Simplify ResultsHandle.

The `Borrowed` variant is no longer used. This commit removes it, along
with the `as_results_cursor` method that produces it, and renames
`as_results_cursor_mut` as `as_results_cursor`.

Author: nnethercote

compiler/rustc_mir_dataflow/src/framework/cursor.rs

@@ -15,7 +15,6 @@ pub enum ResultsHandle<'a, 'tcx, A>
 where
     A: Analysis<'tcx>,
 {
-    Borrowed(&'a Results<'tcx, A>),
     BorrowedMut(&'a mut Results<'tcx, A>),
     Owned(Results<'tcx, A>),
 }
@@ -28,7 +27,6 @@ where
 
     fn deref(&self) -> &Results<'tcx, A> {
         match self {
-            ResultsHandle::Borrowed(borrowed) => borrowed,
             ResultsHandle::BorrowedMut(borrowed) => borrowed,
             ResultsHandle::Owned(owned) => owned,
         }
@@ -41,9 +39,6 @@ where
 {
     fn deref_mut(&mut self) -> &mut Results<'tcx, A> {
         match self {
-            ResultsHandle::Borrowed(_borrowed) => {
-                panic!("tried to deref_mut a `ResultsHandle::Borrowed")
-            }
             ResultsHandle::BorrowedMut(borrowed) => borrowed,
             ResultsHandle::Owned(owned) => owned,
         }

compiler/rustc_mir_dataflow/src/framework/graphviz.rs

@@ -51,7 +51,7 @@ where
         style: OutputStyle,
     ) -> Self {
         let reachable = mir::traversal::reachable_as_bitset(body);
-        Formatter { cursor: results.as_results_cursor_mut(body).into(), style, reachable }
+        Formatter { cursor: results.as_results_cursor(body).into(), style, reachable }
     }
 
     fn body(&self) -> &'mir Body<'tcx> {

compiler/rustc_mir_dataflow/src/framework/results.rs

@@ -37,18 +37,9 @@ impl<'tcx, A> Results<'tcx, A>
 where
     A: Analysis<'tcx>,
 {
-    /// Creates a `ResultsCursor` that can inspect these `Results`. Immutably borrows the `Results`,
-    /// which is appropriate when the `Results` is used outside the cursor.
+    /// Creates a `ResultsCursor` that mutably borrows the `Results`, which is appropriate when the
+    /// `Results` is also used outside the cursor.
     pub fn as_results_cursor<'mir>(
-        &'mir self,
-        body: &'mir mir::Body<'tcx>,
-    ) -> ResultsCursor<'mir, 'tcx, A> {
-        ResultsCursor::new(body, ResultsHandle::Borrowed(self))
-    }
-
-    /// Creates a `ResultsCursor` that can mutate these `Results`. Mutably borrows the `Results`,
-    /// which is appropriate when the `Results` is used outside the cursor.
-    pub fn as_results_cursor_mut<'mir>(
         &'mir mut self,
         body: &'mir mir::Body<'tcx>,
     ) -> ResultsCursor<'mir, 'tcx, A> {

compiler/rustc_mir_transform/src/coroutine.rs

@@ -680,7 +680,7 @@ fn locals_live_across_suspend_points<'tcx>(
     let mut requires_storage_results =
         MaybeRequiresStorage::new(borrowed_locals_results.into_results_cursor(body))
             .iterate_to_fixpoint(tcx, body, None);
-    let mut requires_storage_cursor = requires_storage_results.as_results_cursor_mut(body);
+    let mut requires_storage_cursor = requires_storage_results.as_results_cursor(body);
 
     // Calculate the liveness of MIR locals ignoring borrows.
     let mut liveness =