more efficient array indexing with AbstractUnitRange (JuliaLang#39896)

Co-authored-by: Sebastian Stock <[email protected]>

base/array.jl

@@ -834,7 +834,7 @@ function getindex end
 @eval getindex(A::Array, i1::Int, i2::Int, I::Int...) = (@_inline_meta; arrayref($(Expr(:boundscheck)), A, i1, i2, I...))
 
 # Faster contiguous indexing using copyto! for UnitRange and Colon
-function getindex(A::Array, I::UnitRange{Int})
+function getindex(A::Array, I::AbstractUnitRange{<:Integer})
  @_inline_meta
  @boundscheck checkbounds(A, I)
  lI = length(I)
@@ -844,6 +844,10 @@ function getindex(A::Array, I::UnitRange{Int})
  end
  return X
 end
+
+# getindex for carrying out logical indexing for AbstractUnitRange{Bool} as Bool <: Integer
+getindex(a::Array, r::AbstractUnitRange{Bool}) = getindex(a, to_index(r))
+
 function getindex(A::Array, c::Colon)
  lI = length(A)
  X = similar(A, lI)

test/abstractarray.jl

@@ -1293,6 +1293,25 @@ end
  @test_throws ArgumentError Int[t...; 3 4 5]
 end
 
+@testset "issue #39896, modified getindex " begin
+ for arr = ([1:10;], reshape([1.0:16.0;],4,4), reshape(['a':'h';],2,2,2))
+ for inds = (2:5, Base.OneTo(5), BigInt(3):BigInt(5), UInt(4):UInt(3))
+ @test arr[inds] == arr[collect(inds)]
+ @test arr[inds] isa AbstractVector{eltype(arr)}
+ end
+ end
+ for arr = ([1], reshape([1.0],1,1), reshape(['a'],1,1,1))
+ @test arr[true:true] == [arr[1]]
+ @test arr[true:true] isa AbstractVector{eltype(arr)}
+ @test arr[false:false] == []
+ @test arr[false:false] isa AbstractVector{eltype(arr)}
+ end
+ for arr = ([1:10;], reshape([1.0:16.0;],4,4), reshape(['a':'h';],2,2,2))
+ @test_throws BoundsError arr[true:true]
+ @test_throws BoundsError arr[false:false]
+ end
+end
+
 @testset "reduce(vcat, ...) inferrence #40277" begin
  x_vecs = ([5, ], [1.0, 2.0, 3.0])
  @test @inferred(reduce(vcat, x_vecs)) == [5.0, 1.0, 2.0, 3.0]