KT-8879 Stackoverflow exception on completion from inference

#KT-8879 Fixed
Added ConstraintContext storing 'derivedFrom' variables.
This information is used to prevent infinite recursion:
if a variable was substituted in a type of a bound, it shouldn't be substituted there for the second time.

compiler/testData/constraintSystem/declarations.kt

@@ -6,6 +6,7 @@ interface C : B
 
 interface Consumer<in T>
 interface Producer<out T>
+interface Inv<T>
 
 interface My<T>
 interface Successor<T> : My<T>

compiler/testData/constraintSystem/severalVariables/recursive/kt8879.bounds

@@ -0,0 +1,23 @@
+VARIABLES T P
+
+T <: My<T>
+Inv<P> <: Inv<T>
+
+type parameter bounds:
+T <: My<T>*, := P*, <: My<out My<T>>*, <: My<P>*, <: My<out My<P>>*, <: My<out My<out My<T>>>*
+P := T*, <: My<T>*, <: My<out My<T>>*, <: My<P>*, <: My<out My<P>>*, <: My<out My<out My<T>>>*
+
+status:
+-hasCannotCaptureTypesError: false
+-hasConflictingConstraints: false
+-hasContradiction: false
+-hasErrorInConstrainingTypes: false
+-hasParameterConstraintError: false
+-hasTypeInferenceIncorporationError: false
+-hasUnknownParameters: true
+-hasViolatedUpperBound: false
+-isSuccessful: false
+
+result:
+T=???
+P=???

compiler/testData/constraintSystem/severalVariables/recursive/kt8879.constraints

@@ -0,0 +1,4 @@
+VARIABLES T P
+
+T <: My<T>
+Inv<P> <: Inv<T>

compiler/testData/diagnostics/tests/inference/constraints/kt8879.kt

@@ -0,0 +1,12 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+interface Inv<I>
+interface Inv2<I>
+
+fun <T: Inv2<T>> foo(klass: Inv<T>): String? = null
+
+fun <X> bar(): Inv<X> = null!!
+
+fun test() {
+    <!TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>foo<!>(<!TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>bar<!>())
+}

compiler/testData/diagnostics/tests/inference/constraints/kt8879.txt

@@ -0,0 +1,17 @@
+package
+
+internal fun </*0*/ X> bar(): Inv<X>
+internal fun </*0*/ T : Inv2<T>> foo(/*0*/ klass: Inv<T>): kotlin.String?
+internal fun test(): kotlin.Unit
+
+internal interface Inv</*0*/ I> {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+internal interface Inv2</*0*/ I> {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/tests/org/jetbrains/kotlin/checkers/JetDiagnosticsTestGenerated.java

@@ -7226,6 +7226,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                     doTest(fileName);
                 }
 
+                @TestMetadata("kt8879.kt")
+                public void testKt8879() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/inference/constraints/kt8879.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("notNullConstraintOnNullableType.kt")
                 public void testNotNullConstraintOnNullableType() throws Exception {
                     String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/inference/constraints/notNullConstraintOnNullableType.kt");

compiler/tests/org/jetbrains/kotlin/resolve/constraintSystem/AbstractConstraintSystemTest.kt

