diff options
| -rw-r--r-- | compiler/rustc_abi/src/layout.rs | 30 |
1 files changed, 18 insertions, 12 deletions
diff --git a/compiler/rustc_abi/src/layout.rs b/compiler/rustc_abi/src/layout.rs index 5252472261f..e73170c01f8 100644 --- a/compiler/rustc_abi/src/layout.rs +++ b/compiler/rustc_abi/src/layout.rs @@ -11,6 +11,24 @@ use crate::{ Variants, WrappingRange, }; +// A variant is absent if it's uninhabited and only has ZST fields. +// Present uninhabited variants only require space for their fields, +// but *not* an encoding of the discriminant (e.g., a tag value). +// See issue #49298 for more details on the need to leave space +// for non-ZST uninhabited data (mostly partial initialization). +fn absent<'a, FieldIdx, VariantIdx, F>(fields: &IndexSlice<FieldIdx, F>) -> bool +where + FieldIdx: Idx, + VariantIdx: Idx, + F: Deref<Target = &'a LayoutS<FieldIdx, VariantIdx>> + fmt::Debug, +{ + let uninhabited = fields.iter().any(|f| f.abi.is_uninhabited()); + // We cannot ignore alignment; that might lead us to entirely discard a variant and + // produce an enum that is less aligned than it should be! + let is_1zst = fields.iter().all(|f| f.is_1zst()); + uninhabited && is_1zst +} + pub trait LayoutCalculator { type TargetDataLayoutRef: Borrow<TargetDataLayout>; @@ -168,18 +186,6 @@ pub trait LayoutCalculator { Scalar::Initialized { value, valid_range: WrappingRange::full(size) } }; - // A variant is absent if it's uninhabited and only has ZST fields. - // Present uninhabited variants only require space for their fields, - // but *not* an encoding of the discriminant (e.g., a tag value). - // See issue #49298 for more details on the need to leave space - // for non-ZST uninhabited data (mostly partial initialization). - let absent = |fields: &IndexSlice<FieldIdx, F>| { - let uninhabited = fields.iter().any(|f| f.abi.is_uninhabited()); - // We cannot ignore alignment; that might lead us to entirely discard a variant and - // produce an enum that is less aligned than it should be! - let is_1zst = fields.iter().all(|f| f.is_1zst()); - uninhabited && is_1zst - }; let (present_first, present_second) = { let mut present_variants = variants .iter_enumerated() |