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doc comments for layout components

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Ralf Jung 2020-02-17 22:58:24 +01:00
parent 3c4590facc
commit ee49e95e78
1 changed files with 19 additions and 1 deletions
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20
src/librustc_target/abi/mod.rs
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@ -871,8 +871,26 @@ impl Niche {
#[derive(PartialEq, Eq, Hash, Debug, HashStable_Generic)]
pub struct LayoutDetails {
pub variants: Variants,
/// Says where the fields are located.
/// Primitives and fieldless enums appear as unions without fields.
pub fields: FieldPlacement,
/// Encodes information about multi-variant layouts.
/// Even with `Multiple` variants, a layout can still have fields! Those are then
/// shared between all variants. One of them will be the discriminant,
/// but e.g. generators can have more.
///
/// A layout-guided recursive descent must first look at all the fields,
/// and only then check if this is a multi-variant layout and if so, proceed
/// with the active variant.
pub variants: Variants,
/// The `abi` defines how this data is passed between functions, and it defines
/// value restrictions via `valid_range`.
///
/// Note that this is entirely orthogonal to the recursive structrue defined by
/// `variants` and `fields`; for example, `ManuallyDrop<Result<isize, isize>>` has
/// `Abi::ScalarPair`! So, having a non-`Aggregate` `abi` should not stop a recursive descent.
pub abi: Abi,
/// The leaf scalar with the largest number of invalid values