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Fix issue 11223: add check for identical guards in lint match_same_arms #12059

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merged 1 commit into from
Feb 19, 2024
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Fix issue 11223: add check for identical guards in lint match_same_arms #12059

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3 changes: 1 addition & 2 deletions clippy_lints/src/casts/cast_possible_truncation.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -131,8 +131,7 @@ pub(super) fn check(

let cast_from_ptr_size = def.repr().int.map_or(true, |ty| matches!(ty, IntegerType::Pointer(_),));
let suffix = match (cast_from_ptr_size, is_isize_or_usize(cast_to)) {
(false, false) if from_nbits > to_nbits => "",
(true, false) if from_nbits > to_nbits => "",
(_, false) if from_nbits > to_nbits => "",
(false, true) if from_nbits > 64 => "",
(false, true) if from_nbits > 32 => " on targets with 32-bit wide pointers",
_ => return,
Expand Down
66 changes: 39 additions & 27 deletions clippy_lints/src/matches/match_same_arms.rs
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Expand Up @@ -64,38 +64,50 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>]) {
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 let Some(a_id) = path_to_local(a)
&& let Some(b_id) = path_to_local(b)
&& let entry = match local_map.entry(a_id) {
HirIdMapEntry::Vacant(entry) => entry,
// check if using the same bindings as before
HirIdMapEntry::Occupied(entry) => return *entry.get() == b_id,
}
let check_eq_with_pat = |expr_a: &Expr<'_>, expr_b: &Expr<'_>| {
let mut local_map: HirIdMap<HirId> = HirIdMap::default();
let eq_fallback = |a: &Expr<'_>, b: &Expr<'_>| {
if let Some(a_id) = path_to_local(a)
&& let Some(b_id) = path_to_local(b)
&& let entry = match local_map.entry(a_id) {
HirIdMapEntry::Vacant(entry) => entry,
// check if using the same bindings as before
HirIdMapEntry::Occupied(entry) => return *entry.get() == b_id,
}
// the names technically don't have to match; this makes the lint more conservative
&& cx.tcx.hir().name(a_id) == cx.tcx.hir().name(b_id)
&& cx.typeck_results().expr_ty(a) == cx.typeck_results().expr_ty(b)
&& pat_contains_local(lhs.pat, a_id)
&& pat_contains_local(rhs.pat, b_id)
{
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)
&& cx.typeck_results().expr_ty(a) == cx.typeck_results().expr_ty(b)
&& pat_contains_local(lhs.pat, a_id)
&& pat_contains_local(rhs.pat, b_id)
{
entry.insert(b_id);
true
} else {
false
}
};

SpanlessEq::new(cx)
.expr_fallback(eq_fallback)
.eq_expr(expr_a, expr_b)
// 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 check_same_guard = || match (&lhs.guard, &rhs.guard) {
(None, None) => true,
(Some(lhs_guard), Some(rhs_guard)) => check_eq_with_pat(lhs_guard, rhs_guard),
_ => false,
};

let check_same_body = || check_eq_with_pat(lhs.body, rhs.body);

// Arms with different 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)
&& check_same_guard()
&& check_same_body()
};

let indexed_arms: Vec<(usize, &Arm<'_>)> = arms.iter().enumerate().collect();
Expand Down
14 changes: 14 additions & 0 deletions tests/ui/match_same_arms2.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -67,6 +67,20 @@ fn match_same_arms() {
_ => (),
}

// No warning because guards are different
let _ = match Some(42) {
Some(a) if a == 42 => a,
Some(a) if a == 24 => a,
Some(_) => 24,
None => 0,
};

let _ = match (Some(42), Some(42)) {
(Some(a), None) if a == 42 => a,
(None, Some(a)) if a == 42 => a, //~ ERROR: this match arm has an identical body to another arm
_ => 0,
};

match (Some(42), Some(42)) {
(Some(a), ..) => bar(a), //~ ERROR: this match arm has an identical body to another arm
(.., Some(a)) => bar(a),
Expand Down
51 changes: 33 additions & 18 deletions tests/ui/match_same_arms2.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -71,7 +71,22 @@ LL | (Some(a), None) => bar(a),
| ^^^^^^^^^^^^^^^^^^^^^^^^^

error: this match arm has an identical body to another arm
--> tests/ui/match_same_arms2.rs:71:9
--> tests/ui/match_same_arms2.rs:80:9
|
LL | (None, Some(a)) if a == 42 => a,
| ---------------^^^^^^^^^^^^^^^^
| |
| help: try merging the arm patterns: `(None, Some(a)) | (Some(a), None)`
|
= help: or try changing either arm body
note: other arm here
--> tests/ui/match_same_arms2.rs:79:9
|
LL | (Some(a), None) if a == 42 => a,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: this match arm has an identical body to another arm
--> tests/ui/match_same_arms2.rs:85:9
|
LL | (Some(a), ..) => bar(a),
| -------------^^^^^^^^^^
Expand All @@ -80,13 +95,13 @@ LL | (Some(a), ..) => bar(a),
|
= help: or try changing either arm body
note: other arm here
--> tests/ui/match_same_arms2.rs:72:9
--> tests/ui/match_same_arms2.rs:86:9
|
LL | (.., Some(a)) => bar(a),
| ^^^^^^^^^^^^^^^^^^^^^^^

