leave a minimal implementation of passmissing

src/Missings.jl

@@ -1,8 +1,7 @@
 module Missings
 
 export allowmissing, disallowmissing, ismissing, missing, missings,
-       Missing, MissingException, levels, coalesce,
-       conditional, passmissing
+       Missing, MissingException, levels, coalesce, passmissing
 
 using Base: ismissing, missing, Missing, MissingException
 
@@ -166,32 +165,10 @@ function levels(x)
     levs
 end
 
-struct Conditional{P,X,Y} <: Function end
+struct PassMissing{F} <: Function end
 
-"""
-    conditional(predicate, x, y)
-
-Return a function that that applies function `predicate` to its positional and keyword
-arguments and returns the value of `x` applied to those arguments if `predicate`
-returns true and otherwise returns the value of `y` applied to those arguments.
-
-# Examples
-```jldoctest
-julia> f = conditional(x -> x ≥ 0, sqrt, x -> sqrt(complex(x)));
-
-julia> f.([4, -4])
-2-element Array{Number,1}:
-     2.0
-      0.0 + 2.0im
-"""
-conditional(predicate::Function, x::Base.Callable, y::Base.Callable) =
-    Conditional{predicate, x, y}()
-(::Conditional{P,X,Y})(xs...;kw...) where {P,X,Y} =
-    P(xs...; kw...) ? X(xs...; kw...) : Y(xs...; kw...)
-
-_passmissing_predicate(xs...;kw...) =
-    any(ismissing.(xs)) || any(ismissing.(values(values(kw))))
-_passmissing_value(xs...;kw...) = missing
+(::PassMissing{F})(xs...;kw...) where {F} =
+     any(ismissing, xs) || any(ismissing, values(values(kw))) ? missing : F(xs...; kw...)
 
 """
     passmissing(f)
@@ -206,6 +183,6 @@ julia> passmissing(sqrt).([missing, 4])
   missing
    2.0
 """
-passmissing(f) = conditional(_passmissing_predicate, _passmissing_value, f)
+passmissing(f::Base.Callable) = PassMissing{f}()
 
 end # module

test/runtests.jl

@@ -357,8 +357,6 @@ using Test, Dates, InteractiveUtils, SparseArrays, Missings
     @test sprint(showerror, MissingException("test")) == "MissingException: test"
 
     # Lifting
-    fun1 = conditional(x -> x ≥ 0, sqrt, x -> sqrt(complex(x)));
-    @test fun1(4) === 2.0
-    @test fun1(-4) === 2.0im
     @test isequal(passmissing(sqrt).([missing, 4]), [missing, 2.0])
+    @test isequal(passmissing(parse)(Int, "a", base=missing), missing)
 end