Cone conflict resolver: extract JVM equivalent call filtering to a separate class

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

@@ -7,7 +7,6 @@ package org.jetbrains.kotlin.fir
 
 import org.jetbrains.kotlin.fir.declarations.FirFile
 import org.jetbrains.kotlin.fir.declarations.FirMemberDeclaration
-import org.jetbrains.kotlin.fir.diagnostics.FirSimpleDiagnostic
 import org.jetbrains.kotlin.fir.expressions.*
 import org.jetbrains.kotlin.fir.expressions.impl.FirExpressionStub
 import org.jetbrains.kotlin.fir.expressions.impl.FirResolvedQualifierImpl
@@ -19,6 +18,7 @@ import org.jetbrains.kotlin.fir.references.impl.FirResolvedNamedReferenceImpl
 import org.jetbrains.kotlin.fir.references.impl.FirSimpleNamedReference
 import org.jetbrains.kotlin.fir.resolve.*
 import org.jetbrains.kotlin.fir.resolve.calls.*
+import org.jetbrains.kotlin.fir.resolve.calls.jvm.ConeEquivalentCallConflictResolver
 import org.jetbrains.kotlin.fir.resolve.diagnostics.FirAmbiguityError
 import org.jetbrains.kotlin.fir.resolve.diagnostics.FirInapplicableCandidateError
 import org.jetbrains.kotlin.fir.resolve.diagnostics.FirUnresolvedNameError
@@ -61,7 +61,11 @@ class FirCallResolver(
         topLevelScopes = topLevelScopes.asReversed(),
         localScopes = localScopes.asReversed()
     )
-    private val conflictResolver = ConeOverloadConflictResolver(TypeSpecificityComparator.NONE, inferenceComponents)
+
+    private val conflictResolver = ConeCompositeConflictResolver(
+        ConeOverloadConflictResolver(TypeSpecificityComparator.NONE, inferenceComponents),
+        ConeEquivalentCallConflictResolver(TypeSpecificityComparator.NONE, inferenceComponents)
+    )
 
     fun resolveCallAndSelectCandidate(functionCall: FirFunctionCall, expectedTypeRef: FirTypeRef?, file: FirFile): FirFunctionCall {
         qualifiedResolver.reset()

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/AbstractConeCallConflictResolver.kt

