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Bug 370232 - Casts don't appear to coerce closures
Summary: Casts don't appear to coerce closures
Status: NEW
Alias: None
Product: Xtend
Classification: Tools
Component: Core (show other bugs)
Version: 2.3.0   Edit
Hardware: All All
: P3 enhancement (vote)
Target Milestone: ---   Edit
Assignee: Project Inbox CLA
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Keywords:
: 370173 403032 (view as bug list)
Depends on: 376037
Blocks:
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Reported: 2012-01-31 10:43 EST by William R. Burdick Jr. CLA
Modified: 2013-05-27 06:10 EDT (History)
4 users (show)

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Description William R. Burdick Jr. CLA 2012-01-31 10:43:04 EST 
Build Identifier: 

Closures don't get type information from a cast.

This works:

var Function<Integer,Integer> s = [x|x * 2]


but this doesn't:

var s = [x|x * 2] as Function<Integer,Integer>

Reproducible: Always

Steps to Reproduce:
1. try to compile this declaraion:

var s = [x|x * 2] as Function<Integer,Integer>
Comment 1 Sven Efftinge CLA 2012-01-31 11:04:03 EST 
*** Bug 370173 has been marked as a duplicate of this bug. ***
Comment 2 Sven Efftinge CLA 2012-01-31 11:05:10 EST 
Casts are generally not used in expected type inference. See also : http://groups.google.com/group/xtend-lang/browse_thread/thread/63a2181439fef757
Comment 3 William R. Burdick Jr. CLA 2012-02-01 12:02:20 EST 
This becomes more important when closures can coerce to abstract classes, because you may have several abstract classes implementing the same interface.

With your patch to allow casts to work for this, I can now choose an abstract class by casting a literal closure.  I have a closure-compatible abstract class (given my patch), called SimpleSelectionAdapter, that implements SWT's SelectionListener interface and leaves only widgetSelected() abstract and I can use a closure for it, like this:


menuItem.addSelectionListener([e|...] as SimpleSelectionAdapter)


If the cast doesn't work, I need to declare a new variable for this, which seems counter to Xtend's focus on programmer convenience.
Comment 4 Sven Efftinge CLA 2012-04-04 02:25:16 EDT 
Something we should look at while reworking the linking / type system
Comment 5 Dennis Huebner CLA 2013-02-14 04:35:44 EST 
Is an enhancement.
Comment 6 Sebastian Zarnekow CLA 2013-03-12 09:06:19 EDT 
see also bug 403032
Comment 7 Sven Efftinge CLA 2013-03-12 09:07:07 EDT 
*** Bug 403032 has been marked as a duplicate of this bug. ***