From edd130626491b4a57ae9a1937b254acacb25a0c2 Mon Sep 17 00:00:00 2001
From: Curtis Vogt <curtis.vogt@gmail.com>
Date: Thu, 30 Nov 2017 19:05:36 -0600
Subject: [PATCH] Support one and oneunit (#59)

* Support one and oneunit

* Handle StackOverflow error with Any
---
 src/Missings.jl  | 10 +++++++---
 test/runtests.jl | 16 +++++++++++++---
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/src/Missings.jl b/src/Missings.jl
index 97eacac..e1613e7 100644
--- a/src/Missings.jl
+++ b/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 (:(+), :(-), :(*), :(/), :(^),
diff --git a/test/runtests.jl b/test/runtests.jl
index b9eef59..fe082c6 100644
--- a/test/runtests.jl
+++ b/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