@@ -0,0 +1,139 @@
+/*
+ * Copyright 2010-2019 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.fir.resolve.calls
+
+import org.jetbrains.kotlin.fir.declarations.*
+import org.jetbrains.kotlin.fir.types.ConeKotlinType
+import org.jetbrains.kotlin.fir.types.arrayElementType
+import org.jetbrains.kotlin.fir.types.coneTypeUnsafe
+import org.jetbrains.kotlin.resolve.OverloadabilitySpecificityCallbacks
+import org.jetbrains.kotlin.resolve.calls.results.FlatSignature
+import org.jetbrains.kotlin.resolve.calls.results.SimpleConstraintSystem
+import org.jetbrains.kotlin.resolve.calls.results.TypeSpecificityComparator
+import org.jetbrains.kotlin.resolve.calls.results.isSignatureNotLessSpecific
+
+abstract class AbstractConeCallConflictResolver(
+    private val specificityComparator: TypeSpecificityComparator,
+    protected val inferenceComponents: InferenceComponents
+) : ConeCallConflictResolver {
+    protected fun Collection<Candidate>.setIfOneOrEmpty(): Set<Candidate>? = when (size) {
+        0 -> emptySet()
+        1 -> setOf(single())
+        else -> null
+    }
+
+    /**
+     * Returns `true` if [call1] is definitely more or equally specific [call2],
+     * `false` otherwise.
+     */
+    protected fun compareCallsByUsedArguments(
+        call1: FlatSignature<Candidate>,
+        call2: FlatSignature<Candidate>,
+        discriminateGenerics: Boolean
+    ): Boolean {
+        if (discriminateGenerics) {
+            val isGeneric1 = call1.isGeneric
+            val isGeneric2 = call2.isGeneric
+            // generic loses to non-generic
+            if (isGeneric1 && !isGeneric2) return false
+            if (!isGeneric1 && isGeneric2) return true
+            // two generics are non-comparable
+            if (isGeneric1 && isGeneric2) return false
+        }
+
+        if (!call1.isExpect && call2.isExpect) return true
+        if (call1.isExpect && !call2.isExpect) return false
+
+        return createEmptyConstraintSystem().isSignatureNotLessSpecific(
+            call1,
+            call2,
+            OverloadabilitySpecificityCallbacks,
+            specificityComparator
+        )
+    }
+
+    protected fun createFlatSignature(call: Candidate): FlatSignature<Candidate> {
+        return when (val declaration = call.symbol.fir) {
+            is FirSimpleFunction -> createFlatSignature(call, declaration)
+            is FirConstructor -> createFlatSignature(call, declaration)
+            is FirVariable<*> -> createFlatSignature(call, declaration)
+            is FirClass<*> -> createFlatSignature(call, declaration)
+            else -> error("Not supported: $declaration")
+        }
+    }
+
+    protected fun createFlatSignature(call: Candidate, variable: FirVariable<*>): FlatSignature<Candidate> {
+        return FlatSignature(
+            call,
+            (variable as? FirProperty)?.typeParameters?.map { it.symbol }.orEmpty(),
+            listOfNotNull<ConeKotlinType>(variable.receiverTypeRef?.coneTypeUnsafe()),
+            variable.receiverTypeRef != null,
+            false,
+            0,
+            (variable as? FirProperty)?.isExpect == true,
+            false // TODO
+        )
+    }
+
+    protected fun createFlatSignature(call: Candidate, constructor: FirConstructor): FlatSignature<Candidate> {
+        return FlatSignature(
+            call,
+            constructor.typeParameters.map { it.symbol },
+            computeParameterTypes(call, constructor),
+            //constructor.receiverTypeRef != null,
+            false,
+            constructor.valueParameters.any { it.isVararg },
+            constructor.valueParameters.count { it.defaultValue != null },
+            constructor.isExpect,
+            false // TODO
+        )
+    }
+
+    protected fun createFlatSignature(call: Candidate, function: FirSimpleFunction): FlatSignature<Candidate> {
+        return FlatSignature(
+            call,
+            function.typeParameters.map { it.symbol },
+            computeParameterTypes(call, function),
+            function.receiverTypeRef != null,
+            function.valueParameters.any { it.isVararg },
+            function.valueParameters.count { it.defaultValue != null },
+            function.isExpect,
+            false // TODO
+        )
+    }
+
+    private fun FirValueParameter.argumentType(): ConeKotlinType {
+        val type = returnTypeRef.coneTypeUnsafe<ConeKotlinType>()
+        if (isVararg) return type.arrayElementType(inferenceComponents.session)!!
+        return type
+    }
+
+    private fun computeParameterTypes(
+        call: Candidate,
+        function: FirFunction<*>
+    ): List<ConeKotlinType> {
+        return (call.resultingTypeForCallableReference?.typeArguments?.map { it as ConeKotlinType }
+            ?: (listOfNotNull(function.receiverTypeRef?.coneTypeUnsafe()) +
+                    call.argumentMapping?.map { it.value.argumentType() }.orEmpty()))
+    }
+
+    private fun createFlatSignature(call: Candidate, klass: FirClass<*>): FlatSignature<Candidate> {
+        return FlatSignature(
+            call,
+            (klass as? FirRegularClass)?.typeParameters?.map { it.symbol }.orEmpty(),
+            valueParameterTypes = emptyList(),
+            hasExtensionReceiver = false,
+            hasVarargs = false,
+            numDefaults = 0,
+            isExpect = (klass as? FirRegularClass)?.isExpect == true,
+            isSyntheticMember = false
+        )
+    }
+
+    private fun createEmptyConstraintSystem(): SimpleConstraintSystem {
+        return ConeSimpleConstraintSystemImpl(inferenceComponents.createConstraintSystem())
+    }
+}

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/ConeCallConflictResolver.kt

@@ -0,0 +1,18 @@
+/*
+ * Copyright 2010-2019 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.fir.resolve.calls
+
+interface ConeCallConflictResolver {
+    fun chooseMaximallySpecificCandidates(
+        candidates: Collection<Candidate>,
+        discriminateGenerics: Boolean
+    ): Set<Candidate> = chooseMaximallySpecificCandidates(candidates.toSet(), discriminateGenerics)
+
+    fun chooseMaximallySpecificCandidates(
+        candidates: Set<Candidate>,
+        discriminateGenerics: Boolean
+    ): Set<Candidate>
+}

