Use isa instead of dyn_cast (NFC)
diff --git a/lld/ELF/Symbols.cpp b/lld/ELF/Symbols.cpp
index 23f8d3e..2030149 100644
--- a/lld/ELF/Symbols.cpp
+++ b/lld/ELF/Symbols.cpp
@@ -550,7 +550,7 @@
   }
 
   // Undefined symbols in a SharedFile do not change the binding.
-  if (dyn_cast_or_null<SharedFile>(other.file))
+  if (isa_and_nonnull<SharedFile>(other.file))
     return;
 
   if (isUndefined() || isShared()) {
@@ -608,7 +608,7 @@
   auto *oldSym = cast<Defined>(this);
   auto *newSym = cast<Defined>(other);
 
-  if (dyn_cast_or_null<BitcodeFile>(other->file))
+  if (isa_and_nonnull<BitcodeFile>(other->file))
     return 0;
 
   if (!oldSym->section && !newSym->section && oldSym->value == newSym->value &&