Add doctests to kernel guards (#14544)

Author: dmitrykleymenov

lib/elixir/lib/kernel.ex

@@ -735,6 +735,17 @@ defmodule Kernel do
   Returns `true` if `term` is a floating-point number, otherwise returns `false`.
 
   Allowed in guard tests. Inlined by the compiler.
+
+  ## Examples
+
+      iex> is_float(2.15)
+      true
+
+      iex> is_float(3.45e5)
+      true
+
+      iex> is_float(5)
+      false
   """
   @doc guard: true
   @spec is_float(term) :: boolean
@@ -786,6 +797,14 @@ defmodule Kernel do
   Returns `true` if `term` is an integer, otherwise returns `false`.
 
   Allowed in guard tests. Inlined by the compiler.
+
+  ## Examples
+
+      iex> is_integer(5)
+      true
+
+      iex> is_integer(5.0)
+      false
   """
   @doc guard: true
   @spec is_integer(term) :: boolean
@@ -797,6 +816,17 @@ defmodule Kernel do
   Returns `true` if `term` is a list with zero or more elements, otherwise returns `false`.
 
   Allowed in guard tests. Inlined by the compiler.
+
+  ## Examples
+
+      iex> is_list([1, 2, 3])
+      true
+
+      iex> is_list(key: :sum, value: 3)
+      true
+
+      iex> is_list({1, 2, 3})
+      false
   """
   @doc guard: true
   @spec is_list(term) :: boolean
@@ -809,6 +839,17 @@ defmodule Kernel do
   otherwise returns `false`.
 
   Allowed in guard tests. Inlined by the compiler.
+
+  ## Examples
+
+      iex> is_number(2.15)
+      true
+
+      iex> is_number(5)
+      true
+
+      iex> is_number(:one)
+      false
   """
   @doc guard: true
   @spec is_number(term) :: boolean
@@ -820,6 +861,18 @@ defmodule Kernel do
   Returns `true` if `term` is a PID (process identifier), otherwise returns `false`.
 
   Allowed in guard tests. Inlined by the compiler.
+
+  ## Examples
+
+      iex> {:ok, agent_pid} = Agent.start_link(fn -> 0 end)
+      iex> is_pid(agent_pid)
+      true
+
+      iex> is_pid(self())
+      true
+
+      iex> is_pid(:pid)
+      false
   """
   @doc guard: true
   @spec is_pid(term) :: boolean
@@ -831,6 +884,15 @@ defmodule Kernel do
   Returns `true` if `term` is a port identifier, otherwise returns `false`.
 
   Allowed in guard tests. Inlined by the compiler.
+
+  ## Examples
+
+      iex> [port | _] = Port.list()
+      iex> is_port(port)
+      true
+
+      iex> is_port(:port)
+      false
   """
   @doc guard: true
   @spec is_port(term) :: boolean
@@ -842,6 +904,15 @@ defmodule Kernel do
   Returns `true` if `term` is a reference, otherwise returns `false`.
 
   Allowed in guard tests. Inlined by the compiler.
+
+  ## Examples
+
+      iex> ref = make_ref()
+      iex> is_reference(ref)
+      true
+
+      iex> is_reference(:ref)
+      false
   """
   @doc guard: true
   @spec is_reference(term) :: boolean
@@ -853,6 +924,17 @@ defmodule Kernel do
   Returns `true` if `term` is a tuple, otherwise returns `false`.
 
   Allowed in guard tests. Inlined by the compiler.
+
+  ## Examples
+
+      iex> is_tuple({1, 2, 3})
+      true
+
+      iex> is_tuple({})
+      true
+
+      iex> is_tuple(true)
+      false
   """
   @doc guard: true
   @spec is_tuple(term) :: boolean