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.cli.jvm.compiler.KotlinCoreEnvironment
 import org.jetbrains.kotlin.diagnostics.rendering.Renderers
 import org.jetbrains.kotlin.renderer.DescriptorRenderer
 import org.jetbrains.kotlin.resolve.TypeResolver
+import org.jetbrains.kotlin.resolve.calls.inference.ConstraintContext
 import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystemImpl
 import org.jetbrains.kotlin.resolve.calls.inference.constraintPosition.ConstraintPositionKind.SPECIAL
 import org.jetbrains.kotlin.resolve.calls.inference.registerTypeVariables
@@ -92,12 +93,12 @@ abstract public class AbstractConstraintSystemTest() : JetLiteFixture() {
         for (constraint in constraints) {
             val firstType = testDeclarations.getType(constraint.firstType).assertNotError()
             val secondType = testDeclarations.getType(constraint.secondType).assertNotError()
-            val position = SPECIAL.position()
+            val context = ConstraintContext(SPECIAL.position())
             when (constraint.kind) {
-                MyConstraintKind.SUBTYPE -> constraintSystem.addSubtypeConstraint(firstType, secondType, position)
-                MyConstraintKind.SUPERTYPE -> constraintSystem.addSupertypeConstraint(firstType, secondType, position)
+                MyConstraintKind.SUBTYPE -> constraintSystem.addSubtypeConstraint(firstType, secondType, context.position)
+                MyConstraintKind.SUPERTYPE -> constraintSystem.addSupertypeConstraint(firstType, secondType, context.position)
                 MyConstraintKind.EQUAL -> constraintSystem.addConstraint(
-                        ConstraintSystemImpl.ConstraintKind.EQUAL, firstType, secondType, position, topLevel = true)
+                        ConstraintSystemImpl.ConstraintKind.EQUAL, firstType, secondType, context, topLevel = true)
             }
         }
         if (fixVariables) constraintSystem.fixVariables()

compiler/tests/org/jetbrains/kotlin/resolve/constraintSystem/ConstraintSystemTestGenerated.java

@@ -720,6 +720,12 @@ public class ConstraintSystemTestGenerated extends AbstractConstraintSystemTest
                 doTest(fileName);
             }
 
+            @TestMetadata("kt8879.constraints")
+            public void testKt8879() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/constraintSystem/severalVariables/recursive/kt8879.constraints");
+                doTest(fileName);
+            }
+
             @TestMetadata("mutuallyRecursive.constraints")
             public void testMutuallyRecursive() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/constraintSystem/severalVariables/recursive/mutuallyRecursive.constraints");

core/descriptors/src/org/jetbrains/kotlin/resolve/calls/inference/ConstraintSystemImpl.kt

@@ -153,8 +153,8 @@ public class ConstraintSystemImpl : ConstraintSystem {
         for ((typeVariable, typeBounds) in allTypeParameterBounds) {
             for (declaredUpperBound in typeVariable.getUpperBounds()) {
                 if (declaredUpperBound.isDefaultBound()) continue //todo remove this line (?)
-                val position = TYPE_BOUND_POSITION.position(typeVariable.getIndex())
-                addBound(typeVariable, declaredUpperBound, UPPER_BOUND, position)
+                val context = ConstraintContext(TYPE_BOUND_POSITION.position(typeVariable.getIndex()))
+                addBound(typeVariable, declaredUpperBound, UPPER_BOUND, context)
             }
         }
     }
@@ -204,27 +204,31 @@ public class ConstraintSystemImpl : ConstraintSystem {
         if (constrainingType != null && TypeUtils.noExpectedType(constrainingType)) return
 
         val newSubjectType = originalToVariablesSubstitutor.substitute(subjectType, Variance.INVARIANT)
-        addConstraint(SUB_TYPE, newSubjectType, constrainingType, constraintPosition, topLevel = true)
+        addConstraint(SUB_TYPE, newSubjectType, constrainingType, ConstraintContext(constraintPosition), topLevel = true)
     }
 
     override fun addSubtypeConstraint(constrainingType: JetType?, subjectType: JetType, constraintPosition: ConstraintPosition) {
         val newSubjectType = originalToVariablesSubstitutor.substitute(subjectType, Variance.INVARIANT)
-        addConstraint(SUB_TYPE, constrainingType, newSubjectType, constraintPosition, topLevel = true)
+        addConstraint(SUB_TYPE, constrainingType, newSubjectType, ConstraintContext(constraintPosition), topLevel = true)
     }
 
     fun addConstraint(
             constraintKind: ConstraintKind,
             subType: JetType?,
             superType: JetType?,
-            constraintPosition: ConstraintPosition,
+            constraintContext: ConstraintContext,
             topLevel: Boolean
     ) {
+        val constraintPosition = constraintContext.position
+
+        // when processing nested constraints, `derivedFrom` information should be reset
+        val newConstraintContext = ConstraintContext(constraintContext.position, derivedFrom = null)
         val typeCheckingProcedure = TypeCheckingProcedure(object : TypeCheckingProcedureCallbacks {
             private var depth = 0
 
             override fun assertEqualTypes(a: JetType, b: JetType, typeCheckingProcedure: TypeCheckingProcedure): Boolean {
                 depth++
-                doAddConstraint(EQUAL, a, b, constraintPosition, typeCheckingProcedure, topLevel = false)
+                doAddConstraint(EQUAL, a, b, newConstraintContext, typeCheckingProcedure, topLevel = false)
                 depth--
                 return true
 