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/ConeCompositeConflictResolver.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2010-2019 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.fir.resolve.calls
+
+class ConeCompositeConflictResolver(
+    private vararg val conflictResolvers: AbstractConeCallConflictResolver
+) : ConeCallConflictResolver {
+    override fun chooseMaximallySpecificCandidates(candidates: Set<Candidate>, discriminateGenerics: Boolean): Set<Candidate> {
+        if (candidates.size <= 1) return candidates
+        var currentCandidates = candidates
+        var index = 0
+        while (currentCandidates.size > 1 && index < conflictResolvers.size) {
+            val conflictResolver = conflictResolvers[index++]
+            currentCandidates = conflictResolver.chooseMaximallySpecificCandidates(candidates, discriminateGenerics)
+        }
+        return currentCandidates
+    }
+}

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/ConeOverloadConflictResolver.kt

@@ -5,19 +5,15 @@
 
 package org.jetbrains.kotlin.fir.resolve.calls
 
-import org.jetbrains.kotlin.fir.declarations.*
+import org.jetbrains.kotlin.fir.render
 import org.jetbrains.kotlin.fir.resolve.substitution.substitutorByMap
 import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
-import org.jetbrains.kotlin.fir.types.ConeKotlinType
-import org.jetbrains.kotlin.fir.types.arrayElementType
 import org.jetbrains.kotlin.fir.types.coneTypeUnsafe
-import org.jetbrains.kotlin.resolve.OverloadabilitySpecificityCallbacks
 import org.jetbrains.kotlin.resolve.calls.inference.model.NewConstraintSystemImpl
 import org.jetbrains.kotlin.resolve.calls.inference.model.SimpleConstraintSystemConstraintPosition
 import org.jetbrains.kotlin.resolve.calls.results.FlatSignature
 import org.jetbrains.kotlin.resolve.calls.results.SimpleConstraintSystem
 import org.jetbrains.kotlin.resolve.calls.results.TypeSpecificityComparator
-import org.jetbrains.kotlin.resolve.calls.results.isSignatureNotLessSpecific
 import org.jetbrains.kotlin.types.model.KotlinTypeMarker
 import org.jetbrains.kotlin.types.model.TypeParameterMarker
 import org.jetbrains.kotlin.types.model.TypeSubstitutorMarker
@@ -25,154 +21,21 @@ import org.jetbrains.kotlin.types.model.TypeSystemInferenceExtensionContext
 import org.jetbrains.kotlin.utils.addToStdlib.cast
 
 class ConeOverloadConflictResolver(
-    val specificityComparator: TypeSpecificityComparator,
-    val inferenceComponents: InferenceComponents
+    specificityComparator: TypeSpecificityComparator,
+    inferenceComponents: InferenceComponents
+) : AbstractConeCallConflictResolver(specificityComparator, inferenceComponents) {
 
-) {
-
-    fun chooseMaximallySpecificCandidates(
-        candidates: Collection<Candidate>,
-        //checkArgumentsMode: CheckArgumentTypesMode,
+    override fun chooseMaximallySpecificCandidates(
+        candidates: Set<Candidate>,
         discriminateGenerics: Boolean
     ): Set<Candidate> {
-        candidates.setIfOneOrEmpty()?.let { return it }
-
-        val candidatesSet = filterOutEquivalentCalls(candidates)
-
-        findMaximallySpecificCall(candidatesSet, false)?.let { return setOf(it) }
+        findMaximallySpecificCall(candidates, false)?.let { return setOf(it) }
 
         if (discriminateGenerics) {
-            findMaximallySpecificCall(candidatesSet, true)?.let { return setOf(it) }
+            findMaximallySpecificCall(candidates, true)?.let { return setOf(it) }
         }
 