error: this match arm has an identical body to another arm
--> tests/ui/match_same_arms2.rs:105:9
--> tests/ui/match_same_arms2.rs:119:9
|
LL | (Ok(x), Some(_)) => println!("ok {}", x),
| ----------------^^^^^^^^^^^^^^^^^^^^^^^^
Expand All @@ -95,13 +110,13 @@ LL | (Ok(x), Some(_)) => println!("ok {}", x),
|
= help: or try changing either arm body
note: other arm here
--> tests/ui/match_same_arms2.rs:106:9
--> tests/ui/match_same_arms2.rs:120:9
|
LL | (Ok(_), Some(x)) => println!("ok {}", x),
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: this match arm has an identical body to another arm
--> tests/ui/match_same_arms2.rs:121:9
--> tests/ui/match_same_arms2.rs:135:9
|
LL | Ok(_) => println!("ok"),
| -----^^^^^^^^^^^^^^^^^^
Expand All @@ -110,13 +125,13 @@ LL | Ok(_) => println!("ok"),
|
= help: or try changing either arm body
note: other arm here
--> tests/ui/match_same_arms2.rs:120:9
--> tests/ui/match_same_arms2.rs:134:9
|
LL | Ok(3) => println!("ok"),
| ^^^^^^^^^^^^^^^^^^^^^^^

error: this match arm has an identical body to another arm
--> tests/ui/match_same_arms2.rs:148:9
--> tests/ui/match_same_arms2.rs:162:9
|
LL | 1 => {
| ^ help: try merging the arm patterns: `1 | 0`
Expand All @@ -128,15 +143,15 @@ LL | | },
|
= help: or try changing either arm body
note: other arm here
--> tests/ui/match_same_arms2.rs:145:9
--> tests/ui/match_same_arms2.rs:159:9
|
LL | / 0 => {
LL | | empty!(0);
LL | | },
| |_________^

error: match expression looks like `matches!` macro
--> tests/ui/match_same_arms2.rs:167:16
--> tests/ui/match_same_arms2.rs:181:16
|
LL | let _ans = match x {
| ________________^
Expand All @@ -150,7 +165,7 @@ LL | | };
= help: to override `-D warnings` add `#[allow(clippy::match_like_matches_macro)]`

error: this match arm has an identical body to another arm
--> tests/ui/match_same_arms2.rs:199:9
--> tests/ui/match_same_arms2.rs:213:9
|
LL | Foo::X(0) => 1,
| ---------^^^^^
Expand All @@ -159,13 +174,13 @@ LL | Foo::X(0) => 1,
|
= help: or try changing either arm body
note: other arm here
--> tests/ui/match_same_arms2.rs:201:9
--> tests/ui/match_same_arms2.rs:215:9
|
LL | Foo::Z(_) => 1,
| ^^^^^^^^^^^^^^

error: this match arm has an identical body to another arm
--> tests/ui/match_same_arms2.rs:209:9
--> tests/ui/match_same_arms2.rs:223:9
|
LL | Foo::Z(_) => 1,
| ---------^^^^^
Expand All @@ -174,13 +189,13 @@ LL | Foo::Z(_) => 1,
|
= help: or try changing either arm body
note: other arm here
--> tests/ui/match_same_arms2.rs:207:9
--> tests/ui/match_same_arms2.rs:221:9
|
LL | Foo::X(0) => 1,
| ^^^^^^^^^^^^^^

error: this match arm has an identical body to another arm
--> tests/ui/match_same_arms2.rs:232:9
--> tests/ui/match_same_arms2.rs:246:9
|
LL | Some(Bar { y: 0, x: 5, .. }) => 1,
| ----------------------------^^^^^
Expand All @@ -189,13 +204,13 @@ LL | Some(Bar { y: 0, x: 5, .. }) => 1,
|
= help: or try changing either arm body
note: other arm here
--> tests/ui/match_same_arms2.rs:229:9
--> tests/ui/match_same_arms2.rs:243:9
|
LL | Some(Bar { x: 0, y: 5, .. }) => 1,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: this match arm has an identical body to another arm
--> tests/ui/match_same_arms2.rs:246:9
--> tests/ui/match_same_arms2.rs:260:9
|
LL | 1 => cfg!(not_enable),
| -^^^^^^^^^^^^^^^^^^^^
Expand All @@ -204,10 +219,10 @@ LL | 1 => cfg!(not_enable),
|
= help: or try changing either arm body
note: other arm here
--> tests/ui/match_same_arms2.rs:245:9
--> tests/ui/match_same_arms2.rs:259:9
|
LL | 0 => cfg!(not_enable),
| ^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 13 previous errors
error: aborting due to 14 previous errors

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