
||
use clippy_utils::{path_to_local, search_same, SpanlessEq, SpanlessHash};
|
||
use core::cmp::Ordering;
|
||
use core::iter;
|
||
use core::slice;
|
||
use rustc_arena::DroplessArena;
|
||
use rustc_ast::ast::LitKind;
|
||
use rustc_errors::Applicability;
|
||
use rustc_hir::def_id::DefId;
|
||
use rustc_hir::{Arm, Expr, ExprKind, HirId, HirIdMap, HirIdSet, Pat, PatKind, RangeEnd};
|
||
use rustc_lint::LateContext;
|
||
use rustc_middle::ty;
|
||
use rustc_span::Symbol;
|
||
use std::collections::hash_map::Entry;
|
||
|
||
use super::MATCH_SAME_ARMS;
|
||
|
||
#[expect(clippy::too_many_lines)]
|
||
pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>]) {
|
||
let hash = |&(_, arm): &(usize, &Arm<'_>)| -> u64 {
|
||
let mut h = SpanlessHash::new(cx);
|
||
h.hash_expr(arm.body);
|
||
h.finish()
|
||
};
|
||
|
||
let arena = DroplessArena::default();
|
||
let normalized_pats: Vec<_> = arms
|
||
.iter()
|
||
.map(|a| NormalizedPat::from_pat(cx, &arena, a.pat))
|
||
.collect();
|
||
|
||
// The furthest forwards a pattern can move without semantic changes
|
||
let forwards_blocking_idxs: Vec<_> = normalized_pats
|
||
.iter()
|
||
.enumerate()
|
||
.map(|(i, pat)| {
|
||
normalized_pats[i + 1..]
|
||
.iter()
|
||
.enumerate()
|
||
.find_map(|(j, other)| pat.has_overlapping_values(other).then_some(i + 1 + j))
|
||
.unwrap_or(normalized_pats.len())
|
||
})
|
||
.collect();
|
||
|
||
// The furthest backwards a pattern can move without semantic changes
|
||
let backwards_blocking_idxs: Vec<_> = normalized_pats
|
||
.iter()
|
||
.enumerate()
|
||
.map(|(i, pat)| {
|
||
normalized_pats[..i]
|
||
.iter()
|
||
.enumerate()
|
||
.rev()
|
||
.zip(forwards_blocking_idxs[..i].iter().copied().rev())
|
||
.skip_while(|&(_, forward_block)| forward_block > i)
|
||
.find_map(|((j, other), forward_block)| {
|
||
(forward_block == i || pat.has_overlapping_values(other)).then_some(j)
|
||
})
|
||
.unwrap_or(0)
|
||
})
|
||
.collect();
|
||
|
||
let eq = |&(lindex, lhs): &(usize, &Arm<'_>), &(rindex, rhs): &(usize, &Arm<'_>)| -> bool {
|
||
let min_index = usize::min(lindex, rindex);
|
||
let max_index = usize::max(lindex, rindex);
|
||
|
||
let mut local_map: HirIdMap<HirId> = HirIdMap::default();
|
||
let eq_fallback = |a: &Expr<'_>, b: &Expr<'_>| {
|
||
if_chain! {
|
||
if let Some(a_id) = path_to_local(a);
|
||
if let Some(b_id) = path_to_local(b);
|
||
let entry = match local_map.entry(a_id) {
|
||
Entry::Vacant(entry) => entry,
|
||
// check if using the same bindings as before
|
||
Entry::Occupied(entry) => return *entry.get() == b_id,
|
||
};
|
||
// the names technically don't have to match; this makes the lint more conservative
|
||
if cx.tcx.hir().name(a_id) == cx.tcx.hir().name(b_id);
|
||
if cx.typeck_results().expr_ty(a) == cx.typeck_results().expr_ty(b);
|
||
if pat_contains_local(lhs.pat, a_id);
|
||
if pat_contains_local(rhs.pat, b_id);
|
||
then {
|
||
entry.insert(b_id);
|
||
true
|
||
} else {
|
||
false
|
||
}
|
||
}
|
||
};
|
||
// Arms with a guard are ignored, those can’t always be merged together
|
||
// If both arms overlap with an arm in between then these can't be merged either.
