Revert "Void is not required to be `null` anymore."

runtime/vm/flow_graph_compiler_arm.cc

Index: runtime/vm/flow_graph_compiler_arm.cc
diff --git a/runtime/vm/flow_graph_compiler_arm.cc b/runtime/vm/flow_graph_compiler_arm.cc
index 7e5daa0601f397b13bb31f7d123612bd8b288118..b0b936d6fc1689aee0b9248f93df2531108dcf84 100644
--- a/runtime/vm/flow_graph_compiler_arm.cc
+++ b/runtime/vm/flow_graph_compiler_arm.cc
@@ -532,6 +532,11 @@ 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
@@ -574,7 +579,7 @@ void FlowGraphCompiler::GenerateInstanceOf(TokenPosition token_pos,
                                            const AbstractType& type,
                                            LocationSummary* locs) {
   ASSERT(type.IsFinalized() && !type.IsMalformed() && !type.IsMalbounded());
-  ASSERT(!type.IsObjectType() && !type.IsDynamicType() && !type.IsVoidType());
+  ASSERT(!type.IsObjectType() && !type.IsDynamicType());
   const Register kInstantiatorTypeArgumentsReg = R2;
   const Register kFunctionTypeArgumentsReg = R1;
   __ PushList((1 << kInstantiatorTypeArgumentsReg) |
@@ -653,8 +658,7 @@ 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.IsVoidType()));
+         (!dst_type.IsDynamicType() && !dst_type.IsObjectType()));
   const Register kInstantiatorTypeArgumentsReg = R2;
   const Register kFunctionTypeArgumentsReg = R1;
   __ PushList((1 << kInstantiatorTypeArgumentsReg) |