@@ -236,7 +240,7 @@ public class ConstraintSystemImpl : ConstraintSystem {
 
             override fun assertSubtype(subtype: JetType, supertype: JetType, typeCheckingProcedure: TypeCheckingProcedure): Boolean {
                 depth++
-                doAddConstraint(SUB_TYPE, subtype, supertype, constraintPosition, typeCheckingProcedure, topLevel = false)
+                doAddConstraint(SUB_TYPE, subtype, supertype, newConstraintContext, typeCheckingProcedure, topLevel = false)
                 depth--
                 return true
             }
@@ -249,7 +253,7 @@ public class ConstraintSystemImpl : ConstraintSystem {
                     if (depth > 0) {
                         errors.add(CannotCapture(constraintPosition, myTypeVariable))
                     }
-                    generateTypeParameterCaptureConstraint(typeVariable, typeProjection, constraintPosition)
+                    generateTypeParameterCaptureConstraint(typeVariable, typeProjection, newConstraintContext)
                     return true
                 }
                 return false
@@ -260,7 +264,7 @@ public class ConstraintSystemImpl : ConstraintSystem {
                 return true
             }
         })
-        doAddConstraint(constraintKind, subType, superType, constraintPosition, typeCheckingProcedure, topLevel)
+        doAddConstraint(constraintKind, subType, superType, constraintContext, typeCheckingProcedure, topLevel)
     }
 
     private fun isErrorOrSpecialType(type: JetType?, constraintPosition: ConstraintPosition): Boolean {
@@ -279,10 +283,11 @@ public class ConstraintSystemImpl : ConstraintSystem {
             constraintKind: ConstraintKind,
             subType: JetType?,
             superType: JetType?,
-            constraintPosition: ConstraintPosition,
+            constraintContext: ConstraintContext,
             typeCheckingProcedure: TypeCheckingProcedure,
             topLevel: Boolean
     ) {
+        val constraintPosition = constraintContext.position
         if (isErrorOrSpecialType(subType, constraintPosition) || isErrorOrSpecialType(superType, constraintPosition)) return
         if (subType == null || superType == null) return
 
@@ -306,11 +311,11 @@ public class ConstraintSystemImpl : ConstraintSystem {
 
         fun simplifyConstraint(subType: JetType, superType: JetType) {
             if (isMyTypeVariable(subType)) {
-                generateTypeParameterBound(subType, superType, constraintKind.toBound(), constraintPosition)
+                generateTypeParameterBound(subType, superType, constraintKind.toBound(), constraintContext)
                 return
             }
             if (isMyTypeVariable(superType)) {
-                generateTypeParameterBound(superType, subType, constraintKind.toBound().reverse(), constraintPosition)
+                generateTypeParameterBound(superType, subType, constraintKind.toBound().reverse(), constraintContext)
                 return
             }
             // if subType is nullable and superType is not nullable, unsafe call or type mismatch error will be generated later,
@@ -335,10 +340,10 @@ public class ConstraintSystemImpl : ConstraintSystem {
             typeVariable: TypeParameterDescriptor,
             constrainingType: JetType,
             kind: TypeBounds.BoundKind,
-            position: ConstraintPosition,
-            derivedFrom: Set<TypeParameterDescriptor> = emptySet()
+            constraintContext: ConstraintContext
     ) {
-        val bound = Bound(typeVariable, constrainingType, kind, position, constrainingType.isProper(), derivedFrom)
+        val bound = Bound(typeVariable, constrainingType, kind, constraintContext.position,
+                          constrainingType.isProper(), constraintContext.derivedFrom ?: emptySet())
         val typeBounds = getTypeBounds(typeVariable)
         if (typeBounds.bounds.contains(bound)) return
 
