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Add Base.fieldtypes. #29600

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Nov 1, 2018
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Add Base.fieldtypes. #29600

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1 change: 1 addition & 0 deletions base/exports.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -694,6 +694,7 @@ export
fieldname,
fieldnames,
fieldcount,
fieldtypes,
propertynames,
isabstracttype,
isbitstype,
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18 changes: 18 additions & 0 deletions base/reflection.jl
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Expand Up @@ -623,6 +623,24 @@ function fieldcount(@nospecialize t)
return length(t.types)
end

"""
fieldtypes(T::Type)
The declared types of all fields in a composite DataType `T` as a tuple.
# Examples
```jldoctest
julia> struct Foo
x::Int64
y::String
end
julia> fieldtypes(Foo)
(Int64, String)
```
"""
fieldtypes(T::Type) = ntuple(i -> fieldtype(T, i), fieldcount(T))

# return all instances, for types that can be enumerated

"""
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1 change: 1 addition & 0 deletions doc/src/base/base.md
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Expand Up @@ -167,6 +167,7 @@ Base.isconcretetype
Base.isbits
Base.isbitstype
Core.fieldtype
Base.fieldtypes
Base.fieldcount
Base.fieldoffset
Base.datatype_alignment
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4 changes: 4 additions & 0 deletions test/reflection.jl
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Expand Up @@ -262,6 +262,10 @@ tlayout = TLayout(5,7,11)
@test fieldtype((NamedTuple{(:a,:b),T} where T<:Tuple{Vararg{Integer}}), 2) === Integer
@test_throws BoundsError fieldtype(NamedTuple{(:a,:b)}, 3)

@test fieldtypes(NamedTuple{(:a,:b)}) == (Any, Any)
@test fieldtypes((NamedTuple{T,Tuple{Int,String}} where T)) === (Int, String)
@test fieldtypes(TLayout) === (Int8, Int16, Int32)
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Can we test that these are inferred correctly? Or are they inferred as Tuple{Datatype,Datatype,...}?

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Would adding an @inferred be a satisfactory test? Because that passes.

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AFAICT @inferred won't work since typeof((Int8, Int16, Int32)) == Tuple{DataType,DataType,DataType}.

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Then I am not sure how to do what @martinholters is asking for, but given an explanation or an example (eg some test in Base) I would be happy to learn it and add those tests.


import Base: datatype_alignment, return_types
@test datatype_alignment(UInt16) == 2
@test datatype_alignment(TLayout) == 4
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