[jira] [Commented] (GROOVY-9946) Add `@Pure` to mark constant result of method

["Daniel Sun (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/GROOVY-9946?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17285650#comment-17285650 ] 

Daniel Sun commented on GROOVY-9946:
------------------------------------

[~paulk] According to your suggestion for PR1492, I've renamed annotation {{ConstantString}} to {{Pure}} and change its target elment to {{METHOD}}.

> Add `@Pure` to mark constant result of method
> ---------------------------------------------
>
>                 Key: GROOVY-9946
>                 URL: https://issues.apache.org/jira/browse/GROOVY-9946
>             Project: Groovy
>          Issue Type: Improvement
>            Reporter: Daniel Sun
>            Assignee: Daniel Sun
>            Priority: Major
>             Fix For: 4.0.0-alpha-3
>
>          Time Spent: 50m
>  Remaining Estimate: 0h
>
> In order to fully leverage the power of {{GString}} caching(GROOVY-9637), it would be good to have an annotaton to mark constant result of {{toString}}.
> Currently we could mark classes immutable, but it's too restricted for many cases. Currently we just cache literal of {{GString}} when its all values are immutable, but for more common cases, if the result of value's {{toString}} is constant, we could cache too. For example:
> {code:java}
> final class Test {
>     @groovy.transform.KnownImmutable // actually the class is not immutable...
>     private static final class Item {
>         private int toStringInvocationCount = 0
>         @Override
>         synchronized String toString() {
>             toStringInvocationCount++
>             return "item"
>         }
>     }
>     static void main(String[] args) {
>         Item item = new Item()
>         new StringBuilder().append("item: ${item}")
>         System.out.println(item.toStringInvocationCount)  // yield 1
>     }
> }
> {code}
> *Better annotation:*
> {code:java}
> final class Test {
>     private static final class Item {
>         private int toStringInvocationCount = 0
>         @Override
>         @groovy.transform.Pure
>         synchronized String toString() {
>             toStringInvocationCount++
>             return "item"
>         }
>     }
>     static void main(String[] args) {
>         Item item = new Item()
>         new StringBuilder().append("item: ${item}")
>         System.out.println(item.toStringInvocationCount)  // yield 1
>     }
> }
> {code}



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