Support one and oneunit (#59)

* Support one and oneunit

* Handle StackOverflow error with Any

src/Missings.jl

@@ -83,7 +83,7 @@ if VERSION < v"0.7.0-DEV.300"
 end
 
 # Unary operators/functions
-for f in (:(!), :(+), :(-), :(Base.identity), :(Base.zero),
+for f in (:(!), :(+), :(-), :(Base.identity), :(Base.zero), :(Base.one), :(Base.oneunit),
  :(Base.abs), :(Base.abs2), :(Base.sign),
  :(Base.acos), :(Base.acosh), :(Base.asin), :(Base.asinh), :(Base.atan), :(Base.atanh),
  :(Base.sin), :(Base.sinh), :(Base.cos), :(Base.cosh), :(Base.tan), :(Base.tanh),
@@ -95,8 +95,12 @@ for f in (:(!), :(+), :(-), :(Base.identity), :(Base.zero),
  @eval $(f)(d::Missing) = missing
 end
 
-Base.zero(::Type{Union{T, Missing}}) where {T <: Number} = zero(T)
-Base.zero(::Type{Union{T, Missing}}) where {T <: Compat.Dates.Period} = zero(T)
+for f in (:(Base.zero), :(Base.one), :(Base.oneunit))
+ @eval function $(f)(::Type{Union{T, Missing}}) where T
+ T === Any && throw(MethodError($f, (Any,)))
+ $f(T)
+ end
+end
 
 # Binary operators/functions
 for f in (:(+), :(-), :(*), :(/), :(^),

test/runtests.jl

@@ -28,7 +28,7 @@ using Base.Test, Missings, Compat
  conj, cos, cosh, tan, tanh,
  exp, exp2, expm1, log, log10, log1p, log2,
  exponent, sqrt, gamma, lgamma,
- identity, zero,
+ identity, zero, one, oneunit,
  iseven, isodd, ispow2,
  isfinite, isinf, isnan, iszero,
  isinteger, isreal, isimag,
@@ -55,14 +55,24 @@ using Base.Test, Missings, Compat
  @test_throws MissingException f(Int, missing)
  end
 
- @test zero(Union{Int, Missing}) === 0
- @test zero(Union{Float64, Missing}) === 0.0
+ for T in (Int, Float64)
+ @test zero(Union{T, Missing}) === T(0)
+ @test one(Union{T, Missing}) === T(1)
+ @test oneunit(Union{T, Missing}) === T(1)
+ end
 
  for T in (subtypes(Compat.Dates.DatePeriod)...,
  subtypes(Compat.Dates.TimePeriod)...)
  @test zero(Union{T, Missing}) === T(0)
+ @test one(Union{T, Missing}) === 1
+ @test oneunit(Union{T, Missing}) === T(1)
  end
 
+ # Make sure we didn't introduce a StackOverflow error
+ @test_throws MethodError zero(Any)
+ @test_throws MethodError one(Any)
+ @test_throws MethodError oneunit(Any)
+
  # Comparison operators
  @test (missing == missing) === missing
  @test (1 == missing) === missing