[jira] [Commented] (GROOVY-8342) Static compilation error with a method returning an array in a type parameter

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[jira] [Commented] (GROOVY-8342) Static compilation error with a method returning an array in a type parameter

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    [ https://issues.apache.org/jira/browse/GROOVY-8342?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16645251#comment-16645251 ]

Eric Milles commented on GROOVY-8342:

{{StaticTypeCheckingVisitor}} seems to have a handle on the generics.  When visiting method {{testListMethod}}, it does manage to understand the link between {{E}} and {{Integer}}.
    protected ClassNode inferReturnTypeGenerics(
            ClassNode receiver,
            MethodNode method,
            Expression arguments,
            GenericsType[] explicitTypeHints) {
        // resolvedPlaceholders: {E=java.lang.Integer}
        // returnType: java.util.Optional <[LE;> -> java.util.Optional <T extends java.lang.Object>
        return applyGenericsContext(resolvedPlaceholders, returnType);

> Static compilation error with a method returning an array in a type parameter
> -----------------------------------------------------------------------------
>                 Key: GROOVY-8342
>                 URL: https://issues.apache.org/jira/browse/GROOVY-8342
>             Project: Groovy
>          Issue Type: Bug
>          Components: Static compilation
>            Reporter: M. Justin
>            Priority: Major
> A compilation error occurs when using static compilation and attempting to assign the result of a method that returns a parameterized argument that contains an array in the type parameter.  The equivalent Java code has no issues.
> Here is a specific example:
> {code}@CompileStatic
> class ArrayGenericsIssue {
>   static void main(String[] args) {
>     Optional<Integer[]> value = testArrayMethod(1) //This fails to compile
>   }
>   static <E> Optional<E[]> testArrayMethod(E ignored) {
>     return Optional.empty()
>   }
> }{code}
> The error returned is:
> {code}Error:(11, 33) Groovyc: [Static type checking] - Incompatible generic argument types. Cannot assign java.util.Optional <E[]> to: java.util.Optional <Integer[]>{code}
> The expected behavior is that this code would compile and run successfully with @CompileStatic enabled.
> Note that equivalent code with a non-array generic parameter works just fine:
> {code}
>   static void main(String[] args) {
>     Optional<List<Integer>> value = testListMethod(1)
>   }
>   static <E> Optional<List<E>> testListMethod(E ignored) {
>     return Optional.empty()
>   }
> {code}
> Additionally, there is no compilation issue if the value is cast:
> {code}Optional<Integer[]> value = (Optional<Integer[]>) testArrayMethod(1){code}
> For some context, I'm running into this issue when working with [jOOQ|https://www.jooq.org/], as some of its API involves working with array type parameters.

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