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Update RValue::Discriminant documentation

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`RValue::Discriminant` returns zero for types without discriminant.
This guarantee is already documented for `discriminant_value`
intrinsics which is implemented in terms of `RValue::Discriminant`.
This commit is contained in:
Tomasz Miąsko 2022-05-01 00:00:00 +00:00
parent f75d884046
commit b37fb23d9f
1 changed files with 1 additions and 5 deletions
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6
compiler/rustc_middle/src/mir/mod.rs
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@ -2559,16 +2559,12 @@ pub enum Rvalue<'tcx> {
UnaryOp(UnOp, Operand<'tcx>), UnaryOp(UnOp, Operand<'tcx>),
/// Computes the discriminant of the place, returning it as an integer of type /// Computes the discriminant of the place, returning it as an integer of type
/// [`discriminant_ty`]. /// [`discriminant_ty`]. Returns zero for types without discriminant.
/// ///
/// The validity requirements for the underlying value are undecided for this rvalue, see /// The validity requirements for the underlying value are undecided for this rvalue, see
/// [#91095]. Note too that the value of the discriminant is not the same thing as the /// [#91095]. Note too that the value of the discriminant is not the same thing as the
/// variant index; use [`discriminant_for_variant`] to convert. /// variant index; use [`discriminant_for_variant`] to convert.
/// ///
/// For types defined in the source code as enums, this is well behaved. This is also well
/// formed for other types, but yields no particular value - there is no reason it couldn't be
/// defined to yield eg zero though.
///
/// [`discriminant_ty`]: crate::ty::Ty::discriminant_ty /// [`discriminant_ty`]: crate::ty::Ty::discriminant_ty
/// [#91095]: https://github.com/rust-lang/rust/issues/91095 /// [#91095]: https://github.com/rust-lang/rust/issues/91095
/// [`discriminant_for_variant`]: crate::ty::Ty::discriminant_for_variant /// [`discriminant_for_variant`]: crate::ty::Ty::discriminant_for_variant