Prohibit recursive inline classes

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java

@@ -329,6 +329,7 @@ public interface Errors {
     DiagnosticFactory1<KtTypeReference, KotlinType> INLINE_CLASS_HAS_INAPPLICABLE_PARAMETER_TYPE = DiagnosticFactory1.create(ERROR);
     DiagnosticFactory0<PsiElement> INLINE_CLASS_CANNOT_IMPLEMENT_INTERFACE_BY_DELEGATION = DiagnosticFactory0.create(ERROR);
     DiagnosticFactory0<KtTypeReference> INLINE_CLASS_CANNOT_EXTEND_CLASSES = DiagnosticFactory0.create(ERROR);
+    DiagnosticFactory0<KtTypeReference> INLINE_CLASS_CANNOT_BE_RECURSIVE = DiagnosticFactory0.create(ERROR);
 
     // Secondary constructors
 

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java

@@ -658,6 +658,7 @@ public class DefaultErrorMessages {
         MAP.put(INLINE_CLASS_HAS_INAPPLICABLE_PARAMETER_TYPE, "Inline class cannot have value parameter of type ''{0}''", RENDER_TYPE);
         MAP.put(INLINE_CLASS_CANNOT_IMPLEMENT_INTERFACE_BY_DELEGATION, "Inline class cannot implement an interface by delegation");
         MAP.put(INLINE_CLASS_CANNOT_EXTEND_CLASSES, "Inline class cannot extend classes");
+        MAP.put(INLINE_CLASS_CANNOT_BE_RECURSIVE, "Inline class cannot be recursive");
 
         MAP.put(VARIANCE_ON_TYPE_PARAMETER_NOT_ALLOWED, "Variance annotations are only allowed for type parameters of classes and interfaces");
         MAP.put(BOUND_ON_TYPE_ALIAS_PARAMETER_NOT_ALLOWED, "Bounds are not allowed on type alias parameters");

compiler/frontend/src/org/jetbrains/kotlin/resolve/checkers/InlineClassDeclarationChecker.kt

@@ -12,10 +12,7 @@ import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.modalityModifier
 import org.jetbrains.kotlin.psi.psiUtil.visibilityModifier
-import org.jetbrains.kotlin.resolve.BindingContext
-import org.jetbrains.kotlin.resolve.DescriptorUtils
-import org.jetbrains.kotlin.resolve.isInlineClass
-import org.jetbrains.kotlin.resolve.substitutedUnderlyingType
+import org.jetbrains.kotlin.resolve.*
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.typeUtil.isNothing
 import org.jetbrains.kotlin.types.typeUtil.isTypeParameter
@@ -80,10 +77,15 @@ object InlineClassDeclarationChecker : DeclarationChecker {
         }
 
         val baseParameterType = descriptor.safeAs<ClassDescriptor>()?.defaultType?.substitutedUnderlyingType()
-        if (baseParameterType != null && baseParameterType.isInapplicableParameterType()) {
-            val typeReference = baseParameter.typeReference
-            if (typeReference != null) {
-                trace.report(Errors.INLINE_CLASS_HAS_INAPPLICABLE_PARAMETER_TYPE.on(typeReference, baseParameterType))
+        val baseParameterTypeReference = baseParameter.typeReference
+        if (baseParameterType != null && baseParameterTypeReference != null) {
+            if (baseParameterType.isInapplicableParameterType()) {
+                trace.report(Errors.INLINE_CLASS_HAS_INAPPLICABLE_PARAMETER_TYPE.on(baseParameterTypeReference, baseParameterType))
+                return
+            }
+
+            if (baseParameterType.isRecursiveInlineClassType()) {
+                trace.report(Errors.INLINE_CLASS_CANNOT_BE_RECURSIVE.on(baseParameterTypeReference))
                 return
             }
         }

compiler/testData/diagnostics/tests/inlineClasses/recursiveInlineClasses.kt

@@ -0,0 +1,16 @@
+// !LANGUAGE: +InlineClasses
+
+inline class Test1(val x: <!INLINE_CLASS_CANNOT_BE_RECURSIVE!>Test1<!>)
+
+inline class Test2A(val x: <!INLINE_CLASS_CANNOT_BE_RECURSIVE!>Test2B<!>)
+inline class Test2B(val x: <!INLINE_CLASS_CANNOT_BE_RECURSIVE!>Test2A<!>)
+
+inline class Test3A(val x: <!INLINE_CLASS_CANNOT_BE_RECURSIVE!>Test3B<!>)
+inline class Test3B(val x: <!INLINE_CLASS_CANNOT_BE_RECURSIVE!>Test3C<!>)
+inline class Test3C(val x: <!INLINE_CLASS_CANNOT_BE_RECURSIVE!>Test3A<!>)
+
+inline class TestNullable(val x: <!INLINE_CLASS_CANNOT_BE_RECURSIVE!>TestNullable?<!>)
+
+inline class TestRecursionInTypeArguments(val x: List<TestRecursionInTypeArguments>)
+
+inline class TestRecursionInArray(val x: Array<TestRecursionInArray>)

