[gw]

Not the commenter but which one of these is the defer generating?

    // option 1
    try {
      fp = os.open(x)
      fp.read()
    }
    finally {
      fp.close()
    }

    // option 2
    fp = os.open(x)
    try {
      fp.read()
    }
    finally {
      fp.close()
    }

Should we close if open fails? Maybe, maybe not, but with try/finally it is obvious which one it is doing.

[jerf]

The first one is obviously wrong, which I mean in the sense that anyone who knows what defer is will know that, not in the sense that you've posted an obviously bad post (it is a fair question!). defer is a statement, not a declaration, and does not take effect until it is executed like any other statement. It follows standard structured programming rules; line 2 does not execute until line 1 is done. (A rule so simple and obvious we often don't think about, especially since structured programming has basically won and everything we use nowadays is structured, but it is still a rule that we use in programming.)

[CodesInChaos]

The first one doesn't compile in any language that requires variables to be initialized before use.

[chomp]

In nim, it generates code analogous to option 2.

[gw]

You sure? https://forum.nim-lang.org/t/4022#25046 edit: the docs seem to say you're right, maybe that forum post is outdated but it's from nim's author.