38 lines
1.8 KiB
Rust
38 lines
1.8 KiB
Rust
//! The move-analysis portion of borrowck needs to work in an abstract
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//! domain of lifted `Place`s. Most of the `Place` variants fall into a
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//! one-to-one mapping between the concrete and abstract (e.g., a
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//! field-deref on a local variable, `x.field`, has the same meaning
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//! in both domains). Indexed projections are the exception: `a[x]`
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//! needs to be treated as mapping to the same move path as `a[y]` as
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//! well as `a[13]`, etc. So we map these `x`/`y` values to `()`.
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//!
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//! (In theory, the analysis could be extended to work with sets of
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//! paths, so that `a[0]` and `a[13]` could be kept distinct, while
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//! `a[x]` would still overlap them both. But that is not this
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//! representation does today.)
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use rustc_middle::mir::{PlaceElem, ProjectionElem, ProjectionKind};
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pub(crate) trait Lift {
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fn lift(&self) -> ProjectionKind;
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}
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impl<'tcx> Lift for PlaceElem<'tcx> {
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fn lift(&self) -> ProjectionKind {
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match *self {
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ProjectionElem::Deref => ProjectionElem::Deref,
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ProjectionElem::Field(f, _ty) => ProjectionElem::Field(f, ()),
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ProjectionElem::OpaqueCast(_ty) => ProjectionElem::OpaqueCast(()),
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ProjectionElem::Index(_i) => ProjectionElem::Index(()),
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ProjectionElem::Subslice { from, to, from_end } => {
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ProjectionElem::Subslice { from, to, from_end }
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}
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ProjectionElem::ConstantIndex { offset, min_length, from_end } => {
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ProjectionElem::ConstantIndex { offset, min_length, from_end }
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}
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ProjectionElem::Downcast(a, u) => ProjectionElem::Downcast(a, u),
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ProjectionElem::Subtype(_ty) => ProjectionElem::Subtype(()),
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ProjectionElem::UnwrapUnsafeBinder(_ty) => ProjectionElem::UnwrapUnsafeBinder(()),
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}
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}
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}
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