From 682033c4e47cf0cca5b4b96b07123da8807254f6 Mon Sep 17 00:00:00 2001
From: Crazycolorz5 <Crazycolorz5@gmail.com>
Date: Fri, 25 May 2018 16:40:16 -0400
Subject: [PATCH] Implemented eat_plus and used it in parsing
 parse_ty_param_bounds_common.

---
 src/libsyntax/parse/parser.rs | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 28f93328e95..a4e2b96c5f9 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -880,6 +880,27 @@ impl<'a> Parser<'a> {
             false
         }
     }
+    
+    /// Expect and consume a `+`. if `+=` is seen, replace it with a `=`
+    /// and continue. If a `+` is not seen, return false.
+    ///
+    /// This is using when token splitting += into +. 
+    /// See issue 47856 for an example of when this may occur.
+    fn eat_plus(&mut self) -> bool {
+        self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
+        match self.token {
+            token::BinOp(token::Plus) => {
+                self.bump();
+                true
+            }
+            token::BinOpEq(token::Plus) => {
+                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                self.bump_with(token::Eq, span);
+                true
+            }
+            _ => false,
+        }
+    }
 
     /// Expect and consume an `&`. If `&&` is seen, replace it with a single
     /// `&` and continue. If an `&` is not seen, signal an error.
@@ -4801,7 +4822,7 @@ impl<'a> Parser<'a> {
                 break
             }
 
-            if !allow_plus || !self.eat(&token::BinOp(token::Plus)) {
+            if !allow_plus || !self.eat_plus() {
                 break
             }
         }