From 83f93ba87b5d079071cbde1cf3d7acf2e177a24b Mon Sep 17 00:00:00 2001
From: Seiichi Uchida <seuchida@gmail.com>
Date: Wed, 8 Jan 2020 00:07:18 +0900
Subject: [PATCH] Backport 3999

Do not remove comment from an import with a single item
---
 src/imports.rs          | 13 +++++--------
 tests/source/imports.rs |  3 +++
 tests/target/imports.rs |  3 +++
 3 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/src/imports.rs b/src/imports.rs
index 02319809486..aaf7811ec72 100644
--- a/src/imports.rs
+++ b/src/imports.rs
@@ -509,7 +509,7 @@ impl UseTree {
 
         // Normalise foo::{bar} -> foo::bar
         if let UseSegment::List(ref list) = last {
-            if list.len() == 1 && list[0].to_string() != "self" {
+            if list.len() == 1 && !list[0].has_comment() && list[0].to_string() != "self" {
                 normalize_sole_list = true;
             }
         }
@@ -582,11 +582,8 @@ impl UseTree {
     }
 
     fn flatten(self) -> Vec<UseTree> {
-        if self.path.is_empty() {
-            return vec![self];
-        }
-        match self.path.clone().last().unwrap() {
-            UseSegment::List(list) => {
+        match self.path.clone().last() {
+            Some(UseSegment::List(list)) => {
                 if list.len() == 1 && list[0].path.len() == 1 {
                     if let UseSegment::Slf(..) = list[0].path[0] {
                         return vec![self];
@@ -595,9 +592,9 @@ impl UseTree {
                 let prefix = &self.path[..self.path.len() - 1];
                 let mut result = vec![];
                 for nested_use_tree in list {
-                    for flattend in &mut nested_use_tree.clone().flatten() {
+                    for flattened in &mut nested_use_tree.clone().flatten() {
                         let mut new_path = prefix.to_vec();
-                        new_path.append(&mut flattend.path);
+                        new_path.append(&mut flattened.path);
                         result.push(UseTree {
                             path: new_path,
                             span: self.span,
diff --git a/tests/source/imports.rs b/tests/source/imports.rs
index 4dfc6ed94e3..1df83f9a646 100644
--- a/tests/source/imports.rs
+++ b/tests/source/imports.rs
@@ -27,6 +27,9 @@ use self;
 use std::io::{self};
 use std::io::self;
 
+use a::{/* comment */ item};
+use a::{item /* comment */};
+
 mod Foo {
     pub use rustc_ast::ast::{
         ItemForeignMod,
diff --git a/tests/target/imports.rs b/tests/target/imports.rs
index 87584d89f66..12a958a78ad 100644
--- a/tests/target/imports.rs
+++ b/tests/target/imports.rs
@@ -30,6 +30,9 @@ use {Bar /* comment */, /* Pre-comment! */ Foo};
 use std::io;
 use std::io::{self};
 
+use a::{/* comment */ item};
+use a::{item /* comment */};
+
 mod Foo {
     pub use rustc_ast::ast::{
         ItemDefaultImpl, ItemForeignMod, ItemImpl, ItemMac, ItemMod, ItemStatic,