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

["Sterling Greene (Jira)" <ji...@apache.org>]

Sterling Greene created GROOVY-10807:
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             Summary: 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: 3.0.13, 3.0.12
            Reporter: Sterling Greene


This compiles in Groovy 3.0.11, but it does not compile in Groovy 3.0.12 or 3.0.13.

{{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;
    }
} 
}}

The error is
    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.
    private static final Comparator<String> COMPARATOR = Comparator.comparing(NoticeRenderer::getComponentDisplayName)

The type bound could be on the method itself. This produces the same error.
    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.
    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)

BUG! exception in phase 'instruction selection' in source unit 'ConsoleScript34' Expected earlier checking to detect generics parameter arity mismatch
Expected: java.util.Comparator<T> 
Supplied: java.util.Comparator<java.lang.String,java.lang.String> 

In Java, you don't need the type information at all:
    private static final Comparator<String> COMPARATOR = Comparator.comparing(NoticeRenderer::getComponentDisplayName);

If you wanted to be verbose in Java, you could specify the bounds:
    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:
    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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