Add isnothing

base/exports.jl

@@ -669,6 +669,7 @@ export
     missing,
     skipmissing,
     something,
+    isnothing,
 
 # time
     sleep,

base/some.jl

@@ -40,6 +40,15 @@ Throw an error if `x === nothing`, and return `x` if not.
 notnothing(x::Any) = x
 notnothing(::Nothing) = throw(ArgumentError("nothing passed to notnothing"))
 
+"""
+    isnothing(x)
+
+Return `true` if `x === nothing`, and return `false` if not.
+"""
+isnothing(::Any) = false
+isnothing(::Nothing) = true
+
+
 """
     something(x, y...)
 

test/some.jl

@@ -94,3 +94,7 @@ b = [ "replacement", "replacement", nothing, missing ]
 using Base: notnothing
 @test notnothing(1) === 1
 @test_throws ArgumentError notnothing(nothing)
+
+# isnothing()
+@test !isnothing(1)
+@test isnothing(nothing)