Merge pull request #13811 from JuliaLang/teh/more_linearslow

Fix `first` for LinearSlow arrays

Author: timholy

base/abstractarray.jl

@@ -60,7 +60,7 @@ ndims{T,n}(::Type{AbstractArray{T,n}}) = n
 ndims{T<:AbstractArray}(::Type{T}) = ndims(super(T))
 length(t::AbstractArray) = prod(size(t))::Int
 endof(a::AbstractArray) = length(a)
-first(a::AbstractArray) = a[1]
+first(a::AbstractArray) = a[first(eachindex(a))]
 
 function first(itr)
     state = start(itr)

test/abstractarray.jl

@@ -370,6 +370,17 @@ function test_ind2sub(::Type{TestAbstractArray})
     end
 end
 
+# A custom linear slow array that insists upon Cartesian indexing
+type TSlowNIndexes{T,N} <: AbstractArray{T,N}
+    data::Array{T,N}
+end
+Base.linearindexing{A<:TSlowNIndexes}(::Type{A}) = Base.LinearSlow()
+Base.size(A::TSlowNIndexes) = size(A.data)
+Base.getindex(A::TSlowNIndexes, index::Int...) = error("Must use $(ndims(A)) indexes")
+Base.getindex{T}(A::TSlowNIndexes{T,2}, i::Int, j::Int) = A.data[i,j]
+
+
+
 type GenericIterator{N} end
 Base.start{N}(::GenericIterator{N}) = 1
 Base.next{N}(::GenericIterator{N}, i) = (i, i + 1)
@@ -478,3 +489,8 @@ test_map_promote(TestAbstractArray)
 test_UInt_indexing(TestAbstractArray)
 test_vcat_depwarn(TestAbstractArray)
 test_13315(TestAbstractArray)
+
+A = TSlowNIndexes(rand(2,2))
+@test_throws ErrorException A[1]
+@test A[1,1] == A.data[1]
+@test first(A) == A.data[1]