Merge pull request #1 from shati-patel/typeunions-edits

Editorial suggestions for "type unions"

Author: ginsbach

docs/language/ql-handbook/aliases.rst

@@ -42,6 +42,8 @@ of ``OldVersion``, you could deprecate the name ``OldVersion`` as follows::
 That way both names resolve to the same module, but if you use the name ``OldVersion``,
 a deprecation warning is displayed.
 
+.. _type-aliases:
+
 Type aliases
 ============
 

docs/language/ql-handbook/types.rst

@@ -482,35 +482,35 @@ program, so it's helpful to extend a new type (namely ``TTaintType``)::
     
 .. _type-unions:
 
-Type Unions
+Type unions
 ***********
 
 .. note::
     The syntax for type unions is considered experimental and is subject to change.
-    However, they appear in the `standard QL libraries <https://github.com/github/codeql>`.
-    The following sections should help you understand those examples
+    However, type unions appear in the `standard QL libraries <https://github.com/github/codeql>`__.
+    The following sections should help you understand those examples.
 
 Type unions are user-defined types that are declared with the keyword ``class``.
-The syntax resembles type aliases, but with two or more type expressions on the right-hand side.
+The syntax resembles :ref:`type aliases <type-aliases>`, but with two or more type expressions on the right-hand side.
 
-Type unions are used for creating restricted versions of existing algebraic datatypes, by explicitly
-selecting a subset of the branches of said datatype and binding them to a new type.
-In addition to this, type unions of database types are also supported.
+Type unions are used for creating restricted versions of an existing :ref:`algebraic datatype <algebraic-datatypes>`, by explicitly
+selecting a subset of the branches of that datatype and binding them to a new type.
+Type unions of :ref:`database types <database-types>` are also supported.
 
-Using a type union to explicitly restrict the permitted branches from an algebraic datatype
-can resolve spurious recursion in predicates.
+You can use a type union to explicitly restrict the permitted branches from an algebraic datatype
+and resolve spurious :ref:`recursion <recursion>` in predicates.
 For example, the following construction is legal::
 
     newtype T =
-       T1(T t) { not exists(T2orT3 s | t = s) } or
-       T2(int x) { x = 1 or x = 2 } or
-       T3(int x) { x = 3 or x = 4 or x = 5 }
+      T1(T t) { not exists(T2orT3 s | t = s) } or
+      T2(int x) { x = 1 or x = 2 } or
+      T3(int x) { x = 3 or x = 4 or x = 5 }
 
     class T2orT3 = T2 or T3;
 
 However, a similar implementation that restricts ``T`` in a class extension is not valid.
 The class ``T2orT3`` triggers a type test for ``T``, which results in an illegal recursion
-``T2orT3->T->T1->¬T2orT2`` due to the reliance of ``T1`` on ``T2orT3``::
+``T2orT3 -> T -> T1 -> ¬T2orT3`` since ``T1`` relies on ``T2orT3``::
 
     class T2orT3 extends T {
       T2orT3() {