@@ -358,7 +363,7 @@ public class ConstraintSystemImpl : ConstraintSystem {
             parameterType: JetType,
             constrainingType: JetType,
             boundKind: TypeBounds.BoundKind,
-            constraintPosition: ConstraintPosition
+            constraintContext: ConstraintContext
     ) {
         val typeVariable = getMyTypeVariable(parameterType)!!
 
@@ -380,7 +385,7 @@ public class ConstraintSystemImpl : ConstraintSystem {
         }
 
         if (!parameterType.isMarkedNullable() || !TypeUtils.isNullableType(newConstrainingType)) {
-            addBound(typeVariable, newConstrainingType, boundKind, constraintPosition)
+            addBound(typeVariable, newConstrainingType, boundKind, constraintContext)
             return
         }
         // For parameter type T:
@@ -390,23 +395,23 @@ public class ConstraintSystemImpl : ConstraintSystem {
         // constraints T? >: Int?; T? >: Int! should transform to T >: Int
         val notNullConstrainingType = TypeUtils.makeNotNullable(newConstrainingType)
         if (boundKind == EXACT_BOUND || boundKind == LOWER_BOUND) {
-            addBound(typeVariable, notNullConstrainingType, LOWER_BOUND, constraintPosition)
+            addBound(typeVariable, notNullConstrainingType, LOWER_BOUND, constraintContext)
         }
         // constraints T? <: Int?; T? <: Int! should transform to T <: Int?; T <: Int! correspondingly
         if (boundKind == EXACT_BOUND || boundKind == UPPER_BOUND) {
-            addBound(typeVariable, newConstrainingType, UPPER_BOUND, constraintPosition)
+            addBound(typeVariable, newConstrainingType, UPPER_BOUND, constraintContext)
         }
     }
 
     private fun generateTypeParameterCaptureConstraint(
             parameterType: JetType,
             constrainingTypeProjection: TypeProjection,
-            constraintPosition: ConstraintPosition
+            constraintContext: ConstraintContext
     ) {
         val typeVariable = getMyTypeVariable(parameterType)!!
         if (!typeVariable.getUpperBoundsAsType().isDefaultBound()
             && constrainingTypeProjection.getProjectionKind() == Variance.IN_VARIANCE) {
-            errors.add(CannotCapture(constraintPosition, typeVariable))
+            errors.add(CannotCapture(constraintContext.position, typeVariable))
         }
         val typeProjection = if (parameterType.isMarkedNullable()) {
             TypeProjectionImpl(constrainingTypeProjection.getProjectionKind(), TypeUtils.makeNotNullable(constrainingTypeProjection.getType()))
@@ -415,7 +420,7 @@ public class ConstraintSystemImpl : ConstraintSystem {
             constrainingTypeProjection
         }
         val capturedType = createCapturedType(typeProjection)
-        addBound(typeVariable, capturedType, EXACT_BOUND, constraintPosition)
+        addBound(typeVariable, capturedType, EXACT_BOUND, constraintContext)
     }
 
     override fun getTypeVariables() = originalToVariables.keySet()
@@ -483,7 +488,7 @@ public class ConstraintSystemImpl : ConstraintSystem {
 
         val value = typeBounds.value ?: return
 
-        addBound(typeVariable, value, TypeBounds.BoundKind.EXACT_BOUND, ConstraintPositionKind.FROM_COMPLETER.position())
+        addBound(typeVariable, value, TypeBounds.BoundKind.EXACT_BOUND, ConstraintContext(ConstraintPositionKind.FROM_COMPLETER.position()))
     }
 
     fun fixVariables() {

core/descriptors/src/org/jetbrains/kotlin/resolve/calls/inference/constraintIncorporation.kt

