Discriminate header classes in member scope.

We made it because of non-stable name resolution when project is multi platform. For such projects in platform module we have two classifiers with the same name, but impl class or type alias should win!

compiler/resolution/src/org/jetbrains/kotlin/resolve/scopes/LexicalChainedScope.kt

@@ -21,7 +21,7 @@ import org.jetbrains.kotlin.descriptors.ReceiverParameterDescriptor
 import org.jetbrains.kotlin.incremental.components.LookupLocation
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.scopes.utils.takeSnapshot
-import org.jetbrains.kotlin.util.collectionUtils.getFirstMatch
+import org.jetbrains.kotlin.util.collectionUtils.getFirstClassifierDiscriminateHeaders
 import org.jetbrains.kotlin.util.collectionUtils.getFromAllScopes
 import org.jetbrains.kotlin.utils.Printer
 
@@ -40,7 +40,7 @@ class LexicalChainedScope @JvmOverloads constructor(
     override fun getContributedDescriptors(kindFilter: DescriptorKindFilter, nameFilter: (Name) -> Boolean)
             = getFromAllScopes(memberScopes) { it.getContributedDescriptors() }
 
-    override fun getContributedClassifier(name: Name, location: LookupLocation) = getFirstMatch(memberScopes) { it.getContributedClassifier(name, location) }
+    override fun getContributedClassifier(name: Name, location: LookupLocation) = getFirstClassifierDiscriminateHeaders(memberScopes) { it.getContributedClassifier(name, location) }
 
     override fun getContributedVariables(name: Name, location: LookupLocation) = getFromAllScopes(memberScopes) { it.getContributedVariables(name, location) }
 

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/lazy/descriptors/JvmPackageScope.kt

@@ -28,7 +28,7 @@ import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.scopes.DescriptorKindFilter
 import org.jetbrains.kotlin.resolve.scopes.MemberScope
 import org.jetbrains.kotlin.storage.getValue
-import org.jetbrains.kotlin.util.collectionUtils.getFirstMatch
+import org.jetbrains.kotlin.util.collectionUtils.getFirstClassifierDiscriminateHeaders
 import org.jetbrains.kotlin.util.collectionUtils.getFromAllScopes
 import org.jetbrains.kotlin.utils.Printer
 import org.jetbrains.kotlin.utils.toReadOnlyList
@@ -52,7 +52,7 @@ class JvmPackageScope(
         val javaClassifier = javaScope.getContributedClassifier(name, location)
         if (javaClassifier != null) return javaClassifier
 
-        return getFirstMatch(kotlinScopes) { it.getContributedClassifier(name, location) }
+        return getFirstClassifierDiscriminateHeaders(kotlinScopes) { it.getContributedClassifier(name, location) }
     }
 
     override fun getContributedVariables(name: Name, location: LookupLocation): Collection<PropertyDescriptor> {

core/descriptors/src/org/jetbrains/kotlin/resolve/scopes/ChainedMemberScope.kt

@@ -21,7 +21,7 @@ import org.jetbrains.kotlin.descriptors.PropertyDescriptor
 import org.jetbrains.kotlin.descriptors.SimpleFunctionDescriptor
 import org.jetbrains.kotlin.incremental.components.LookupLocation
 import org.jetbrains.kotlin.name.Name
-import org.jetbrains.kotlin.util.collectionUtils.getFirstMatch
+import org.jetbrains.kotlin.util.collectionUtils.getFirstClassifierDiscriminateHeaders
 import org.jetbrains.kotlin.util.collectionUtils.getFromAllScopes
 import org.jetbrains.kotlin.utils.Printer
 
@@ -30,7 +30,7 @@ class ChainedMemberScope(
         private val scopes: List<MemberScope>
 ) : MemberScope {
     override fun getContributedClassifier(name: Name, location: LookupLocation): ClassifierDescriptor?
-            = getFirstMatch(scopes) { it.getContributedClassifier(name, location) }
+            = getFirstClassifierDiscriminateHeaders(scopes) { it.getContributedClassifier(name, location) }
 
     override fun getContributedVariables(name: Name, location: LookupLocation): Collection<PropertyDescriptor>
             = getFromAllScopes(scopes) { it.getContributedVariables(name, location) }

core/descriptors/src/org/jetbrains/kotlin/util/scopeUtils.kt

@@ -16,6 +16,8 @@
 
 package org.jetbrains.kotlin.util.collectionUtils
 
+import org.jetbrains.kotlin.descriptors.ClassifierDescriptor
+import org.jetbrains.kotlin.descriptors.ClassifierDescriptorWithTypeParameters
 import java.util.*
 
 /**
@@ -70,11 +72,20 @@ inline fun <Scope, T> getFromAllScopes(firstScope: Scope, restScopes: List<Scope
     return result ?: emptySet()
 }
 
-inline fun <Scope, T : Any> getFirstMatch(scopes: List<Scope>, callback: (Scope) -> T?): T? {
+inline fun <Scope, T : ClassifierDescriptor> getFirstClassifierDiscriminateHeaders(scopes: List<Scope>, callback: (Scope) -> T?): T? {
     // NOTE: This is performance-sensitive; please don't replace with map().firstOrNull()
+    var result: T? = null
     for (scope in scopes) {
-        val result = callback(scope)
+        val newResult = callback(scope)
-        if (result != null) return result
+        if (newResult != null) {
+            if (newResult is ClassifierDescriptorWithTypeParameters && newResult.isHeader) {
+                if (result == null) result = newResult
+            }
+            // this class is Impl or usual class
+            else {
+                return newResult
+            }
+        }
     }
-    return null
+    return result
 }