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Don't capture &[T; N] when contents isn't read #112636

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Merged
merged 1 commit into from
Jun 18, 2023
Merged

Don't capture &[T; N] when contents isn't read #112636

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2 changes: 1 addition & 1 deletion compiler/rustc_hir_typeck/src/expr_use_visitor.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -443,7 +443,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
if matches!((lhs, wild, rhs), (&[], Some(_), &[]))
// Arrays have a statically known size, so
// there is no need to read their length
|| discr_place.place.base_ty.is_array()
|| place.place.ty().peel_refs().is_array()
{
} else {
needs_to_be_read = true;
Expand Down
25 changes: 25 additions & 0 deletions tests/ui/closures/2229_closure_analysis/match/patterns-capture-analysis.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -87,6 +87,31 @@ fn test_4_should_not_capture_array() {
}
};
c();

// We also do not need to capture an array
// behind a reference (#112607)
let array: &[i32; 3] = &[0; 3];
let c = #[rustc_capture_analysis]
|| {
//~^ First Pass analysis includes:
match array {
[_, _, _] => {}
}
};
c();

// We should still not insert a read if the array is inside an
// irrefutable pattern
struct Foo<T>(T);
let f = &Foo(&[10; 3]);
let c = #[rustc_capture_analysis]
|| {
//~^ First Pass analysis includes:
match f {
Foo([_, _, _]) => ()
}
};
c();
}

// Testing MultiVariant patterns
Expand Down
58 changes: 40 additions & 18 deletions tests/ui/closures/2229_closure_analysis/match/patterns-capture-analysis.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -109,7 +109,29 @@ LL | | };
| |_____^

error: First Pass analysis includes:
--> $DIR/patterns-capture-analysis.rs:105:5
--> $DIR/patterns-capture-analysis.rs:95:5
|
LL | / || {
LL | |
LL | | match array {
LL | | [_, _, _] => {}
LL | | }
LL | | };
| |_____^

error: First Pass analysis includes:
--> $DIR/patterns-capture-analysis.rs:108:5
|
LL | / || {
LL | |
LL | | match f {
LL | | Foo([_, _, _]) => ()
LL | | }
LL | | };
| |_____^

error: First Pass analysis includes:
--> $DIR/patterns-capture-analysis.rs:130:5
|
LL | / || {
LL | |
Expand All @@ -121,13 +143,13 @@ LL | | };
| |_____^
|
note: Capturing variant[] -> ImmBorrow
--> $DIR/patterns-capture-analysis.rs:108:15
--> $DIR/patterns-capture-analysis.rs:133:15
|
LL | match variant {
| ^^^^^^^

error: Min Capture analysis includes:
--> $DIR/patterns-capture-analysis.rs:105:5
--> $DIR/patterns-capture-analysis.rs:130:5
|
LL | / || {
LL | |
Expand All @@ -139,13 +161,13 @@ LL | | };
| |_____^
|
note: Min Capture variant[] -> ImmBorrow
--> $DIR/patterns-capture-analysis.rs:108:15
--> $DIR/patterns-capture-analysis.rs:133:15
|
LL | match variant {
| ^^^^^^^

error: First Pass analysis includes:
--> $DIR/patterns-capture-analysis.rs:123:5
--> $DIR/patterns-capture-analysis.rs:148:5
|
LL | / || {
LL | |
Expand All @@ -157,13 +179,13 @@ LL | | };
| |_____^
|
note: Capturing slice[] -> ImmBorrow
--> $DIR/patterns-capture-analysis.rs:126:15
--> $DIR/patterns-capture-analysis.rs:151:15
|
LL | match slice {
| ^^^^^

error: Min Capture analysis includes:
--> $DIR/patterns-capture-analysis.rs:123:5
--> $DIR/patterns-capture-analysis.rs:148:5
|
LL | / || {
LL | |
Expand All @@ -175,13 +197,13 @@ LL | | };
| |_____^
|
note: Min Capture slice[] -> ImmBorrow
--> $DIR/patterns-capture-analysis.rs:126:15
--> $DIR/patterns-capture-analysis.rs:151:15
|
LL | match slice {
| ^^^^^

error: First Pass analysis includes:
--> $DIR/patterns-capture-analysis.rs:135:5
--> $DIR/patterns-capture-analysis.rs:160:5
|
LL | / || {
LL | |
Expand All @@ -193,13 +215,13 @@ LL | | };
| |_____^
|
note: Capturing slice[] -> ImmBorrow
--> $DIR/patterns-capture-analysis.rs:138:15
--> $DIR/patterns-capture-analysis.rs:163:15
|
LL | match slice {
| ^^^^^

error: Min Capture analysis includes:
--> $DIR/patterns-capture-analysis.rs:135:5
--> $DIR/patterns-capture-analysis.rs:160:5
|
LL | / || {
LL | |
Expand All @@ -211,13 +233,13 @@ LL | | };
| |_____^
|
note: Min Capture slice[] -> ImmBorrow
--> $DIR/patterns-capture-analysis.rs:138:15
--> $DIR/patterns-capture-analysis.rs:163:15
|
LL | match slice {
| ^^^^^

error: First Pass analysis includes:
--> $DIR/patterns-capture-analysis.rs:147:5
--> $DIR/patterns-capture-analysis.rs:172:5
|
LL | / || {
LL | |
Expand All @@ -229,13 +251,13 @@ LL | | };
| |_____^
|
note: Capturing slice[] -> ImmBorrow
--> $DIR/patterns-capture-analysis.rs:150:15
--> $DIR/patterns-capture-analysis.rs:175:15
|
LL | match slice {
| ^^^^^

error: Min Capture analysis includes:
--> $DIR/patterns-capture-analysis.rs:147:5
--> $DIR/patterns-capture-analysis.rs:172:5
|
LL | / || {
LL | |
Expand All @@ -247,13 +269,13 @@ LL | | };
| |_____^
|
note: Min Capture slice[] -> ImmBorrow
--> $DIR/patterns-capture-analysis.rs:150:15
--> $DIR/patterns-capture-analysis.rs:175:15
|
LL | match slice {
| ^^^^^

error: First Pass analysis includes:
--> $DIR/patterns-capture-analysis.rs:164:5
--> $DIR/patterns-capture-analysis.rs:189:5
|
LL | / || {
LL | |
Expand All @@ -264,5 +286,5 @@ LL | | }
LL | | };
| |_____^

error: aborting due to 16 previous errors
error: aborting due to 18 previous errors