Remove ResultsVisitable.

Now that `Results` is the only impl of `ResultsVisitable`, the trait can
be removed. This simplifies things by removining unnecessary layers of
indirection and abstraction.

- `ResultsVisitor` is simpler.
  - Its type parameter changes from `R` (an analysis result) to the
    simpler `A` (an analysis).
  - It no longer needs the `Domain` associated type, because it can use
    `A::Domain`.
  - Occurrences of `R` become `Results<'tcx, A>`, because there is now
    only one kind of analysis results.

- `save_as_intervals` also changes type parameter from `R` to `A`.

- The `results.reconstruct_*` method calls are replaced with
  `results.analysis.apply_*` method calls, which are equivalent.

- `Direction::visit_results_in_block` is simpler, with a single generic
  param (`A`) instead of two (`D` and `R`/`F`, with a bound connecting
  them). Likewise for `visit_results`.

- The `ResultsVisitor` impls for `MirBorrowCtxt` and
  `StorageConflictVisitor` are now specific about the type of the
  analysis results they work with. They both used to have a type param
  `R` but they weren't genuinely generic. In both cases there was only a
  single results type that made sense to instantiate them with.

compiler/rustc_mir_transform/src/coroutine.rs

@@ -68,11 +68,11 @@ use rustc_middle::ty::{
     self, CoroutineArgs, CoroutineArgsExt, GenericArgsRef, InstanceKind, Ty, TyCtxt, TypingMode,
 };
 use rustc_middle::{bug, span_bug};
-use rustc_mir_dataflow::Analysis;
 use rustc_mir_dataflow::impls::{
     MaybeBorrowedLocals, MaybeLiveLocals, MaybeRequiresStorage, MaybeStorageLive,
 };
 use rustc_mir_dataflow::storage::always_storage_live_locals;
+use rustc_mir_dataflow::{Analysis, Results, ResultsVisitor};
 use rustc_span::Span;
 use rustc_span::def_id::{DefId, LocalDefId};
 use rustc_span::symbol::sym;
@@ -817,9 +817,9 @@ impl ops::Deref for CoroutineSavedLocals {
 /// computation; see `CoroutineLayout` for more.
 fn compute_storage_conflicts<'mir, 'tcx>(
     body: &'mir Body<'tcx>,
-    saved_locals: &CoroutineSavedLocals,
+    saved_locals: &'mir CoroutineSavedLocals,
     always_live_locals: BitSet<Local>,
-    mut requires_storage: rustc_mir_dataflow::Results<'tcx, MaybeRequiresStorage<'mir, 'tcx>>,
+    mut requires_storage: Results<'tcx, MaybeRequiresStorage<'mir, 'tcx>>,
 ) -> BitMatrix<CoroutineSavedLocal, CoroutineSavedLocal> {
     assert_eq!(body.local_decls.len(), saved_locals.domain_size());
 
@@ -877,15 +877,13 @@ struct StorageConflictVisitor<'a, 'tcx> {
     eligible_storage_live: BitSet<Local>,
 }
 
-impl<'a, 'tcx, R> rustc_mir_dataflow::ResultsVisitor<'a, 'tcx, R>
+impl<'a, 'tcx> ResultsVisitor<'a, 'tcx, MaybeRequiresStorage<'a, 'tcx>>
     for StorageConflictVisitor<'a, 'tcx>
 {
-    type Domain = BitSet<Local>;
-
     fn visit_statement_before_primary_effect(
         &mut self,
-        _results: &mut R,
-        state: &Self::Domain,
+        _results: &mut Results<'tcx, MaybeRequiresStorage<'a, 'tcx>>,
+        state: &BitSet<Local>,
         _statement: &'a Statement<'tcx>,
         loc: Location,
     ) {
@@ -894,8 +892,8 @@ impl<'a, 'tcx, R> rustc_mir_dataflow::ResultsVisitor<'a, 'tcx, R>
 
     fn visit_terminator_before_primary_effect(
         &mut self,
-        _results: &mut R,
-        state: &Self::Domain,
+        _results: &mut Results<'tcx, MaybeRequiresStorage<'a, 'tcx>>,
+        state: &BitSet<Local>,
         _terminator: &'a Terminator<'tcx>,
         loc: Location,
     ) {

compiler/rustc_mir_transform/src/dataflow_const_prop.rs

@@ -941,16 +941,12 @@ fn try_write_constant<'tcx>(
     interp_ok(())
 }
 
-impl<'mir, 'tcx> ResultsVisitor<'mir, 'tcx, Results<'tcx, ConstAnalysis<'_, 'tcx>>>
-    for Collector<'_, 'tcx>
-{
-    type Domain = State<FlatSet<Scalar>>;
-
+impl<'mir, 'tcx> ResultsVisitor<'mir, 'tcx, ConstAnalysis<'_, 'tcx>> for Collector<'_, 'tcx> {
     #[instrument(level = "trace", skip(self, results, statement))]
     fn visit_statement_before_primary_effect(
         &mut self,
         results: &mut Results<'tcx, ConstAnalysis<'_, 'tcx>>,
-        state: &Self::Domain,
+        state: &State<FlatSet<Scalar>>,
         statement: &'mir Statement<'tcx>,
         location: Location,
     ) {
@@ -972,7 +968,7 @@ impl<'mir, 'tcx> ResultsVisitor<'mir, 'tcx, Results<'tcx, ConstAnalysis<'_, 'tcx
     fn visit_statement_after_primary_effect(
         &mut self,
         results: &mut Results<'tcx, ConstAnalysis<'_, 'tcx>>,
-        state: &Self::Domain,
+        state: &State<FlatSet<Scalar>>,
         statement: &'mir Statement<'tcx>,
         location: Location,
     ) {
@@ -997,7 +993,7 @@ impl<'mir, 'tcx> ResultsVisitor<'mir, 'tcx, Results<'tcx, ConstAnalysis<'_, 'tcx
     fn visit_terminator_before_primary_effect(
         &mut self,
         results: &mut Results<'tcx, ConstAnalysis<'_, 'tcx>>,
-        state: &Self::Domain,
+        state: &State<FlatSet<Scalar>>,
         terminator: &'mir Terminator<'tcx>,
         location: Location,
     ) {