Make the most special expression even more special

Add or-pattern syntax in argument position

Author: oberien

src/test/ui/weird-exprs.rs

@@ -115,7 +115,7 @@ fn union() {
 }
 
 fn special_characters() {
-    let val = !((|(..):(_,_),__@_|__)((&*"\\",'🤔')/**/,{})=={&[..=..][..];})//
+    let val = !((|(..):(_,_),(|__@_|__)|__)((&*"\\",'#')/**/,{})=={&[..=..][..];})//
     ;
     assert!(!val);
 }