KotlinDeclarationSearcher: return backing fields for parameters (KT-29034)

idea/src/org/jetbrains/kotlin/idea/jvm/KotlinDeclarationSearcher.kt

@@ -9,9 +9,14 @@ import com.intellij.lang.jvm.JvmElement
 import com.intellij.lang.jvm.source.JvmDeclarationSearcher
 import com.intellij.psi.PsiElement
 import com.intellij.psi.PsiNamedElement
+import org.jetbrains.kotlin.asJava.LightClassUtil
 import org.jetbrains.kotlin.asJava.toLightElements
+import org.jetbrains.kotlin.asJava.toPsiParameters
 import org.jetbrains.kotlin.psi.KtClass
 import org.jetbrains.kotlin.psi.KtElement
+import org.jetbrains.kotlin.psi.KtParameter
+import org.jetbrains.kotlin.utils.SmartList
+import org.jetbrains.kotlin.utils.addIfNotNull
 
 class KotlinDeclarationSearcher : JvmDeclarationSearcher {
     override fun findDeclarations(declaringElement: PsiElement): Collection<JvmElement> =
@@ -25,6 +30,13 @@ class KotlinDeclarationSearcher : JvmDeclarationSearcher {
             else
                 declaringElement.toLightElements() + primaryConstructor.toLightElements()
         }
+        is KtParameter -> {
+            SmartList<PsiNamedElement>().apply {
+                addAll(declaringElement.toPsiParameters())
+                addIfNotNull(LightClassUtil.getLightClassBackingField(declaringElement))
+                addAll(LightClassUtil.getLightClassPropertyMethods(declaringElement))
+            }
+        }
         is KtElement -> declaringElement.toLightElements()
         else -> emptyList()
     }

idea/tests/org/jetbrains/kotlin/idea/jvm/KotlinJvmDeclarationSearcherTest.kt

@@ -27,6 +27,8 @@ class KotlinJvmDeclarationSearcherTest : KotlinLightCodeInsightFixtureTestCase()
 
             class SomeClass(val field: String) {
 
+                private var privateField: Int = 1
+
                 lateinit var anotherField:String
 
                 constructor(i: Int): this(i.toString()){}
@@ -41,8 +43,9 @@ class KotlinJvmDeclarationSearcherTest : KotlinLightCodeInsightFixtureTestCase()
         """,
         JvmDeclared("class SomeClass", JvmClass::class, JvmMethod::class),
         JvmDeclared("(val field: String)", JvmMethod::class),
+        JvmDeclared("private var privateField", com.intellij.lang.jvm.JvmField::class),
         JvmDeclared("lateinit var anotherField", JvmMethod::class, JvmMethod::class, com.intellij.lang.jvm.JvmField::class),
-        JvmDeclared("val field: String", JvmParameter::class, JvmMethod::class),
+        JvmDeclared("val field: String", JvmParameter::class, JvmMethod::class, com.intellij.lang.jvm.JvmField::class),
         JvmDeclared("constructor(i: Int)", JvmMethod::class),
         JvmDeclared("i: Int", JvmParameter::class),
         JvmDeclared("a: Long", JvmParameter::class, JvmParameter::class),