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From "Piotr Zarzycki (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (FLEX-34984) for-each loops cross-compile incorrectly
Date Tue, 03 May 2016 06:31:12 GMT

     [ https://issues.apache.org/jira/browse/FLEX-34984?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Piotr Zarzycki updated FLEX-34984:
----------------------------------
    Fix Version/s:     (was: Apache FlexJS 0.6.0)
                   Apache FalconJX 0.6.0

> for-each loops cross-compile incorrectly
> ----------------------------------------
>
>                 Key: FLEX-34984
>                 URL: https://issues.apache.org/jira/browse/FLEX-34984
>             Project: Apache Flex
>          Issue Type: Bug
>          Components: Falcon, FlexJS
>    Affects Versions: Apache FlexJS 0.5.0
>            Reporter: Andy Dufilie
>            Assignee: Alex Harui
>             Fix For: Apache FalconJX 0.6.0
>
>
> When you write a for-each loop, the iterable gets re-evaluated on every iteration.
> Example code:
> {code}
> for each (var item:Object in Test.getItems()) {
> 	Test.doSomething(item);
> }
> {code}
> Cross-compiled:
> {code}
>   for (var foreachiter0 in Test.getItems()) 
>   {
>   var item = Test.getItems()[foreachiter0];
>   {
>     Test.doSomething(item);
>   }}
> {code}
> It should not call Test.getItems() on every loop iteration. Instead, it should generate
a new local variable prior to entering the loop to store the result:
> {code}
> var foreachiter0_target = Test.getItems();
> for (var foreachiter0 in foreachiter0_target)
> {
>     var item = foreachiter0_target[foreachiter0];
>     Test.doSomething(item);
> }
> {code}
> I can see problematic code in three places:
> * JSGeneratingReducer.java: https://github.com/apache/flex-falcon/blob/develop/compiler.js/src/org/apache/flex/compiler/internal/as/codegen/JSGeneratingReducer.java#L3426
> * ForEachEmitter.java: https://github.com/apache/flex-falcon/blob/develop/compiler.jx/src/org/apache/flex/compiler/internal/codegen/js/jx/ForEachEmitter.java
> * JSVF2JSEmitter.java: https://github.com/apache/flex-falcon/blob/develop/compiler.jx/src/org/apache/flex/compiler/internal/codegen/js/vf2js/JSVF2JSEmitter.java#L1708
> Another solution would be to use a for...of loop, Standard in ES6, though that won't
work in Internet Explorer: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...of



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