[1.8.x] Refs #24485 -- Renamed some expression types

Backport of 88d798d71a from master

docs/ref/models/expressions.txt

@@ -284,9 +284,9 @@ should define the desired ``output_field``. For example, adding an
     arithmetic between different types, it's necessary to surround the
     expression in another expression::
 
-        from django.db.models import DateTimeField, ExpressionNode, F
+        from django.db.models import DateTimeField, Expression, F
 
-        Race.objects.annotate(finish=ExpressionNode(
+        Race.objects.annotate(finish=Expression(
             F('start') + F('duration'), output_field=DateTimeField()))
 
 .. versionchanged:: 1.8
@@ -369,13 +369,13 @@ Expression API
 
 Query expressions implement the :ref:`query expression API <query-expression>`,
 but also expose a number of extra methods and attributes listed below. All
-query expressions must inherit from ``ExpressionNode()`` or a relevant
+query expressions must inherit from ``Expression()`` or a relevant
 subclass.
 
 When a query expression wraps another expression, it is responsible for
 calling the appropriate methods on the wrapped expression.
 
-.. class:: ExpressionNode
+.. class:: Expression
 
     .. attribute:: contains_aggregate
 
@@ -489,9 +489,9 @@ We'll start by defining the template to be used for SQL generation and
 an ``__init__()`` method to set some attributes::
 
   import copy
-  from django.db.models import ExpressionNode
+  from django.db.models import Expression
 
-  class Coalesce(ExpressionNode):
+  class Coalesce(Expression):
       template = 'COALESCE( %(expressions)s )'
 
       def __init__(self, expressions, output_field, **extra):