Fix Broadcast.broadcast_shape inference

Author: charleskawczynski

src/blockbroadcast.jl

@@ -30,13 +30,14 @@ BroadcastStyle(::PseudoBlockStyle{M}, ::BlockStyle{N}) where {M,N} = BlockStyle(
 
 # sortedunion can assume inputs are already sorted so this could be improved
 sortedunion(a,b) = sort!(union(a,b))
+sortedunion(a::Tuple, b::Tuple) = (a..., b...)
 sortedunion(a::Base.OneTo, b::Base.OneTo) = Base.OneTo(max(last(a),last(b)))
 sortedunion(a::AbstractUnitRange, b::AbstractUnitRange) = min(first(a),first(b)):max(last(a),last(b))
 combine_blockaxes(a, b) = _BlockedUnitRange(sortedunion(blocklasts(a), blocklasts(b)))
 
-Base.Broadcast.axistype(a::BlockedUnitRange, b::BlockedUnitRange) = length(b) == 1 ? a : combine_blockaxes(a, b)
-Base.Broadcast.axistype(a::BlockedUnitRange, b) = length(b) == 1 ? a : combine_blockaxes(a, b)
-Base.Broadcast.axistype(a, b::BlockedUnitRange) = length(b) == 1 ? a : combine_blockaxes(a, b)
+Base.Broadcast.axistype(a::BlockedUnitRange, b::BlockedUnitRange) = combine_blockaxes(a, b)
+Base.Broadcast.axistype(a::BlockedUnitRange, b) = combine_blockaxes(a, b)
+Base.Broadcast.axistype(a, b::BlockedUnitRange) = combine_blockaxes(a, b)
 
 
 similar(bc::Broadcasted{<:AbstractBlockStyle{N}}, ::Type{T}) where {T,N} =

test/test_blockbroadcast.jl

@@ -182,6 +182,19 @@ import BlockArrays: SubBlockIterator, BlockIndexRange, Diagonal
         u = BlockArray(randn(5), [2,3]);
         @inferred(copyto!(similar(u), Base.broadcasted(exp, u)))
         @test exp.(u) == exp.(Vector(u))
+
+        function test_allocation!(shape1, shape2)
+            x = Base.Broadcast.broadcast_shape(shape1, shape2)
+            return nothing
+        end
+        shape1 = (BlockArrays._BlockedUnitRange((2,)),);
+        shape2 = (BlockArrays._BlockedUnitRange((2,)),);
+        @inferred Base.Broadcast.axistype(shape1[1], shape2[1])
+        @inferred BlockArrays.combine_blockaxes(shape1[1], shape2[1])
+        @inferred Base.Broadcast.broadcast_shape(shape1, shape2)
+        test_allocation!(shape1, shape2) # compile first
+        p = @allocated test_allocation!(shape1, shape2)
+        @test p == 0
     end
 
     @testset "adjtrans" begin