Use captured instance in interface companion object initializer

Similar to enum entry initialization, when we have a companion object
in an interface, its constructor (or clinit) initializes its state
before the instance field in corresponding interface is initialized.
So, interface companion object must be accessed via a captured object
reference (#0, or #0.this$0 for inner anonymous objects).

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

@@ -104,6 +104,7 @@ import java.util.*;
 import static org.jetbrains.kotlin.builtins.KotlinBuiltIns.isInt;
 import static org.jetbrains.kotlin.codegen.AsmUtil.*;
 import static org.jetbrains.kotlin.codegen.CodegenUtilKt.extractReificationArgument;
+import static org.jetbrains.kotlin.codegen.CodegenUtilKt.isPossiblyUninitializedSingleton;
 import static org.jetbrains.kotlin.codegen.CodegenUtilKt.unwrapInitialSignatureDescriptor;
 import static org.jetbrains.kotlin.codegen.JvmCodegenUtil.*;
 import static org.jetbrains.kotlin.codegen.binding.CodegenBinding.*;
@@ -1737,16 +1738,14 @@ public class ExpressionCodegen extends KtVisitor<StackValue, StackValue> impleme
 
         if (descriptor instanceof ClassDescriptor) {
             ClassDescriptor classDescriptor = (ClassDescriptor) descriptor;
+            if (isPossiblyUninitializedSingleton(classDescriptor) && isInsideSingleton(classDescriptor)) {
+                return generateThisOrOuterFromContext(classDescriptor, false, false);
+            }
             if (isObject(classDescriptor)) {
                 return StackValue.singleton(classDescriptor, typeMapper);
             }
             if (isEnumEntry(classDescriptor)) {
-                if (isInsideEnumEntry(classDescriptor)) {
+                return StackValue.enumEntry(classDescriptor, typeMapper);
-                    return generateThisOrOuterFromContext(classDescriptor, false, false);
-                }
-                else {
-                    return StackValue.enumEntry(classDescriptor, typeMapper);
-                }
             }
             ClassDescriptor companionObjectDescriptor = classDescriptor.getCompanionObjectDescriptor();
             if (companionObjectDescriptor != null) {
@@ -2488,6 +2487,9 @@ public class ExpressionCodegen extends KtVisitor<StackValue, StackValue> impleme
                 if (contextDescriptor instanceof FunctionDescriptor && receiverDescriptor == contextDescriptor.getContainingDeclaration()) {
                     return StackValue.LOCAL_0;
                 }
+                else if (isPossiblyUninitializedSingleton(receiverDescriptor) && isInsideSingleton(receiverDescriptor)) {
+                    return generateThisOrOuterFromContext(receiverDescriptor, false, false);
+                }
                 else {
                     return StackValue.singleton(receiverDescriptor, typeMapper);
                 }
@@ -2572,13 +2574,13 @@ public class ExpressionCodegen extends KtVisitor<StackValue, StackValue> impleme
         return generateThisOrOuter(calleeContainingClass, isSuper, false);
     }
 
-    private boolean isInsideEnumEntry(@NotNull ClassDescriptor enumEntryDescriptor) {
+    private boolean isInsideSingleton(@NotNull ClassDescriptor singletonClassDescriptor) {
-        assert DescriptorUtils.isEnumEntry(enumEntryDescriptor) :
+        assert singletonClassDescriptor.getKind().isSingleton() :
-                "Enum entry reference expected: " + enumEntryDescriptor;
+                "Singleton expected: " + singletonClassDescriptor;
 
         DeclarationDescriptor descriptor = context.getContextDescriptor();
         while (descriptor != null) {
-            if (descriptor == enumEntryDescriptor) return true;
+            if (descriptor == singletonClassDescriptor) return true;
 
             if (descriptor instanceof ClassDescriptor &&
                 !(((ClassDescriptor) descriptor).isInner() || DescriptorUtils.isAnonymousObject(descriptor))) {
@@ -2593,24 +2595,23 @@ public class ExpressionCodegen extends KtVisitor<StackValue, StackValue> impleme
 
     @NotNull
     public StackValue generateThisOrOuter(@NotNull ClassDescriptor calleeContainingClass, boolean isSuper, boolean forceOuter) {
-        boolean isSingleton = calleeContainingClass.getKind().isSingleton();
+        if (!calleeContainingClass.getKind().isSingleton()) {
-        if (isSingleton) {
+            return generateThisOrOuterFromContext(calleeContainingClass, isSuper, forceOuter);
-            if (calleeContainingClass.equals(context.getThisDescriptor()) &&
-                !CodegenUtilKt.isJvmStaticInObjectOrClass(context.getFunctionDescriptor())) {
-                return StackValue.local(0, typeMapper.mapType(calleeContainingClass));
-            }
-            else if (isEnumEntry(calleeContainingClass)) {
-                if (!isInsideEnumEntry(calleeContainingClass)) {
-                    return StackValue.enumEntry(calleeContainingClass, typeMapper);
-                }
-                // else fall-through
-            }
-            else {
-                return StackValue.singleton(calleeContainingClass, typeMapper);
-            }
         }
 
