Introduce SimpleConstraintSystem for OverloadChecker and OverloadingConflictResolver

compiler/frontend/src/org/jetbrains/kotlin/resolve/OverloadChecker.kt

@@ -21,7 +21,11 @@ import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.incremental.components.NoLookupLocation
 import org.jetbrains.kotlin.name.FqNameUnsafe
 import org.jetbrains.kotlin.name.Name
-import org.jetbrains.kotlin.resolve.calls.results.*
+import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystemBuilderImpl
+import org.jetbrains.kotlin.resolve.calls.results.FlatSignature
+import org.jetbrains.kotlin.resolve.calls.results.SpecificityComparisonCallbacks
+import org.jetbrains.kotlin.resolve.calls.results.TypeSpecificityComparator
+import org.jetbrains.kotlin.resolve.calls.results.isSignatureNotLessSpecific
 import org.jetbrains.kotlin.resolve.calls.tower.getTypeAliasConstructors
 import org.jetbrains.kotlin.resolve.descriptorUtil.hasLowPriorityInOverloadResolution
 import org.jetbrains.kotlin.resolve.descriptorUtil.varargParameterPosition
@@ -63,8 +67,8 @@ class OverloadChecker(val specificityComparator: TypeSpecificityComparator) {
         val aSignature = FlatSignature.createFromCallableDescriptor(a)
         val bSignature = FlatSignature.createFromCallableDescriptor(b)
 
-        val aIsNotLessSpecificThanB = isSignatureNotLessSpecific(aSignature, bSignature, OverloadabilitySpecificityCallbacks, specificityComparator)
-        val bIsNotLessSpecificThanA = isSignatureNotLessSpecific(bSignature, aSignature, OverloadabilitySpecificityCallbacks, specificityComparator)
+        val aIsNotLessSpecificThanB = ConstraintSystemBuilderImpl.forSpecificity().isSignatureNotLessSpecific (aSignature, bSignature, OverloadabilitySpecificityCallbacks, specificityComparator)
+        val bIsNotLessSpecificThanA = ConstraintSystemBuilderImpl.forSpecificity().isSignatureNotLessSpecific(bSignature, aSignature, OverloadabilitySpecificityCallbacks, specificityComparator)
 
         return !(aIsNotLessSpecificThanB && bIsNotLessSpecificThanA)
     }

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/inference/ConstraintSystemBuilderImpl.kt

@@ -26,6 +26,7 @@ import org.jetbrains.kotlin.resolve.calls.inference.TypeBounds.BoundKind.*
 import org.jetbrains.kotlin.resolve.calls.inference.constraintPosition.ConstraintPosition
 import org.jetbrains.kotlin.resolve.calls.inference.constraintPosition.ConstraintPositionKind
 import org.jetbrains.kotlin.resolve.calls.inference.constraintPosition.ConstraintPositionKind.TYPE_BOUND_POSITION
+import org.jetbrains.kotlin.resolve.calls.results.SimpleConstraintSystem
 import org.jetbrains.kotlin.resolve.calls.util.createFunctionType
 import org.jetbrains.kotlin.resolve.descriptorUtil.hasExactAnnotation
 import org.jetbrains.kotlin.resolve.descriptorUtil.hasNoInferAnnotation
@@ -38,7 +39,7 @@ import org.jetbrains.kotlin.types.typeUtil.defaultProjections
 import org.jetbrains.kotlin.types.typeUtil.isDefaultBound
 import java.util.*
 
-class ConstraintSystemBuilderImpl(private val mode: Mode = ConstraintSystemBuilderImpl.Mode.INFERENCE) : ConstraintSystem.Builder {
+open class ConstraintSystemBuilderImpl(private val mode: Mode = ConstraintSystemBuilderImpl.Mode.INFERENCE) : ConstraintSystem.Builder {
     enum class Mode {
         INFERENCE,
         SPECIFICITY
@@ -409,7 +410,20 @@ class ConstraintSystemBuilderImpl(private val mode: Mode = ConstraintSystemBuild
     }
 
     companion object {
-        fun forSpecificity() = ConstraintSystemBuilderImpl(Mode.SPECIFICITY)
+        fun forSpecificity(): SimpleConstraintSystem = object : ConstraintSystemBuilderImpl(Mode.SPECIFICITY), SimpleConstraintSystem {
+            var counter = 0
+
+            override fun registerTypeVariables(typeParameters: Collection<TypeParameterDescriptor>) =
+                    registerTypeVariables(CallHandle.NONE, typeParameters)
+
+            override fun addSubtypeConstraint(subType: UnwrappedType, superType: UnwrappedType) =
+                    addSubtypeConstraint(subType, superType, ConstraintPositionKind.VALUE_PARAMETER_POSITION.position(counter++))
+
+            override fun hasContradiction(): Boolean {
+                fixVariables()
+                return build().status.hasContradiction()
+            }
+        }
     }
 }
 

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/results/FlatSignatureSpecificity.kt

