Remove dead code after destination propagation

compiler/rustc_mir_transform/src/dest_prop.rs

@@ -129,6 +129,7 @@
 
 use std::collections::hash_map::{Entry, OccupiedEntry};
 
+use crate::simplify::remove_dead_blocks;
 use crate::MirPass;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_index::bit_set::BitSet;
@@ -235,6 +236,12 @@ impl<'tcx> MirPass<'tcx> for DestinationPropagation {
             apply_merges(body, tcx, &merges, &merged_locals);
         }
 
+        if round_count != 0 {
+            // Merging can introduce overlap between moved arguments and/or call destination in an
+            // unreachable code, which validator considers to be ill-formed.
+            remove_dead_blocks(tcx, body);
+        }
+
         trace!(round_count);
     }
 }