Auto merge of #55221 - matthewjasper:fewer-duplicate-migrate-messages, r=pnkfelix

Don't emit cannot move errors twice in migrate mode

Closes #55154
cc #53004

r? @pnkfelix

Author: bors

src/librustc_mir/borrow_check/mod.rs

@@ -1831,7 +1831,10 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
             | Write(wk @ WriteKind::StorageDeadOrDrop)
             | Write(wk @ WriteKind::MutableBorrow(BorrowKind::Shared))
             | Write(wk @ WriteKind::MutableBorrow(BorrowKind::Shallow)) => {
-                if let Err(_place_err) = self.is_mutable(place, is_local_mutation_allowed) {
+                if let (Err(_place_err), true) = (
+                    self.is_mutable(place, is_local_mutation_allowed),
+                    self.errors_buffer.is_empty()
+                ) {
                     if self.infcx.tcx.migrate_borrowck() {
                         // rust-lang/rust#46908: In pure NLL mode this
                         // code path should be unreachable (and thus
@@ -1855,12 +1858,11 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
                             location,
                         );
                     } else {
-                        self.infcx.tcx.sess.delay_span_bug(
+                        span_bug!(
                             span,
-                            &format!(
-                                "Accessing `{:?}` with the kind `{:?}` shouldn't be possible",
-                                place, kind
-                            ),
+                            "Accessing `{:?}` with the kind `{:?}` shouldn't be possible",
+                            place,
+                            kind,
                         );
                     }
                 }

src/librustc_mir/borrow_check/mutability_errors.rs

@@ -180,9 +180,9 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
             AccessKind::Move => {
                 err = self.infcx.tcx
                     .cannot_move_out_of(span, &(item_msg + &reason), Origin::Mir);
-                act = "move";
-                acted_on = "moved";
-                span
+                err.span_label(span, "cannot move");
+                err.buffer(&mut self.errors_buffer);
+                return;
             }
             AccessKind::Mutate => {
                 err = self.infcx.tcx