J2K: Fix type parameters in LHS of callable reference

nj2k/src/org/jetbrains/kotlin/nj2k/JavaToJKTreeBuilder.kt

@@ -450,13 +450,20 @@ class JavaToJKTreeBuilder constructor(
             }
 
             return JKMethodReferenceExpression(
-                qualifierExpression?.toJK() ?: JKStubExpression(),
+                methodReferenceQualifier(),
                 symbol,
                 functionalType(),
                 isConstructor
             )
         }
 
+        fun PsiMethodReferenceExpression.methodReferenceQualifier(): JKExpression {
+            val qualifierType = qualifierType
+            if (qualifierType != null) return JKTypeQualifierExpression(typeFactory.fromPsiType(qualifierType.type))
+
+            return qualifierExpression?.toJK() ?: JKStubExpression()
+        }
+
         fun PsiReferenceExpression.toJK(): JKExpression {
             if (this is PsiMethodReferenceExpression) return toJK()
             val target = resolve()
@@ -476,6 +483,7 @@ class JavaToJKTreeBuilder constructor(
                 is JKFieldSymbol -> JKFieldAccessExpression(symbol)
                 is JKPackageSymbol -> JKPackageAccessExpression(symbol)
                 is JKMethodSymbol -> JKMethodAccessExpression(symbol)
+                is JKTypeParameterSymbol -> JKTypeQualifierExpression(JKTypeParameterType(symbol))
                 else -> throwCanNotConvertError("unexpected symbol ${symbol::class}")
             }.qualified(qualifierExpression?.toJK()).also {
                 it.withFormattingFrom(this)

nj2k/src/org/jetbrains/kotlin/nj2k/conversions/MethodReferenceToLambdaConversion.kt

@@ -32,19 +32,25 @@ class MethodReferenceToLambdaConversion(context: NewJ2kConverterContext) : Recur
             .safeAs<JKClassType>()
             ?.singleFunctionParameterTypes()
 
-        val receiverParameter = element.qualifier
+        val qualifierExpression = element.qualifier
             .nullIfStubExpression()
-            ?.safeAs<JKClassAccessExpression>()
-            ?.takeIf { symbol.safeAs<JKMethodSymbol>()?.isStatic == false && !element.isConstructorCall }
-            ?.let { classAccessExpression ->
+
+        val receiverParameter = if (symbol.safeAs<JKMethodSymbol>()?.isStatic == false && !element.isConstructorCall) {
+            val type = when (qualifierExpression) {
+                is JKTypeQualifierExpression -> qualifierExpression.type
+                is JKClassAccessExpression -> JKClassType(qualifierExpression.identifier)
+                else -> null
+            }
+            if (type != null) {
                 JKParameter(
                     JKTypeElement(
-                        parametersTypesByFunctionalInterface?.firstOrNull() ?: JKClassType(classAccessExpression.identifier)
+                        parametersTypesByFunctionalInterface?.firstOrNull() ?: type
                     ),
                     JKNameIdentifier(RECEIVER_NAME),
                     isVarArgs = false
                 )
-            }
+            } else null
+        } else null
 
         val explicitParameterTypesByFunctionalInterface =
             if (receiverParameter != null) parametersTypesByFunctionalInterface?.drop(1)

nj2k/src/org/jetbrains/kotlin/nj2k/printing/JKCodeBuilder.kt

@@ -146,6 +146,10 @@ internal class JKCodeBuilder(context: NewJ2kConverterContext) {
             printer.renderSymbol(methodAccessExpression.identifier, methodAccessExpression)
         }
 
+        override fun visitTypeQualifierExpression(typeQualifierExpression: JKTypeQualifierExpression) {
+            printer.renderType(typeQualifierExpression.type, typeQualifierExpression)
+        }
+
         override fun visitFileRaw(file: JKFile) {
             if (file.packageDeclaration.name.value.isNotEmpty()) {
                 file.packageDeclaration.accept(this)

nj2k/src/org/jetbrains/kotlin/nj2k/tree/expressions.kt

@@ -201,6 +201,11 @@ class JKMethodAccessExpression(val identifier: JKMethodSymbol) : JKExpression()
     override fun accept(visitor: JKVisitor) = visitor.visitMethodAccessExpression(this)
 }
 
+class JKTypeQualifierExpression(val type: JKType) : JKExpression() {
+    override fun calculateType(typeFactory: JKTypeFactory): JKType? = null
+    override fun accept(visitor: JKVisitor) = visitor.visitTypeQualifierExpression(this)
+}
+
 class JKMethodReferenceExpression(
     qualifier: JKExpression,
     val identifier: JKSymbol,

nj2k/src/org/jetbrains/kotlin/nj2k/tree/visitors/JKVisitor.kt

@@ -84,6 +84,7 @@ abstract class JKVisitor {
     open fun visitPackageAccessExpression(packageAccessExpression: JKPackageAccessExpression) = visitExpression(packageAccessExpression)
     open fun visitClassAccessExpression(classAccessExpression: JKClassAccessExpression) = visitExpression(classAccessExpression)
     open fun visitMethodAccessExpression(methodAccessExpression: JKMethodAccessExpression) = visitExpression(methodAccessExpression)
+    open fun visitTypeQualifierExpression(typeQualifierExpression: JKTypeQualifierExpression) = visitExpression(typeQualifierExpression)
     open fun visitMethodReferenceExpression(methodReferenceExpression: JKMethodReferenceExpression) =
         visitExpression(methodReferenceExpression)
 

nj2k/testData/newJ2k/function/genericMemberFunctionRef.java

@@ -0,0 +1,21 @@
+// RUNTIME_WITH_FULL_JDK
+
+import java.util.List;
+
+public class TestLambda<T> {
+    public static class Box<Q> {
+
+        private Q value;
+        public Q unbox() {
+            return value;
+        }
+
+        public Box(Q q) {
+            value = q;
+        }
+    }
+
+    public String toStringAllBox(List<Box<T>> list) {
+        return list.stream().map(Box<T>::unbox).map(T::toString).reduce((s1,s2) -> s1 + ", " + s2 ).orElse("");
+    }
+}

nj2k/testData/newJ2k/function/genericMemberFunctionRef.kt

@@ -0,0 +1,12 @@
+class TestLambda<T> {
+    class Box<Q>(private val value: Q) {
+        fun unbox(): Q {
+            return value
+        }
+    }
+
+    fun toStringAllBox(list: List<Box<T>>): String {
+        return list.stream().map { obj: Box<T> -> obj.unbox() }.map { obj: T -> obj.toString() }
+            .reduce { s1: String, s2: String -> "$s1, $s2" }.orElse("")
+    }
+}

nj2k/tests/org/jetbrains/kotlin/nj2k/NewJavaToKotlinConverterSingleFileTestGenerated.java

@@ -2422,6 +2422,11 @@ public class NewJavaToKotlinConverterSingleFileTestGenerated extends AbstractNew
             runTest("nj2k/testData/newJ2k/function/functionInFinalClass.java");
         }
 
+        @TestMetadata("genericMemberFunctionRef.java")
+        public void testGenericMemberFunctionRef() throws Exception {
+            runTest("nj2k/testData/newJ2k/function/genericMemberFunctionRef.java");
+        }
+
         @TestMetadata("internal.java")
         public void testInternal() throws Exception {
             runTest("nj2k/testData/newJ2k/function/internal.java");