[mtasc] Boolean expressions and ECMA-262

[Steve Webster]

Hi Robert,

> 11.11
> NOTE  The value produced by a && or || operator is not necessarily of type
> Boolean. The value produced will always be the value of one of the two
> operand expressions.

Interesting. So I guess that for an assignment MTASC should check that 
all operands for a boolean expression return a datatype that validly can 
be stored in the target...

// Some vars
var a:String = "Hello";
var b:Object = new Object();
var c:Number = 0;

// Correct - both String and Object can be stored in Test1
var test1:Object = a || b; // Would be String(hello)

// Incorrect - cannot sture Object in String without cast.
// Should the compiler throw an error here?
var test2:String = a || b;

// What happens here?
var test3:Object = a && b;

// And here?
var test4:Object = a && c;


I'm slightly confused over the values of 'test3' and 'test4'. For 
'test3' both of the operands in the expression will convert to 
Boolean(true), but which one (if either) gets assigned to 'test3'? What 
about 'test4'? Since 'c' will convert to Boolean(false) making the 
expression fail, does the value of 'test4' become Boolean(false) or 'null'?

I'm not necessarily expecting conclusive answers here. I still believe 
that boolean expressions should return Boolean results - that would 
certainly clear up the uncertanties presented above - but I guess we're 
stuck with what we have.

Steve

-- 
Steve Webster
Interactive Developer

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