# Type must be (Int64 | Int8), not Int32 **URL:** \ **Category:** Help & Support\ **Created:** [March 20, 2019, 1:58am UTC](https://forum.crystal-lang.org/t/type-must-be-int64-int8-not-int32/574 "2019-03-20T01:58:52Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![angryrabbit](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/angryrabbit/32/313_2.png) [@angryrabbit](https://forum.crystal-lang.org/u/angryrabbit)\ **Post date:** [March 20, 2019, 1:58am UTC](https://forum.crystal-lang.org/t/type-must-be-int64-int8-not-int32/574/1 "2019-03-20T01:58:52Z")
Following code: ``` x : Int64 | Int8 = 0 ``` Yields error: ``` type must be (Int64 | Int8), not Int32 ``` What’s happening? ---
**Author:** ![Blacksmoke16](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/blacksmoke16/32/1241_2.png) [@Blacksmoke16](https://forum.crystal-lang.org/u/Blacksmoke16)\ **Post date:** [March 20, 2019, 2:03am UTC](https://forum.crystal-lang.org/t/type-must-be-int64-int8-not-int32/574/2 "2019-03-20T02:03:31Z")
You are giving `x` a type restriction of `Int64 | Int8`, but are assigning a value that is of type `Int32`. ---
**Author:** ![angryrabbit](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/angryrabbit/32/313_2.png) [@angryrabbit](https://forum.crystal-lang.org/u/angryrabbit)\ **Post date:** [March 20, 2019, 2:05am UTC](https://forum.crystal-lang.org/t/type-must-be-int64-int8-not-int32/574/3 "2019-03-20T02:05:44Z")
Crystal docs say -128…127 are valid Int8. [https://crystal-lang.org/reference/syntax\_and\_semantics/literals/integers.html](https://crystal-lang.org/reference/syntax_and_semantics/literals/integers.html) Now what? ---
**Author:** ![Blacksmoke16](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/blacksmoke16/32/1241_2.png) [@Blacksmoke16](https://forum.crystal-lang.org/u/Blacksmoke16)\ **Post date:** [March 20, 2019, 2:08am UTC](https://forum.crystal-lang.org/t/type-must-be-int64-int8-not-int32/574/4 "2019-03-20T02:08:08Z")
Yes but in this context `0` has a type of `Int32` by default. You would have to tell the compiler that you want `0` to be of type `Int8`, i.e. `0_i8`. `If no suffix is present, the literal's type is the lowest between Int32, Int64 and UInt64 in which the number fits`. Notice the little example they have in the doc you linked. ---
**Author:** ![angryrabbit](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/angryrabbit/32/313_2.png) [@angryrabbit](https://forum.crystal-lang.org/u/angryrabbit)\ **Post date:** [March 20, 2019, 2:10am UTC](https://forum.crystal-lang.org/t/type-must-be-int64-int8-not-int32/574/5 "2019-03-20T02:10:12Z")
Okay yes I remember reading that now. By my previous statement, reading doesn’t imply learning, in my case. So I must actually TYPE Crystal in order to learn, which I am enjoying btw. 🙂 Thank-you for responding quickly. ---
**Author:** ![angryrabbit](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/angryrabbit/32/313_2.png) [@angryrabbit](https://forum.crystal-lang.org/u/angryrabbit)\ **Post date:** [March 20, 2019, 2:10am UTC](https://forum.crystal-lang.org/t/type-must-be-int64-int8-not-int32/574/6 "2019-03-20T02:10:50Z")
I really, really like having types. I learned to love types via SQL. And now I get it in “Ruby”. ---
**Author:** ![Blacksmoke16](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/blacksmoke16/32/1241_2.png) [@Blacksmoke16](https://forum.crystal-lang.org/u/Blacksmoke16)\ **Post date:** [March 20, 2019, 2:12am UTC](https://forum.crystal-lang.org/t/type-must-be-int64-int8-not-int32/574/7 "2019-03-20T02:12:17Z")
No problem. Yes the type system is quite handy :) ---
