REPL - after failed assignment identifier cannot be reused

[SamuelMarks]

A:\floppy>node -r lodash
> const _ = require('lodash');
const _ = require('lodash');
TypeError: Cannot assign to read only property '_' of #<Object>
    at finish (repl.js:438:24)
    at REPLServer.defaultEval (repl.js:185:5)
    at bound (domain.js:280:14)
    at REPLServer.runBound [as eval] (domain.js:293:12)
    at REPLServer.<anonymous> (repl.js:393:12)
    at emitOne (events.js:82:20)
    at REPLServer.emit (events.js:169:7)
    at REPLServer.Interface._onLine (readline.js:210:10)
    at REPLServer.Interface._line (readline.js:549:8)
    at REPLServer.Interface._ttyWrite (readline.js:826:14)
>
> ;
TypeError: Cannot assign to read only property '_' of #<Object>
    at finish (repl.js:438:24)
    at REPLServer.defaultEval (repl.js:185:5)
    at bound (domain.js:280:14)
    at REPLServer.runBound [as eval] (domain.js:293:12)
    at REPLServer.<anonymous> (repl.js:393:12)
    at emitOne (events.js:82:20)
    at REPLServer.emit (events.js:169:7)
    at REPLServer.Interface._onLine (readline.js:210:10)
    at REPLServer.Interface._line (readline.js:549:8)
    at REPLServer.Interface._ttyWrite (readline.js:826:14)
> let _ = require('lodash');
TypeError: Identifier '_' has already been declared
    at repl:1:1
    at REPLServer.defaultEval (repl.js:164:27)
    at bound (domain.js:280:14)
    at REPLServer.runBound [as eval] (domain.js:293:12)
    at REPLServer.<anonymous> (repl.js:393:12)
    at emitOne (events.js:82:20)
    at REPLServer.emit (events.js:169:7)
    at REPLServer.Interface._onLine (readline.js:210:10)
    at REPLServer.Interface._line (readline.js:549:8)
    at REPLServer.Interface._ttyWrite (readline.js:826:14)
> process.version
TypeError: Cannot assign to read only property '_' of #<Object>
    at finish (repl.js:438:24)
    at REPLServer.defaultEval (repl.js:185:5)
    at bound (domain.js:280:14)
    at REPLServer.runBound [as eval] (domain.js:293:12)
    at REPLServer.<anonymous> (repl.js:393:12)
    at emitOne (events.js:82:20)
    at REPLServer.emit (events.js:169:7)
    at REPLServer.Interface._onLine (readline.js:210:10)
    at REPLServer.Interface._line (readline.js:549:8)
    at REPLServer.Interface._ttyWrite (readline.js:826:14)

I am running Node 4.2.1 x64 on Windows 8.1 x64.

[thefourtheye]

@SamuelMarks _ is used internally to track the result of the last evaluated expression. Please check this section of the REPL doc. Since you are making it a const, internally, when REPL tries to store the result on _, it fails because it is read-only now. So, I don't think this is a bug per-se and closing the issue. Please feel free to comment if you have strong reasons to believe that this should be fixed and we can reopen this and find a solution.

[SamuelMarks]

Oh right, forgot about that. When I was coding Node years ago I now remember setting l = require('lodash').

[thefourtheye]

@SamuelMarks No problem :-) I created a PR (#3729) with doc changes regarding the same. Please feel free to review it.