Strangeness in error message when node gives call stack, if error had occured in specially declared function

[nickkolok]

• Version: v5.5.0
• Platform: Linux nicknout 3.2.0-25-generic-pae Working with nvm, nvmw and similar installation managers #40-Ubuntu SMP Wed May 23 22:11:24 UTC 2012 i686 i686 i386 GNU/Linux
• Subsystem: probably V8 (Chrome 44.0.2403.155 behaves similarly)

MWE:

nickolaus@nicknout:~/git/fraction.js$ js
> var obj = {};
undefined
> obj.a = obj.b = function(){throw err};
[Function]
> obj.b();
ReferenceError: err is not defined
    at Object.obj.a.obj.b (repl:1:34)
    at repl:1:5
    at REPLServer.defaultEval (repl.js:252:27)
    at bound (domain.js:287:14)
    at REPLServer.runBound [as eval] (domain.js:300:12)
    at REPLServer.<anonymous> (repl.js:417:12)
    at emitOne (events.js:95:20)
    at REPLServer.emit (events.js:182:7)
    at REPLServer.Interface._onLine (readline.js:211:10)
    at REPLServer.Interface._line (readline.js:550:8)
> obj.a();
ReferenceError: err is not defined
    at Object.obj.a.obj.b (repl:1:34)
    at repl:1:5
    at REPLServer.defaultEval (repl.js:252:27)
    at bound (domain.js:287:14)
    at REPLServer.runBound [as eval] (domain.js:300:12)
    at REPLServer.<anonymous> (repl.js:417:12)
    at emitOne (events.js:95:20)
    at REPLServer.emit (events.js:182:7)
    at REPLServer.Interface._onLine (readline.js:211:10)
    at REPLServer.Interface._line (readline.js:550:8)
> 

The strangeness is at Object.obj.a.obj.b (repl:1:34)

Pure MWE JS:

var obj = {};
obj.a = obj.b = function(){throw err};
obj.b();

Is it an error?

If the same object is declared in another way, everything is OK:

> var obj = {};
undefined
> obj.b = function(){throw err};
[Function]
> obj.a = obj.b;
[Function]
> obj.a();
ReferenceError: err is not defined
    at Object.obj.b (repl:1:26)
    at repl:1:5
    at REPLServer.defaultEval (repl.js:252:27)
    at bound (domain.js:287:14)
    at REPLServer.runBound [as eval] (domain.js:300:12)
    at REPLServer.<anonymous> (repl.js:417:12)
    at emitOne (events.js:95:20)
    at REPLServer.emit (events.js:182:7)
    at REPLServer.Interface._onLine (readline.js:211:10)
    at REPLServer.Interface._line (readline.js:550:8)
> obj.b();
ReferenceError: err is not defined
    at Object.obj.b (repl:1:26)
    at repl:1:5
    at REPLServer.defaultEval (repl.js:252:27)
    at bound (domain.js:287:14)
    at REPLServer.runBound [as eval] (domain.js:300:12)
    at REPLServer.<anonymous> (repl.js:417:12)
    at emitOne (events.js:95:20)
    at REPLServer.emit (events.js:182:7)
    at REPLServer.Interface._onLine (readline.js:211:10)
    at REPLServer.Interface._line (readline.js:550:8)
> 

[nickkolok]

A bit fuller example:

> var obj = {};
undefined
> obj.b = function(){throw err};
[Function]
> obj.a = obj.b;
[Function]
> obj.a();
ReferenceError: err is not defined
    at Object.obj.b (repl:1:26)
    at repl:1:5
    at REPLServer.defaultEval (repl.js:252:27)
    at bound (domain.js:287:14)
    at REPLServer.runBound [as eval] (domain.js:300:12)
    at REPLServer.<anonymous> (repl.js:417:12)
    at emitOne (events.js:95:20)
    at REPLServer.emit (events.js:182:7)
    at REPLServer.Interface._onLine (readline.js:211:10)
    at REPLServer.Interface._line (readline.js:550:8)
> obj.b();
ReferenceError: err is not defined
    at Object.obj.b (repl:1:26)
    at repl:1:5
    at REPLServer.defaultEval (repl.js:252:27)
    at bound (domain.js:287:14)
    at REPLServer.runBound [as eval] (domain.js:300:12)
    at REPLServer.<anonymous> (repl.js:417:12)
    at emitOne (events.js:95:20)
    at REPLServer.emit (events.js:182:7)
    at REPLServer.Interface._onLine (readline.js:211:10)
    at REPLServer.Interface._line (readline.js:550:8)
> obj.c = obj.d = obj.a;
[Function]
> obj.c();
ReferenceError: err is not defined
    at Object.obj.b (repl:1:26)
    at repl:1:5
    at REPLServer.defaultEval (repl.js:252:27)
    at bound (domain.js:287:14)
    at REPLServer.runBound [as eval] (domain.js:300:12)
    at REPLServer.<anonymous> (repl.js:417:12)
    at emitOne (events.js:95:20)
    at REPLServer.emit (events.js:182:7)
    at REPLServer.Interface._onLine (readline.js:211:10)
    at REPLServer.Interface._line (readline.js:550:8)
> 

[nickkolok]

@vkurchatkin, should I report this to V8 now?

[evanlucas]

@nickkolok can you try with the v6.5.0 and see if you can reproduce? v5.x hit end of life a few months ago.

[princejwesley]

Tested against chrome 52.0.2743.116 (64-bit) & 55.0.2843.0 canary (64-bit).

Only difference is, there is no Object. prefix in chrome console.

[nickkolok]

@evanlucas I'd be be glad if you helped me to install it on Ubuntu 12.04.

[Slayer95]

I've seen all sorts of weird stack traces before.
Glad to see that someone has found a reduced test case for at least a subset of them!

[bnoordhuis]

This is a V8 issue, not something we have direct control over. Can you report it here: https://bugs.chromium.org/p/v8/issues/list? Thanks.

FWIW, the output doesn't seem unreasonable to me given the constraints. The function has no name so V8 tries to infer one from context. If you write it like obj.a = obj.b = function f(){throw err}, you get Object.f in the stack trace.