`rustc_mir_dataflow/src/elaborate_drops.rs` contains some infrastructure
used by a few MIR passes: the `elaborate_drop` function, the
`DropElaborator` trait, etc.
`rustc_mir_transform/src/elaborate_drops.rs` (same file name, different
crate) contains the `ElaborateDrops` pass. It relies on a lot of the
infrastructure from `rustc_mir_dataflow/src/elaborate_drops.rs`.
It turns out that the drop infrastructure is only used in
`rustc_mir_transform`, so this commit moves it there. (The only
exception is the small `DropFlagState` type, which is moved to the
existing `rustc_mir_dataflow/src/drop_flag_effects.rs`.) The file is
renamed from `rustc_mir_dataflow/src/elaborate_drops.rs` to
`rustc_mir_transform/src/elaborate_drop.rs` (with no trailing `s`)
because (a) the `elaborate_drop` function is the most important export,
and (b) `rustc_mir_transform/src/elaborate_drops.rs` already exists.
All the infrastructure pieces that used to be `pub` are now
`pub(crate)`, because they are now only used within
`rustc_mir_transform`.
Current `SwitchInt` handling has complicated control flow.
- The dataflow engine calls `Analysis::apply_switch_int_edge_effects`,
passing in an "applier" that impls `SwitchIntEdgeEffects`.
- `apply_switch_int_edge_effects` possibly calls `apply` on the applier,
passing it a closure.
- The `apply` method calls the closure on each `SwitchInt` edge.
- The closure operates on the edge.
I.e. control flow goes from the engine, to the analysis, to the applier
(which came from the engine), to the closure (which came from the
analysis). It took me a while to work this out.
This commit changes to a simpler structure that maintains the important
characteristics.
- The dataflow engine calls `Analysis::get_switch_int_data`.
- `get_switch_int_data` returns an `Option<Self::SwitchIntData>` value.
- If that returned value was `Some`, the dataflow engine calls
`Analysis::apply_switch_int_edge_effect` on each edge, passing the
`Self::SwitchIntData` value.
- `Analysis::apply_switch_int_edge_effect` operates on the edge.
I.e. control flow goes from the engine, to the analysis, to the
engine, to the analysis.
Added:
- The `Analysis::SwitchIntData` assoc type and the
`Analysis::get_switch_int_data` method. Both only need to be
defined by analyses that look at `SwitchInt` terminators.
- The `MaybePlacesSwitchIntData` struct, which has three fields.
Changes:
- `Analysis::apply_switch_int_edge_effects` becomes
`Analysis::apply_switch_int_edge_effect`, which is a little simpler
because it's dealing with a single edge instead of all edges.
Removed:
- The `SwitchIntEdgeEffects` trait, and its two impls:
`BackwardSwitchIntEdgeEffectsApplier` (which has six fields) and
`ForwardSwitchIntEdgeEffectsApplier` structs (which has four fields).
- The closure.
The new structure is more concise and simpler.
The words "before" and "after" have an obvious temporal meaning, e.g.
`seek_before_primary_effect`,
`visit_statement_{before,after}_primary_effect`. But "before" is also
used to name the effect that occurs before the primary effect of a
statement/terminator; this is `Effect::Before`. This leads to the
confusing possibility of talking about things happening "before/after
the before event".
This commit removes this awkward overloading of "before" by renaming
`Effect::Before` as `Effect::Early`. It also renames some of the
`Analysis` and `ResultsVisitor` methods to be more consistent.
Here are the before and after names:
- `Effect::{Before,Primary}` -> `Effect::{Early,Primary}`
- `apply_before_statement_effect` -> `apply_early_statement_effect`
- `apply_statement_effect` -> `apply_primary_statement_effect`
- `visit_statement_before_primary_effect` -> `visit_after_early_statement_effect`
- `visit_statement_after_primary_effect` -> `visit_after_primary_statement_effect`
(And s/statement/terminator/ for all the terminator events.)
Currently they are called (most common) `state`, or `trans`, or (rare)
`on_entry`. I think `trans` is short for "transfer function", which
perhaps made more sense when `GenKillAnalysis` existed. Using `state`
everywhere now is more consistent.
They are only present because it's currently defined in terms of the
domains of `Borrows` and `MaybeUninitializedPlaces` and
`EverInitializedPlaces` via associated types. This commit introduces
typedefs for those domains, avoiding the lifetimes.