-        return generateThisOrOuterFromContext(calleeContainingClass, isSuper, forceOuter);
+        if (calleeContainingClass.equals(context.getThisDescriptor()) &&
+            !CodegenUtilKt.isJvmStaticInObjectOrClass(context.getFunctionDescriptor())) {
+            return StackValue.local(0, typeMapper.mapType(calleeContainingClass));
+        }
+        else if (CodegenUtilKt.isPossiblyUninitializedSingleton(calleeContainingClass) && isInsideSingleton(calleeContainingClass)) {
+            return generateThisOrOuterFromContext(calleeContainingClass, isSuper, forceOuter);
+        }
+        else if (isEnumEntry(calleeContainingClass)) {
+            return StackValue.enumEntry(calleeContainingClass, typeMapper);
+        }
+        else {
+            return StackValue.singleton(calleeContainingClass, typeMapper);
+        }
     }
 
     private StackValue generateThisOrOuterFromContext(@NotNull ClassDescriptor calleeContainingClass, boolean isSuper, boolean forceOuter) {

compiler/backend/src/org/jetbrains/kotlin/codegen/codegenUtil.kt

@@ -420,3 +420,7 @@ fun ExpressionCodegen.generateCallReceiver(rangeCall: ResolvedCall<out CallableD
 
 fun ExpressionCodegen.generateCallSingleArgument(rangeCall: ResolvedCall<out CallableDescriptor>): StackValue =
         gen(ExpressionCodegen.getSingleArgumentExpression(rangeCall)!!)
+
+fun ClassDescriptor.isPossiblyUninitializedSingleton() =
+        DescriptorUtils.isEnumEntry(this) ||
+        DescriptorUtils.isCompanionObject(this) && DescriptorUtils.isInterface(this.containingDeclaration)

compiler/testData/codegen/box/objects/interfaceCompanionObjectReference.kt

@@ -0,0 +1,37 @@
+// WITH_RUNTIME
+
+import kotlin.test.*
+
+interface Test {
+    companion object {
+        val x = "OK"
+
+        val y1 = Test.x
+
+        val y2 = 42.let { x }
+
+        val y3: String
+        init {
+            fun localFun() = x
+            y3 = localFun()
+        }
+
+        fun method() = x
+        val y4 = method()
+
+        val anonObject = object {
+            override fun toString() = x
+        }
+        val y5 = anonObject.toString()
+
+        init {
+            assertEquals(x, y1)
+            assertEquals(x, y2)
+            assertEquals(x, y3)
+            assertEquals(x, y4)
+            assertEquals(x, y5)
+        }
+    }
+}
+
+fun box() = Test.x

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

@@ -11846,6 +11846,12 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             doTest(fileName);
         }
 
+        @TestMetadata("interfaceCompanionObjectReference.kt")
+        public void testInterfaceCompanionObjectReference() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/objects/interfaceCompanionObjectReference.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("kt1047.kt")
         public void testKt1047() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/objects/kt1047.kt");

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

@@ -11846,6 +11846,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             doTest(fileName);
         }
 
+        @TestMetadata("interfaceCompanionObjectReference.kt")
+        public void testInterfaceCompanionObjectReference() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/objects/interfaceCompanionObjectReference.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("kt1047.kt")
         public void testKt1047() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/objects/kt1047.kt");

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

@@ -11846,6 +11846,12 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             doTest(fileName);
         }
 
+        @TestMetadata("interfaceCompanionObjectReference.kt")
+        public void testInterfaceCompanionObjectReference() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/objects/interfaceCompanionObjectReference.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("kt1047.kt")
         public void testKt1047() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/objects/kt1047.kt");

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java

@@ -13106,6 +13106,12 @@ public class JsCodegenBoxTestGenerated extends AbstractJsCodegenBoxTest {
             doTest(fileName);
         }
 
+        @TestMetadata("interfaceCompanionObjectReference.kt")
+        public void testInterfaceCompanionObjectReference() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/objects/interfaceCompanionObjectReference.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("kt1047.kt")
         public void testKt1047() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/objects/kt1047.kt");