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Add more enum layout tests. The comments will be accurate after the commits which add the relevant layout optimizations.
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‎tests/ui/layout/enum.rs‎

Lines changed: 93 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -22,3 +22,96 @@ enum ScalarPairDifferingSign { //~ERROR: abi: ScalarPair
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A(u8),
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B(i8),
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}
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// Enums with only a single inhabited variant can be laid out as just that variant,
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// if the uninhabited variants are all "absent" (only have 1-ZST fields)
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#[rustc_layout(size, abi)]
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enum AbsentVariantUntagged { //~ERROR: size: Size(4 bytes)
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//~^ ERROR: abi: Scalar(Initialized
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A(i32),
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B((), !),
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}
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// Even if uninhabited variants are not absent, the enum can still be laid out without
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// a tag.
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#[rustc_layout(size, abi)]
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enum UninhabitedVariantUntagged { //~ERROR: size: Size(8 bytes)
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//~^ ERROR: abi: ScalarPair(Initialized
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A(i32),
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B(i32, !),
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}
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// A single-inhabited-variant enum may still be laid out with a tag,
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// if that leads to a better niche for the same size layout.
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// This enum uses the tagged representation, since the untagged representation would be
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// the same size, but without a niche.
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#[rustc_layout(size, abi)]
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enum UninhabitedVariantUntaggedBigger { //~ERROR: size: Size(8 bytes)
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//~^ ERROR: abi: Memory
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A(i32),
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B([u8; 5], !),
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}
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#[rustc_layout(size, abi)]
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enum UninhabitedVariantWithNiche { //~ERROR: size: Size(3 bytes)
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//~^ERROR: abi: Memory
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A(i8, bool),
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B(u8, u8, !),
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}
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#[rustc_layout(debug)]
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enum UninhabitedVariantLargeWithNiche {
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//~^ ERROR: layout_of
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//~| ERROR: size: Size(3 bytes)
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//~| ERROR: backend_repr: Memory
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//~| ERROR: valid_range: 0..=0
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// Should use the tagged representation, since that gives a 255-slot niche,
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// instead of a 254-slot niche if it used the niche-filling representation on the `bool`
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A(i8, bool),
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B(u8, u8, u8, !),
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}
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// This uses the tagged layout, but since all variants are uninhabited, none of them store the tag,
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// so we only need space for the fields, and the abi is Memory.
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#[rustc_layout(size, abi)]
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enum AllUninhabitedVariants { //~ERROR: size: Size(3 bytes)
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//~^ERROR: abi: Memory
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A(i8, bool, !),
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B(u8, u8, !),
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}
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#[repr(align(2))]
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struct AlignedNever(!);
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// Tagged `(i8, padding)`
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#[rustc_layout(size, abi)]
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enum AlignedI8 { //~ERROR: size: Size(2 bytes)
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//~^ERROR: abi: Memory
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A(i8),
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B(AlignedNever)
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}
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// Tagged `(u8, i8, padding, padding)`
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#[rustc_layout(size, abi)]
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enum TaggedI8 { //~ERROR: size: Size(4 bytes)
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//~^ERROR: abi: Memory
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A(i8),
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B(i8, i8, i8, AlignedNever)
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}
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// Tagged `(u16, i16)`
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#[rustc_layout(size, abi)]
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enum TaggedI16 { //~ERROR: size: Size(4 bytes)
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//~^ERROR: abi: Memory
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A(i16),
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B(i8, i8, i8, AlignedNever)
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}
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// This must not use tagged representation, since it's zero-sized.
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#[rustc_layout(size, abi)]
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enum AllUninhabitedVariantsAlignedZst { //~ERROR: size: Size(2 bytes)
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//~^ERROR: abi: Scalar
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A(AlignedNever),
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B(AlignedNever),
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}

‎tests/ui/layout/enum.stderr‎

Lines changed: 227 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -16,5 +16,231 @@ error: abi: ScalarPair(Initialized { value: Int(I8, false), valid_range: 0..=1 }
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LL | enum ScalarPairDifferingSign {
1717
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1818