-        return candidatesSet
-    }
-
-    private fun filterOutEquivalentCalls(candidates: Collection<Candidate>): Set<Candidate> {
-        val result = mutableSetOf<Candidate>()
-        outerLoop@ for (myCandidate in candidates) {
-            val me = myCandidate.symbol.fir
-            if (me is FirCallableMemberDeclaration<*> && me.symbol.callableId.className == null) {
-                for (otherCandidate in result) {
-                    val other = otherCandidate.symbol.fir
-                    if (other is FirCallableMemberDeclaration<*> && other.symbol.callableId.className == null) {
-                        if (areEquivalentTopLevelCallables(me, myCandidate, other, otherCandidate)) {
-                            continue@outerLoop
-                        }
-                    }
-                }
-            }
-            result += myCandidate
-        }
-        return result
-    }
-
-    private fun areEquivalentTopLevelCallables(
-        first: FirCallableMemberDeclaration<*>,
-        firstCandidate: Candidate,
-        second: FirCallableMemberDeclaration<*>,
-        secondCandidate: Candidate
-    ): Boolean {
-        if (first.symbol.callableId != second.symbol.callableId) return false
-        if (first.isExpect != second.isExpect) return false
-        if (first.receiverTypeRef?.coneTypeUnsafe<ConeKotlinType>() != second.receiverTypeRef?.coneTypeUnsafe()) {
-            return false
-        }
-        val firstSignature = createFlatSignature(firstCandidate, first)
-        val secondSignature = createFlatSignature(secondCandidate, second)
-        return compareCallsByUsedArguments(firstSignature, secondSignature, false) &&
-                compareCallsByUsedArguments(secondSignature, firstSignature, false)
-    }
-
-    private fun createFlatSignature(call: Candidate): FlatSignature<Candidate> {
-        return when (val declaration = call.symbol.fir) {
-            is FirSimpleFunction -> createFlatSignature(call, declaration)
-            is FirConstructor -> createFlatSignature(call, declaration)
-            is FirVariable<*> -> createFlatSignature(call, declaration)
-            is FirClass<*> -> createFlatSignature(call, declaration)
-            else -> error("Not supported: $declaration")
-        }
-    }
-
-    private fun createFlatSignature(call: Candidate, declaration: FirCallableMemberDeclaration<*>): FlatSignature<Candidate> {
-        return when (declaration) {
-            is FirSimpleFunction -> createFlatSignature(call, declaration)
-            is FirConstructor -> createFlatSignature(call, declaration)
-            is FirVariable<*> -> createFlatSignature(call, declaration as FirVariable<*>)
-            else -> error("Not supported: $declaration")
-        }
-    }
-
-    private fun createFlatSignature(call: Candidate, constructor: FirConstructor): FlatSignature<Candidate> {
-        return FlatSignature(
-            call,
-            constructor.typeParameters.map { it.symbol },
-            computeParameterTypes(call, constructor),
-            //constructor.receiverTypeRef != null,
-            false,
-            constructor.valueParameters.any { it.isVararg },
-            constructor.valueParameters.count { it.defaultValue != null },
-            constructor.isExpect,
-            false // TODO
-        )
-    }
-
-    private fun FirValueParameter.argumentType(): ConeKotlinType {
-        val type = returnTypeRef.coneTypeUnsafe<ConeKotlinType>()
-        if (isVararg) return type.arrayElementType(inferenceComponents.session)!!
-        return type
-    }
-
-    private fun createFlatSignature(call: Candidate, function: FirSimpleFunction): FlatSignature<Candidate> {
-        return FlatSignature(
-            call,
-            function.typeParameters.map { it.symbol },
-            computeParameterTypes(call, function),
-            function.receiverTypeRef != null,
-            function.valueParameters.any { it.isVararg },
-            function.valueParameters.count { it.defaultValue != null },
-            function.isExpect,
-            false // TODO
-        )
-    }
-
-    private fun computeParameterTypes(
-        call: Candidate,
-        function: FirFunction<*>
-    ): List<ConeKotlinType> {
-        return (call.resultingTypeForCallableReference?.typeArguments?.map { it as ConeKotlinType }
-            ?: (listOfNotNull<ConeKotlinType>(function.receiverTypeRef?.coneTypeUnsafe()) +
-                    call.argumentMapping?.map { it.value.argumentType() }.orEmpty()))
-    }
-
-    private fun createFlatSignature(call: Candidate, variable: FirVariable<*>): FlatSignature<Candidate> {
-        return FlatSignature(
-            call,
-            (variable as? FirProperty)?.typeParameters?.map { it.symbol }.orEmpty(),
-            listOfNotNull<ConeKotlinType>(variable.receiverTypeRef?.coneTypeUnsafe()),
-            variable.receiverTypeRef != null,
-            false,
-            0,
-            (variable as? FirProperty)?.isExpect == true,
-            false // TODO
-        )
-    }
-
-    private fun createFlatSignature(call: Candidate, klass: FirClass<*>): FlatSignature<Candidate> {
-        return FlatSignature(
-            call,
-            (klass as? FirRegularClass)?.typeParameters?.map { it.symbol }.orEmpty(),
-            valueParameterTypes = emptyList(),
-            hasExtensionReceiver = false,
-            hasVarargs = false,
-            numDefaults = 0,
-            isExpect = (klass as? FirRegularClass)?.isExpect == true,
-            isSyntheticMember = false
-        )
-    }
-
-    private fun createEmptyConstraintSystem(): SimpleConstraintSystem {
-        return ConeSimpleConstraintSystemImpl(inferenceComponents.createConstraintSystem())
+        return candidates
     }
 
