# How to create a type from Symbol in a macro
**URL:** https://discourse.julialang.org/t/how-to-create-a-type-from-symbol-in-a-macro/8749
**Category:** General Usage
**Created:** [February 1, 2018, 6:17pm UTC](https://discourse.julialang.org/t/how-to-create-a-type-from-symbol-in-a-macro/8749 "2018-02-01T18:17:21Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@Qiyamah](https://discourse.julialang.org/u/Qiyamah)
#### Post date: [February 1, 2018, 6:17pm UTC](https://discourse.julialang.org/t/how-to-create-a-type-from-symbol-in-a-macro/8749/1 "2018-02-01T18:17:21Z")
```nohighlight
module X
export MM
struct MM
end
end
using X
Base.@pure get_module(::Type{T}) where T = T.name.module
macro mod_check(sym)
amod = get_module(Type(sym))
end
@mod_check MM
```
My problem is to create a type from Symbol in the macro?
How can i do that?
Thanks
---
### Author:  [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)
#### Post date: [February 1, 2018, 6:22pm UTC](https://discourse.julialang.org/t/how-to-create-a-type-from-symbol-in-a-macro/8749/2 "2018-02-01T18:22:41Z")
> [@Qiyamah](#):
>
> My problem is to create a type from Symbol in the macro?
`eval`, but you should really be retuning expressions from macros instead of values.
---
### Author:  [@Qiyamah](https://discourse.julialang.org/u/Qiyamah)
#### Post date: [February 1, 2018, 6:24pm UTC](https://discourse.julialang.org/t/how-to-create-a-type-from-symbol-in-a-macro/8749/3 "2018-02-01T18:24:19Z")
Any side effect of eval for using Type Creation from Symbol?
What should i be aware of?
Thanks
---
### Author:  [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)
#### Post date: [February 1, 2018, 6:28pm UTC](https://discourse.julialang.org/t/how-to-create-a-type-from-symbol-in-a-macro/8749/4 "2018-02-01T18:28:23Z")
> [@Qiyamah](#):
>
> Any side effect of eval for using Type Creation from Symbol?
>
> What should i be aware of?
Why do you want this to be a macro?
Macros are called at compile-time. Functions are compiled once with only the types of the arguments known at compile-time, not the values. The global scope would have the values. So if what you’re evaling is based on the values of things, I would expect this to fail if you put it in a function. Things like that will trip you up. You really should only use macros to generate expressions, and use functions to return values.
---
### Author:  [@Qiyamah](https://discourse.julialang.org/u/Qiyamah)
#### Post date: [February 1, 2018, 6:34pm UTC](https://discourse.julialang.org/t/how-to-create-a-type-from-symbol-in-a-macro/8749/5 "2018-02-01T18:34:09Z")
I am developing a trait system where i parse some super traits(more than one), here is an example:
```nohighlight
@mixin MyMixin{T,N}(ST2,ST3) <: ST1
#stuff goes here
end
```
I look up info for super traits like ST1 from a toptable which makes addressing using module info and then the name of the type. You can think of it as:
toptable[MODULE][NAME] , eg: toptable[XX][ST1]
In the mixin macro, i need to have access to the module where ST1 is defined. That’s why.
Returning a value is for the sake of a simple example, i am using the value in mixin macro.
Thanks
---
### Author:  [@NaOH](https://discourse.julialang.org/u/NaOH)
#### Post date: [February 2, 2018, 12:45am UTC](https://discourse.julialang.org/t/how-to-create-a-type-from-symbol-in-a-macro/8749/6 "2018-02-02T00:45:14Z")
You need to return an escaped expression that does what you want at run-time:
```julia
julia> macro mod_check(sym::Symbol)
:(get_module(Type($sym))) |> esc
end
@mod_check (macro with 1 method)
julia> @mod_check MM
X
```
---
### Author:  [@yuyichao](https://discourse.julialang.org/u/yuyichao)
#### Post date: [February 2, 2018, 3:12am UTC](https://discourse.julialang.org/t/how-to-create-a-type-from-symbol-in-a-macro/8749/7 "2018-02-02T03:12:28Z")
Don’t esc the whole thing. `esc` only user input.
---
### Author:  [@Qiyamah](https://discourse.julialang.org/u/Qiyamah)
#### Post date: [February 5, 2018, 10:51pm UTC](https://discourse.julialang.org/t/how-to-create-a-type-from-symbol-in-a-macro/8749/8 "2018-02-05T22:51:14Z")
I was trying to find it in compile time (macro time) . That’s why i was using a pure function.
Thanks