|
||
!(backwards_blocking_idxs[max_index] > min_index && forwards_blocking_idxs[min_index] < max_index)
|
||
&& lhs.guard.is_none()
|
||
&& rhs.guard.is_none()
|
||
&& SpanlessEq::new(cx)
|
||
.expr_fallback(eq_fallback)
|
||
.eq_expr(lhs.body, rhs.body)
|
||
// these checks could be removed to allow unused bindings
|
||
&& bindings_eq(lhs.pat, local_map.keys().copied().collect())
|
||
&& bindings_eq(rhs.pat, local_map.values().copied().collect())
|
||
};
|
||
|
||
let indexed_arms: Vec<(usize, &Arm<'_>)> = arms.iter().enumerate().collect();
|
||
for (&(i, arm1), &(j, arm2)) in search_same(&indexed_arms, hash, eq) {
|
||
if matches!(arm2.pat.kind, PatKind::Wild) {
|
||
span_lint_and_then(
|
||
cx,
|
||
MATCH_SAME_ARMS,
|
||
arm1.span,
|
||
"this match arm has an identical body to the `_` wildcard arm",
|
||
|diag| {
|
||
diag.span_suggestion(arm1.span, "try removing the arm", "", Applicability::MaybeIncorrect)
|
||
.help("or try changing either arm body")
|
||
.span_note(arm2.span, "`_` wildcard arm here");
|
||
},
|
||
);
|
||
} else {
|
||
let back_block = backwards_blocking_idxs[j];
|
||
let (keep_arm, move_arm) = if back_block < i || (back_block == 0 && forwards_blocking_idxs[i] <= j) {
|
||
(arm1, arm2)
|
||
} else {
|
||
(arm2, arm1)
|
||
};
|
||
|
||
span_lint_and_then(
|
||
cx,
|
||
MATCH_SAME_ARMS,
|
||
keep_arm.span,
|
||
"this match arm has an identical body to another arm",
|
||
|diag| {
|
||
let move_pat_snip = snippet(cx, move_arm.pat.span, "<pat2>");
|
||
let keep_pat_snip = snippet(cx, keep_arm.pat.span, "<pat1>");
|
||
|
||
diag.span_suggestion(
|
||
keep_arm.pat.span,
|
||
"try merging the arm patterns",
|
||
format!("{} | {}", keep_pat_snip, move_pat_snip),
|
||
Applicability::MaybeIncorrect,
|
||
)
|
||
.help("or try changing either arm body")
|
||
.span_note(move_arm.span, "other arm here");
|
||
},
|
||
);
|
||
}
|
||
}
|
||
}
|
||
|
||
#[derive(Clone, Copy)]
|
||
enum NormalizedPat<'a> {
|
||
Wild,
|
||
Struct(Option<DefId>, &'a [(Symbol, Self)]),
|
||
Tuple(Option<DefId>, &'a [Self]),
|
||
Or(&'a [Self]),
|
||
Path(Option<DefId>),
|
||
LitStr(Symbol),
|
||
LitBytes(&'a [u8]),
|
||
LitInt(u128),
|
||
LitBool(bool),
|
||
Range(PatRange),
|
||
/// A slice pattern. If the second value is `None`, then this matches an exact size. Otherwise
|
||
/// the first value contains everything before the `..` wildcard pattern, and the second value
|
||
/// contains everything afterwards. Note that either side, or both sides, may contain zero
|
||
/// patterns.
|
||
Slice(&'a [Self], Option<&'a [Self]>),
|
||
}
|
||
|
||
#[derive(Clone, Copy)]
|
||
struct PatRange {
|
||
start: u128,
|
||
end: u128,
|
||
bounds: RangeEnd,
|
||
}
|
||
impl PatRange {
|
||
fn contains(&self, x: u128) -> bool {
|
||
x >= self.start
|
||
&& match self.bounds {
|
||
RangeEnd::Included => x <= self.end,
|
||
RangeEnd::Excluded => x < self.end,
|
||
}
|
||
}
|
||
|
||
fn overlaps(&self, other: &Self) -> bool {
|
||
// Note: Empty ranges are impossible, so this is correct even though it would return true if an
|
||
// empty exclusive range were to reside within an inclusive range.