The part about zero-sized structures is totally wrong. The rest of
it has almost no explanatory value; there are better explanations in
comments elsewhere.
It's a performance win because `MixedBitSet` is faster and uses less
memory than `ChunkedBitSet`.
Also reflow some overlong comment lines in
`lint_tail_expr_drop_order.rs`.
Remove the `DefinitelyInitializedPlaces` analysis.
Its only use is in the `tests/ui/mir-dataflow/def_inits-1.rs` where it is tested via `rustc_peek_definite_init`.
Also, it's probably buggy. It's supposed to be the inverse of `MaybeUninitializedPlaces`, and it mostly is, except that `apply_terminator_effect` is a little different, and `apply_switch_int_edge_effects` is missing. Unlike `MaybeUninitializedPlaces`, which is used extensively in borrow checking, any bugs in `DefinitelyInitializedPlaces` are easy to overlook because it is only used in one small test.
This commit removes the analysis. It also removes
`rustc_peek_definite_init`, `Dual` and `MeetSemiLattice`, all of which are no longer needed.
r? ``@cjgillot``
In `MaybeRequiresStorage::apply_before_statement_effect`, call
`transfer_function` directly, as is already done in
`MaybeRequiresStorage::apply_before_terminator_effect`. This makes it clear
that the operation doesn't rely on the `MaybeBorrowedLocals` results.
Its only use is in the `tests/ui/mir-dataflow/def_inits-1.rs` where it
is tested via `rustc_peek_definite_init`.
Also, it's probably buggy. It's supposed to be the inverse of
`MaybeUninitializedPlaces`, and it mostly is, except that
`apply_terminator_effect` is a little different, and
`apply_switch_int_edge_effects` is missing. Unlike
`MaybeUninitializedPlaces`, which is used extensively in borrow
checking, any bugs in `DefinitelyInitializedPlaces` are easy to overlook
because it is only used in one small test.
This commit removes the analysis. It also removes
`rustc_peek_definite_init`, `Dual` and `MeetSemiLattice`, all of which
are no longer needed.
take 2
open up coroutines
tweak the wordings
the lint works up until 2021
We were missing one case, for ADTs, which was
causing `Result` to yield incorrect results.
only include field spans with significant types
deduplicate and eliminate field spans
switch to emit spans to impl Drops
Co-authored-by: Niko Matsakis <nikomat@amazon.com>
collect drops instead of taking liveness diff
apply some suggestions and add explantory notes
small fix on the cache
let the query recurse through coroutine
new suggestion format with extracted variable name
fine-tune the drop span and messages
bugfix on runtime borrows
tweak message wording
filter out ecosystem types earlier
apply suggestions
clippy
check lint level at session level
further restrict applicability of the lint
translate bid into nop for stable mir
detect cycle in type structure
`GenKillAnalysis` has very similar methods to `Analysis`, but the first
two have a notable difference: the second argument is `&mut impl
GenKill<Self::Idx>` instead of `&mut Self::Domain`. But thanks to the
previous commit, this difference is no longer necessary.
- Replace non-standard names like 's, 'p, 'rg, 'ck, 'parent, 'this, and
'me with vanilla 'a. These are cases where the original name isn't
really any more informative than 'a.
- Replace names like 'cx, 'mir, and 'body with vanilla 'a when the lifetime
applies to multiple fields and so the original lifetime name isn't
really accurate.
- Put 'tcx last in lifetime lists, and 'a before 'b.
No analysis needs `Copy`, and `MaybeBorrowedLocals` is the only analysis
that needs `Clone`. In `locals_live_across_suspend_points` it gets
cloned so it can be used within a `MaybeRequiresStorage`.
There are four related dataflow structs: `MaybeInitializedPlaces`,
`MaybeUninitializedPlaces`, and `EverInitializedPlaces`,
`DefinitelyInitializedPlaces`. They all have a `&Body` and a
`&MoveData<'tcx>` field. The first three use different lifetimes for the
two fields, but the last one uses the same lifetime for both.
This commit changes the first three to use the same lifetime, removing
the need for one of the lifetimes. Other structs that also lose a
lifetime as a result of this are `LivenessContext`, `LivenessResults`,
`InitializationData`.
It then does similar things in various other structs.
Clean up a few minor refs in `format!` macro, as it has a performance cost. Apparently the compiler is unable to inline `format!("{}", &variable)`, and does a run-time double-reference instead (format macro already does one level referencing). Inlining format args prevents accidental `&` misuse.
