KT-6803 Subtyping breaks on star-projections for recursive generics

Star-projections have upper bounds of the form "parameter's bound where all parameter of the same class are substituted with their star-projections"

  #KT-6803 Fixed

compiler/testData/diagnostics/tests/TypeInference.kt

@@ -9,10 +9,10 @@ fun main(args : Array<String>) {
   val <!UNUSED_VARIABLE!>a<!> : C<Int> = C();
   val <!UNUSED_VARIABLE!>x<!> : C<in String> = C()
   val <!UNUSED_VARIABLE!>y<!> : C<out String> = C()
-  val <!UNUSED_VARIABLE!>z<!> : C<*> = C()
+  val <!UNUSED_VARIABLE!>z<!> : C<*> = <!TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>C<!>()
 
   val <!UNUSED_VARIABLE!>ba<!> : C<Int> = bar();
   val <!UNUSED_VARIABLE!>bx<!> : C<in String> = bar()
   val <!UNUSED_VARIABLE!>by<!> : C<out String> = bar()
-  val <!UNUSED_VARIABLE!>bz<!> : C<*> = bar()
+  val <!UNUSED_VARIABLE!>bz<!> : C<*> = <!TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>bar<!>()
-}
+}

compiler/testData/diagnostics/tests/substitutions/starProjections.kt

@@ -0,0 +1,24 @@
+// !CHECK_TYPE
+
+trait A<R, T: A<R, T>> {
+    fun r(): R
+    fun t(): T
+}
+
+fun testA(a: A<*, *>) {
+    a.r().checkType { it : _<Any?> }
+    a.t().checkType { it : _<A<*, *>> }
+}
+
+trait B<R, T: B<List<R>, <!UPPER_BOUND_VIOLATED!>T<!>>> {
+    fun r(): R
+    fun t(): T
+}
+
+fun testB(b: B<*, *>) {
+    b.r().checkType { it : _<Any?> }
+    b.t().checkType { it : _<B<List<*>, *>> }
+
+    b.t().r().size()
+}
+

compiler/testData/diagnostics/tests/substitutions/starProjections.txt

@@ -0,0 +1,20 @@
+package
+
+internal fun testA(/*0*/ a: A<*, *>): kotlin.Unit
+internal fun testB(/*0*/ b: B<*, *>): kotlin.Unit
+
+internal trait A</*0*/ R, /*1*/ T : A<R, T>> {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    internal abstract fun r(): R
+    internal abstract fun t(): T
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+internal trait B</*0*/ R, /*1*/ T : B<kotlin.List<R>, T>> {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    internal abstract fun r(): R
+    internal abstract fun t(): T
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/type-checker-test.kt

@@ -44,4 +44,8 @@ trait B: Parent
 
 trait Rec<T>
 class ARec : Rec<ARec>
-class BRec : Rec<BRec>
+class BRec : Rec<BRec>
+trait SubRec<T>: Rec<T>
+
+trait Star<T : Star<T>>
+trait SubStar<T : SubStar<T>> : Star<T>

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

@@ -10901,6 +10901,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("starProjections.kt")
+            public void testStarProjections() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/substitutions/starProjections.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("upperBoundsSubstitutionForOverloadResolutionWithAmbiguity.kt")
             public void testUpperBoundsSubstitutionForOverloadResolutionWithAmbiguity() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/substitutions/upperBoundsSubstitutionForOverloadResolutionWithAmbiguity.kt");

compiler/tests/org/jetbrains/kotlin/types/JetTypeCheckerTest.java

@@ -328,6 +328,23 @@ public class JetTypeCheckerTest extends JetLiteFixture {
         assertSubtype("Nothing?", "Derived_T<*>?");
     }
 
