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https://issues.apache.org/jira/browse/GROOVY-12601?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18135575#comment-18135575
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ASF GitHub Bot commented on GROOVY-12601:
-----------------------------------------
codeconsole opened a new pull request, #3128:
URL: https://github.com/apache/groovy/pull/3128
Under `@CompileStatic`, a call from trait code to a `@Virtual` static method
whose name matches a `java.lang.Class` method binds to the `Class` method:
```groovy
import groovy.transform.Virtual
@groovy.transform.CompileStatic
trait T {
@Virtual static String getName() { 'trait' }
static String sm() { getName() }
}
class C implements T { static String getName() { 'impl' } }
class D implements T {}
assert C.sm() == 'impl' // 'C'
assert D.sm() == 'trait' // 'D'
```
The same happens for `getSimpleName`, `isInterface`, `getModifiers` and DGM
methods such as `dump()`. A `@Virtual static Object cast(Object)` fails with a
`ClassCastException`, because the call takes `Class<C>.cast`'s return type. It
also happens for calls from instance trait methods and for a `@Virtual` static
of a super trait, and in 6.0.0. Dynamic Groovy and `@TypeChecked` run the
implementing class's method.
The trait transformation rewrites the call to `$static$self.getName()` (or
`((Class) $self.getClass()).getName()`) and marks it for dynamic dispatch.
`TraitTypeCheckingExtension.handleMissingMethod` honours that mark only when no
method is found, and here the type checker finds `Class.getName()` on the
`Class<T>` receiver.
`TraitTypeCheckingExtension.onMethodSelection` now makes a call carrying
that mark dynamic even when a method was selected, with the return type of the
`@Virtual` method. The type checker treats the replaced target as an extension
intervention, so static compilation emits a dynamic call through the
implementing class.
The property form (`name` for `@Virtual static String getName()`) is handled
with #3121 (GROOVY-12594), which adds property-syntax support for `@Virtual`
static accessors.
## Tests
`VirtualAnnotationTest.virtualStatic_namedLikeClassMethod` and
`virtualStatic_ofSuperTrait_namedLikeClassMethod` run dynamic, `@TypeChecked`
and `@CompileStatic`. Their `@CompileStatic` variants fail without the change.
The `groovy.transform.stc`, `org.codehaus.groovy.classgen.asm.sc`,
`org.codehaus.groovy.transform.traitx` and `gls` packages,
`groovy.ThisAndSuperTest` and `TraitsSpecificationTest` pass. The Checkstyle
and CodeNarc gates pass.
> SC calls the java.lang.Class method instead of a @Virtual trait static method
> of the same name
> ----------------------------------------------------------------------------------------------
>
> Key: GROOVY-12601
> URL: https://issues.apache.org/jira/browse/GROOVY-12601
> Project: Groovy
> Issue Type: Bug
> Affects Versions: 6.0.0
> Reporter: Scott Murphy Heiberg
> Priority: Major
>
> {code:groovy}
> import groovy.transform.Virtual
> @groovy.transform.CompileStatic
> trait T {
> @Virtual static String getName() { 'trait' }
> static String sm() { getName() }
> }
> class C implements T { static String getName() { 'impl' } }
> class D implements T {}
> assert C.sm() == 'impl'
> assert D.sm() == 'trait'
> {code}
> Actual: {{C.sm()}} returns {{'C'}} and {{D.sm()}} returns {{'D'}}. The trait
> calls {{Class.getName()}}. The same happens for other {{Class}} and DGM names
> such as {{getSimpleName}}, {{isInterface}}, {{getModifiers}} and {{dump}}. A
> {{@Virtual static Object cast(Object)}} fails with a {{ClassCastException}}.
> It also happens from instance trait methods and for a {{@Virtual}} static of
> a super trait.
> Expected: {{'impl'}} and {{'trait'}}, as dynamic Groovy and {{@TypeChecked}}
> give.
> The trait transformation rewrites the call to a call on the static self (a
> Class) and marks it for dynamic dispatch. Static type checking finds
> {{Class.getName()}} on that receiver, so the trait type checking extension is
> never asked and static compilation binds the call to the {{Class}} method.
> Seen in 6.0.0 (the first version with @Virtual).
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