From bf6f80b2ae012a387f278cfd4481c96807cf9db7 Mon Sep 17 00:00:00 2001
From: Matt Fishman <mtfishman@users.noreply.github.com>
Date: Fri, 22 Nov 2024 11:59:49 -0500
Subject: [PATCH] Zero dimensional `BlockIndex` (#431)

* Zero dimensional `BlockIndex`

---------

Co-authored-by: Sheehan Olver <solver@mac.com>
---
 Project.toml              | 2 +-
 src/blockindices.jl       | 7 ++++---
 test/test_blockarrays.jl  | 4 ++--
 test/test_blockindices.jl | 1 +
 4 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/Project.toml b/Project.toml
index 48f106a1..acbb824d 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "BlockArrays"
 uuid = "8e7c35d0-a365-5155-bbbb-fb81a777f24e"
-version = "1.1.1"
+version = "1.2.0"
 
 [deps]
 ArrayLayouts = "4c555306-a7a7-4459-81d9-ec55ddd5c99a"
diff --git a/src/blockindices.jl b/src/blockindices.jl
index f00f54a0..a5b5119e 100644
--- a/src/blockindices.jl
+++ b/src/blockindices.jl
@@ -52,11 +52,10 @@ last(b::Block) = b
 iterate(x::Block) = (x, nothing)
 iterate(x::Block, ::Any) = nothing
 isempty(x::Block) = false
-broadcastable(x::Block) = x
+broadcastable(x::Block) = Ref(x)
 ndims(::Type{<:Block}) = 0
 ndims(::Block) = 0
 eltype(::Type{B}) where B<:Block = B
-getindex(B::Block, ::CartesianIndex{0}) = B
 
 # The following code is taken from CartesianIndex
 @inline (+)(index::Block{N}) where {N} = Block{N}(map(+, index.n))
@@ -147,10 +146,12 @@ struct BlockIndex{N,TI<:Tuple{Vararg{Integer,N}},Tα<:Tuple{Vararg{Integer,N}}}
 end
 
 @inline BlockIndex(a::NTuple{N,Block{1}}, b::Tuple) where N = BlockIndex(Int.(a), b)
+@inline BlockIndex(::Tuple{}, b::Tuple{}) = BlockIndex{0,Tuple{},Tuple{}}((), ())
 
 @inline BlockIndex(a::Integer, b::Integer) = BlockIndex((a,), (b,))
 @inline BlockIndex(a::Tuple, b::Integer) = BlockIndex(a, (b,))
 @inline BlockIndex(a::Integer, b::Tuple) = BlockIndex((a,), b)
+@inline BlockIndex() = BlockIndex((), ())
 
 @inline BlockIndex(a::Block, b::Tuple) = BlockIndex(a.n, b)
 @inline BlockIndex(a::Block, b::Integer) = BlockIndex(a, (b,))
@@ -202,7 +203,7 @@ BlockIndexRange(block::Block{N}, inds::Vararg{AbstractUnitRange{<:Integer},N}) w
 
 block(R::BlockIndexRange) = R.block
 
-getindex(::Block{0}) = Block()
+getindex(::Block{0}) = BlockIndex()
 getindex(B::Block{N}, inds::Vararg{Integer,N}) where N = BlockIndex(B,inds)
 getindex(B::Block{N}, inds::Vararg{AbstractUnitRange{<:Integer},N}) where N = BlockIndexRange(B,inds)
 getindex(B::Block{1}, inds::Colon) = B
diff --git a/test/test_blockarrays.jl b/test/test_blockarrays.jl
index f6ff21a4..d24fb52e 100644
--- a/test/test_blockarrays.jl
+++ b/test/test_blockarrays.jl
@@ -333,7 +333,7 @@ end
             @test size(ret) == ()
             @test all(iszero, ret)
             @test ret[Block()] == zeros()
-            @test ret[Block()[]] == zeros()
+            @test ret[Block()[]] == 0
             @test ret[] == 0
             @test view(ret, Block()) == zeros()
             @test Array(ret) == zeros()
@@ -360,7 +360,7 @@ end
             @test all(iszero, ret)
             @test ret[] == 0
             @test ret[Block()] == zeros()
-            @test ret[Block()[]] == zeros()
+            @test ret[Block()[]] == 0
             @test Array(ret) == zeros()
             ret[] = 1
             @test ret[] == 1
diff --git a/test/test_blockindices.jl b/test/test_blockindices.jl
index d14ce4d2..d6e4b67b 100644
--- a/test/test_blockindices.jl
+++ b/test/test_blockindices.jl
@@ -84,6 +84,7 @@ import BlockArrays: BlockIndex, BlockIndexRange, BlockSlice
     end
 
     @testset "BlockIndex" begin
+        @test Block()[] == BlockIndex()
         @test Block(1)[1] == BlockIndex((1,),(1,))
         @test Block(1)[1:2] == BlockIndexRange(Block(1),(1:2,))
         @test Block(1,1)[1,1] == BlockIndex((1,1),(1,1)) == BlockIndex((1,1),(1,))