Fix overload resolution ambiguity for types intersection

There are two different forms of types intestion:
1. Type parameters with multiple bounds
2. Smart casts

The problem was that when member scope of type intersection contained
effective duplicates and that lead to overload resolution ambiguity in
strange cases like `x.hashCode()`

For first type we do effectively the same thing as when building member
scope for class extending several interfaces: group all descriptors by
both-way-overridability relation and then choose most-specific in each
group.

For smart casts we do basically the same thing but with special
treatments:
1. From all descriptors that _equal_ to most specific we choose
   the one that works without smartcast if possible (i.e. we choose first from candidates list)
2. If smart-cast value seems to be unstable we use only member scope
   of receiver type + all descriptors from smart cast possible types
   that has incompatible signature. If we'd include all of them and
   choose one as more specific, and it would lead to false
   SMART_CAST_IMPOSIBLE (see test unstableSmartCast.kt)

 #KT-3996 Fixed
 #KT-10315 Fixed

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tasks/TaskPrioritizer.kt

@@ -42,7 +42,7 @@ import org.jetbrains.kotlin.resolve.scopes.receivers.*
 import org.jetbrains.kotlin.resolve.scopes.receivers.ReceiverValue.NO_RECEIVER
 import org.jetbrains.kotlin.resolve.scopes.utils.getImplicitReceiversHierarchy
 import org.jetbrains.kotlin.resolve.scopes.utils.memberScopeAsImportingScope
-import org.jetbrains.kotlin.resolve.validation.InfixValidator
+import org.jetbrains.kotlin.resolve.selectMostSpecificInEachOverridableGroup
 import org.jetbrains.kotlin.storage.StorageManager
 import org.jetbrains.kotlin.types.ErrorUtils
 import org.jetbrains.kotlin.types.KotlinType
@@ -251,6 +251,11 @@ public class TaskPrioritizer(
                             c.context.call
                     )
                 }
+
+                if (explicitReceiver.types.size > 1) {
+                    members.retainAll( members.selectMostSpecificInEachOverridableGroup { descriptor } )
+                }
+
                 members
             }
         }

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tower/TowerLevels.kt

@@ -25,7 +25,11 @@ import org.jetbrains.kotlin.resolve.descriptorUtil.hasClassValueDescriptor
 import org.jetbrains.kotlin.resolve.scopes.ImportingScope
 import org.jetbrains.kotlin.resolve.scopes.LexicalScope
 import org.jetbrains.kotlin.resolve.scopes.ResolutionScope
-import org.jetbrains.kotlin.resolve.scopes.receivers.*
+import org.jetbrains.kotlin.resolve.scopes.receivers.CastImplicitClassReceiver
+import org.jetbrains.kotlin.resolve.scopes.receivers.ImplicitClassReceiver
+import org.jetbrains.kotlin.resolve.scopes.receivers.QualifierReceiver
+import org.jetbrains.kotlin.resolve.scopes.receivers.ReceiverValue
+import org.jetbrains.kotlin.resolve.selectMostSpecificInEachOverridableGroup
 import org.jetbrains.kotlin.types.ErrorUtils
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.isDynamic
@@ -71,7 +75,7 @@ internal class ReceiverScopeTowerLevel(
         val dispatchReceiver: ReceiverValue
 ): AbstractScopeTowerLevel(scopeTower) {
 
-    private fun <D: CallableDescriptor> collectMembers(
+    private fun <D : CallableDescriptor> collectMembers(
             getMembers: ResolutionScope.(KotlinType?) -> Collection<D>
     ): Collection<CandidateWithBoundDispatchReceiver<D>> {
         val result = ArrayList<CandidateWithBoundDispatchReceiver<D>>(0)
@@ -81,13 +85,23 @@ internal class ReceiverScopeTowerLevel(
 
         val smartCastPossibleTypes = scopeTower.dataFlowInfo.getSmartCastTypes(dispatchReceiver)
         val unstableError = if (scopeTower.dataFlowInfo.isStableReceiver(dispatchReceiver)) null else UnstableSmartCastDiagnostic
+        val unstableCandidates = if (unstableError != null) ArrayList<CandidateWithBoundDispatchReceiver<D>>(0) else null
 
         for (possibleType in smartCastPossibleTypes) {
-            possibleType.memberScope.getMembers(possibleType).mapTo(result) {
+            possibleType.memberScope.getMembers(possibleType).mapTo(unstableCandidates ?: result) {
                 createCandidateDescriptor(it, dispatchReceiver.smartCastReceiver(possibleType), unstableError, dispatchReceiverSmartCastType = possibleType)
             }
         }
 
+        if (smartCastPossibleTypes.isNotEmpty()) {
+            if (unstableCandidates == null) {
+                result.retainAll(result.selectMostSpecificInEachOverridableGroup { descriptor })
+            }
+            else {
+                result.addAll(unstableCandidates.selectMostSpecificInEachOverridableGroup { descriptor })
+            }
+        }
+
         if (dispatchReceiver.type.isDynamic()) {
             scopeTower.dynamicScope.getMembers(null).mapTo(result) {
                 createCandidateDescriptor(it, dispatchReceiver, DynamicDescriptorDiagnostic)

compiler/frontend/src/org/jetbrains/kotlin/types/TypeIntersector.java

@@ -29,6 +29,7 @@ import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystem;
 import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystemBuilderImpl;
 import org.jetbrains.kotlin.resolve.scopes.ChainedScope;
 import org.jetbrains.kotlin.resolve.scopes.MemberScope;
+import org.jetbrains.kotlin.resolve.scopes.TypeIntersectionScope;
 import org.jetbrains.kotlin.types.checker.KotlinTypeChecker;
 
 import java.util.*;
@@ -124,19 +125,12 @@ public class TypeIntersector {
 
         TypeConstructor constructor = new IntersectionTypeConstructor(Annotations.Companion.getEMPTY(), resultingTypes);
 
-        MemberScope[] scopes = new MemberScope[resultingTypes.size()];
-        int i = 0;
-        for (KotlinType type : resultingTypes) {
-            scopes[i] = type.getMemberScope();
-            i++;
-        }
-
         return KotlinTypeImpl.create(
                 Annotations.Companion.getEMPTY(),
                 constructor,
                 allNullable,
                 Collections.<TypeProjection>emptyList(),
-                new ChainedScope("member scope for intersection type " + constructor, scopes)
+                TypeIntersectionScope.create("member scope for intersection type " + constructor, resultingTypes)
         );
     }