     private fun findMaximallySpecificCall(
@@ -180,11 +43,9 @@ class ConeOverloadConflictResolver(
         discriminateGenerics: Boolean//,
         //isDebuggerContext: Boolean
     ): Candidate? {
-        val filteredCandidates = candidates//uniquifyCandidatesSet(candidates)
+        if (candidates.size <= 1) return candidates.singleOrNull()
 
-        if (filteredCandidates.size <= 1) return filteredCandidates.singleOrNull()
-
-        val conflictingCandidates = filteredCandidates.map { candidateCall ->
+        val conflictingCandidates = candidates.map { candidateCall ->
             createFlatSignature(candidateCall)
         }
 
@@ -208,7 +69,7 @@ class ConeOverloadConflictResolver(
             }
         }
         if (result == null) return null
-        if (any { it != result && isNotWorse(it, result!!) }) {
+        if (any { it != result && isNotWorse(it, result) }) {
             return null
         }
         return result
@@ -235,38 +96,6 @@ class ConeOverloadConflictResolver(
         )
     }
 
-
-
-    /**
-     * Returns `true` if [call1] is definitely more or equally specific [call2],
-     * `false` otherwise.
-     */
-    private fun compareCallsByUsedArguments(
-        call1: FlatSignature<Candidate>,
-        call2: FlatSignature<Candidate>,
-        discriminateGenerics: Boolean
-    ): Boolean {
-        if (discriminateGenerics) {
-            val isGeneric1 = call1.isGeneric
-            val isGeneric2 = call2.isGeneric
-            // generic loses to non-generic
-            if (isGeneric1 && !isGeneric2) return false
-            if (!isGeneric1 && isGeneric2) return true
-            // two generics are non-comparable
-            if (isGeneric1 && isGeneric2) return false
-        }
-
-        if (!call1.isExpect && call2.isExpect) return true
-        if (call1.isExpect && !call2.isExpect) return false
-
-        return createEmptyConstraintSystem().isSignatureNotLessSpecific(
-            call1,
-            call2,
-            OverloadabilitySpecificityCallbacks,
-            specificityComparator
-        )
-    }
-
     private fun isOfNotLessSpecificShape(
         call1: FlatSignature<Candidate>,
         call2: FlatSignature<Candidate>
@@ -282,12 +111,6 @@ class ConeOverloadConflictResolver(
 
         return true
     }
-
-    private fun <C> Collection<C>.setIfOneOrEmpty(): Set<C>? = when (size) {
-        0 -> emptySet()
-        1 -> setOf(single())
-        else -> null
-    }
 }
 
 object NoSubstitutor : TypeSubstitutorMarker
@@ -295,19 +118,21 @@ object NoSubstitutor : TypeSubstitutorMarker
 class ConeSimpleConstraintSystemImpl(val system: NewConstraintSystemImpl) : SimpleConstraintSystem {
     override fun registerTypeVariables(typeParameters: Collection<TypeParameterMarker>): TypeSubstitutorMarker = with(context) {
         val csBuilder = system.getBuilder()
-        val substitutionMap = typeParameters.associate {
+        val substitutionMap = typeParameters.associateWith {
             require(it is FirTypeParameterSymbol)
             val variable = TypeParameterBasedTypeVariable(it)
             csBuilder.registerVariable(variable)
 
