Fix for KT-12127: Undeclared type variable on delegated property backing field

#KT-12127 Fixed

compiler/backend/src/org/jetbrains/kotlin/codegen/PropertyCodegen.java

@@ -348,7 +348,7 @@ public class PropertyCodegen {
 
         FieldVisitor fv = builder.newField(
                 JvmDeclarationOriginKt.OtherOrigin(element, propertyDescriptor), modifiers, name, type.getDescriptor(),
-                typeMapper.mapFieldSignature(kotlinType, propertyDescriptor), defaultValue
+                isDelegate ? null : typeMapper.mapFieldSignature(kotlinType, propertyDescriptor), defaultValue
         );
 
         Annotated fieldAnnotated = new AnnotatedWithFakeAnnotations(propertyDescriptor, annotations);

compiler/testData/codegen/box/reflection/genericSignature/genericBackingFieldSignature.kt

@@ -48,35 +48,35 @@ fun box(): String {
     val classField = clz.getDeclaredField("classField1");
 
     if (classField.getGenericType().toString() != "Z<T>")
-        return "fail1:" + classField.getGenericType();
+        return "fail1: " + classField.getGenericType();
 
 
     val classField2 = clz.getDeclaredField("classField2");
 
     if (classField2.getGenericType().toString() != "Z<java.lang.String>")
-        return "fail2:" + classField2.getGenericType();
+        return "fail2: " + classField2.getGenericType();
 
 
     val classField3 = clz.getDeclaredField("classField3");
 
     if (classField3.getGenericType().toString() != "Zout<java.lang.String>")
-        return "fail3:" + classField3.getGenericType();
+        return "fail3: " + classField3.getGenericType();
 
 
     val classField4 = clz.getDeclaredField("classField4");
 
     if (classField4.getGenericType().toString() != "Zin<TParam>")
-        return "fail4:" + classField4.getGenericType();
+        return "fail4: " + classField4.getGenericType();
 
     val classField5 = clz.getDeclaredField("delegateLazy\$delegate");
 
-    if (classField5.getGenericType().toString() != "kotlin.Lazy<Z<TParam>>")
-        return "fail5:" + classField5.getGenericType();
+    if (classField5.getGenericType().toString() != "interface kotlin.Lazy")
+        return "fail5: " + classField5.getGenericType();
 
     val classField6 = clz.getDeclaredField("delegateNotNull\$delegate");
 
-    if (classField6.getGenericType().toString() != "kotlin.properties.ReadWriteProperty<java.lang.Object, Z<TParam>>")
-        return "fail6:" + classField6.getGenericType();
+    if (classField6.getGenericType().toString() != "interface kotlin.properties.ReadWriteProperty")
+        return "fail6: " + classField6.getGenericType();
 
 
     return "OK"

compiler/testData/writeSignature/backingFieldForGenericDelegated.kt

@@ -0,0 +1,18 @@
+import kotlin.reflect.KProperty
+import kotlin.reflect.KProperty1
+
+class DVal<T, R, P: KProperty1<T, R>>(val kmember: P) {
+    operator fun getValue(t: T, p: KProperty<*>): R {
+        return kmember.get(t)
+    }
+}
+
+class Value<T>(var text: String? = null)
+
+class Test {
+    val <T> Value<T>.additionalText by DVal(Value<T>::text)
+}
+
+// field: Test::additionalText$delegate
+// jvm signature: LDVal;
+// generic signature: null

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

@@ -47,6 +47,12 @@ public class WriteSignatureTestGenerated extends AbstractWriteSignatureTest {
         doTest(fileName);
     }
 
+    @TestMetadata("backingFieldForGenericDelegated.kt")
+    public void testBackingFieldForGenericDelegated() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/writeSignature/backingFieldForGenericDelegated.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("Comparable.kt")
     public void testComparable() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/writeSignature/Comparable.kt");