**Author:** ![angryrabbit](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/angryrabbit/32/313_2.png) [@angryrabbit](https://forum.crystal-lang.org/u/angryrabbit)\ **Post date:** [March 20, 2019, 2:12am UTC](https://forum.crystal-lang.org/t/type-must-be-int64-int8-not-int32/574/8 "2019-03-20T02:12:27Z")
Is there a way to see the set of types for a variable? `typeof` only shows me what the type of the variable’s current value is. … Maybe my question is not so good. First, I see there are functions for objects like `tuple` that give the set of types. If I always declare my types, which I plan to, I should be able to find the variable’s declaration and know from that. ---
**Author:** ![Blacksmoke16](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/blacksmoke16/32/1241_2.png) [@Blacksmoke16](https://forum.crystal-lang.org/u/Blacksmoke16)\ **Post date:** [March 20, 2019, 2:16am UTC](https://forum.crystal-lang.org/t/type-must-be-int64-int8-not-int32/574/9 "2019-03-20T02:16:19Z")
`typeof` is kinda smart in that it shows you the types a variable have a chance of being. In your case `x` is only ever assigned to `0_i8` so the type of `x` is always going to be `Int8`. However if you do like: ```crystal val = "Foo" if val == "bar" val = 123 end typeof(val) # => (String | Int32) ``` In this case val is initialized as a string, but is _possible_ it could be an `Int32` as well. `typeof(val)` reflects that. `Tuple` is a bit unique as the types of each element are known at compile time. ---
**Author:** ![angryrabbit](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/angryrabbit/32/313_2.png) [@angryrabbit](https://forum.crystal-lang.org/u/angryrabbit)\ **Post date:** [March 20, 2019, 2:19am UTC](https://forum.crystal-lang.org/t/type-must-be-int64-int8-not-int32/574/10 "2019-03-20T02:19:35Z")
Very cool example. I hope to never do such things in my own code. Specifically, have union-type of 2 disparate types, e.g. String, Integer. Obviously Int8, Int32 is less disparate. My training in relational-theory taught me to avoid NULL at almost any cost. I intend to carry that into Crystal. Time shall tell. ---
**Author:** ![bcardiff](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/bcardiff/32/3_2.png) [@bcardiff](https://forum.crystal-lang.org/u/bcardiff)\ **Post date:** [March 20, 2019, 3:34am UTC](https://forum.crystal-lang.org/t/type-must-be-int64-int8-not-int32/574/11 "2019-03-20T03:34:40Z")
Note that `x : Int64 = 0` or `x : Int8 = 0` works thanks to auto-casting, but `x : Int64 | Int8 = 0` does not. ---
**Author:** ![angryrabbit](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/angryrabbit/32/313_2.png) [@angryrabbit](https://forum.crystal-lang.org/u/angryrabbit)\ **Post date:** [March 20, 2019, 3:40am UTC](https://forum.crystal-lang.org/t/type-must-be-int64-int8-not-int32/574/12 "2019-03-20T03:40:47Z")
What do you mean by “works”? `x : Int64 = 0` does-not look “auto-casted” to me; it looks explicit. ---
**Author:** ![angryrabbit](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/angryrabbit/32/313_2.png) [@angryrabbit](https://forum.crystal-lang.org/u/angryrabbit)\ **Post date:** [March 20, 2019, 3:43am UTC](https://forum.crystal-lang.org/t/type-must-be-int64-int8-not-int32/574/13 "2019-03-20T03:43:24Z")
I think I get what you’re saying. Absent a union-type, Crystal will assign the right type based on the singular type given. Oh… okay. Auto-casting of the LITERAL value, 0. Gotcha. Cool. Yes, lots to learn, lots of nuance. ---
**Author:** ![bcardiff](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.crystal-lang.org/bcardiff/32/3_2.png) [@bcardiff](https://forum.crystal-lang.org/u/bcardiff)\ **Post date:** [March 20, 2019, 3:44am UTC](https://forum.crystal-lang.org/t/type-must-be-int64-int8-not-int32/574/14 "2019-03-20T03:44:07Z")
> [@angryrabbit](#): > > What do you mean by “works”? That it compiles and does what you would expect 🙂 `0` as an expression is of type Int32. But the compiler will notice on some cases that literals are used as values of other types and will interpret them different. More about it [here](https://crystal-lang.org/2018/06/15/crystal-0.25.0-released.html#automatic-casts-for-literal-values).