Refine type mapping for nullable inline class types

compiler/testData/writeSignature/inlineClasses/nullableInlineClassType.kt

@@ -0,0 +1,30 @@
+// !LANGUAGE: +InlineClasses
+
+inline class InlinePrimitive(val x: Int)
+inline class InlineReference(val y: String)
+inline class InlineNullablePrimitive(val x: Int?)
+inline class InlineNullableReference(val y: String?)
+
+object Test {
+    fun withPrimitiveAsNullable(a: InlinePrimitive?) {}
+    fun withReferenceAsNullable(a: InlineReference?) {}
+
+    fun withNullablePrimitiveAsNullable(a: InlineNullablePrimitive?) {}
+    fun withNullableReferenceAsNullable(a: InlineNullableReference?) {}
+}
+
+// method: Test::withPrimitiveAsNullable
+// jvm signature: (LInlinePrimitive;)V
+// generic signature: null
+
+// method: Test::withReferenceAsNullable
+// jvm signature: (Ljava/lang/String;)V
+// generic signature: null
+
+// method: Test::withNullablePrimitiveAsNullable
+// jvm signature: (LInlineNullablePrimitive;)V
+// generic signature: null
+
+// method: Test::withNullableReferenceAsNullable
+// jvm signature: (LInlineNullableReference;)V
+// generic signature: null

compiler/tests/org/jetbrains/kotlin/jvm/compiler/WriteSignatureTestGenerated.java

@@ -558,6 +558,12 @@ public class WriteSignatureTestGenerated extends AbstractWriteSignatureTest {
             KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/writeSignature/inlineClasses"), Pattern.compile("^(.+)\\.kt$"), TargetBackend.ANY, true);
         }
 
+        @TestMetadata("nullableInlineClassType.kt")
+        public void testNullableInlineClassType() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/writeSignature/inlineClasses/nullableInlineClassType.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("simpleSignatureWithInlineClassTypesAsPrimitive.kt")
         public void testSimpleSignatureWithInlineClassTypesAsPrimitive() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/writeSignature/inlineClasses/simpleSignatureWithInlineClassTypesAsPrimitive.kt");

core/descriptors.jvm/src/org/jetbrains/kotlin/load/kotlin/typeSignatureMapping.kt

@@ -132,7 +132,13 @@ fun <T : Any> mapType(
             if (descriptor.isInline && !mode.needInlineClassWrapping) {
                 val underlyingType = descriptor.underlyingRepresentation()?.type
                 if (underlyingType != null) {
-                    return mapType(underlyingType, factory, mode, typeMappingConfiguration, descriptorTypeWriter, writeGenericType)
+                    if (!kotlinType.isMarkedNullable) {
+                        return mapType(underlyingType, factory, mode, typeMappingConfiguration, descriptorTypeWriter, writeGenericType)
+                    }
+
+                    if (!underlyingType.isMarkedNullable && !KotlinBuiltIns.isPrimitiveType(underlyingType)) {
+                        return mapType(underlyingType, factory, mode, typeMappingConfiguration, descriptorTypeWriter, writeGenericType)
+                    }
                 }
             }