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MIR validation: ensure that downcast projection is followed by field projection

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This commit is contained in:
Ralf Jung
2024-05-27 15:28:51 +02:00
parent cdc509f7c0
commit 7d24f87068
3 changed files with 26 additions and 6 deletions
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4
compiler/rustc_middle/src/mir/syntax.rs
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@@ -1008,8 +1008,8 @@ pub type AssertMessage<'tcx> = AssertKind<Operand<'tcx>>;
/// element:
///
/// - [`Downcast`](ProjectionElem::Downcast): This projection sets the place's variant index to the
/// given one, and makes no other changes. A `Downcast` projection on a place with its variant
/// index already set is not well-formed.
/// given one, and makes no other changes. A `Downcast` projection must always be followed
/// immediately by a `Field` projection.
/// - [`Field`](ProjectionElem::Field): `Field` projections take their parent place and create a
/// place referring to one of the fields of the type. The resulting address is the parent
/// address, plus the offset of the field. The type becomes the type of the field. If the parent