|
||
(match self.bounds {
|
||
RangeEnd::Included => self.end >= other.start,
|
||
RangeEnd::Excluded => self.end > other.start,
|
||
} && match other.bounds {
|
||
RangeEnd::Included => self.start <= other.end,
|
||
RangeEnd::Excluded => self.start < other.end,
|
||
})
|
||
}
|
||
}
|
||
|
||
/// Iterates over the pairs of fields with matching names.
|
||
fn iter_matching_struct_fields<'a>(
|
||
left: &'a [(Symbol, NormalizedPat<'a>)],
|
||
right: &'a [(Symbol, NormalizedPat<'a>)],
|
||
) -> impl Iterator<Item = (&'a NormalizedPat<'a>, &'a NormalizedPat<'a>)> + 'a {
|
||
struct Iter<'a>(
|
||
slice::Iter<'a, (Symbol, NormalizedPat<'a>)>,
|
||
slice::Iter<'a, (Symbol, NormalizedPat<'a>)>,
|
||
);
|
||
impl<'a> Iterator for Iter<'a> {
|
||
type Item = (&'a NormalizedPat<'a>, &'a NormalizedPat<'a>);
|
||
fn next(&mut self) -> Option<Self::Item> {
|
||
// Note: all the fields in each slice are sorted by symbol value.
|
||
let mut left = self.0.next()?;
|
||
let mut right = self.1.next()?;
|
||
loop {
|
||
match left.0.cmp(&right.0) {
|
||
Ordering::Equal => return Some((&left.1, &right.1)),
|
||
Ordering::Less => left = self.0.next()?,
|
||
Ordering::Greater => right = self.1.next()?,
|
||
}
|
||
}
|
||
}
|
||
}
|
||
Iter(left.iter(), right.iter())
|
||
}
|
||
|
||
#[expect(clippy::similar_names)]
|
||
impl<'a> NormalizedPat<'a> {
|
||
#[expect(clippy::too_many_lines)]
|
||
fn from_pat(cx: &LateContext<'_>, arena: &'a DroplessArena, pat: &'a Pat<'_>) -> Self {
|
||
match pat.kind {
|
||
PatKind::Wild | PatKind::Binding(.., None) => Self::Wild,
|
||
PatKind::Binding(.., Some(pat)) | PatKind::Box(pat) | PatKind::Ref(pat, _) => {
|
||
Self::from_pat(cx, arena, pat)
|
||
},
|
||
PatKind::Struct(ref path, fields, _) => {
|
||
let fields =
|
||
arena.alloc_from_iter(fields.iter().map(|f| (f.ident.name, Self::from_pat(cx, arena, f.pat))));
|
||
fields.sort_by_key(|&(name, _)| name);
|
||
Self::Struct(cx.qpath_res(path, pat.hir_id).opt_def_id(), fields)
|
||
},
|
||
PatKind::TupleStruct(ref path, pats, wild_idx) => {
|
||
let adt = match cx.typeck_results().pat_ty(pat).ty_adt_def() {
|
||
Some(x) => x,
|
||
None => return Self::Wild,
|
||
};
|
||
let (var_id, variant) = if adt.is_enum() {
|
||
match cx.qpath_res(path, pat.hir_id).opt_def_id() {
|
||
Some(x) => (Some(x), adt.variant_with_ctor_id(x)),
|
||
None => return Self::Wild,
|
||
}
|
||
} else {
|
||
(None, adt.non_enum_variant())
|
||
};
|
||
let (front, back) = match wild_idx {
|
||
Some(i) => pats.split_at(i),
|
||
None => (pats, [].as_slice()),
|
||
};
|
||
let pats = arena.alloc_from_iter(
|
||
front
|
||
.iter()
|
||
.map(|pat| Self::from_pat(cx, arena, pat))
|
||
.chain(iter::repeat_with(|| Self::Wild).take(variant.fields.len() - pats.len()))
|
||
