fix(Exact): fix type when class present

[zorji]

This is an attempt to fix the issue reported in #909

I previously attempted to fix the issue in #902

My original approach was use JsonObject to determine object with primitive type and assume all types not match are classes. However, I found that JsonObject also rejects normal object containing any class type.

I also can't find a way to reliable determine a class, I used Class<any> but it seems can't detect Date because Date is a built-in type and only interface is available.

What's changed

• updated the type to leave Function check as is
• updated the type to return primitive type early to avoid the generated type becomes too complex.