From 840af4f84d32934d210f254a8d710aae972948b1 Mon Sep 17 00:00:00 2001
From: Nick Cameron <ncameron@mozilla.com>
Date: Mon, 28 Sep 2015 08:46:05 +1300
Subject: [PATCH] Option for putting the where clause on the same line as the
 function if the body is empty.

---
 src/config.rs         |  6 ++++--
 src/items.rs          | 12 +++++++++---
 tests/target/trait.rs |  3 +--
 3 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/src/config.rs b/src/config.rs
index b21fe3d2a07..7460f581205 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -74,6 +74,8 @@ pub enum Density {
     Compressed,
     // Use more lines.
     Tall,
+    // Try to compress if the body is empty.
+    CompressedIfEmpty,
 }
 
 impl_enum_decodable!(Density, Compressed, Tall);
@@ -82,7 +84,7 @@ impl Density {
     pub fn to_list_tactic(self) -> ListTactic {
         match self {
             Density::Compressed => ListTactic::Mixed,
-            Density::Tall => ListTactic::HorizontalVertical,
+            Density::Tall | Density::CompressedIfEmpty => ListTactic::HorizontalVertical,
         }
     }
 }
@@ -267,7 +269,7 @@ impl Default for Config {
             fn_args_density: Density::Tall,
             fn_args_layout: StructLitStyle::Visual,
             fn_arg_indent: BlockIndentStyle::Visual,
-            where_density: Density::Tall,
+            where_density: Density::CompressedIfEmpty,
             where_indent: BlockIndentStyle::Tabbed,
             where_layout: ListTactic::Vertical,
             where_pred_indent: BlockIndentStyle::Visual,
diff --git a/src/items.rs b/src/items.rs
index 754d98793b9..e6a334d9ad3 100644
--- a/src/items.rs
+++ b/src/items.rs
@@ -144,6 +144,7 @@ impl<'a> FmtVisitor<'a> {
                                                    abi::Abi::Rust,
                                                    ast::Visibility::Inherited,
                                                    span,
+                                                   false,
                                                    false);
 
                 match rewrite {
@@ -210,7 +211,8 @@ impl<'a> FmtVisitor<'a> {
                                                        abi,
                                                        vis,
                                                        span,
-                                                       newline_brace));
+                                                       newline_brace,
+                                                       true));
 
         if self.config.fn_brace_style != BraceStyle::AlwaysNextLine && !result.contains('\n') {
             newline_brace = false;
@@ -250,6 +252,7 @@ impl<'a> FmtVisitor<'a> {
                                                        sig.abi,
                                                        ast::Visibility::Inherited,
                                                        span,
+                                                       false,
                                                        false));
 
         // Re-attach semicolon
@@ -269,7 +272,8 @@ impl<'a> FmtVisitor<'a> {
                        abi: abi::Abi,
                        vis: ast::Visibility,
                        span: Span,
-                       newline_brace: bool)
+                       newline_brace: bool,
+                       has_body: bool)
                        -> Option<String> {
         // FIXME we'll lose any comments in between parts of the function decl, but anyone
         // who comments there probably deserves what they get.
@@ -407,7 +411,9 @@ impl<'a> FmtVisitor<'a> {
                                 (!result.contains('\n') ||
                                  self.config.fn_args_layout == StructLitStyle::Block)) ||
                                (self.config.fn_args_layout == StructLitStyle::Block &&
-                                ret_str.is_empty()) {
+                                ret_str.is_empty()) ||
+                               (self.config.where_density == Density::CompressedIfEmpty &&
+                                !has_body) {
             Density::Compressed
         } else {
             Density::Tall
diff --git a/tests/target/trait.rs b/tests/target/trait.rs
index 5b69c46b18d..3e0a7ed692a 100644
--- a/tests/target/trait.rs
+++ b/tests/target/trait.rs
@@ -15,8 +15,7 @@ trait Foo {
 
     fn increment(&mut self, x: i32);
 
-    fn read(&mut self, x: BufReader<R> /* Used to be MemReader */)
-        where R: Read;
+    fn read(&mut self, x: BufReader<R> /* Used to be MemReader */) where R: Read;
 }
 
 pub trait WriteMessage {