rustc_target: factor out common fields of non-Single Variants. #59519
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| @@ -1586,8 +1596,11 @@ fn prepare_enum_metadata( | |||
| let layout = cx.layout_of(enum_type); | |||
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| match (&layout.abi, &layout.variants) { | |||
| (&layout::Abi::Scalar(_), &layout::Variants::Tagged {ref tag, .. }) => | |||
| return FinalMetadata(discriminant_type_metadata(tag.value)), | |||
| (&layout::Abi::Scalar(_), &layout::Variants::Multiple { | |||
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I've seen this code twice now (extracting the discr field if disc_kind is Tag. Pull it out into a method returning Option?
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I disagree, these are orthogonal. I didn't want to rewrite too much code, but arguably everything should match on Variants and then match on DiscriminantKind inside the Multiple case.
That way, code common to both niches and tags can be reused. Adding a .tag() method runs counter to that.
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I get that, but the three cases that I saw here all are very "tagged" special and can't share code with the niche part. Or do you see any additional refactorings that can be done here in the future?
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Ah this is the special case for C-like enums. Either way, I don't see a point in catering to this pattern, but I'll leave comments regarding the possibility of refactoring on the other 2 cases.
| discr_kind: layout::DiscriminantKind::Niche { .. }, | ||
| .. | ||
| } => None, | ||
| layout::Variants::Multiple { |
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This is in if use_enum_fallback(cx) and will eventually be removed when we stop supporting LLVM versions that predate the addition of variant debuginfo.
| record(adt_kind.into(), adt_packed, match layout.variants { | ||
| Variants::Tagged { ref tag, .. } => Some(tag.value.size(self)), | ||
| record(adt_kind.into(), adt_packed, match discr_kind { | ||
| DiscriminantKind::Tag => Some(discr.value.size(self)), |
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This whole thing needs to be rewritten to pretty-print layouts losslessly (or we can just use {:#?}, heh).
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@bors r+ |
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📌 Commit 5b7f4e9 has been approved by |
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…li-obk rustc_target: factor out common fields of non-Single Variants. @tmandry and I were discussing ways to generalize the current variants/discriminant layout to allow more fields in the "`enum`" (or another multi-variant types, such as potentially generator state, in the future), shared by all variants, than just the tag/niche discriminant. This refactor should make it easier to extend multi-variant layouts, as nothing is duplicating anymore between "tagged enums" and "niche-filling enums". r? @oli-obk
Rollup of 7 pull requests Successful merges: - #58805 (Lint for redundant imports) - #59506 (Use platform dependent mcount function) - #59519 (rustc_target: factor out common fields of non-Single Variants.) - #59580 (Allow closure to unsafe fn coercion) - #59581 (Stabilize refcell_replace_swap feature) - #59583 (match match match match match) - #59587 (Remove #[doc(hidden)] from Error::type_id) Failed merges: r? @ghost
@tmandry and I were discussing ways to generalize the current variants/discriminant layout to allow more fields in the "
enum" (or another multi-variant types, such as potentially generator state, in the future), shared by all variants, than just the tag/niche discriminant.This refactor should make it easier to extend multi-variant layouts, as nothing is duplicating anymore between "tagged enums" and "niche-filling enums".
r? @oli-obk