diff options
Diffstat (limited to 'compiler/rustc_middle/src/mir/syntax.rs')
| -rw-r--r-- | compiler/rustc_middle/src/mir/syntax.rs | 58 |
1 files changed, 14 insertions, 44 deletions
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs index a6ca04f5e62..6b4489026d3 100644 --- a/compiler/rustc_middle/src/mir/syntax.rs +++ b/compiler/rustc_middle/src/mir/syntax.rs @@ -320,8 +320,10 @@ pub enum StatementKind<'tcx> { /// <https://internals.rust-lang.org/t/stacked-borrows-an-aliasing-model-for-rust/8153/> for /// more details. /// - /// For code that is not specific to stacked borrows, you should consider retags to read - /// and modify the place in an opaque way. + /// For code that is not specific to stacked borrows, you should consider retags to read and + /// modify the place in an opaque way. + /// + /// Only `RetagKind::Default` and `RetagKind::FnEntry` are permitted. Retag(RetagKind, Box<Place<'tcx>>), /// Encodes a user's type ascription. These need to be preserved @@ -562,14 +564,13 @@ pub enum TerminatorKind<'tcx> { Unreachable, /// The behavior of this statement differs significantly before and after drop elaboration. - /// After drop elaboration, `Drop` executes the drop glue for the specified place, after which - /// it continues execution/unwinds at the given basic blocks. It is possible that executing drop - /// glue is special - this would be part of Rust's memory model. (**FIXME**: due we have an - /// issue tracking if drop glue has any interesting semantics in addition to those of a function - /// call?) /// - /// `Drop` before drop elaboration is a *conditional* execution of the drop glue. Specifically, the - /// `Drop` will be executed if... + /// After drop elaboration: `Drop` terminators are a complete nop for types that have no drop + /// glue. For other types, `Drop` terminators behave exactly like a call to + /// `core::mem::drop_in_place` with a pointer to the given place. + /// + /// `Drop` before drop elaboration is a *conditional* execution of the drop glue. Specifically, + /// the `Drop` will be executed if... /// /// **Needs clarification**: End of that sentence. This in effect should document the exact /// behavior of drop elaboration. The following sounds vaguely right, but I'm not quite sure: @@ -890,18 +891,11 @@ pub struct Place<'tcx> { pub projection: &'tcx List<PlaceElem<'tcx>>, } -/// The different kinds of projections that can be used in the projection of a `Place`. -/// -/// `T1` is the generic type for a field projection. For an actual projection on a `Place` -/// this parameter will always be `Ty`, but the field type can be unavailable when -/// building (by using `PlaceBuilder`) places that correspond to upvars. -/// `T2` is the generic type for an `OpaqueCast` (is generic since it's abstracted over -/// in dataflow analysis, see `AbstractElem`). #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)] #[derive(TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)] -pub enum ProjectionElem<V, T1, T2> { +pub enum ProjectionElem<V, T> { Deref, - Field(Field, T1), + Field(Field, T), /// Index into a slice/array. /// /// Note that this does not also dereference, and so it does not exactly correspond to slice @@ -957,36 +951,12 @@ pub enum ProjectionElem<V, T1, T2> { /// Like an explicit cast from an opaque type to a concrete type, but without /// requiring an intermediate variable. - OpaqueCast(T2), + OpaqueCast(T), } /// Alias for projections as they appear in places, where the base is a place /// and the index is a local. -pub type PlaceElem<'tcx> = ProjectionElem<Local, Ty<'tcx>, Ty<'tcx>>; - -/// Alias for projections that appear in `PlaceBuilder::Upvar`, for which -/// we cannot provide any field types. -pub type UpvarProjectionElem<'tcx> = ProjectionElem<Local, (), Ty<'tcx>>; - -impl<'tcx> From<PlaceElem<'tcx>> for UpvarProjectionElem<'tcx> { - fn from(elem: PlaceElem<'tcx>) -> Self { - match elem { - ProjectionElem::Deref => ProjectionElem::Deref, - ProjectionElem::Field(field, _) => ProjectionElem::Field(field, ()), - ProjectionElem::Index(v) => ProjectionElem::Index(v), - ProjectionElem::ConstantIndex { offset, min_length, from_end } => { - ProjectionElem::ConstantIndex { offset, min_length, from_end } - } - ProjectionElem::Subslice { from, to, from_end } => { - ProjectionElem::Subslice { from, to, from_end } - } - ProjectionElem::Downcast(opt_sym, variant_idx) => { - ProjectionElem::Downcast(opt_sym, variant_idx) - } - ProjectionElem::OpaqueCast(ty) => ProjectionElem::OpaqueCast(ty), - } - } -} +pub type PlaceElem<'tcx> = ProjectionElem<Local, Ty<'tcx>>; /////////////////////////////////////////////////////////////////////////// // Operands |