Add similar(::QuantityArray, ::Type{<:UnionAbstractQuantity})

Author: MilesCranmer

src/arrays.jl

@@ -196,6 +196,9 @@ end
 
 Base.similar(A::QuantityArray) = QuantityArray(similar(ustrip(A)), dimension(A), quantity_type(A))
 Base.similar(A::QuantityArray, ::Type{S}) where {S} = QuantityArray(similar(ustrip(A), S), dimension(A), quantity_type(A))
+for (type, _, _) in ABSTRACT_QUANTITY_TYPES
+    @eval Base.similar(A::QuantityArray, ::Type{S}) where {S<:$type} = QuantityArray(similar(ustrip(A), value_type(S)), dimension(A), S)
+end
 
 # Unfortunately this mess of `similar` is required to avoid ambiguous methods.
 # c.f. base/abstractarray.jl

test/unittests.jl

@@ -983,6 +983,14 @@ end
             @test dimension(new_qa) == dimension(qa)
             @test isa(ustrip(new_qa), Array{Float32,2})
 
+            if Q !== GenericQuantity
+                new_qa = similar(qa, typeof(GenericQuantity{Float16}(u"km/s")))
+                @test eltype(new_qa) <: GenericQuantity{Float16}
+                @test dim_type(new_qa) == dim_type(qa)
+                @test dimension(new_qa) == dimension(qa)
+                @test isa(ustrip(new_qa), Array{Float16,2})
+            end
+
             new_qa = similar(qa, axes(ones(6, 8)))
             @test size(new_qa) == (6, 8)
             @test eltype(new_qa) <: Q{Float64}