These passes were buggy, MIR building is now responsible for
canonicalizing `ConstantIndex` projections and `MoveData` is responsible
for splitting `Subslice` projections.
* `min_length` is now exact for const index elements.
* const index elements are always from the start.
* make array `Subslice` `PlaceElems` count both `from` and `to` from the
start.
This prepares the code base for when projection is interned. Place's
projection field is going to be `&List<PlaceElem<'tcx>>` so we won't be
able to pattern match against it.
The commit should have changed comments as well.
At the time of writting, it passes the tidy and check tool.
Revisions asked by eddyb :
- Renamed of all the occurences of {visit/super}_mir
- Renamed test structures `CachedMir` to `Cached`
Fixing the missing import on `AggregateKind`
Once upon a time (commit 9bd35c07c26) there were two kinds of
projection: one for places, and one for constants. It therefore made
sense to share the `Projection` struct for both. Although the different
use-cases used different concrete types, sharing was made possible by
type-parameterisation of `Projection`.
Since then, however, the usage of projections in constants has
disappeared, meaning that (forgetting lifetimes for a moment) the
parameterised type is only every instantiated under one guise. So it may
as well be a concrete type.
This commit extends previous work to kill borrows from a local after
assignment into that local to kill borrows from a projection after
assignment into a prefix of that place.
Enum layout optimizations mean that the discriminant of an enum may not
be stored in a tag disjoint from the rest of the fields of the enum.
Stop borrow checking as though they are.
Previously, we would split the drop access into multiple checks for each
field of a struct/tuple/closure and through `Box` dereferences. This
changes this to check if the borrow is accessed by the drop in
places_conflict.
This also allows us to handle enums in a simpler way, since we don't
have to construct any new places.
