qdoc: properly implement \typealias command

\typealias was already a command recognized by QDoc, but it was simply
treated as a synonym for \typedef and was not documented. Implement
proper support for the command:

 - Add [alias] designation both in type summary and details.
 - Auto-generate information about the aliased type, including a link
   if aliasing a public, documented type.
 - Auto-convert aliases documented with \typedef to type aliases.
 - Add basic support for aliases also to DocBook and WebXML generators.
 - Document \typealias.

Fixes: QTBUG-82712
Change-Id: Iafa8c7def0a7488d7521fbc2862290a9bb3167ff
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

1 files changed, 36 insertions, 0 deletions

diff --git a/src/qdoc/doc/qdoc-manual-topiccmds.qdoc b/src/qdoc/doc/qdoc-manual-topiccmds.qdoc
index 8e142f5af..a537c7499 100644
--- a/src/qdoc/doc/qdoc-manual-topiccmds.qdoc
+++ b/src/qdoc/doc/qdoc-manual-topiccmds.qdoc
@@ -1410,6 +1410,40 @@
     {\\instantiates} to specify that a Transform is instantiated by
     the C++ class QGraphicsTransform. A \\qmltype comment should
 
+    \target typealias-command
+    \section1 \\typealias
+
+    The \\typealias command is similar to \l {typedef-command}{\\typedef},
+    but specific to documenting a C++ type alias:
+
+    \code
+    class Foo
+    {
+    public:
+        using ptr = void*;
+    // ...
+    }
+    \endcode
+
+    This can be documented as
+
+    \badcode *
+    /\1!
+        \typealias Foo::ptr
+    \1/
+    \endcode
+
+    QDoc will automatically generate a sentence in the documentation describing
+    the alias:
+
+    \quotation
+    This is a type alias for \c {void*}.
+    \endquotation
+
+    The \\typealias command was introduced in QDoc 5.15.
+
+    See also \l {typedef-command}{\\typedef}.
+
     \target typedef-command
     \section1 \\typedef
 
@@ -1498,6 +1532,8 @@
         Qt-style synonym for QList::iterator.
     \endquotation
 
+    See also \l {typealias-command}{\\typealias}.
+
     \target variable-command
     \section1 \\variable