Add docs for runtime groovydoc
diff --git a/src/spec/doc/core-syntax.adoc b/src/spec/doc/core-syntax.adoc
index 72c0a4b..2b947ee 100644
--- a/src/spec/doc/core-syntax.adoc
+++ b/src/spec/doc/core-syntax.adoc
@@ -70,6 +70,31 @@
Groovydoc follows the same conventions as Java's own Javadoc.
So you'll be able to use the same tags as with Javadoc.
+In addition, Groovy supports *Runtime Groovydoc* since 3.0.0, i.e. Groovydoc can be retained at runtime.
+
+NOTE: Runtime Groovydoc is disabled by default. It can be enabled by adding JVM option `-Dgroovy.attach.runtime.groovydoc=true`
+
+The Runtime Groovydoc starts with `/\**@` and ends with `*/`, for example:
+
+[source,groovy]
+----
+/**@
+ * Some class groovydoc for Foo
+ */
+class Foo {
+ /**@
+ * Some method groovydoc for bar
+ */
+ void bar() {
+ }
+}
+
+assert Foo.class.groovydoc.content.contains('Some class groovydoc for Foo') // <1>
+assert Foo.class.getMethod('bar', new Class[0]).groovydoc.content.contains('Some method groovydoc for bar') // <2>
+----
+<1> Get the runtime groovydoc for class `Foo`
+<2> Get the runtime groovydoc for method `bar`
+
=== Shebang line
Beside the single-line comment, there is a special line comment, often called the _shebang_ line understood by UNIX systems
