Void is not required to be `null` anymore.

runtime/vm/flow_graph_compiler_arm64.cc

Index: runtime/vm/flow_graph_compiler_arm64.cc
diff --git a/runtime/vm/flow_graph_compiler_arm64.cc b/runtime/vm/flow_graph_compiler_arm64.cc
index d320028ed281ed224ef0ced56b684e116fa838c6..14d744a837a7293930e4db33363acf917cc629d2 100644
--- a/runtime/vm/flow_graph_compiler_arm64.cc
+++ b/runtime/vm/flow_graph_compiler_arm64.cc
@@ -505,11 +505,6 @@ RawSubtypeTestCache* FlowGraphCompiler::GenerateInlineInstanceof(
     Label* is_instance_lbl,
     Label* is_not_instance_lbl) {
   __ Comment("InlineInstanceof");
-  if (type.IsVoidType()) {
-    // A non-null value is returned from a void function, which will result in a
-    // type error. A null value is handled prior to executing this inline code.
-    return SubtypeTestCache::null();
-  }
   if (type.IsInstantiated()) {
     const Class& type_class = Class::ZoneHandle(zone(), type.type_class());
     // A class equality check is only applicable with a dst type (not a
@@ -552,7 +547,7 @@ void FlowGraphCompiler::GenerateInstanceOf(TokenPosition token_pos,
                                            bool negate_result,
                                            LocationSummary* locs) {
   ASSERT(type.IsFinalized() && !type.IsMalformed() && !type.IsMalbounded());
-  ASSERT(!type.IsObjectType() && !type.IsDynamicType());
+  ASSERT(!type.IsObjectType() && !type.IsDynamicType() && !type.IsVoidType());
 
   // Preserve instantiator type arguments (R1).
   __ Push(R1);
@@ -637,7 +632,8 @@ void FlowGraphCompiler::GenerateAssertAssignable(TokenPosition token_pos,
   ASSERT(dst_type.IsFinalized());
   // Assignable check is skipped in FlowGraphBuilder, not here.
   ASSERT(dst_type.IsMalformedOrMalbounded() ||
-         (!dst_type.IsDynamicType() && !dst_type.IsObjectType()));
+         (!dst_type.IsDynamicType() && !dst_type.IsObjectType() &&
+          !dst_type.IsVoidType()));
   // Preserve instantiator type arguments (R1).
   __ Push(R1);
   // A null object is always assignable and is returned as result.