kotlin support for google guice

KotlinSupportImpl.kt

package com.google.inject

import com.google.inject.internal.Errors
import com.google.inject.internal.KotlinSupportInterface
import java.lang.reflect.Constructor
import java.lang.reflect.Field
import java.lang.reflect.Method
import java.util.function.Predicate
import kotlin.reflect.full.declaredFunctions
import kotlin.reflect.full.declaredMemberProperties
import kotlin.reflect.jvm.jvmErasure

class KotlinSupportImpl : KotlinSupportInterface {
  companion object {
    @JvmField
    val INSTANCE = KotlinSupportImpl()
  }

  override fun getAnnotations(field: Field?): Array<Annotation> {
    if (field == null) {
      return emptyArray()
    }

    field.declaringClass.kotlin.declaredMemberProperties.forEach {
      if (it.name == field.name) {
        return it.annotations.toTypedArray()
      }
    }
    return emptyArray()
  }

  override fun isNullable(field: Field?): Boolean {
    if (field != null) {
      field.declaringClass.kotlin.declaredMemberProperties.forEach {
        if (it.name == field.name) {
          return it.returnType.isMarkedNullable
        }
      }
      return false
    } else {
      return false
    }
  }

  override fun getIsParameterKotlinNullablePredicate(constructor: Constructor<*>?): Predicate<Int> {
    if (constructor == null) {
      return Predicate { false }
    }

    constructor.declaringClass.kotlin.constructors.forEach {
      if (it.parameters.zip(constructor.parameters).all { (kotlinParam, javaParam) -> kotlinParam.type.jvmErasure.java == javaParam.type }) {
        return Predicate { index -> it.parameters[index].type.isMarkedNullable }
      }
    }
    return Predicate { false }
  }

  override fun getIsParameterKotlinNullablePredicate(method: Method?): Predicate<Int> {
    if (method == null) {
      return Predicate { false }
    }

    method.declaringClass.kotlin.declaredFunctions.forEach {
      if (it.name == method.name &&
        it.parameters.zip(method.parameters).all { (kotlinParam, javaParam) -> kotlinParam.type.jvmErasure.java == javaParam.type }) {
        return Predicate { index -> it.returnType.isMarkedNullable }
      }
    }
    return Predicate { false }
  }

  override fun checkConstructorParameterAnnotations(constructor: Constructor<*>?, errors: Errors?) {
    if (constructor == null) {
      return
    }

    // do nothing, I have no clue what might actually be bad
    return
  }

  override fun isLocalClass(clazz: Class<*>?): Boolean {
    return clazz != null && clazz.kotlin.isInner
  }
}