Improve docs and type for Kernel.send/2 & Process.send/3 (#7862)

Kernel.send/2:
- Simplify/Improve description of `dest`

Process.send/3:
- Refer to `dest` and not just "process"
- Duplicate definition of `dest` in Process.send/3

Author: eksperimental

lib/elixir/lib/kernel.ex

@@ -797,9 +797,9 @@ defmodule Kernel do
   @doc """
   Sends a message to the given `dest` and returns the message.
 
-  `dest` may be a remote or local PID, a (local) port, a locally
-  registered name, or a tuple `{registered_name, node}` for a registered
-  name at another node.
+  `dest` may be a remote or local PID, a local port, a locally
+  registered name, or a tuple in the form of `{registered_name, node}` for a
+  registered name at another node.
 
   Inlined by the compiler.
 
@@ -809,7 +809,7 @@ defmodule Kernel do
       :hello
 
   """
-  @spec send(dest :: pid | port | atom | {atom, node}, message) :: message when message: any
+  @spec send(dest :: Process.dest(), message) :: message when message: any
   def send(dest, message) do
     :erlang.send(dest, message)
   end

lib/elixir/lib/process.ex

@@ -30,6 +30,15 @@ defmodule Process do
 
   Inlined by the compiler.
   """
+
+  @typedoc """
+  A process destination.
+
+  A remote or local PID, a local port, a locally registered name, or a tuple in
+  the form of `{registered_name, node}` for a registered name at another node.
+  """
+  @type dest :: pid | port | registered_name :: atom | {registered_name :: atom, node}
+
   @spec alive?(pid) :: boolean
   defdelegate alive?(pid), to: :erlang, as: :is_process_alive
 
@@ -220,7 +229,11 @@ defmodule Process do
   end
 
   @doc """
-  Sends a message to the given process.
+  Sends a message to the given `dest`.
+
+  `dest` may be a remote or local PID, a local port, a locally
+  registered name, or a tuple in the form of `{registered_name, node}` for a
+  registered name at another node.
 
   Inlined by the compiler.
 
@@ -242,7 +255,7 @@ defmodule Process do
 
   """
   @spec send(dest, msg, [option]) :: :ok | :noconnect | :nosuspend
-        when dest: pid | port | atom | {atom, node},
+        when dest: dest(),
              msg: any,
              option: :noconnect | :nosuspend
   defdelegate send(dest, msg, options), to: :erlang
@@ -395,7 +408,7 @@ defmodule Process do
     * `object` is either a `pid` of the monitored process (if monitoring
       a PID) or `{name, node}` (if monitoring a remote or local name);
     * `reason` is the exit reason.
-    
+
   If the process is already dead when calling `Process.monitor/1`, a
   `:DOWN` message is delivered immediately.