Fix for issue 29350 - VM Crashes when covariant is used incorrectly.

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 2cbd331ace2c25433c19b3c2a2a68a16c01cde46..d7640482c0235ea3f5274477ca033a386ab12a82 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -2433,6 +2433,7 @@ class Function : public Object {
       case RawFunction::kInvokeFieldDispatcher:
         return true;
       case RawFunction::kClosureFunction:
+      case RawFunction::kSignatureFunction:
       case RawFunction::kConstructor:
       case RawFunction::kImplicitStaticFinalGetter:
       case RawFunction::kIrregexpFunction:
@@ -2456,7 +2457,11 @@ class Function : public Object {
       case RawFunction::kIrregexpFunction:
         return true;
       case RawFunction::kClosureFunction:
+      case RawFunction::kSignatureFunction:
       case RawFunction::kConstructor:
+      case RawFunction::kMethodExtractor:
+      case RawFunction::kNoSuchMethodDispatcher:
+      case RawFunction::kInvokeFieldDispatcher:
         return false;
       default:
         UNREACHABLE();