KT-41346 Move removing non-available functions to protected method

This would allow to stricten contract on `computeNonDeclaredFunctions`

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/descriptors/DeserializedClassDescriptor.kt

@@ -246,16 +246,16 @@ class DeserializedClassDescriptor(
             return super.getContributedVariables(name, location)
         }
 
+        override fun isDeclaredFunctionAvailable(function: SimpleFunctionDescriptor): Boolean {
+            return c.components.platformDependentDeclarationFilter.isFunctionAvailable(this@DeserializedClassDescriptor, function)
+        }
+
         override fun computeNonDeclaredFunctions(name: Name, functions: MutableCollection<SimpleFunctionDescriptor>) {
             val fromSupertypes = ArrayList<SimpleFunctionDescriptor>()
             for (supertype in refinedSupertypes()) {
                 fromSupertypes.addAll(supertype.memberScope.getContributedFunctions(name, NoLookupLocation.FOR_ALREADY_TRACKED))
             }
 
-            functions.retainAll {
-                c.components.platformDependentDeclarationFilter.isFunctionAvailable(this@DeserializedClassDescriptor, it)
-            }
-
             functions.addAll(c.components.additionalClassPartsProvider.getFunctions(name, this@DeserializedClassDescriptor))
             generateFakeOverrides(name, fromSupertypes, functions)
         }

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/descriptors/DeserializedMemberScope.kt

@@ -35,7 +35,7 @@ import org.jetbrains.kotlin.utils.addIfNotNull
 import org.jetbrains.kotlin.utils.compact
 import java.io.ByteArrayInputStream
 import java.io.ByteArrayOutputStream
-import java.util.*
+import kotlin.collections.ArrayList
 
 abstract class DeserializedMemberScope protected constructor(
     protected val c: DeserializationContext,
@@ -104,7 +104,7 @@ abstract class DeserializedMemberScope protected constructor(
             name,
             functionProtosBytes,
             ProtoBuf.Function.PARSER,
-            { c.memberDeserializer.loadFunction(it) },
+            { c.memberDeserializer.loadFunction(it).takeIf(::isDeclaredFunctionAvailable) },
             { computeNonDeclaredFunctions(name, it) }
         )
 
@@ -112,7 +112,7 @@ abstract class DeserializedMemberScope protected constructor(
         name: Name,
         bytesByName: Map<Name, ByteArray>,
         parser: Parser<M>,
-        factory: (M) -> D,
+        factory: (M) -> D?,
         computeNonDeclared: (MutableCollection<D>) -> Unit
     ): Collection<D> =
         computeDescriptors(
@@ -128,15 +128,20 @@ abstract class DeserializedMemberScope protected constructor(
 
     private inline fun <M : MessageLite, D : DeclarationDescriptor> computeDescriptors(
         protos: Collection<M>,
-        factory: (M) -> D,
+        factory: (M) -> D?,
         computeNonDeclared: (MutableCollection<D>) -> Unit
     ): Collection<D> {
-        val descriptors = protos.mapTo(arrayListOf(), factory)
+        val descriptors = protos.mapNotNullTo(ArrayList(protos.size), factory)
 
         computeNonDeclared(descriptors)
         return descriptors.compact()
     }
 
+    /**
+     * Can be overridden to filter specific declared functions. Not called on non-declared functions.
+     */
+    protected open fun isDeclaredFunctionAvailable(function: SimpleFunctionDescriptor): Boolean = true
+
     protected open fun computeNonDeclaredFunctions(name: Name, functions: MutableCollection<SimpleFunctionDescriptor>) {
     }