Add simple support for tags in YAML I/O

llvm-svn: 194644

1 files changed, 14 insertions, 0 deletions

diff --git a/llvm/docs/YamlIO.rst b/llvm/docs/YamlIO.rst
index 79e07cd9897..3ecd03afb24 100644
--- a/llvm/docs/YamlIO.rst
+++ b/llvm/docs/YamlIO.rst
@@ -633,6 +633,20 @@ This works for both reading and writing. For example:
     };
 
 
+Tags
+----
+
+The YAML syntax supports tags as a way to specify the type of a node before
+it is parsed. This allows dynamic types of nodes.  But the YAML I/O model uses
+static typing, so there are limits to how you can use tags with the YAML I/O
+model. Recently, we added support to YAML I/O for checking/setting the optional 
+tag on a map. Using this functionality it is even possbile to support differnt 
+mappings, as long as they are convertable.  
+
+To check a tag, inside your mapping() method you can use io.mapTag() to specify
+what the tag should be.  This will also add that tag when writing yaml.
+
+
 Sequence
 ========