FIR: Drop MutableImplicitReceiverStack and its implementation

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/ImplicitReceiverStack.kt

@@ -5,15 +5,8 @@
 
 package org.jetbrains.kotlin.fir.resolve
 
-import kotlinx.collections.immutable.PersistentList
-import kotlinx.collections.immutable.PersistentMap
-import kotlinx.collections.immutable.persistentListOf
-import kotlinx.collections.immutable.persistentMapOf
 import org.jetbrains.kotlin.fir.resolve.calls.ImplicitDispatchReceiverValue
 import org.jetbrains.kotlin.fir.resolve.calls.ImplicitReceiverValue
-import org.jetbrains.kotlin.fir.symbols.FirBasedSymbol
-import org.jetbrains.kotlin.fir.types.ConeKotlinType
-import org.jetbrains.kotlin.name.Name
 
 abstract class ImplicitReceiverStack : Iterable<ImplicitReceiverValue<*>> {
     abstract operator fun get(name: String?): ImplicitReceiverValue<*>?
@@ -22,88 +15,3 @@ abstract class ImplicitReceiverStack : Iterable<ImplicitReceiverValue<*>> {
     abstract fun lastDispatchReceiver(lookupCondition: (ImplicitReceiverValue<*>) -> Boolean): ImplicitDispatchReceiverValue?
     abstract fun receiversAsReversed(): List<ImplicitReceiverValue<*>>
 }
-
-abstract class MutableImplicitReceiverStack : ImplicitReceiverStack() {
-    abstract fun add(name: Name?, value: ImplicitReceiverValue<*>)
-    abstract fun pop(name: Name?)
-
-    abstract fun snapshot(): MutableImplicitReceiverStack
-}
-
-class ImplicitReceiverStackImpl private constructor(
-    private var stack: PersistentList<ImplicitReceiverValue<*>>,
-    // This multi-map holds indexes of the stack ^
-    private var originalTypes: PersistentList<ConeKotlinType>,
-    private var indexesPerLabel: PersistentSetMultimap<Name, Int>,
-    private var indexesPerSymbol: PersistentMap<FirBasedSymbol<*>, Int>
-) : MutableImplicitReceiverStack() {
-    val size: Int get() = stack.size
-
-    constructor() : this(
-        persistentListOf(),
-        persistentListOf(),
-        PersistentSetMultimap(),
-        persistentMapOf()
-    )
-
-    override fun add(name: Name?, value: ImplicitReceiverValue<*>) {
-        stack = stack.add(value)
-        originalTypes = originalTypes.add(value.type)
-        val index = stack.size - 1
-        if (name != null) {
-            indexesPerLabel = indexesPerLabel.put(name, index)
-        }
-        indexesPerSymbol = indexesPerSymbol.put(value.boundSymbol, index)
-    }
-
-    override fun pop(name: Name?) {
-        val index = stack.size - 1
-        if (name != null) {
-            indexesPerLabel = indexesPerLabel.remove(name, index)
-        }
-        originalTypes = originalTypes.removeAt(index)
-        val value = stack.get(index)
-        stack = stack.removeAt(index)
-        indexesPerSymbol = indexesPerSymbol.remove(value.boundSymbol)
-    }
-
-    override operator fun get(name: String?): ImplicitReceiverValue<*>? {
-        if (name == null) {
-            return stack.lastOrNull {
-                it !is ImplicitDispatchReceiverValue || !it.inDelegated
-            }
-        }
-        return indexesPerLabel[Name.identifier(name)].lastOrNull()?.let { stack[it] }?.takeIf {
-            it !is ImplicitDispatchReceiverValue || !it.inDelegated
-        }
-    }
-
-    override fun lastDispatchReceiver(): ImplicitDispatchReceiverValue? {
-        return stack.filterIsInstance<ImplicitDispatchReceiverValue>().lastOrNull()
-    }
-
-    override fun lastDispatchReceiver(lookupCondition: (ImplicitReceiverValue<*>) -> Boolean): ImplicitDispatchReceiverValue? {
-        return stack.filterIsInstance<ImplicitDispatchReceiverValue>().lastOrNull(lookupCondition)
-    }
-
-    override fun receiversAsReversed(): List<ImplicitReceiverValue<*>> = stack.asReversed()
-
-    fun getReceiverIndex(symbol: FirBasedSymbol<*>): Int? = indexesPerSymbol[symbol]
-
-    fun getOriginalType(index: Int): ConeKotlinType {
-        return originalTypes[index]
-    }
-
-    fun replaceReceiverType(index: Int, type: ConeKotlinType) {
-        assert(index >= 0 && index < stack.size)
-        stack[index].replaceType(type)
-    }
-
-    override operator fun iterator(): Iterator<ImplicitReceiverValue<*>> {
-        return stack.iterator()
-    }
-
-    override fun snapshot(): ImplicitReceiverStackImpl {
-        return ImplicitReceiverStackImpl(stack, originalTypes, indexesPerLabel, indexesPerSymbol)
-    }
-}