Fix captured approximation for case of flexible types

#KT-9294 Fixed

compiler/testData/diagnostics/tests/generics/projectionsScope/platformSuperClass.kt

@@ -0,0 +1,22 @@
+// !CHECK_TYPE
+
+// FILE: Clazz.java
+public class Clazz<T> {
+    public T getT() { return null; }
+    public Clazz<? super T> getSuperClass() { return null; }
+}
+
+// FILE: main.kt
+fun test(clazz: Clazz<*>) {
+    clazz.t checkType { _<Any?>() }
+    clazz.getSuperClass() checkType { _<Clazz<*>?>() }
+    clazz.getSuperClass().t checkType { _<Any?>() }
+
+    clazz.superClass checkType { _<Clazz<*>?>() }
+    clazz.superClass.t checkType { _<Any?>() }
+
+    // See KT-9294
+    if (clazz.superClass == null) {
+        throw NullPointerException()
+    }
+}

compiler/testData/diagnostics/tests/generics/projectionsScope/platformSuperClass.txt

@@ -0,0 +1,12 @@
+package
+
+public fun test(/*0*/ clazz: Clazz<*>): kotlin.Unit
+
+public open class Clazz</*0*/ T : kotlin.Any!> {
+    public constructor Clazz</*0*/ T : kotlin.Any!>()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open fun getSuperClass(): Clazz<in T!>!
+    public open fun getT(): T!
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/inference/capturedTypes/captureForPlatformTypes.kt

@@ -16,14 +16,12 @@ fun test1(clazz: Class<out Int>) {
     val foo0: Class<out Int> = A.foo(clazz)
     val foo1 = A.foo(clazz)
     foo1 checkType { _< Class<out Int> >() }
-//    should be ok
-    foo1 checkType { <!TYPE_MISMATCH!>_<!>< Class<out Int?> >() }
+    foo1 checkType { _< Class<out Int?> >() }
 }
 
 fun tes2t(clazz: Class<in Int>) {
     val foo0: Class<out Class<in Int>> = A.bar(clazz)
     val foo1 = A.bar(clazz)
     foo1 checkType { _< Class<out Class<in Int>> >() }
-//    should be ok
-    foo1 checkType { <!TYPE_MISMATCH!>_<!>< Class<out Class<in Int?>> >() }
+    foo1 checkType { _< Class<out Class<in Int?>> >() }
 }

compiler/testData/diagnostics/tests/j+k/arrayOfStarParametrized.txt

@@ -1,6 +1,6 @@
 package
 
-public fun foo1(/*0*/ x: A<*>): kotlin.Array<out A<out kotlin.Any!>>
+public fun foo1(/*0*/ x: A<*>): kotlin.Array<out A<out kotlin.Any!>!>!
 public fun foo2(/*0*/ x: A<*>): kotlin.Unit
 
 public open class A</*0*/ T : kotlin.Any!> {

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

@@ -7160,6 +7160,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                     doTest(fileName);
                 }
 
+                @TestMetadata("platformSuperClass.kt")
+                public void testPlatformSuperClass() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/generics/projectionsScope/platformSuperClass.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("recursiveUpperBoundStar.kt")
                 public void testRecursiveUpperBoundStar() throws Exception {
                     String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/generics/projectionsScope/recursiveUpperBoundStar.kt");

core/descriptors/src/org/jetbrains/kotlin/types/CapturedTypeApproximation.kt

@@ -53,7 +53,7 @@ private fun TypeArgument.toTypeProjection(): TypeProjection {
 }
 
 private fun TypeProjection.toTypeArgument(typeParameter: TypeParameterDescriptor) =
-        when (TypeSubstitutor.combine(typeParameter.variance, projectionKind)) {
+        when (TypeSubstitutor.combine(typeParameter.variance, this)) {
             Variance.INVARIANT -> TypeArgument(typeParameter, type, type)
             Variance.IN_VARIANCE -> TypeArgument(typeParameter, type, typeParameter.builtIns.nullableAnyType)
             Variance.OUT_VARIANCE -> TypeArgument(typeParameter, typeParameter.builtIns.nothingType, type)
@@ -93,10 +93,21 @@ private fun substituteCapturedTypesWithProjections(typeProjection: TypeProjectio
 }
 
 public fun approximateCapturedTypes(type: KotlinType): ApproximationBounds<KotlinType> {
+    if (type.isFlexible()) {
+        val boundsForFlexibleLower = approximateCapturedTypes(type.lowerIfFlexible())
+        val boundsForFlexibleUpper = approximateCapturedTypes(type.upperIfFlexible())
+
+        val extraCapabilities = type.flexibility().extraCapabilities
+        return ApproximationBounds(
+                DelegatingFlexibleType.create(
+                        boundsForFlexibleLower.lower.lowerIfFlexible(), boundsForFlexibleUpper.lower.upperIfFlexible(), extraCapabilities),
+                DelegatingFlexibleType.create(
+                        boundsForFlexibleLower.upper.lowerIfFlexible(), boundsForFlexibleUpper.upper.upperIfFlexible(), extraCapabilities))
+    }
+
     val typeConstructor = type.constructor
     if (type.isCaptured()) {
         val typeProjection = (typeConstructor as CapturedTypeConstructor).typeProjection
-        // todo: preserve flexibility as well
         fun KotlinType.makeNullableIfNeeded() = TypeUtils.makeNullableIfNeeded(this, type.isMarkedNullable)
         val bound = typeProjection.type.makeNullableIfNeeded()
 
@@ -112,9 +123,18 @@ public fun approximateCapturedTypes(type: KotlinType): ApproximationBounds<Kotli
     val lowerBoundArguments = ArrayList<TypeArgument>()
     val upperBoundArguments = ArrayList<TypeArgument>()
     for ((typeProjection, typeParameter) in type.arguments.zip(typeConstructor.parameters)) {
-        val (lower, upper) = approximateProjection(typeProjection.toTypeArgument(typeParameter))
-        lowerBoundArguments.add(lower)
-        upperBoundArguments.add(upper)
+        val typeArgument = typeProjection.toTypeArgument(typeParameter)
+
+        // Protection from infinite recursion caused by star projection
+        if (typeProjection.isStarProjection) {
+            lowerBoundArguments.add(typeArgument)
+            upperBoundArguments.add(typeArgument)
+        }
+        else {
+            val (lower, upper) = approximateProjection(typeArgument)
+            lowerBoundArguments.add(lower)
+            upperBoundArguments.add(upper)
+        }
     }
     val lowerBoundIsTrivial = lowerBoundArguments.any { !it.isConsistent }
     return ApproximationBounds(

core/descriptors/src/org/jetbrains/kotlin/types/TypeSubstitutor.java

@@ -260,6 +260,13 @@ public class TypeSubstitutor {
         return substitutedArguments;
     }
 
+    @NotNull
+    public static Variance combine(@NotNull Variance typeParameterVariance, @NotNull TypeProjection typeProjection) {
+        if (typeProjection.isStarProjection()) return Variance.OUT_VARIANCE;
+
+        return combine(typeParameterVariance, typeProjection.getProjectionKind());
+    }
+
     @NotNull
     public static Variance combine(@NotNull Variance typeParameterVariance, @NotNull Variance projectionKind) {
         if (typeParameterVariance == Variance.INVARIANT) return projectionKind;