[jira] [Comment Edited] (GROOVY-10807) STC seems to lose type information through method references

["Eric Milles (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/GROOVY-10807?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17629068#comment-17629068 ] 

Eric Milles edited comment on GROOVY-10807 at 11/4/22 4:18 PM:
---------------------------------------------------------------

I'm still investigating "Comparator.comparing(NoticeRenderer::getComponentDisplayName)".  The type parameters of {{comparing(Function)}} are the source of the issue.

I do have a fix so you can write:
{code:groovy}
Comparator<String> COMPARATOR =
  Comparator.<String,String>comparing(NoticeRenderer::getComponentDisplayName)
{code}

For now you can also write:
{code:groovy}
Comparator<String> COMPARATOR =
  Comparator.comparing((Function<String,String>) NoticeRenderer::getComponentDisplayName)
{code}


was (Author: emilles):
I'm still investigating "Comparator.comparing(NoticeRenderer::getComponentDisplayName)".  The type parameters of {{comparing(Function)}} are the source of the issue.

I do have a fix so you can write:
{code:groovy}
Comparator<String> COMPARATOR =
  Comparator.<String,String>comparing(NoticeRenderer::getComponentDisplayName)
{code}

For now you can write:
{code:groovy}
Comparator<String> COMPARATOR =
  Comparator.comparing((Function<String,String>) NoticeRenderer::getComponentDisplayName)
{code}

> STC seems to lose type information through method references
> ------------------------------------------------------------
>
>                 Key: GROOVY-10807
>                 URL: https://issues.apache.org/jira/browse/GROOVY-10807
>             Project: Groovy
>          Issue Type: Bug
>          Components: Static compilation
>    Affects Versions: 3.0.12, 3.0.13, 4.0.6
>            Reporter: Sterling Greene
>            Assignee: Eric Milles
>            Priority: Major
>
> This compiles in Groovy 3.0.11, but it does not compile in Groovy 3.0.12 or 3.0.13.
> {code:java}
> import groovy.transform.CompileStatic
> @CompileStatic
> abstract class NoticeRenderer {
>     private static final Comparator<String> COMPARATOR = Comparator<String>.comparing(NoticeRenderer::getComponentDisplayName)
>    
>     public static String getComponentDisplayName(String component) {
>         return component;
>     }
> } 
> {code}
> The error is
> bq. Failed to find the expected method[getComponentDisplayName(java.lang.Object)] in the type[NoticeRenderer] at line: 5, column: 79
> I think something is going sideways when inferring the types to comparing.
> Removing the type bound on the Comparator doesn't change the error.
> bq. private static final Comparator<String> COMPARATOR = Comparator.comparing(NoticeRenderer::getComponentDisplayName)
> The type bound could be on the method itself. This produces the same error.
> bq. private static final Comparator<String> COMPARATOR = Comparator.<String>comparing(NoticeRenderer::getComponentDisplayName)
> But comparing actually has two type parameters, so it's a little weird that the above doesn't complain. Specifying both type parameters still produces the same error.
> bq. private static final Comparator<String> COMPARATOR = Comparator.<String, String>comparing(NoticeRenderer::getComponentDisplayName)
> If I mistakenly put the type bounds on Comparator, I don't expect this to work, but it produces BUG! output:
> private static final Comparator<String> COMPARATOR = Comparator<String, String>.comparing(NoticeRenderer::getComponentDisplayName)
> bq. BUG! exception in phase 'instruction selection' in source unit 'ConsoleScript34' Expected earlier checking to detect generics parameter arity mismatch
> bq. Expected: java.util.Comparator<T> 
> bq. Supplied: java.util.Comparator<java.lang.String,java.lang.String>
> In Java, you don't need the type information at all:
> bq. private static final Comparator<String> COMPARATOR = Comparator.comparing(NoticeRenderer::getComponentDisplayName);
> If you wanted to be verbose in Java, you could specify the bounds:
> bq. private static final Comparator<String> COMPARATOR = Comparator.<String, String>comparing(NoticeRenderer::getComponentDisplayName);
> As a workaround...
> If I avoid the use of the method reference, I can make something pass the static compiler:
> bq. private static final Comparator<String> COMPARATOR = Comparator.<String>comparing( { String it -> getComponentDisplayName(it) })
> I need both the type bound on comparing and the type of the parameter.



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