make parentindices consistent with Base (#250)

* make parentindices consistent with Base

* remove allequal

Author: aplavin

src/structarray.jl

@@ -368,6 +368,12 @@ end
     StructArray{T}(map(v -> @inbounds(view(v, I...)), components(s)))
 end
 
+function Base.parentindices(s::StructArray)
+    res = parentindices(component(s, 1))
+    all(c -> parentindices(c) == res, components(s)) || throw(ArgumentError("inconsistent parentindices of components"))
+    return res
+end
+
 Base.@propagate_inbounds function Base.setindex!(s::StructArray{T, <:Any, <:Any, CartesianIndex{N}}, vals, I::Vararg{Int, N}) where {T,N}
     @boundscheck checkbounds(s, I...)
     valsT = maybe_convert_elt(T, vals)

test/runtests.jl

@@ -37,6 +37,8 @@ Base.convert(::Type{Millimeters}, x::Meters) = Millimeters(x.x*1000)
     @test (@inferred t[2,1:2]) == StructArray((a = [3, 4], b = [6, 7]))
     @test_throws BoundsError t[3,3]
     @test (@inferred view(t, 2, 1:2)) == StructArray((a = view(a, 2, 1:2), b = view(b, 2, 1:2)))
+    @test @inferred(parentindices(view(t, 2, 1:2))) == (2, 1:2)
+    @test_throws ArgumentError parentindices(StructArray((view([1, 2], [1]), view([1, 2], [2]))))
 
     # Element type conversion (issue #216)
     x = StructArray{Complex{Int}}((a, b))