Set haszero in special test for TypeWithoutZero

Author: jishnub

src/dense.jl

@@ -114,7 +114,8 @@ norm2(x::Union{Array{T},StridedVector{T}}) where {T<:BlasFloat} =
 Return whether a type `T` has a unique zero element defined using `zero(T)`.
 If a type `M` specializes `zero(M)`, it may also choose to set `haszero(M)` to `true`.
 By default, `haszero` is assumed to be `false`, in which case the zero elements
-are deduced from values rather than the type.
+are deduced from values rather than the type. In general, if a type defines `zero(::Type{MyType})`,
+it should also define `haszero(::Type{MyType}) = true`.
 
 !!! note
     `haszero` is a conservative check that is used to dispatch to

test/special.jl

@@ -115,6 +115,8 @@ Random.seed!(1)
         struct TypeWithZero end
         Base.promote_rule(::Type{TypeWithoutZero}, ::Type{TypeWithZero}) = TypeWithZero
         Base.convert(::Type{TypeWithZero}, ::TypeWithoutZero) = TypeWithZero()
+        LinearAlgebra.haszero(::Type{TypeWithoutZero}) = true
+        LinearAlgebra.haszero(::Type{TypeWithZero}) = true
         Base.zero(x::Union{TypeWithoutZero, TypeWithZero}) = zero(typeof(x))
         Base.zero(::Type{<:Union{TypeWithoutZero, TypeWithZero}}) = TypeWithZero()
         LinearAlgebra.symmetric(::TypeWithoutZero, ::Symbol) = TypeWithoutZero()