Remove redundancy in abstract type interface

Author: MilesCranmer

src/types.jl

@@ -54,11 +54,6 @@ struct Dimensions{R<:Real} <: AbstractDimensions{R}
     Dimensions{_R}(d::Dimensions) where {_R} = Dimensions{_R}(d.length, d.mass, d.time, d.current, d.temperature, d.luminosity, d.amount)
 end
 
-new_dimensions(::Type{<:Dimensions}, l...) = Dimensions(l...)
-
-const DIMENSION_NAMES = Base.fieldnames(Dimensions)
-const DIMENSION_SYNONYMS = (:m, :kg, :s, :A, :K, :cd, :mol)
-const SYNONYM_MAPPING = NamedTuple(DIMENSION_NAMES .=> DIMENSION_SYNONYMS)
 
 """
     Quantity{T}
@@ -89,8 +84,10 @@ struct Quantity{T,R} <: AbstractQuantity{T,R}
     Quantity{T,R}(q::Quantity) where {T,R} = Quantity(convert(T, q.value), Dimensions{R}(dimension(q)))
 end
 
-new_quantity(::Type{<:Quantity}, value, dim) = Quantity(value, dim)
-new_quantity(::Type{<:Dimensions}, value, dim) = Quantity(value, dim)
+# All that is needed to make an `AbstractQuantity` work:
+dimension_name(::Dimensions, k::Symbol) = (length="m", mass="kg", time="s", current="A", temperature="K", luminosity="cd", amount="mol")[k]
+new_dimensions(::Type{<:Dimensions}, dims...) = Dimensions(dims...)
+new_quantity(::Type{<:Union{<:Quantity,<:Dimensions}}, l, r) = Quantity(l, r)
 
 struct DimensionError{Q1,Q2} <: Exception
     q1::Q1

src/utils.jl

@@ -69,7 +69,6 @@ Base.oneunit(::Dimensions) = error("There is no such thing as a dimensionful 1 f
 Base.oneunit(::Type{<:Quantity}) = error("Cannot create a dimensionful 1 for a `Quantity` type without knowing the dimensions. Please use `oneunit(::Quantity)` instead.")
 Base.oneunit(::Type{<:Dimensions}) = error("There is no such thing as a dimensionful 1 for a `Dimensions` type, as + is only defined for `Quantity`.")
 
-dimension_name(::Dimensions, k::Symbol) = SYNONYM_MAPPING[k]
 Base.show(io::IO, d::AbstractDimensions) =
     let tmp_io = IOBuffer()
         for k in keys(d)

test/unittests.jl

@@ -1,5 +1,5 @@
 using DynamicQuantities
-using DynamicQuantities: DEFAULT_DIM_TYPE, DEFAULT_VALUE_TYPE, DIMENSION_NAMES
+using DynamicQuantities: DEFAULT_DIM_TYPE, DEFAULT_VALUE_TYPE
 using Ratios: SimpleRatio
 using SaferIntegers: SafeInt16
 using Test
@@ -182,7 +182,7 @@ end
     @test Quantity(0.5, length=2) / Dimensions(length=1) == Quantity(0.5, length=1)
     @test Dimensions(length=1) / Quantity(0.5, length=2, mass=-5) == Quantity(2, length=-1, mass=5)
 
-    @test Dimensions{Int8}([0 for i=1:length(DIMENSION_NAMES)]...) == Dimensions{Int8}()
+    @test Dimensions{Int8}(zeros(Int, 7)...) == Dimensions{Int8}()
 
     @test zero(Quantity(0.0+0.0im)) + Quantity(1) == Quantity(1.0+0.0im, length=Int8(0))
     @test oneunit(Quantity(0.0+0.0im)) - Quantity(1) == Quantity(0.0+0.0im, length=Int8(0))