-
-            it to variable.defaultType
+            variable.defaultType
         }
         val substitutor = substitutorByMap(substitutionMap.cast())
         for (typeParameter in typeParameters) {
             require(typeParameter is FirTypeParameterSymbol)
             for (upperBound in typeParameter.fir.bounds) {
-                addSubtypeConstraint(substitutionMap[typeParameter]!!, substitutor.substituteOrSelf(upperBound.coneTypeUnsafe()))
+                addSubtypeConstraint(
+                    substitutionMap[typeParameter] ?: error("No ${typeParameter.fir.render()} in substitution map"),
+                    substitutor.substituteOrSelf(upperBound.coneTypeUnsafe())
+                )
             }
         }
         return substitutor

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/jvm/ConeEquivalentCallConflictResolver.kt

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2010-2019 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.fir.resolve.calls.jvm
+
+import org.jetbrains.kotlin.fir.declarations.*
+import org.jetbrains.kotlin.fir.resolve.calls.Candidate
+import org.jetbrains.kotlin.fir.resolve.calls.AbstractConeCallConflictResolver
+import org.jetbrains.kotlin.fir.resolve.calls.InferenceComponents
+import org.jetbrains.kotlin.fir.types.ConeKotlinType
+import org.jetbrains.kotlin.fir.types.coneTypeUnsafe
+import org.jetbrains.kotlin.resolve.calls.results.FlatSignature
+import org.jetbrains.kotlin.resolve.calls.results.TypeSpecificityComparator
+
+// This conflict resolver filters JVM equivalent top-level functions
+// like emptyArray() from intrinsics and built-ins
+class ConeEquivalentCallConflictResolver(
+    specificityComparator: TypeSpecificityComparator,
+    inferenceComponents: InferenceComponents
+) : AbstractConeCallConflictResolver(specificityComparator, inferenceComponents) {
+    override fun chooseMaximallySpecificCandidates(
+        candidates: Set<Candidate>,
+        discriminateGenerics: Boolean
+    ): Set<Candidate> {
+        return filterOutEquivalentCalls(candidates)
+    }
+
+    private fun filterOutEquivalentCalls(candidates: Collection<Candidate>): Set<Candidate> {
+        val result = mutableSetOf<Candidate>()
+        outerLoop@ for (myCandidate in candidates) {
+            val me = myCandidate.symbol.fir
+            if (me is FirCallableMemberDeclaration<*> && me.symbol.callableId.className == null) {
+                for (otherCandidate in result) {
+                    val other = otherCandidate.symbol.fir
+                    if (other is FirCallableMemberDeclaration<*> && other.symbol.callableId.className == null) {
+                        if (areEquivalentTopLevelCallables(me, myCandidate, other, otherCandidate)) {
+                            continue@outerLoop
+                        }
+                    }
+                }
+            }
+            result += myCandidate
+        }
+        return result
+    }
+
+    private fun areEquivalentTopLevelCallables(
+        first: FirCallableMemberDeclaration<*>,
+        firstCandidate: Candidate,
+        second: FirCallableMemberDeclaration<*>,
+        secondCandidate: Candidate
+    ): Boolean {
+        if (first.symbol.callableId != second.symbol.callableId) return false
+        if (first.isExpect != second.isExpect) return false
+        if (first.receiverTypeRef?.coneTypeUnsafe<ConeKotlinType>() != second.receiverTypeRef?.coneTypeUnsafe()) {
+            return false
+        }
+        val firstSignature = createFlatSignature(firstCandidate, first)
+        val secondSignature = createFlatSignature(secondCandidate, second)
+        return compareCallsByUsedArguments(firstSignature, secondSignature, false) &&
+                compareCallsByUsedArguments(secondSignature, firstSignature, false)
+    }
+
+    private fun createFlatSignature(call: Candidate, declaration: FirCallableMemberDeclaration<*>): FlatSignature<Candidate> {
+        return when (declaration) {
+            is FirSimpleFunction -> createFlatSignature(call, declaration)
+            is FirConstructor -> createFlatSignature(call, declaration)
+            is FirVariable<*> -> createFlatSignature(call, declaration as FirVariable<*>)
+            else -> error("Not supported: $declaration")
+        }
+    }
+}