Spec violation?

[ghost]

• Version: 10.3.0
• Platform: windows 10
• Subsystem: v8

Shouldn't this

(a=>a``==a``)(a=>a)

evaluate to true according to the ES specification? I found this yesterday on Firefox (gecko) bug tracker, but I can't find the issue right now. It seems that Node.js has the same issue. I also read the spec and IIUC it seems like this snippet should evaluate to true but I'm not sure.

Any opinions?

[vsemozhetbyt]

Tagged template functions (a`` here) get an array of strings as the first argument. In your case, a=>a function just returns this array. So your code is equivalent of [ '' ] == [ '' ] wich is false due to two separate (though similar) objects comparison.

[ghost]

@vsemozhetbyt

No, my point is that it should indeed be the same reference to the same array. See this: https://www.ecma-international.org/ecma-262/8.0/index.html#sec-gettemplateobject

Paragraph 4:

I tested on Chrome 63 and it logs true, so I suppose it is a regression in v8.

@Trott PTAL

[vsemozhetbyt]

cc @nodejs/v8

[bnoordhuis]

This was also reported over at https://bugs.chromium.org/p/v8/issues/detail?id=7801. Since this is a V8 issue and it doesn't look like V8 will change behavior right now, I'll go ahead and close this out.