Replace `BorrowckResults` with `Borrowck`.

The results of most analyses end up in a `Results<'tcx, A>`, where `A`
is the analysis. It's then possible to traverse the results via a
`ResultsVisitor`, which relies on the `ResultsVisitable` trait. (That
trait ends up using the same `apply_*` methods that were used when
computing the analysis, albeit indirectly.)

This pattern of "compute analysis results, then visit them" is common.
But there is one exception. For borrow checking we compute three
separate analyses (`Borrows`, `MaybeUninitializedPlaces`, and
`EverInitializedPlaces`), combine them into a single `BorrowckResults`,
and then do a single visit of that `BorrowckResults` with
`MirBorrowckResults`. `BorrowckResults` is just different enough from
`Results` that it requires the existence of `ResultsVisitable`, which
abstracts over the traversal differences between `Results` and
`BorrowckResults`.

This commit changes things by introducing `Borrowck` and bundling the
three borrowck analysis results into a standard `Results<Borrowck>`
instead of the exceptional `BorrowckResults`. Once that's done, the
results can be visited like any other analysis results.
`BorrowckResults` is removed, as is `impl ResultsVisitable for
BorrowckResults`. (It's instructive to see how similar the added `impl
Analysis for Borrowck` is to the removed `impl ResultsVisitable for
BorrowckResults`. They're both doing exactly the same things.)

Overall this increases the number of lines of code and might not seem
like a win. But it enables the removal of `ResultsVisitable` in the next
commit, which results in many simplifications.

3 files changed, 6 insertions, 6 deletions

diff --git a/compiler/rustc_mir_dataflow/src/framework/mod.rs b/compiler/rustc_mir_dataflow/src/framework/mod.rs
index 8f81da8bb04..4ad68193528 100644
--- a/compiler/rustc_mir_dataflow/src/framework/mod.rs
+++ b/compiler/rustc_mir_dataflow/src/framework/mod.rs
@@ -55,7 +55,7 @@ mod visitor;
 pub use self::cursor::ResultsCursor;
 pub use self::direction::{Backward, Direction, Forward};
 pub use self::lattice::{JoinSemiLattice, MaybeReachable};
-pub use self::results::Results;
+pub use self::results::{EntrySets, Results};
 pub use self::visitor::{ResultsVisitable, ResultsVisitor, visit_results};
 
 /// Analysis domains are all bitsets of various kinds. This trait holds
diff --git a/compiler/rustc_mir_dataflow/src/framework/results.rs b/compiler/rustc_mir_dataflow/src/framework/results.rs
index 366fcbf33ba..2269c4ec226 100644
--- a/compiler/rustc_mir_dataflow/src/framework/results.rs
+++ b/compiler/rustc_mir_dataflow/src/framework/results.rs
@@ -18,7 +18,7 @@ use crate::errors::{
     DuplicateValuesFor, PathMustEndInFilename, RequiresAnArgument, UnknownFormatter,
 };
 
-type EntrySets<'tcx, A> = IndexVec<BasicBlock, <A as Analysis<'tcx>>::Domain>;
+pub type EntrySets<'tcx, A> = IndexVec<BasicBlock, <A as Analysis<'tcx>>::Domain>;
 
 /// A dataflow analysis that has converged to fixpoint.
 #[derive(Clone)]
@@ -27,7 +27,7 @@ where
     A: Analysis<'tcx>,
 {
     pub analysis: A,
-    pub(super) entry_sets: EntrySets<'tcx, A>,
+    pub entry_sets: EntrySets<'tcx, A>,
 }
 
 impl<'tcx, A> Results<'tcx, A>
diff --git a/compiler/rustc_mir_dataflow/src/lib.rs b/compiler/rustc_mir_dataflow/src/lib.rs
index b404e3bfb72..8ebe7d59309 100644
--- a/compiler/rustc_mir_dataflow/src/lib.rs
+++ b/compiler/rustc_mir_dataflow/src/lib.rs
@@ -18,9 +18,9 @@ pub use self::drop_flag_effects::{
     move_path_children_matching, on_all_children_bits, on_lookup_result_bits,
 };
 pub use self::framework::{
-    Analysis, Backward, Direction, Forward, GenKill, JoinSemiLattice, MaybeReachable, Results,
-    ResultsCursor, ResultsVisitable, ResultsVisitor, SwitchIntEdgeEffects, fmt, graphviz, lattice,
-    visit_results,
+    Analysis, Backward, Direction, EntrySets, Forward, GenKill, JoinSemiLattice, MaybeReachable,
+    Results, ResultsCursor, ResultsVisitable, ResultsVisitor, SwitchIntEdgeEffects, fmt, graphviz,
+    lattice, visit_results,
 };
 use self::move_paths::MoveData;