19-
error: aborting due to 3 previous errors
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error: size: Size(4 bytes)
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--> $DIR/enum.rs:29:1
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|
22+
LL | enum AbsentVariantUntagged {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: abi: Scalar(Initialized { value: Int(I32, true), valid_range: 0..=4294967295 })
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--> $DIR/enum.rs:29:1
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|
28+
LL | enum AbsentVariantUntagged {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: size: Size(8 bytes)
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--> $DIR/enum.rs:38:1
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|
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LL | enum UninhabitedVariantUntagged {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: abi: ScalarPair(Initialized { value: Int(I32, false), valid_range: 0..=0 }, Initialized { value: Int(I32, true), valid_range: 0..=4294967295 })
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--> $DIR/enum.rs:38:1
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|
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LL | enum UninhabitedVariantUntagged {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: size: Size(8 bytes)
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--> $DIR/enum.rs:49:1
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|
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LL | enum UninhabitedVariantUntaggedBigger {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: abi: Memory { sized: true }
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--> $DIR/enum.rs:49:1
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|
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LL | enum UninhabitedVariantUntaggedBigger {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: size: Size(3 bytes)
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--> $DIR/enum.rs:56:1
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|
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LL | enum UninhabitedVariantWithNiche {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: abi: Memory { sized: true }
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--> $DIR/enum.rs:56:1
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|
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LL | enum UninhabitedVariantWithNiche {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: layout_of(UninhabitedVariantLargeWithNiche) = Layout {
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size: Size(4 bytes),
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align: AbiAlign {
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abi: Align(1 bytes),
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},
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backend_repr: Memory {
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sized: true,
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},
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fields: Arbitrary {
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offsets: [
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Size(0 bytes),
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],
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memory_index: [
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0,
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],
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},
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largest_niche: Some(
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Niche {
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offset: Size(0 bytes),
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value: Int(
87+
I8,
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false,
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),
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valid_range: 0..=0,
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},
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),
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uninhabited: false,
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variants: Multiple {
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tag: Initialized {
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value: Int(
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I8,
98+
false,
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),
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valid_range: 0..=0,
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},
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tag_encoding: Direct,
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tag_field: 0,
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variants: [
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Layout {
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size: Size(3 bytes),
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align: AbiAlign {
108+
abi: Align(1 bytes),
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},
110+
backend_repr: Memory {
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sized: true,
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},
113+
fields: Arbitrary {
114+
offsets: [
115+
Size(1 bytes),
116+
Size(2 bytes),
117+
],
118+
memory_index: [
119+
0,
120+
1,
121+
],
122+
},
123+
largest_niche: Some(
124+
Niche {
125+
offset: Size(2 bytes),
126+
value: Int(
127+
I8,
128+
false,
129+
),
130+
valid_range: 0..=1,
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},
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),
133+
uninhabited: false,
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variants: Single {
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index: 0,
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variants: None,
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},
138+
max_repr_align: None,
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unadjusted_abi_align: Align(1 bytes),
140+
randomization_seed: 17394913183323368564,
141+
},
142+
Layout {
143+
size: Size(4 bytes),
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align: AbiAlign {
145+
abi: Align(1 bytes),
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},
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backend_repr: Memory {
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sized: true,
149+
},
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fields: Arbitrary {
151+
offsets: [
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Size(1 bytes),
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Size(2 bytes),
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Size(3 bytes),
155+
Size(4 bytes),
156+
],
157+
memory_index: [
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0,
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1,
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2,
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3,
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],
163+
},
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largest_niche: None,
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uninhabited: true,
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variants: Single {
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index: 1,
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variants: None,
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},
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max_repr_align: None,
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unadjusted_abi_align: Align(1 bytes),
172+
randomization_seed: 17538183959353994357,
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},
174+
],
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},
176+
max_repr_align: None,
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unadjusted_abi_align: Align(1 bytes),
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randomization_seed: 15362464571658798427,
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}
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--> $DIR/enum.rs:63:1
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|
182+
LL | enum UninhabitedVariantLargeWithNiche {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: size: Size(3 bytes)
186+
--> $DIR/enum.rs:77:1
187+
|
188+
LL | enum AllUninhabitedVariants {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
190+
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error: abi: Memory { sized: true }
192+
--> $DIR/enum.rs:77:1
193+
|
194+
LL | enum AllUninhabitedVariants {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: size: Size(2 bytes)
198+
--> $DIR/enum.rs:88:1
199+
|
200+
LL | enum AlignedI8 {
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| ^^^^^^^^^^^^^^
202+
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error: abi: Memory { sized: true }
204+
--> $DIR/enum.rs:88:1
205+
|
206+
LL | enum AlignedI8 {
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| ^^^^^^^^^^^^^^
208+
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error: size: Size(4 bytes)
210+
--> $DIR/enum.rs:96:1
211+
|
212+
LL | enum TaggedI8 {
213+
| ^^^^^^^^^^^^^
214+
215+
error: abi: Memory { sized: true }
216+
--> $DIR/enum.rs:96:1
217+
|
218+
LL | enum TaggedI8 {
219+
| ^^^^^^^^^^^^^
220+
221+
error: size: Size(4 bytes)
222+
--> $DIR/enum.rs:105:1
223+
|
224+
LL | enum TaggedI16 {
225+
| ^^^^^^^^^^^^^^
226+
227+
error: abi: Memory { sized: true }
228+
--> $DIR/enum.rs:105:1
229+
|
230+
LL | enum TaggedI16 {
231+
| ^^^^^^^^^^^^^^
232+
233+
error: size: Size(2 bytes)
234+
--> $DIR/enum.rs:113:1
235+
|
236+
LL | enum AllUninhabitedVariantsAlignedZst {
237+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
238+
239+
error: abi: Scalar(Initialized { value: Int(I16, false), valid_range: 0..=0 })
240+
--> $DIR/enum.rs:113:1
241+
|
242+
LL | enum AllUninhabitedVariantsAlignedZst {
243+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: aborting due to 22 previous errors
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