.chain(back.iter().map(|pat| Self::from_pat(cx, arena, pat))),
|
||
);
|
||
Self::Tuple(var_id, pats)
|
||
},
|
||
PatKind::Or(pats) => Self::Or(arena.alloc_from_iter(pats.iter().map(|pat| Self::from_pat(cx, arena, pat)))),
|
||
PatKind::Path(ref path) => Self::Path(cx.qpath_res(path, pat.hir_id).opt_def_id()),
|
||
PatKind::Tuple(pats, wild_idx) => {
|
||
let field_count = match cx.typeck_results().pat_ty(pat).kind() {
|
||
ty::Tuple(subs) => subs.len(),
|
||
_ => return Self::Wild,
|
||
};
|
||
let (front, back) = match wild_idx {
|
||
Some(i) => pats.split_at(i),
|
||
None => (pats, [].as_slice()),
|
||
};
|
||
let pats = arena.alloc_from_iter(
|
||
front
|
||
.iter()
|
||
.map(|pat| Self::from_pat(cx, arena, pat))
|
||
.chain(iter::repeat_with(|| Self::Wild).take(field_count - pats.len()))
|
||
.chain(back.iter().map(|pat| Self::from_pat(cx, arena, pat))),
|
||
);
|
||
Self::Tuple(None, pats)
|
||
},
|
||
PatKind::Lit(e) => match &e.kind {
|
||
// TODO: Handle negative integers. They're currently treated as a wild match.
|
||
ExprKind::Lit(lit) => match lit.node {
|
||
LitKind::Str(sym, _) => Self::LitStr(sym),
|
||
LitKind::ByteStr(ref bytes) => Self::LitBytes(bytes),
|
||
LitKind::Byte(val) => Self::LitInt(val.into()),
|
||
LitKind::Char(val) => Self::LitInt(val.into()),
|
||
LitKind::Int(val, _) => Self::LitInt(val),
|
||
LitKind::Bool(val) => Self::LitBool(val),
|
||
LitKind::Float(..) | LitKind::Err(_) => Self::Wild,
|
||
},
|
||
_ => Self::Wild,
|
||
},
|
||
PatKind::Range(start, end, bounds) => {
|
||
// TODO: Handle negative integers. They're currently treated as a wild match.
|
||
let start = match start {
|
||
None => 0,
|
||
Some(e) => match &e.kind {
|
||
ExprKind::Lit(lit) => match lit.node {
|
||
LitKind::Int(val, _) => val,
|
||
LitKind::Char(val) => val.into(),
|
||
LitKind::Byte(val) => val.into(),
|
||
_ => return Self::Wild,
|
||
},
|
||
_ => return Self::Wild,
|
||
},
|
||
};
|
||
let (end, bounds) = match end {
|
||
None => (u128::MAX, RangeEnd::Included),
|
||
Some(e) => match &e.kind {
|
||
ExprKind::Lit(lit) => match lit.node {
|
||
LitKind::Int(val, _) => (val, bounds),
|
||
LitKind::Char(val) => (val.into(), bounds),
|
||
LitKind::Byte(val) => (val.into(), bounds),
|
||
_ => return Self::Wild,
|
||
},
|
||
_ => return Self::Wild,
|
||
},
|
||
};
|
||
Self::Range(PatRange { start, end, bounds })
|
||
},
|
||
PatKind::Slice(front, wild_pat, back) => Self::Slice(
|
||
arena.alloc_from_iter(front.iter().map(|pat| Self::from_pat(cx, arena, pat))),
|
||
wild_pat.map(|_| &*arena.alloc_from_iter(back.iter().map(|pat| Self::from_pat(cx, arena, pat)))),
|
||
),
|
||
}
|
||
}
|
||
|
||
/// Checks if two patterns overlap in the values they can match assuming they are for the same
|
||
/// type.
