Proper enhancement for type parameters

compiler/frontend.java/src/org/jetbrains/kotlin/load/java/components/typeEnhancement.kt

@@ -17,6 +17,8 @@
 package org.jetbrains.kotlin.load.java.components
 
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
+import org.jetbrains.kotlin.descriptors.ClassifierDescriptor
+import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
 import org.jetbrains.kotlin.load.java.components.MutabilityQualifier.MUTABLE
 import org.jetbrains.kotlin.load.java.components.MutabilityQualifier.READ_ONLY
 import org.jetbrains.kotlin.load.java.components.NullabilityQualifier.NOT_NULL
@@ -62,18 +64,18 @@ private fun JetType.enhanceInflexible(qualifiers: (Int) -> JavaTypeQualifiers, i
     val shouldEnhance = position.shouldEnhance()
     if (!shouldEnhance && getArguments().isEmpty()) return Result(this, 1)
 
-    val originalClass = getConstructor().getDeclarationDescriptor() as? ClassDescriptor
+    val originalClass = getConstructor().getDeclarationDescriptor()
                         ?: return Result(this, 1)
 
     val effectiveQualifiers = qualifiers(index)
-    val enhancedClass = originalClass.enhanceMutability(effectiveQualifiers, position)
+    val enhancedClassifier = originalClass.enhanceMutability(effectiveQualifiers, position)
 
     var globalArgIndex = index + 1
     val enhancedArguments = getArguments().mapIndexed {
         localArgIndex, arg ->
         if (arg.isStarProjection()) {
             globalArgIndex++
-            TypeUtils.makeStarProjection(enhancedClass.getTypeConstructor().getParameters()[localArgIndex])
+            TypeUtils.makeStarProjection(enhancedClassifier.getTypeConstructor().getParameters()[localArgIndex])
         }
         else {
             val (enhancedType, subtreeSize) = arg.getType().enhancePossiblyFlexible(qualifiers, globalArgIndex)
@@ -87,18 +89,21 @@ private fun JetType.enhanceInflexible(qualifiers: (Int) -> JavaTypeQualifiers, i
 
     val enhancedType = JetTypeImpl(
             getAnnotations(),
-            enhancedClass.getTypeConstructor(),
+            enhancedClassifier.getTypeConstructor(),
             this.getEnhancedNullability(effectiveQualifiers, position),
             enhancedArguments,
-            enhancedClass.getMemberScope(enhancedArguments)
+            if (enhancedClassifier is ClassDescriptor)
+                enhancedClassifier.getMemberScope(enhancedArguments)
+            else enhancedClassifier.getDefaultType().getMemberScope()
     )
     return Result(enhancedType, globalArgIndex - index)
 }
 
 private fun TypeComponentPosition.shouldEnhance() = this != TypeComponentPosition.INFLEXIBLE
 
-private fun ClassDescriptor.enhanceMutability(qualifiers: JavaTypeQualifiers, position: TypeComponentPosition): ClassDescriptor {
+private fun ClassifierDescriptor.enhanceMutability(qualifiers: JavaTypeQualifiers, position: TypeComponentPosition): ClassifierDescriptor {
     if (!position.shouldEnhance()) return this
+    if (this !is ClassDescriptor) return this // mutability is not applicable for type parameters
 
     val mapping = JavaToKotlinClassMap.INSTANCE
 

compiler/testData/diagnostics/tests/j+k/types/arrayList.kt

@@ -0,0 +1,15 @@
+// FILE: k.kt
+
+trait ML<T> {
+    public fun foo(): MutableList<T>
+}
+
+class K : J<String>(), ML<String>
+
+// FILE: J.java
+
+import java.util.*;
+
+class J<T> extends ML<T> {
+    public List<T> foo() { return null; }
+}

compiler/testData/diagnostics/tests/j+k/types/arrayList.txt

@@ -0,0 +1,24 @@
+package
+
+public/*package*/ open class J</*0*/ T> : ML<T!> {
+    public/*package*/ constructor J</*0*/ T>()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ fun foo(): kotlin.MutableList<T!>
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+internal final class K : J<kotlin.String>, ML<kotlin.String> {
+    public constructor K()
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*2*/ /*fake_override*/ fun foo(): kotlin.MutableList<kotlin.String>
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+internal trait ML</*0*/ T> {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(): kotlin.MutableList<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/j+k/types/typeParameter.kt

@@ -0,0 +1,11 @@
+// FILE: k.kt
+
+trait K {
+    fun <T> foo(t: T)
+}
+
+// FILE: J.java
+
+interface J extends K {
+    <T> void foo(T t);
+}

compiler/testData/diagnostics/tests/j+k/types/typeParameter.txt

@@ -0,0 +1,15 @@
+package
+
+public/*package*/ trait J : K {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract override /*1*/ fun </*0*/ T> foo(/*0*/ t: T): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+internal trait K {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    internal abstract fun </*0*/ T> foo(/*0*/ t: T): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TypeParamOfClass.txt

@@ -9,6 +9,6 @@ public interface TypeParamOfClass {
 
     public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
-        org.jetbrains.annotations.NotNull() public abstract fun foo(): T!
+        org.jetbrains.annotations.NotNull() public abstract fun foo(): T
     }
 }

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TypeParamOfClassSubstituted.txt

@@ -9,6 +9,6 @@ public interface TypeParamOfClassSubstituted {
 
     public interface Super</*0*/ T> {
         public abstract fun dummy(): kotlin.Unit
-        org.jetbrains.annotations.NotNull() public abstract fun foo(): T!
+        org.jetbrains.annotations.NotNull() public abstract fun foo(): T
     }
 }

compiler/testData/loadJava/compiledJava/kotlinSignature/propagation/return/TypeParamOfFun.txt

@@ -4,11 +4,11 @@ public interface TypeParamOfFun {
 
     public interface Sub : test.TypeParamOfFun.Super {
         public abstract override /*1*/ /*fake_override*/ fun dummy(): kotlin.Unit
-        public abstract override /*1*/ fun </*0*/ E> foo(): E!
+        public abstract override /*1*/ fun </*0*/ E> foo(): E
     }
 
     public interface Super {
         public abstract fun dummy(): kotlin.Unit
-        org.jetbrains.annotations.NotNull() public abstract fun </*0*/ T> foo(): T!
+        org.jetbrains.annotations.NotNull() public abstract fun </*0*/ T> foo(): T
     }
 }

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

@@ -8192,6 +8192,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                     JetTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/diagnostics/tests/j+k/types"), Pattern.compile("^(.+)\\.kt$"), true);
                 }
 
+                @TestMetadata("arrayList.kt")
+                public void testArrayList() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/j+k/types/arrayList.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("returnCollection.kt")
                 public void testReturnCollection() throws Exception {
                     String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/j+k/types/returnCollection.kt");
@@ -8209,6 +8215,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                     String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/j+k/types/shapeMismatchInCovariantPositionGeneric.kt");
                     doTest(fileName);
                 }
+
+                @TestMetadata("typeParameter.kt")
+                public void testTypeParameter() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/j+k/types/typeParameter.kt");
+                    doTest(fileName);
+                }
             }
         }