bpo-29463: Add docstring field to some AST nodes. (#46)

* bpo-29463: Add docstring field to some AST nodes.

ClassDef, ModuleDef, FunctionDef, and AsyncFunctionDef has docstring
field for now.  It was first statement of there body.

* fix document.  thanks travis!

* doc fixes

1 files changed, 7 insertions, 4 deletions

diff --git a/Parser/Python.asdl b/Parser/Python.asdl
index f470ad13b6..526cffbce0 100644
--- a/Parser/Python.asdl
+++ b/Parser/Python.asdl
@@ -6,7 +6,7 @@
 
 module Python
 {
-    mod = Module(stmt* body)
+    mod = Module(stmt* body, string? docstring)
         | Interactive(stmt* body)
         | Expression(expr body)
 
@@ -14,15 +14,18 @@ module Python
         | Suite(stmt* body)
 
     stmt = FunctionDef(identifier name, arguments args,
-                       stmt* body, expr* decorator_list, expr? returns)
+                       stmt* body, expr* decorator_list, expr? returns,
+                       string? docstring)
           | AsyncFunctionDef(identifier name, arguments args,
-                             stmt* body, expr* decorator_list, expr? returns)
+                             stmt* body, expr* decorator_list, expr? returns,
+                             string? docstring)
 
           | ClassDef(identifier name,
              expr* bases,
              keyword* keywords,
              stmt* body,
-             expr* decorator_list)
+             expr* decorator_list,
+             string? docstring)
           | Return(expr? value)
 
           | Delete(expr* targets)