+    public void testStars() throws Exception {
+        assertSubtype("SubStar<*>", "Star<*>");
+        assertSubtype("SubStar<SubStar<*>>", "Star<*>");
+        assertSubtype("SubStar<SubStar<*>>", "Star<SubStar<*>>");
+        assertNotSubtype("SubStar<SubStar<*>>", "Star<Star<*>>");
+
+        assertSubtype("Star<Star<*>>", "Star<*>");
+        assertSubtype("Star<*>", "Star<out Star<*>>");
+
+        assertNotSubtype("Star<*>", "Star<Star<*>>");
+
+        assertSubtype("SubRec<*>", "Rec<*>");
+        assertSubtype("SubRec<*>", "Rec<out Any?>");
+        assertSubtype("Rec<*>", "Rec<out Any?>");
+        assertNotSubtype("Rec<*>", "Rec<out Any>");
+    }
+
     public void testThis() throws Exception {
         assertType("Derived_T<Int>", "this", "Derived_T<Int>");
 //        assertType("Derived_T<Int>", "super<Base_T>", "Base_T<Int>");

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

@@ -69,6 +69,10 @@ public class CommonSupertypes {
         return 1 + maxDepth(KotlinPackage.map(type.getArguments(), new Function1<TypeProjection, JetType>() {
             @Override
             public JetType invoke(TypeProjection projection) {
+                if (projection.isStarProjection()) {
+                    // any type is good enough for depth here
+                    return KotlinBuiltIns.getInstance().getAnyType();
+                }
                 return projection.getType();
             }
         }));

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

@@ -377,7 +377,7 @@ public class ErrorUtils {
         if (type == null) return false;
         if (type.isError()) return true;
         for (TypeProjection projection : type.getArguments()) {
-            if (containsErrorType(projection.getType())) return true;
+            if (!projection.isStarProjection() && containsErrorType(projection.getType())) return true;
         }
         return false;
     }

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

@@ -16,9 +16,35 @@
 
 package org.jetbrains.kotlin.types
 
-import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
+import kotlin.properties.*
+import org.jetbrains.kotlin.descriptors.*
 
 class StarProjectionImpl(
+        private val typeParameter: TypeParameterDescriptor
+) : TypeProjectionBase() {
+    override fun isStarProjection() = true
+
+    override fun getProjectionKind() = Variance.OUT_VARIANCE
+
+    private val _type: JetType by Delegates.lazy {
+        val classDescriptor = typeParameter.getContainingDeclaration() as ClassDescriptor
+        val typeParameters = classDescriptor.getTypeConstructor().getParameters().map { it.getTypeConstructor() }
+        TypeSubstitutor.create(
+                object : TypeSubstitution() {
+                    override fun get(key: TypeConstructor) = when (key) {
+                        typeParameter.getTypeConstructor() -> this@StarProjectionImpl
+                        in typeParameters -> TypeUtils.makeStarProjection(key.getDeclarationDescriptor() as TypeParameterDescriptor)
+                        else -> null
+                    }
+
+                }
+        ).substitute(typeParameter.getUpperBounds().iterator().next(), Variance.OUT_VARIANCE)!!
+    }
+
+    override fun getType() = _type
+}
+
+class TypeBasedStarProjectionImpl(
         private val _type: JetType
 ) : TypeProjectionBase() {
     override fun isStarProjection() = true

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

@@ -45,7 +45,7 @@ public abstract class TypeProjectionBase implements TypeProjection {
     @Override
     public int hashCode() {
         int result = getProjectionKind().hashCode();
-        result = 31 * result + (getType().hashCode());
+        result = 31 * result + (isStarProjection() ? 17 : getType().hashCode());
         return result;
     }
 }

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

@@ -213,6 +213,9 @@ public class TypeSubstitutor {
             if (typeVariable != null) {
                 substitutedType = typeVariable.substitutionResult(replacement.getType());
             }
+            else if (replacement.isStarProjection()) {
+                return replacement;
+            }
             else {
                 // this is a simple type T or T?: if it's T, we should just take replacement, if T? - we make replacement nullable
                 substitutedType = TypeUtils.makeNullableIfNeeded(replacement.getType(), type.isMarkedNullable());

