FULL PRODUCT VERSION :
java version "9"
Java(TM) SE Runtime Environment (build 9+181)
Java HotSpot(TM) 64-Bit Server VM (build 9+181, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 10.0.15063]

A DESCRIPTION OF THE PROBLEM :
When the __proto__ property is accessed for a symbol, the message of the thrown TypeError is a format string with a {0} placeholder.


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run: jjs --language=es6

jjs> var sym = Symbol('foo');
jjs> sym.__proto__
ECMAScript Exception: TypeError: {0} is not a symbol.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Unsure, but not a raw format string.

Node doesn't throw an error:

> var s = Symbol('foo')
undefined
> s.__proto__
Symbol {}
ACTUAL -
ECMAScript Exception: TypeError: {0} is not a symbol.

REPRODUCIBILITY :
This bug can be reproduced always.