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https://issues.apache.org/jira/browse/GROOVY-11453?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17886024#comment-17886024
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Paul King commented on GROOVY-11453:
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Yes, I see the difference now. I mustn't have done a clean in previous testing.
I've added the breaking label to this issue, though I'll note that it is only
breaking if folks were relying on the specific empty list for that one edge
case.
> Spread-safe operator differences and efficiencies
> -------------------------------------------------
>
> Key: GROOVY-11453
> URL: https://issues.apache.org/jira/browse/GROOVY-11453
> Project: Groovy
> Issue Type: Bug
> Components: Static compilation
> Reporter: Eric Milles
> Assignee: Eric Milles
> Priority: Major
> Labels: breaking
> Fix For: 5.0.0-alpha-11
>
>
> The spread-safe operator -- aka {{a*.b}} or {{a*.b(c)}} -- has some
> differences and inefficiencies.
> # When the receiver is null, the expression produces null for dynamic mode
> and an empty list for static compilation. Can this difference be safely
> resolved?
> # When the method return type is {{void}}, there is no need for a list to
> collect up nulls. This is producing "Useless object stored in variable
> var$1" warnings from SpotBugs. The only benefit of this is the ability to
> detect the number of elements.
> # The SC bytecode has a redundant null test in it. Since a for loop is also
> null-safe, guarding the loop bytecode by a null check is producing "Redundant
> check for null" warnings from SpotBugs. *NOTE:* If (1) above is changed in
> the SC classgen, the null check may not be redundant as it would guard list
> construction.
> For reference, {{object*.method(arguments)}} is written by the static
> compiler like this:
> {code:groovy}
> def result = new ArrayList()
> if (object != null) {
> for (Inferred element : object) { // also null-safe
> result.add(element?.method(arguments)
> }
> }
> result
> {code}
> And the dynamic impl:
> https://github.com/apache/groovy/blob/f46103d31b7574ce883ff3b6c01fa8a412f225be/src/main/java/org/codehaus/groovy/runtime/ScriptBytecodeAdapter.java#L189
> GROOVY-7177
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