Indent open brace for impl when nested. (#1227)

* Indent open brace for impl when nested.

Fixes #1226

* Added test case for indented impl with brace on newline

Author: luke-clifton

src/items.rs

@@ -497,7 +497,10 @@ pub fn format_impl(context: &RewriteContext, item: &ast::Item, offset: Indent) -
         result.push_str(&where_clause_str);
 
         match context.config.item_brace_style {
-            BraceStyle::AlwaysNextLine => result.push('\n'),
+            BraceStyle::AlwaysNextLine => {
+                result.push('\n');
+                result.push_str(&offset.to_string(context.config));
+            }
             BraceStyle::PreferSameLine => result.push(' '),
             BraceStyle::SameLineWhere => {
                 if !where_clause_str.is_empty() {

tests/target/indented-impl.rs

@@ -0,0 +1,11 @@
+// rustfmt-item_brace_style: AlwaysNextLine
+mod x {
+    struct X(i8);
+
+    impl Y for X
+    {
+        fn y(self) -> () {
+            println!("ok");
+        }
+    }
+}