Change 'null' and 'false' to be the only falsey values

[DartBot]

This issue was originally filed by jmi...@gmail.com

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I'd like to propose a change to Dart's boolean conversion. I think it is best if "false" and "null" convert to false, and everything else converts to true:

(bool v) {
    return null != v && false !== v;
}(o)

Ruby and Scheme have this behavior. With the change, it is possible to check if a variable is null without including "!= null". Checking for null is common, and this change would get rid of some of verbosity of Java. Not only would this be shorter code, but it would be closer to how most other languages behave. In many languages (C, D, PHP, JavaScript, Python, Ruby, and others), code equivalent to the following works:

obj = getPerson();
if(obj) {
    ...
}

This wouldn't affect the "(a-b)" example in the language spec--it still wouldn't work. It would just be always true instead of always false.

I'm not sure I understand the boolean-being-autoboxed problem mentioned in the spec. I know "new Boolean(false)" is coerced to true in JavaScript, but when is a boolean autoboxed? I know it is if you call one of its methods, but how would you convert it back to a boolean then?

In any case, I don't see how the proposal would affect this. If Dart makes all objects convert to false to make "new Boolean(false)" be false, then wouldn't it also make "new Boolean(true)" be false?

The idea was mentioned on reddit and most people liked it:
http://www.reddit.com/r/programming/comments/l88ny/why_dart_is_not_the_language_of_the_future/c2qlzed
A couple of people didn't, but they weren't happy with the spec as it is either (they wanted 1 to be true and 0 to be false).

[DartBot]

This comment was originally written by drfibonacci@google.com

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Removed Type-Defect label.
Added Type-Enhancement, Area-Language, Triaged labels.

[gbracha]

Set owner to @gbracha.
Added Accepted label.

[gbracha]

Added WontFix label.