Move out JVM debugger functionality

compiler/backend-common/src/org/jetbrains/kotlin/backend/common/CollectionUtil.kt

@@ -0,0 +1,16 @@
+/*
+ * Copyright 2000-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.backend.common
+
+fun <T> Collection<T>.atMostOne(): T? {
+    return when (this.size) {
+        0 -> null
+        1 -> this.iterator().next()
+        else -> throw IllegalArgumentException("Collection has more than one element.")
+    }
+}
+
+inline fun <T> Iterable<T>.atMostOne(predicate: (T) -> Boolean): T? = this.filter(predicate).atMostOne()

compiler/backend-common/src/org/jetbrains/kotlin/backend/common/SimpleMemberScope.kt

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2000-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.backend.common
+
+import org.jetbrains.kotlin.descriptors.*
+import org.jetbrains.kotlin.incremental.components.LookupLocation
+import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.resolve.scopes.DescriptorKindFilter
+import org.jetbrains.kotlin.resolve.scopes.MemberScopeImpl
+import org.jetbrains.kotlin.utils.Printer
+
+class SimpleMemberScope(val members: List<DeclarationDescriptor>) : MemberScopeImpl() {
+
+    override fun getContributedClassifier(name: Name, location: LookupLocation): ClassifierDescriptor? =
+        members.filterIsInstance<ClassifierDescriptor>()
+            .atMostOne { it.name == name }
+
+    override fun getContributedVariables(name: Name, location: LookupLocation): Collection<PropertyDescriptor> =
+        members.filterIsInstance<PropertyDescriptor>()
+            .filter { it.name == name }
+
+    override fun getContributedFunctions(name: Name, location: LookupLocation): Collection<SimpleFunctionDescriptor> =
+        members.filterIsInstance<SimpleFunctionDescriptor>()
+            .filter { it.name == name }
+
+    override fun getContributedDescriptors(
+        kindFilter: DescriptorKindFilter,
+        nameFilter: (Name) -> Boolean
+    ): Collection<DeclarationDescriptor> =
+        members.filter { kindFilter.accepts(it) && nameFilter(it.name) }
+
+    override fun printScopeStructure(p: Printer) = TODO("not implemented")
+}