# What is the correct name of supertype(DataType)?

**URL:** <https://discourse.julialang.org/t/what-is-the-correct-name-of-supertype-datatype/3420>\
**Category:** General Usage\
**Tags:** question\
**Created:** [April 28, 2017, 7:12am UTC](https://discourse.julialang.org/t/what-is-the-correct-name-of-supertype-datatype/3420 "2017-04-28T07:12:12Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![pauljurczak](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/pauljurczak/32/921_2.png) [@pauljurczak](https://discourse.julialang.org/u/pauljurczak)\
**Post date:** [April 28, 2017, 7:12am UTC](https://discourse.julialang.org/t/what-is-the-correct-name-of-supertype-datatype/3420/1 "2017-04-28T07:12:12Z")

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REPL responds with `Type{T}` to `supertype(DataType)`, but  
`DataType <: Type{T}`  
is invalid. What is the correct name of `supertype(DataType)`?

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**Author:** ![pfitzseb](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/pfitzseb/32/45566_2.png) [@pfitzseb](https://discourse.julialang.org/u/pfitzseb)\
**Post date:** [April 28, 2017, 8:31am UTC](https://discourse.julialang.org/t/what-is-the-correct-name-of-supertype-datatype/3420/2 "2017-04-28T08:31:32Z")

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```julia
julia> DataType <: Type
true

```

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**Author:** ![pauljurczak](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/pauljurczak/32/921_2.png) [@pauljurczak](https://discourse.julialang.org/u/pauljurczak)\
**Post date:** [April 28, 2017, 8:35am UTC](https://discourse.julialang.org/t/what-is-the-correct-name-of-supertype-datatype/3420/3 "2017-04-28T08:35:30Z")

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So, should the REPL respond with `Type` to `supertype(DataType)` instead of `Type{T}` ?

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**Author:** ![dfdx](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/dfdx/32/120_2.png) [@dfdx](https://discourse.julialang.org/u/dfdx)\
**Post date:** [April 28, 2017, 12:13pm UTC](https://discourse.julialang.org/t/what-is-the-correct-name-of-supertype-datatype/3420/4 "2017-04-28T12:13:03Z")

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Julia 0.6 made things more clear:

```julia
julia> DataType <: Type{T} where T
true

```

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**Author:** ![fengyang.wang](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/fengyang.wang/32/104_2.png) [@fengyang.wang](https://discourse.julialang.org/u/fengyang.wang)\
**Post date:** [April 28, 2017, 6:02pm UTC](https://discourse.julialang.org/t/what-is-the-correct-name-of-supertype-datatype/3420/5 "2017-04-28T18:02:26Z")

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Returning a type with free type variables seems suspicious on 0.6.