b0dadff6de
Include the computed alignment of the violating field when rejecting
transparent types with non-trivially aligned ZSTs.
ZST member fields in transparent types must have an alignment of 1 (to
ensure it does not raise the layout requirements of the transparent
field). The current error message looks like this:
LL | struct Foobar(u32, [u32; 0]);
| ^^^^^^^^ has alignment larger than 1
This patch changes the report to include the alignment of the violating
field:
LL | struct Foobar(u32, [u32; 0]);
| ^^^^^^^^ has alignment of 4, which is larger than 1
In case of unknown alignments, it will yield:
LL | struct Foobar<T>(u32, [T; 0]);
| ^^^^^^ may have alignment larger than 1
This allows developers to get a better grasp why a specific field is
rejected. Knowing the alignment of the violating field makes it easier
to judge where that alignment-requirement originates, and thus hopefully
provide better hints on how to mitigate the problem.
This idea was proposed in 2022 in #98071 as part of a bigger change.
This commit simply extracts this error-message change, to decouple it
from the other diagnostic improvements.
91 lines
3.3 KiB
Plaintext
91 lines
3.3 KiB
Plaintext
error[E0690]: transparent struct needs at most one non-zero-sized field, but has 2
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--> $DIR/repr-transparent.rs:26:1
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LL | struct MultipleNonZst(u8, u8);
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| ^^^^^^^^^^^^^^^^^^^^^ -- -- this field is non-zero-sized
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| | |
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| | this field is non-zero-sized
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| needs at most one non-zero-sized field, but has 2
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error[E0690]: transparent struct needs at most one non-zero-sized field, but has 2
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--> $DIR/repr-transparent.rs:32:1
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LL | pub struct StructWithProjection(f32, <f32 as Mirror>::It);
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ --- ------------------- this field is non-zero-sized
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| | |
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| | this field is non-zero-sized
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| needs at most one non-zero-sized field, but has 2
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error[E0691]: zero-sized field in transparent struct has alignment larger than 1
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--> $DIR/repr-transparent.rs:36:32
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LL | struct NontrivialAlignZst(u32, [u16; 0]);
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| ^^^^^^^^ has alignment of 2, which is larger than 1
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error[E0691]: zero-sized field in transparent struct has alignment larger than 1
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--> $DIR/repr-transparent.rs:42:24
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LL | struct GenericAlign<T>(ZstAlign32<T>, u32);
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| ^^^^^^^^^^^^^ has alignment of 32, which is larger than 1
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error[E0084]: unsupported representation for zero-variant enum
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--> $DIR/repr-transparent.rs:44:1
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LL | #[repr(transparent)]
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| ^^^^^^^^^^^^^^^^^^^^
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LL | enum Void {}
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| --------- zero-variant enum
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error[E0731]: transparent enum needs exactly one variant, but has 0
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--> $DIR/repr-transparent.rs:45:1
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LL | enum Void {}
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| ^^^^^^^^^ needs exactly one variant, but has 0
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error[E0690]: the variant of a transparent enum needs at most one non-zero-sized field, but has 2
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--> $DIR/repr-transparent.rs:58:1
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LL | enum TooManyFieldsEnum {
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| ^^^^^^^^^^^^^^^^^^^^^^ needs at most one non-zero-sized field, but has 2
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LL | Foo(u32, String),
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| --- ------ this field is non-zero-sized
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| |
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| this field is non-zero-sized
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error[E0731]: transparent enum needs exactly one variant, but has 2
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--> $DIR/repr-transparent.rs:64:1
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LL | enum MultipleVariants {
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| ^^^^^^^^^^^^^^^^^^^^^ needs exactly one variant, but has 2
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LL | Foo(String),
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| --- variant here
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LL | Bar,
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| --- too many variants in `MultipleVariants`
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error[E0691]: zero-sized field in transparent enum has alignment larger than 1
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--> $DIR/repr-transparent.rs:71:14
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LL | Foo(u32, [u16; 0]),
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| ^^^^^^^^ has alignment of 2, which is larger than 1
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error[E0691]: zero-sized field in transparent enum has alignment larger than 1
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--> $DIR/repr-transparent.rs:76:11
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LL | Foo { bar: ZstAlign32<T>, baz: u32 }
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| ^^^^^^^^^^^^^^^^^^ has alignment of 32, which is larger than 1
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error[E0690]: transparent union needs at most one non-zero-sized field, but has 2
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--> $DIR/repr-transparent.rs:85:1
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LL | union TooManyFields {
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| ^^^^^^^^^^^^^^^^^^^ needs at most one non-zero-sized field, but has 2
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LL | u: u32,
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| ------ this field is non-zero-sized
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LL | s: i32
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| ------ this field is non-zero-sized
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error: aborting due to 11 previous errors
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Some errors have detailed explanations: E0084, E0690, E0691, E0731.
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For more information about an error, try `rustc --explain E0084`.
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