|
||
fn has_overlapping_values(&self, other: &Self) -> bool {
|
||
match (*self, *other) {
|
||
(Self::Wild, _) | (_, Self::Wild) => true,
|
||
(Self::Or(pats), ref other) | (ref other, Self::Or(pats)) => {
|
||
pats.iter().any(|pat| pat.has_overlapping_values(other))
|
||
},
|
||
(Self::Struct(lpath, lfields), Self::Struct(rpath, rfields)) => {
|
||
if lpath != rpath {
|
||
return false;
|
||
}
|
||
iter_matching_struct_fields(lfields, rfields).all(|(lpat, rpat)| lpat.has_overlapping_values(rpat))
|
||
},
|
||
(Self::Tuple(lpath, lpats), Self::Tuple(rpath, rpats)) => {
|
||
if lpath != rpath {
|
||
return false;
|
||
}
|
||
lpats
|
||
.iter()
|
||
.zip(rpats.iter())
|
||
.all(|(lpat, rpat)| lpat.has_overlapping_values(rpat))
|
||
},
|
||
(Self::Path(x), Self::Path(y)) => x == y,
|
||
(Self::LitStr(x), Self::LitStr(y)) => x == y,
|
||
(Self::LitBytes(x), Self::LitBytes(y)) => x == y,
|
||
(Self::LitInt(x), Self::LitInt(y)) => x == y,
|
||
(Self::LitBool(x), Self::LitBool(y)) => x == y,
|
||
(Self::Range(ref x), Self::Range(ref y)) => x.overlaps(y),
|
||
(Self::Range(ref range), Self::LitInt(x)) | (Self::LitInt(x), Self::Range(ref range)) => range.contains(x),
|
||
(Self::Slice(lpats, None), Self::Slice(rpats, None)) => {
|
||
lpats.len() == rpats.len() && lpats.iter().zip(rpats.iter()).all(|(x, y)| x.has_overlapping_values(y))
|
||
},
|
||
(Self::Slice(pats, None), Self::Slice(front, Some(back)))
|
||
| (Self::Slice(front, Some(back)), Self::Slice(pats, None)) => {
|
||
// Here `pats` is an exact size match. If the combined lengths of `front` and `back` are greater
|
||
// then the minimum length required will be greater than the length of `pats`.
|
||
if pats.len() < front.len() + back.len() {
|
||
return false;
|
||
}
|
||
pats[..front.len()]
|
||
.iter()
|
||
.zip(front.iter())
|
||
.chain(pats[pats.len() - back.len()..].iter().zip(back.iter()))
|
||
.all(|(x, y)| x.has_overlapping_values(y))
|
||
},
|
||
(Self::Slice(lfront, Some(lback)), Self::Slice(rfront, Some(rback))) => lfront
|
||
.iter()
|
||
.zip(rfront.iter())
|
||
.chain(lback.iter().rev().zip(rback.iter().rev()))
|
||
.all(|(x, y)| x.has_overlapping_values(y)),
|
||
|
||
// Enums can mix unit variants with tuple/struct variants. These can never overlap.
|
||
(Self::Path(_), Self::Tuple(..) | Self::Struct(..))
|
||
| (Self::Tuple(..) | Self::Struct(..), Self::Path(_)) => false,
|
||
|
||
// Tuples can be matched like a struct.
|
||
(Self::Tuple(x, _), Self::Struct(y, _)) | (Self::Struct(x, _), Self::Tuple(y, _)) => {
|
||
// TODO: check fields here.
|
||
x == y
|
||
},
|
||
|
||
// TODO: Lit* with Path, Range with Path, LitBytes with Slice
|
||
_ => true,
|
||
}
|
||
}
|
||
}
|
||
|
||
fn pat_contains_local(pat: &Pat<'_>, id: HirId) -> bool {
|
||
let mut result = false;
|
||
pat.walk_short(|p| {
|
||
result |= matches!(p.kind, PatKind::Binding(_, binding_id, ..) if binding_id == id);
|
||
!result
|
||
});
|
||
result
|
||
}
|
||
|
||
/// Returns true if all the bindings in the `Pat` are in `ids` and vice versa
|
||
fn bindings_eq(pat: &Pat<'_>, mut ids: HirIdSet) -> bool {
|
||
let mut result = true;
|
||
pat.each_binding_or_first(&mut |_, id, _, _| result &= ids.remove(&id));
|
||
result && ids.is_empty()
|
||
}
|