Add UnknownTypeForDeltemplateMigration as an alias for `?`.
@@ -185,6 +185,7 @@ public final class TypeRegistries {
private static final ImmutableMap<String, SoyType> BUILTIN_TYPES =
ImmutableSortedMap.<String, SoyType>naturalOrder()
.put("?", UnknownType.getInstance())
+ .put("UnknownTypeForDeltemplateMigration", UnknownType.getInstance())
.put("any", AnyType.getInstance())
.put("null", NullType.getInstance())
.put("bool", BoolType.getInstance())
