Introduce ProjectionElem::try_map.

3 files changed, 16 insertions, 45 deletions

diff --git a/compiler/rustc_mir_dataflow/src/move_paths/abs_domain.rs b/compiler/rustc_mir_dataflow/src/move_paths/abs_domain.rs
deleted file mode 100644
index d056ad3d4b4..00000000000
--- a/compiler/rustc_mir_dataflow/src/move_paths/abs_domain.rs
+++ /dev/null
@@ -1,38 +0,0 @@
-//! The move-analysis portion of borrowck needs to work in an abstract
-//! domain of lifted `Place`s. Most of the `Place` variants fall into a
-//! one-to-one mapping between the concrete and abstract (e.g., a
-//! field-deref on a local variable, `x.field`, has the same meaning
-//! in both domains). Indexed projections are the exception: `a[x]`
-//! needs to be treated as mapping to the same move path as `a[y]` as
-//! well as `a[13]`, etc. So we map these `x`/`y` values to `()`.
-//!
-//! (In theory, the analysis could be extended to work with sets of
-//! paths, so that `a[0]` and `a[13]` could be kept distinct, while
-//! `a[x]` would still overlap them both. But that is not this
-//! representation does today.)
-
-use rustc_middle::mir::{PlaceElem, ProjectionElem, ProjectionKind};
-
-pub(crate) trait Lift {
-    fn lift(&self) -> ProjectionKind;
-}
-
-impl<'tcx> Lift for PlaceElem<'tcx> {
-    fn lift(&self) -> ProjectionKind {
-        match *self {
-            ProjectionElem::Deref => ProjectionElem::Deref,
-            ProjectionElem::Field(f, _ty) => ProjectionElem::Field(f, ()),
-            ProjectionElem::OpaqueCast(_ty) => ProjectionElem::OpaqueCast(()),
-            ProjectionElem::Index(_i) => ProjectionElem::Index(()),
-            ProjectionElem::Subslice { from, to, from_end } => {
-                ProjectionElem::Subslice { from, to, from_end }
-            }
-            ProjectionElem::ConstantIndex { offset, min_length, from_end } => {
-                ProjectionElem::ConstantIndex { offset, min_length, from_end }
-            }
-            ProjectionElem::Downcast(a, u) => ProjectionElem::Downcast(a, u),
-            ProjectionElem::Subtype(_ty) => ProjectionElem::Subtype(()),
-            ProjectionElem::UnwrapUnsafeBinder(_ty) => ProjectionElem::UnwrapUnsafeBinder(()),
-        }
-    }
-}
diff --git a/compiler/rustc_mir_dataflow/src/move_paths/builder.rs b/compiler/rustc_mir_dataflow/src/move_paths/builder.rs
index 8bbc89fdcec..48718cad597 100644
--- a/compiler/rustc_mir_dataflow/src/move_paths/builder.rs
+++ b/compiler/rustc_mir_dataflow/src/move_paths/builder.rs
@@ -7,7 +7,6 @@ use rustc_middle::{bug, span_bug};
 use smallvec::{SmallVec, smallvec};
 use tracing::debug;
 
-use super::abs_domain::Lift;
 use super::{
     Init, InitIndex, InitKind, InitLocation, LocationMap, LookupResult, MoveData, MoveOut,
     MoveOutIndex, MovePath, MovePathIndex, MovePathLookup,
@@ -241,7 +240,7 @@ impl<'a, 'tcx, F: Fn(Ty<'tcx>) -> bool> MoveDataBuilder<'a, 'tcx, F> {
             if union_path.is_none() {
                 // inlined from add_move_path because of a borrowck conflict with the iterator
                 base =
-                    *data.rev_lookup.projections.entry((base, elem.lift())).or_insert_with(|| {
+                    *data.rev_lookup.projections.entry((base, elem.kind())).or_insert_with(|| {
                         new_move_path(
                             &mut data.move_paths,
                             &mut data.path_map,
@@ -272,7 +271,7 @@ impl<'a, 'tcx, F: Fn(Ty<'tcx>) -> bool> MoveDataBuilder<'a, 'tcx, F> {
             tcx,
             ..
         } = self;
-        *rev_lookup.projections.entry((base, elem.lift())).or_insert_with(move || {
+        *rev_lookup.projections.entry((base, elem.kind())).or_insert_with(move || {
             new_move_path(move_paths, path_map, init_path_map, Some(base), mk_place(*tcx))
         })
     }
diff --git a/compiler/rustc_mir_dataflow/src/move_paths/mod.rs b/compiler/rustc_mir_dataflow/src/move_paths/mod.rs
index 18985ba0da2..80fb47bc6e1 100644
--- a/compiler/rustc_mir_dataflow/src/move_paths/mod.rs
+++ b/compiler/rustc_mir_dataflow/src/move_paths/mod.rs
@@ -1,3 +1,16 @@
+//! The move-analysis portion of borrowck needs to work in an abstract
+//! domain of lifted `Place`s. Most of the `Place` variants fall into a
+//! one-to-one mapping between the concrete and abstract (e.g., a
+//! field-deref on a local variable, `x.field`, has the same meaning
+//! in both domains). Indexed projections are the exception: `a[x]`
+//! needs to be treated as mapping to the same move path as `a[y]` as
+//! well as `a[13]`, etc. So we map these `x`/`y` values to `()`.
+//!
+//! (In theory, the analysis could be extended to work with sets of
+//! paths, so that `a[0]` and `a[13]` could be kept distinct, while
+//! `a[x]` would still overlap them both. But that is not this
+//! representation does today.)
+
 use std::fmt;
 use std::ops::{Index, IndexMut};
 
@@ -8,11 +21,8 @@ use rustc_middle::ty::{Ty, TyCtxt};
 use rustc_span::Span;
 use smallvec::SmallVec;
 
-use self::abs_domain::Lift;
 use crate::un_derefer::UnDerefer;
 
-mod abs_domain;
-
 rustc_index::newtype_index! {
     #[orderable]
     #[debug_format = "mp{}"]
@@ -324,7 +334,7 @@ impl<'tcx> MovePathLookup<'tcx> {
         };
 
         for (_, elem) in self.un_derefer.iter_projections(place) {
-            if let Some(&subpath) = self.projections.get(&(result, elem.lift())) {
+            if let Some(&subpath) = self.projections.get(&(result, elem.kind())) {
                 result = subpath;
             } else {
                 return LookupResult::Parent(Some(result));