Fix problem with empty vararg of boxed primitives in JVM_IR

When calling a generic Java generic method with vararg parameters with empty
vararg, incorrect array creation instruction was generated for primitive type:
NEWARRAY T_INT instead of ANEWARRAY java/lang/Integer. Here for Java method

  public static <T> void takesVarargOfT(T x1, T... xs) {}

corresponding vararg parameter was considered to be of type 'Array<T>?',
which is not a non-null array type, so, NewArray intrinsic failed to generate
proper bytecode.

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/intrinsics/NewArray.kt

@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.backend.jvm.ir.getArrayElementType
 import org.jetbrains.kotlin.codegen.inline.ReifiedTypeInliner
 import org.jetbrains.kotlin.ir.expressions.IrFunctionAccessExpression
 import org.jetbrains.kotlin.ir.types.isArray
+import org.jetbrains.kotlin.ir.types.isNullableArray
 import org.jetbrains.org.objectweb.asm.Type
 
 object NewArray : IntrinsicMethod() {
@@ -19,7 +20,7 @@ object NewArray : IntrinsicMethod() {
         codegen.gen(expression.getValueArgument(0)!!, Type.INT_TYPE, codegen.context.irBuiltIns.intType, data)
         return with(codegen) {
             val elementIrType = expression.type.getArrayElementType(context.irBuiltIns)
-            if (expression.type.isArray()) {
+            if (expression.type.isArray() || expression.type.isNullableArray()) {
                 putReifiedOperationMarkerIfTypeIsReifiedParameter(elementIrType, ReifiedTypeInliner.OperationKind.NEW_ARRAY)
                 mv.newarray(typeMapper.boxType(elementIrType))
             } else {

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/VarargLowering.kt

@@ -23,6 +23,7 @@ import org.jetbrains.kotlin.ir.declarations.IrFunction
 import org.jetbrains.kotlin.ir.declarations.IrPackageFragment
 import org.jetbrains.kotlin.ir.expressions.*
 import org.jetbrains.kotlin.ir.symbols.IrFunctionSymbol
+import org.jetbrains.kotlin.ir.types.makeNotNull
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.util.capitalizeDecapitalize.toLowerCaseAsciiOnly
 
@@ -56,7 +57,7 @@ private class VarargLowering(val context: JvmBackendContext) : FileLoweringPass,
             val parameter = function.owner.valueParameters[i]
             if (parameter.varargElementType != null && !parameter.hasDefaultValue()) {
                 // Compute the correct type for the array argument.
-                val arrayType = parameter.type.substitute(expression.typeSubstitutionMap)
+                val arrayType = parameter.type.substitute(expression.typeSubstitutionMap).makeNotNull()
                 expression.putValueArgument(i, createBuilder().irArrayOf(arrayType))
             }
         }

compiler/testData/codegen/box/vararg/emptyVarargOfBoxedPrimitiveType.kt

@@ -0,0 +1,43 @@
+// TARGET_BACKEND: JVM
+// FILE: emptyVarargOfBoxedPrimitiveType.kt
+
+fun box(): String {
+    takesVarargOfInt(1)
+    takesVarargOfT(1)
+
+    J.takesVarargOfInt(1)
+    J.takesVarargOfInteger(1)
+    J.takesVarargOfT(1)
+
+    takesVarargOfInt(1, 2)
+    takesVarargOfT(1, 2)
+
+    J.takesVarargOfInt(1, 2)
+    J.takesVarargOfInteger(1, 2)
+    J.takesVarargOfT(1, 2)
+
+    return "OK"
+}
+
+fun takesVarargOfInt(x: Int, vararg xs: Int) {}
+fun <T> takesVarargOfT(x: T, vararg xs: T) {}
+
+// FILE: J.java
+public class J {
+    public static void takesVarargOfInt(int x1, int... xs) {}
+
+    public static void takesVarargOfInteger(Integer x1, Integer... xs) {}
+
+    public static <T> void takesVarargOfT(T x1, T... xs) {
+        Class<?> x1Class = x1.getClass();
+        Class<?> xsClass = xs.getClass();
+        Class<?> xsComponentClass = xsClass.getComponentType();
+        if (!xsComponentClass.equals(x1Class)) {
+            throw new AssertionError(
+                    "Wrong array component type " + xsComponentClass +
+                            " for array class " + xsClass +
+                            ", expected: " + x1Class
+            );
+        }
+    }
+}

compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java

@@ -28301,6 +28301,11 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             runTest("compiler/testData/codegen/box/vararg/doNotCopyImmediatelyCreatedArrays.kt");
         }
 
+        @TestMetadata("emptyVarargOfBoxedPrimitiveType.kt")
+        public void testEmptyVarargOfBoxedPrimitiveType() throws Exception {
+            runTest("compiler/testData/codegen/box/vararg/emptyVarargOfBoxedPrimitiveType.kt");
+        }
+
         @TestMetadata("kt1978.kt")
         public void testKt1978() throws Exception {
             runTest("compiler/testData/codegen/box/vararg/kt1978.kt");

compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java

@@ -27118,6 +27118,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             runTest("compiler/testData/codegen/box/vararg/doNotCopyImmediatelyCreatedArrays.kt");
         }
 
+        @TestMetadata("emptyVarargOfBoxedPrimitiveType.kt")
+        public void testEmptyVarargOfBoxedPrimitiveType() throws Exception {
+            runTest("compiler/testData/codegen/box/vararg/emptyVarargOfBoxedPrimitiveType.kt");
+        }
+
         @TestMetadata("kt1978.kt")
         public void testKt1978() throws Exception {
             runTest("compiler/testData/codegen/box/vararg/kt1978.kt");

compiler/tests/org/jetbrains/kotlin/codegen/ir/FirBlackBoxCodegenTestGenerated.java

@@ -26800,6 +26800,11 @@ public class FirBlackBoxCodegenTestGenerated extends AbstractFirBlackBoxCodegenT
             runTest("compiler/testData/codegen/box/vararg/doNotCopyImmediatelyCreatedArrays.kt");
         }
 
+        @TestMetadata("emptyVarargOfBoxedPrimitiveType.kt")
+        public void testEmptyVarargOfBoxedPrimitiveType() throws Exception {
+            runTest("compiler/testData/codegen/box/vararg/emptyVarargOfBoxedPrimitiveType.kt");
+        }
+
         @TestMetadata("kt1978.kt")
         public void testKt1978() throws Exception {
             runTest("compiler/testData/codegen/box/vararg/kt1978.kt");

compiler/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java

@@ -26800,6 +26800,11 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             runTest("compiler/testData/codegen/box/vararg/doNotCopyImmediatelyCreatedArrays.kt");
         }
 
+        @TestMetadata("emptyVarargOfBoxedPrimitiveType.kt")
+        public void testEmptyVarargOfBoxedPrimitiveType() throws Exception {
+            runTest("compiler/testData/codegen/box/vararg/emptyVarargOfBoxedPrimitiveType.kt");
+        }
+
         @TestMetadata("kt1978.kt")
         public void testKt1978() throws Exception {
             runTest("compiler/testData/codegen/box/vararg/kt1978.kt");