@@ -16,6 +16,7 @@
 
 package org.jetbrains.kotlin.resolve.calls.inference
 
+import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
 import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystemImpl.ConstraintKind.EQUAL
 import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystemImpl.ConstraintKind.SUB_TYPE
 import org.jetbrains.kotlin.resolve.calls.inference.TypeBounds.Bound
@@ -24,12 +25,18 @@ import org.jetbrains.kotlin.resolve.calls.inference.TypeBounds.BoundKind.EXACT_B
 import org.jetbrains.kotlin.resolve.calls.inference.TypeBounds.BoundKind.LOWER_BOUND
 import org.jetbrains.kotlin.resolve.calls.inference.TypeBounds.BoundKind.UPPER_BOUND
 import org.jetbrains.kotlin.resolve.calls.inference.constraintPosition.CompoundConstraintPosition
+import org.jetbrains.kotlin.resolve.calls.inference.constraintPosition.ConstraintPosition
 import org.jetbrains.kotlin.types.*
 import org.jetbrains.kotlin.types.Variance.INVARIANT
 import org.jetbrains.kotlin.types.typeUtil.getNestedArguments
 import org.jetbrains.kotlin.types.typesApproximation.approximateCapturedTypes
 import java.util.*
 
+data class ConstraintContext(
+        val position: ConstraintPosition,
+        // see TypeBounds.Bound.derivedFrom
+        val derivedFrom: Set<TypeParameterDescriptor>? = null)
+
 fun ConstraintSystemImpl.incorporateBound(newBound: Bound) {
     val typeVariable = newBound.typeVariable
     val typeBounds = getTypeBounds(typeVariable)
@@ -45,7 +52,8 @@ fun ConstraintSystemImpl.incorporateBound(newBound: Bound) {
 
     val constrainingType = newBound.constrainingType
     if (isMyTypeVariable(constrainingType)) {
-        addBound(getMyTypeVariable(constrainingType)!!, typeVariable.correspondingType, newBound.kind.reverse(), newBound.position)
+        val context = ConstraintContext(newBound.position, newBound.derivedFrom)
+        addBound(getMyTypeVariable(constrainingType)!!, typeVariable.correspondingType, newBound.kind.reverse(), context)
         return
     }
     constrainingType.getNestedTypeVariables().forEach {
@@ -61,12 +69,12 @@ private fun ConstraintSystemImpl.addConstraintFromBounds(old: Bound, new: Bound)
 
     val oldType = old.constrainingType
     val newType = new.constrainingType
-    val position = CompoundConstraintPosition(old.position, new.position)
+    val context = ConstraintContext(CompoundConstraintPosition(old.position, new.position), old.derivedFrom + new.derivedFrom)
 
     when {
-        old.kind.ordinal() < new.kind.ordinal() -> addConstraint(SUB_TYPE, oldType, newType, position, topLevel = false)
-        old.kind.ordinal() > new.kind.ordinal() -> addConstraint(SUB_TYPE, newType, oldType, position, topLevel = false)
-        old.kind == new.kind && old.kind == EXACT_BOUND -> addConstraint(EQUAL, oldType, newType, position, topLevel = false)
+        old.kind.ordinal() < new.kind.ordinal() -> addConstraint(SUB_TYPE, oldType, newType, context, topLevel = false)
+        old.kind.ordinal() > new.kind.ordinal() -> addConstraint(SUB_TYPE, newType, oldType, context, topLevel = false)
+        old.kind == new.kind && old.kind == EXACT_BOUND -> addConstraint(EQUAL, oldType, newType, context, topLevel = false)
     }
 }
 
@@ -97,7 +105,7 @@ private fun ConstraintSystemImpl.generateNewBound(bound: Bound, substitution: Bo
         if (derivedFrom.contains(substitution.typeVariable)) return
 
         derivedFrom.add(substitution.typeVariable)
-        addBound(bound.typeVariable, newConstrainingType, newBoundKind, position, derivedFrom)
+        addBound(bound.typeVariable, newConstrainingType, newBoundKind, ConstraintContext(position, derivedFrom))
     }
 
     if (substitution.kind == EXACT_BOUND) {