Refactor call terminator to always hold a destination place

Author: JakobDegen

compiler/rustc_borrowck/src/constraint_generation.rs

@@ -140,9 +140,7 @@ impl<'cg, 'cx, 'tcx> Visitor<'tcx> for ConstraintGeneration<'cg, 'cx, 'tcx> {
         // A `Call` terminator's return value can be a local which has borrows,
         // so we need to record those as `killed` as well.
         if let TerminatorKind::Call { destination, .. } = terminator.kind {
-            if let Some((place, _)) = destination {
-                self.record_killed_borrows_for_place(place, location);
-            }
+            self.record_killed_borrows_for_place(destination, location);
         }
 
         self.super_terminator(terminator, location);

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -2198,10 +2198,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 "annotate_argument_and_return_for_borrow: target={:?} terminator={:?}",
                 target, terminator
             );
-            if let TerminatorKind::Call { destination: Some((place, _)), args, .. } =
+            if let TerminatorKind::Call { destination, target: Some(_), args, .. } =
                 &terminator.kind
             {
-                if let Some(assigned_to) = place.as_local() {
+                if let Some(assigned_to) = destination.as_local() {
                     debug!(
                         "annotate_argument_and_return_for_borrow: assigned_to={:?} args={:?}",
                         assigned_to, args