Streamline and reduce Kotlin delegates [SPR-16020]

[spring-issuemaster]

Juergen Hoeller opened SPR-16020 and commented

With #20432 leading to yet another need for a Kotlin-specific parameter declaration check, let's take the opportunity to streamline our Kotlin support code: Specifically, we can unify the detection of Kotlin's optional parameters in MethodParameter.isOptional(), reduce BeanUtils.findPrimaryConstructor to Kotlin semantics (for reuse in AutowiredAnnotationBeanPostProcessor as well as data class construction), and finally introduce a common KotlinDetector delegate with an isKotlinType(Class) check.

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Affects: 5.0 RC4

Issue Links:

• #20232 Kotlin class instantiation with optional parameters and default values
• #20402 Add support for Kotlin autowired constructor with optional parameters
• #20432 Revisit handling of missing fields (without default values) for immutable data classes
• #21825 GenericApplicationContext.registerBean should support non-default constructors

Referenced from: commits ec345bf