#![feature(prelude_import)]
//! Test
#[prelude_import]
use std::prelude::v1::*;
#[macro_use]
extern crate std;
/// Test
pub fn test() {}

#![feature(prelude_import)]
#![doc = " Test"]
#[prelude_import]
use std::prelude::v1::*;
#[macro_use]
extern crate std;
#[doc = " Test"]
pub fn test() {}

--- 
+++ 
@@ -1,8 +1,8 @@
 #![feature(prelude_import)]
-#![doc = " Test"]
+//! Test
 #[prelude_import]
 use std::prelude::v1::*;
 #[macro_use]
 extern crate std;
-#[doc = " Test"]
+/// Test
 pub fn test() {}
Update expected output with normalize_doc_attributes = true

Rustfmt supports this configuration on nightly only.
