Augment docstring for Nullable() and move inline; fix doctests for isnull(). (JuliaLang#19067)

Author: xorJane

base/docs/helpdb/Base.jl

@@ -197,15 +197,6 @@ Subtraction operator.
 """
 -(x, y)
 
-"""
-    Nullable(x)
-
-Wrap value `x` in an object of type `Nullable`, which indicates whether a value is present.
-`Nullable(x)` yields a non-empty wrapper, and `Nullable{T}()` yields an empty instance of a
-wrapper that might contain a value of type `T`.
-"""
-Nullable
-
 """
     bits(n)
 

base/nullable.jl

@@ -3,6 +3,34 @@
 immutable NullException <: Exception
 end
 
+"""
+    Nullable(x, hasvalue::Bool=true)
+
+Wrap value `x` in an object of type `Nullable`, which indicates whether a value is present.
+`Nullable(x)` yields a non-empty wrapper and `Nullable{T}()` yields an empty instance of a
+wrapper that might contain a value of type `T`.
+
+`Nullable(x, false)` yields `Nullable{typeof(x)}()` with `x` stored in the result's `value`
+field.
+
+# Examples
+
+```jldoctest
+julia> Nullable(1)
+Nullable{Int64}(1)
+
+julia> Nullable{Int64}()
+Nullable{Int64}()
+
+julia> Nullable(1, false)
+Nullable{Int64}()
+
+julia> dump(Nullable(1, false))
+Nullable{Int64}
+  hasvalue: Bool false
+  value: Int64 1
+```
+"""
 Nullable{T}(value::T, hasvalue::Bool=true) = Nullable{T}(value, hasvalue)
 Nullable() = Nullable{Union{}}()
 
@@ -100,18 +128,20 @@ unsafe_get(x) = x
 Return whether or not `x` is null for [`Nullable`](:obj:`Nullable`) `x`; return
 `false` for all other `x`.
 
+# Examples
+
 ```jldoctest
 julia> x = Nullable(1, false)
-Nullable{Int64}(1)
+Nullable{Int64}()
 
 julia> isnull(x)
-false
+true
 
 julia> x = Nullable(1, true)
-Nullable{Int64}()
+Nullable{Int64}(1)
 
 julia> isnull(x)
-true
+false
 
 julia> x = 1
 1

doc/manual/types.rst

@@ -1487,7 +1487,7 @@ You can safely access the value of a :obj:`Nullable` object using :func:`get`:
 
     julia> get(Nullable{Float64}())
     ERROR: NullException()
-     in get(::Nullable{Float64}) at ./nullable.jl:62
+     in get(::Nullable{Float64}) at ./nullable.jl:90
      ...
 
     julia> get(Nullable(1.0))

doc/stdlib/base.rst

@@ -815,11 +815,31 @@ Syntax
 Nullables
 ---------
 
-.. function:: Nullable(x)
+.. function:: Nullable(x, hasvalue::Bool=true)
 
    .. Docstring generated from Julia source
 
-   Wrap value ``x`` in an object of type ``Nullable``\ , which indicates whether a value is present. ``Nullable(x)`` yields a non-empty wrapper, and ``Nullable{T}()`` yields an empty instance of a wrapper that might contain a value of type ``T``\ .
+   Wrap value ``x`` in an object of type ``Nullable``\ , which indicates whether a value is present. ``Nullable(x)`` yields a non-empty wrapper and ``Nullable{T}()`` yields an empty instance of a wrapper that might contain a value of type ``T``\ .
+
+   ``Nullable(x, false)`` yields ``Nullable{typeof(x)}()`` with ``x`` stored in the result's ``value`` field.
+
+   **Examples**
+
+   .. doctest::
+
+       julia> Nullable(1)
+       Nullable{Int64}(1)
+
+       julia> Nullable{Int64}()
+       Nullable{Int64}()
+
+       julia> Nullable(1, false)
+       Nullable{Int64}()
+
+       julia> dump(Nullable(1, false))
+       Nullable{Int64}
+         hasvalue: Bool false
+         value: Int64 1
 
 .. function:: get(x::Nullable[, y])
 
@@ -833,19 +853,21 @@ Nullables
 
    Return whether or not ``x`` is null for :obj:`Nullable` ``x``\ ; return ``false`` for all other ``x``\ .
 
+   **Examples**
+
    .. doctest::
 
        julia> x = Nullable(1, false)
-       Nullable{Int64}(1)
+       Nullable{Int64}()
 
        julia> isnull(x)
-       false
+       true
 
        julia> x = Nullable(1, true)
-       Nullable{Int64}()
+       Nullable{Int64}(1)
 
        julia> isnull(x)
-       true
+       false
 
        julia> x = 1
        1