@@ -17,21 +17,17 @@
 package org.jetbrains.kotlin.resolve.calls.results
 
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
+import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
 import org.jetbrains.kotlin.psi.ValueArgument
 import org.jetbrains.kotlin.resolve.DescriptorToSourceUtils
-import org.jetbrains.kotlin.resolve.calls.inference.CallHandle
-import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystem
 import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystemBuilderImpl
-import org.jetbrains.kotlin.resolve.calls.inference.constraintPosition.valueParameterPosition
 import org.jetbrains.kotlin.resolve.calls.model.DefaultValueArgument
 import org.jetbrains.kotlin.resolve.calls.model.MutableResolvedCall
 import org.jetbrains.kotlin.resolve.calls.model.ResolvedCall
 import org.jetbrains.kotlin.resolve.calls.model.VariableAsFunctionResolvedCallImpl
 import org.jetbrains.kotlin.resolve.calls.results.FlatSignature.Companion.argumentValueType
 import org.jetbrains.kotlin.resolve.calls.results.FlatSignature.Companion.extensionReceiverTypeOrEmpty
-import org.jetbrains.kotlin.types.KotlinType
-import org.jetbrains.kotlin.types.TypeUtils
-import org.jetbrains.kotlin.types.Variance
+import org.jetbrains.kotlin.types.*
 import org.jetbrains.kotlin.types.checker.KotlinTypeChecker
 import java.util.*
 
@@ -47,21 +43,24 @@ interface TypeSpecificityComparator {
     }
 }
 
-fun <T> isSignatureNotLessSpecific(
+interface SimpleConstraintSystem {
+    fun registerTypeVariables(typeParameters: Collection<TypeParameterDescriptor>): TypeSubstitutor
+    fun addSubtypeConstraint(subType: UnwrappedType, superType: UnwrappedType)
+    fun hasContradiction(): Boolean
+}
+
+fun <T> SimpleConstraintSystem.isSignatureNotLessSpecific(
         specific: FlatSignature<T>,
         general: FlatSignature<T>,
         callbacks: SpecificityComparisonCallbacks,
-        specificityComparator: TypeSpecificityComparator,
-        callHandle: CallHandle = CallHandle.NONE
+        specificityComparator: TypeSpecificityComparator
 ): Boolean {
     if (specific.hasExtensionReceiver != general.hasExtensionReceiver) return false
     if (specific.valueParameterTypes.size != general.valueParameterTypes.size) return false
 
     val typeParameters = general.typeParameters
-    val constraintSystemBuilder: ConstraintSystem.Builder = ConstraintSystemBuilderImpl.forSpecificity()
-    val typeSubstitutor = constraintSystemBuilder.registerTypeVariables(callHandle, typeParameters)
+    val typeSubstitutor = registerTypeVariables(typeParameters)
 
-    var numConstraints = 0
     for ((specificType, generalType) in specific.valueParameterTypes.zip(general.valueParameterTypes)) {
         if (specificType == null || generalType == null) continue
 
@@ -78,13 +77,11 @@ fun <T> isSignatureNotLessSpecific(
         }
         else {
             val substitutedGeneralType = typeSubstitutor.safeSubstitute(generalType, Variance.INVARIANT)
-            constraintSystemBuilder.addSubtypeConstraint(specificType, substitutedGeneralType, valueParameterPosition(numConstraints++))
+            addSubtypeConstraint(specificType.unwrap(), substitutedGeneralType.unwrap())
         }
     }
 
-    constraintSystemBuilder.fixVariables()
-    val constraintSystem = constraintSystemBuilder.build()
-    return !constraintSystem.status.hasContradiction()
+    return !hasContradiction()
 }
 
 
@@ -123,6 +120,7 @@ fun createOverloadingConflictResolver(
         builtIns,
         specificityComparator,
         MutableResolvedCall<*>::getResultingDescriptor,
+        ConstraintSystemBuilderImpl.Companion::forSpecificity,
         MutableResolvedCall<*>::createFlatSignature,
         { (it as? VariableAsFunctionResolvedCallImpl)?.variableCall },
         { DescriptorToSourceUtils.descriptorToDeclaration(it) != null}

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/results/OverloadingConflictResolver.kt

@@ -34,6 +34,7 @@ class OverloadingConflictResolver<C : Any>(
         private val builtIns: KotlinBuiltIns,
         private val specificityComparator: TypeSpecificityComparator,
         private val getResultingDescriptor: (C) -> CallableDescriptor,
+        private val createEmptyConstraintSystem: () -> SimpleConstraintSystem,
         private val createFlatSignature: (C) -> FlatSignature<C>,
         private val getVariableCandidates: (C) -> C?, // vor variable WithInvoke
         private val isFromSources: (CallableDescriptor) -> Boolean
@@ -235,7 +236,7 @@ class OverloadingConflictResolver<C : Any>(
             if (isGeneric1 && isGeneric2) return false
         }
 
-        return isSignatureNotLessSpecific(call1, call2, SpecificityComparisonWithNumerics, specificityComparator)
+        return createEmptyConstraintSystem().isSignatureNotLessSpecific(call1, call2, SpecificityComparisonWithNumerics, specificityComparator)
     }
 
     private val SpecificityComparisonWithNumerics = object : SpecificityComparisonCallbacks {
@@ -321,7 +322,7 @@ class OverloadingConflictResolver<C : Any>(
 
         val fSignature = FlatSignature.createFromCallableDescriptor(f)
         val gSignature = FlatSignature.createFromCallableDescriptor(g)
-        return isSignatureNotLessSpecific(fSignature, gSignature, SpecificityComparisonWithNumerics, specificityComparator)
+        return createEmptyConstraintSystem().isSignatureNotLessSpecific(fSignature, gSignature, SpecificityComparisonWithNumerics, specificityComparator)
     }
 
     private fun isNotLessSpecificCallableReference(f: CallableDescriptor, g: CallableDescriptor): Boolean =