compiler/testData/diagnostics/tests/inlineClasses/recursiveInlineClasses.txt

@@ -0,0 +1,73 @@
+package
+
+public final inline class Test1 {
+    public constructor Test1(/*0*/ x: Test1)
+    public final val x: Test1
+    public open override /*1*/ /*synthesized*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*synthesized*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*synthesized*/ fun toString(): kotlin.String
+}
+
+public final inline class Test2A {
+    public constructor Test2A(/*0*/ x: Test2B)
+    public final val x: Test2B
+    public open override /*1*/ /*synthesized*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*synthesized*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*synthesized*/ fun toString(): kotlin.String
+}
+
+public final inline class Test2B {
+    public constructor Test2B(/*0*/ x: Test2A)
+    public final val x: Test2A
+    public open override /*1*/ /*synthesized*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*synthesized*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*synthesized*/ fun toString(): kotlin.String
+}
+
+public final inline class Test3A {
+    public constructor Test3A(/*0*/ x: Test3B)
+    public final val x: Test3B
+    public open override /*1*/ /*synthesized*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*synthesized*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*synthesized*/ fun toString(): kotlin.String
+}
+
+public final inline class Test3B {
+    public constructor Test3B(/*0*/ x: Test3C)
+    public final val x: Test3C
+    public open override /*1*/ /*synthesized*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*synthesized*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*synthesized*/ fun toString(): kotlin.String
+}
+
+public final inline class Test3C {
+    public constructor Test3C(/*0*/ x: Test3A)
+    public final val x: Test3A
+    public open override /*1*/ /*synthesized*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*synthesized*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*synthesized*/ fun toString(): kotlin.String
+}
+
+public final inline class TestNullable {
+    public constructor TestNullable(/*0*/ x: TestNullable?)
+    public final val x: TestNullable?
+    public open override /*1*/ /*synthesized*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*synthesized*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*synthesized*/ fun toString(): kotlin.String
+}
+
+public final inline class TestRecursionInArray {
+    public constructor TestRecursionInArray(/*0*/ x: kotlin.Array<TestRecursionInArray>)
+    public final val x: kotlin.Array<TestRecursionInArray>
+    public open override /*1*/ /*synthesized*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*synthesized*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*synthesized*/ fun toString(): kotlin.String
+}
+
+public final inline class TestRecursionInTypeArguments {
+    public constructor TestRecursionInTypeArguments(/*0*/ x: kotlin.collections.List<TestRecursionInTypeArguments>)
+    public final val x: kotlin.collections.List<TestRecursionInTypeArguments>
+    public open override /*1*/ /*synthesized*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*synthesized*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*synthesized*/ fun toString(): kotlin.String
+}

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -10917,6 +10917,11 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 runTest("compiler/testData/diagnostics/tests/inlineClasses/propertiesWithBackingFieldsInsideInlineClass.kt");
             }
 
+            @TestMetadata("recursiveInlineClasses.kt")
+            public void testRecursiveInlineClasses() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/inlineClasses/recursiveInlineClasses.kt");
+            }
+
             @TestMetadata("unsignedLiteralsWithoutArtifactOnClasspath.kt")
             public void testUnsignedLiteralsWithoutArtifactOnClasspath() throws Exception {
                 runTest("compiler/testData/diagnostics/tests/inlineClasses/unsignedLiteralsWithoutArtifactOnClasspath.kt");

compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java

@@ -10917,6 +10917,11 @@ public class DiagnosticsUsingJavacTestGenerated extends AbstractDiagnosticsUsing
                 runTest("compiler/testData/diagnostics/tests/inlineClasses/propertiesWithBackingFieldsInsideInlineClass.kt");
             }
 
+            @TestMetadata("recursiveInlineClasses.kt")
+            public void testRecursiveInlineClasses() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/inlineClasses/recursiveInlineClasses.kt");
+            }
+
             @TestMetadata("unsignedLiteralsWithoutArtifactOnClasspath.kt")
             public void testUnsignedLiteralsWithoutArtifactOnClasspath() throws Exception {
                 runTest("compiler/testData/diagnostics/tests/inlineClasses/unsignedLiteralsWithoutArtifactOnClasspath.kt");