Fix mul with quasi-arrays (#292)

Author: dlfivefifty

Project.toml

@@ -1,6 +1,6 @@
 name = "ArrayLayouts"
 uuid = "4c555306-a7a7-4459-81d9-ec55ddd5c99a"
-version = "1.16.1"
+version = "1.16"
 authors = ["Sheehan Olver <solver@mac.com>"]
 
 [deps]

src/mul.jl

@@ -33,8 +33,9 @@ axes(M::Mul) = _mul_axes(axes(M.A), axes(M.B))
 
 zeroeltype(M) = _zeroeltype(eltype(M), M) # allow special casing where we know more about zero
 _zeroeltype(::Type{T}, M) where T = zero(T)
-# zero(T) is not defined for arrays like Vector{Float64} so use the entries to determine the size
-_zeroeltype(::Type{T}, M::Mul) where T<:AbstractArray = convert(T, zero(first(M.A) * first(M.B)))
+# zero(T) is not defined for arrays like Vector{Float64} so use the entries to determine the size.
+# Prefer zero(T) when it exists (e.g. SVector) since first may not be defined (e.g. quasi-arrays)
+_zeroeltype(::Type{T}, M::Mul) where T<:AbstractArray = applicable(zero, T) ? zero(T) : convert(T, zero(first(M.A) * first(M.B)))
 zeroeltype(M::Mul{<:Any,<:Any,<:SubArray}) = zeroeltype(Mul(parent(M.A), M.B))
 
 function _getindex(::Type{Tuple{AA}}, M::Mul, (k,)::Tuple{AA}) where AA

test/test_muladd.jl

@@ -99,6 +99,9 @@ Random.seed!(0)
             @test ArrayLayouts.Mul(X, reshape(c,2,1))[1,1] == X[1] + 2X[2]
             v = reshape([[1.0, 2.0], [3.0, 4.0]], 1, 2)
             @test ArrayLayouts.Mul(v, c)[1] == [7.0, 10.0]
+            # eltypes with zero(T) should not need any entries
+            S = Matrix{SVector{2,Float64}}(undef, 1, 0)
+            @test ArrayLayouts.Mul(S, Float64[])[1] === zero(SVector{2,Float64})
         end
 
         @testset "Diagonal Fill" begin