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

@@ -549,7 +549,7 @@ public class TypeUtils {
     public static boolean dependsOnTypeConstructors(@NotNull JetType type, @NotNull Collection<TypeConstructor> typeParameterConstructors) {
         if (typeParameterConstructors.contains(type.getConstructor())) return true;
         for (TypeProjection typeProjection : type.getArguments()) {
-            if (dependsOnTypeConstructors(typeProjection.getType(), typeParameterConstructors)) {
+            if (!typeProjection.isStarProjection() && dependsOnTypeConstructors(typeProjection.getType(), typeParameterConstructors)) {
                 return true;
             }
         }
@@ -577,14 +577,14 @@ public class TypeUtils {
             return true;
         }
         for (TypeProjection projection : type.getArguments()) {
-            if (containsSpecialType(projection.getType(), isSpecialType)) return true;
+            if (!projection.isStarProjection() && containsSpecialType(projection.getType(), isSpecialType)) return true;
         }
         return false;
     }
 
     @NotNull
     public static TypeProjection makeStarProjection(@NotNull TypeParameterDescriptor parameterDescriptor) {
-        return new StarProjectionImpl(parameterDescriptor.getUpperBoundsAsType());
+        return new StarProjectionImpl(parameterDescriptor);
     }
 
     @Nullable

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

@@ -33,7 +33,7 @@ import org.jetbrains.kotlin.types.TypeProjectionImpl
 import org.jetbrains.kotlin.descriptors.annotations.Annotations
 import org.jetbrains.kotlin.types.DelegatingType
 
-fun JetType.getContainedTypeParameters(): Collection<TypeParameterDescriptor> {
+private fun JetType.getContainedTypeParameters(): Collection<TypeParameterDescriptor> {
     val declarationDescriptor = getConstructor().getDeclarationDescriptor()
     if (declarationDescriptor is TypeParameterDescriptor) return listOf(declarationDescriptor)
 
@@ -41,7 +41,7 @@ fun JetType.getContainedTypeParameters(): Collection<TypeParameterDescriptor> {
     if (flexibility != null) {
         return flexibility.lowerBound.getContainedTypeParameters() + flexibility.upperBound.getContainedTypeParameters()
     }
-    return getArguments().map { it.getType() }.flatMap { it.getContainedTypeParameters() }
+    return getArguments().filter { !it.isStarProjection() }.map { it.getType() }.flatMap { it.getContainedTypeParameters() }
 }
 
 fun DeclarationDescriptor.getCapturedTypeParameters(): Collection<TypeParameterDescriptor> {

core/descriptors/src/org/jetbrains/kotlin/types/checker/TypeCheckingProcedure.java

@@ -106,6 +106,10 @@ public class TypeCheckingProcedure {
             TypeProjection typeProjection1 = type1Arguments.get(i);
             TypeParameterDescriptor typeParameter2 = constructor2.getParameters().get(i);
             TypeProjection typeProjection2 = type2Arguments.get(i);
+            if (typeProjection1.isStarProjection() && typeProjection2.isStarProjection()) {
+                continue;
+            }
+
             if (capture(typeProjection1, typeProjection2, typeParameter1)) {
                 continue;
             }
@@ -227,14 +231,16 @@ public class TypeCheckingProcedure {
         for (int i = 0; i < parameters.size(); i++) {
             TypeParameterDescriptor parameter = parameters.get(i);
 
+            TypeProjection superArgument = superArguments.get(i);
+            if (superArgument.isStarProjection()) continue;
+
+            JetType superIn = getInType(parameter, superArgument);
+            JetType superOut = getOutType(parameter, superArgument);
+
             TypeProjection subArgument = subArguments.get(i);
             JetType subIn = getInType(parameter, subArgument);
             JetType subOut = getOutType(parameter, subArgument);
 
-            TypeProjection superArgument = superArguments.get(i);
-            JetType superIn = getInType(parameter, superArgument);
-            JetType superOut = getOutType(parameter, superArgument);
-
             if (capture(subArgument, superArgument, parameter)) continue;
 
             boolean argumentIsErrorType = subArgument.getType().isError() || superArgument.getType().isError();

core/serialization/src/org/jetbrains/kotlin/serialization/deserialization/TypeDeserializer.kt

@@ -103,7 +103,7 @@ public class TypeDeserializer(
             protos.map { proto ->
                 val type = type(proto.getType())
                 if (proto.getProjection() == ProtoBuf.Type.Argument.Projection.STAR)
-                    StarProjectionImpl(type)
+                    TypeBasedStarProjectionImpl(type)
                 else TypeProjectionImpl(variance(proto.getProjection()), type)
             }.toReadOnlyList()