From 1a3bc79c686e246cb5088ed16bdc648d1564ffb2 Mon Sep 17 00:00:00 2001
From: Kevin Stenerson <kstenerson@developers.wyyerd.com>
Date: Mon, 5 Nov 2018 22:48:49 -0700
Subject: [PATCH] Preserve possibly one whitespace for brace macros

---
 src/macros.rs          | 14 +++++++++++++-
 tests/source/macros.rs |  3 +++
 tests/target/macros.rs |  3 +++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/macros.rs b/src/macros.rs
index a2c1f243879..ca0de8fbb23 100644
--- a/src/macros.rs
+++ b/src/macros.rs
@@ -256,7 +256,19 @@ pub fn rewrite_macro_inner(
             }
             DelimToken::Paren => Some(format!("{}()", macro_name)),
             DelimToken::Bracket => Some(format!("{}[]", macro_name)),
-            DelimToken::Brace => Some(format!("{}{{}}", macro_name)),
+            DelimToken::Brace => {
+                // Preserve at most one space before the braces.
+                let char_after_bang = context
+                    .snippet(mac.span)
+                    .split('!')
+                    .nth(1)
+                    .and_then(|x| x.chars().next());
+                if let Some(' ') = char_after_bang {
+                    Some(format!("{} {{}}", macro_name))
+                } else {
+                    Some(format!("{}{{}}", macro_name))
+                }
+            }
             _ => unreachable!(),
         };
     }
diff --git a/tests/source/macros.rs b/tests/source/macros.rs
index c828ffb881a..383fc723b5b 100644
--- a/tests/source/macros.rs
+++ b/tests/source/macros.rs
@@ -106,6 +106,9 @@ fn main() {
 
 impl X {
     empty_invoc!{}
+
+    // Don't format empty either!
+    empty_invoc! {}
 }
 
 fn issue_1279() {
diff --git a/tests/target/macros.rs b/tests/target/macros.rs
index e16159ced10..70ed0b042fe 100644
--- a/tests/target/macros.rs
+++ b/tests/target/macros.rs
@@ -132,6 +132,9 @@ fn main() {
 
 impl X {
     empty_invoc!{}
+
+    // Don't format empty either!
+    empty_invoc! {}
 }
 
 fn issue_1279() {