Fix pretty printer when there are multiple lifetime parameters

src/libsyntax/print/pprust.rs

@@ -1572,17 +1572,24 @@ fn print_path_(s: @ps,
             }
             word(s.s, "<");
 
+            let mut comma = false;
             for lifetime in segment.lifetimes.iter() {
-                print_lifetime(s, lifetime);
-                if !segment.types.is_empty() {
+                if comma {
                     word_space(s, ",")
                 }
+                print_lifetime(s, lifetime);
+                comma = true;
             }
 
-            commasep(s,
-                     inconsistent,
-                     segment.types.map_to_vec(|t| (*t).clone()),
-                     print_type);
+            if !segment.types.is_empty() {
+                if comma {
+                    word_space(s, ",")
+                }
+                commasep(s,
+                         inconsistent,
+                         segment.types.map_to_vec(|t| (*t).clone()),
+                         print_type);
+            }
 
             word(s.s, ">")
         }