Issue #9738: Document encodings of AST, compiler, parser and PyRun functions
diff --git a/Include/ast.h b/Include/ast.h
index cc14b7f..a015336 100644
--- a/Include/ast.h
+++ b/Include/ast.h
@@ -4,8 +4,11 @@
 extern "C" {
 #endif
 
-PyAPI_FUNC(mod_ty) PyAST_FromNode(const node *, PyCompilerFlags *flags,
-				  const char *, PyArena *);
+PyAPI_FUNC(mod_ty) PyAST_FromNode(
+    const node *n,
+    PyCompilerFlags *flags,
+    const char *filename,       /* decoded from the filesystem encoding */
+    PyArena *arena);
 
 #ifdef __cplusplus
 }