Fix promotion rules for complex

Author: MilesCranmer

src/math.jl

@@ -25,13 +25,15 @@ Base.:+(l, r::AbstractQuantity) = iszero(dimension(r)) ? new_quantity(typeof(r),
 Base.:-(l::AbstractQuantity, r) = l + (-r)
 Base.:-(l, r::AbstractQuantity) = l + (-r)
 
-_pow(l::AbstractDimensions, r) = map_dimensions(Base.Fix1(*, r), l)
-_pow(l::AbstractQuantity{T}, r) where {T} = new_quantity(typeof(l), ustrip(l)^r, _pow(dimension(l), r))
-_pow_as_T(l::AbstractQuantity{T}, r) where {T} = new_quantity(typeof(l), ustrip(l)^convert(T, r), _pow(l.dimensions, r))
-Base.:^(l::AbstractDimensions{R}, r::Integer) where {R} = _pow(l, r)
+# We don't promote on the dimension types:
+_pow(l::AbstractDimensions{R}, r::R) where {R} = map_dimensions(Base.Fix1(*, r), l)
 Base.:^(l::AbstractDimensions{R}, r::Number) where {R} = _pow(l, tryrationalize(R, r))
-Base.:^(l::AbstractQuantity{T,D}, r::Integer) where {T,R,D<:AbstractDimensions{R}} = _pow(l, r)
-Base.:^(l::AbstractQuantity{T,D}, r::Number) where {T,R,D<:AbstractDimensions{R}} = _pow_as_T(l, tryrationalize(R, r))
+Base.:^(l::AbstractQuantity{T,D}, r::Integer) where {T,R,D<:AbstractDimensions{R}} = new_quantity(typeof(l), ustrip(l)^r, dimension(l)^r)
+Base.:^(l::AbstractQuantity{T,D}, r::Number) where {T,R,D<:AbstractDimensions{R}} =
+    let dim_pow = tryrationalize(R, r), val_pow = convert(T, dim_pow)
+        # Need to ensure we take the numerical power by the rationalized quantity:
+        return new_quantity(typeof(l), ustrip(l)^val_pow, dimension(l)^dim_pow)
+    end
 
 Base.inv(d::AbstractDimensions) = map_dimensions(-, d)
 Base.inv(q::AbstractQuantity) = new_quantity(typeof(q), inv(ustrip(q)), inv(dimension(q)))

test/unittests.jl

@@ -123,14 +123,21 @@ using Test
         @test_throws DimensionError 1.0 - Quantity(one(T), D, length=1)
     end
 
-    @test string((0.5 + 0.5im)*u"km/s") == "(500.0 + 500.0im) m s⁻¹"
-
     x = Quantity(-1.2, length=2 // 5)
 
     @test abs(x) == Quantity(1.2, length=2 // 5)
     @test abs(x) == abs(Quantity(1.2, length=2 // 5))
 end
 
+@testset "Complex numbers" begin
+    x = (0.5 + 0.5im) * u"km/s"
+    @test string(x) == "(500.0 + 500.0im) m s⁻¹"
+    @test typeof(x) == Quantity{Complex{Float64}, DEFAULT_DIM_TYPE}
+    @test typeof(x^2) == Quantity{Complex{Float64}, DEFAULT_DIM_TYPE}
+    @test x^2/u"km/s"^2 == Quantity(0.5im)
+    @test x^2.5 ≈ (-5.088059320440205e6 + 1.2283661817565577e7im) * u"m^(5/2) * s^(-5/2)"
+end
+
 @testset "Fallbacks" begin
     @test ustrip(0.5) == 0.5
     @test ustrip(ones(32)) == ones(32)