inlineClassUtils: Fix handling of inline classes without constructors

Fixes KT-50992

DeclarationDescriptor.isInlineClass misidentifies inline classes without
constructors. This can happen for the ABI of inline classes with private
constructors.

plugins/jvm-abi-gen/test/org/jetbrains/kotlin/jvm/abi/CompileAgainstJvmAbiTestGenerated.java

@@ -115,6 +115,11 @@ public class CompileAgainstJvmAbiTestGenerated extends AbstractCompileAgainstJvm
         runTest("plugins/jvm-abi-gen/testData/compile/privateOnlyConstructors/");
     }
 
+    @TestMetadata("privateValueClassConstructor")
+    public void testPrivateValueClassConstructor() throws Exception {
+        runTest("plugins/jvm-abi-gen/testData/compile/privateValueClassConstructor/");
+    }
+
     @TestMetadata("topLevel")
     public void testTopLevel() throws Exception {
         runTest("plugins/jvm-abi-gen/testData/compile/topLevel/");

plugins/jvm-abi-gen/test/org/jetbrains/kotlin/jvm/abi/IrCompileAgainstJvmAbiTestGenerated.java

@@ -115,6 +115,11 @@ public class IrCompileAgainstJvmAbiTestGenerated extends AbstractIrCompileAgains
         runTest("plugins/jvm-abi-gen/testData/compile/privateOnlyConstructors/");
     }
 
+    @TestMetadata("privateValueClassConstructor")
+    public void testPrivateValueClassConstructor() throws Exception {
+        runTest("plugins/jvm-abi-gen/testData/compile/privateValueClassConstructor/");
+    }
+
     @TestMetadata("topLevel")
     public void testTopLevel() throws Exception {
         runTest("plugins/jvm-abi-gen/testData/compile/topLevel/");

plugins/jvm-abi-gen/test/org/jetbrains/kotlin/jvm/abi/LegacyCompileAgainstJvmAbiTestGenerated.java

@@ -115,6 +115,11 @@ public class LegacyCompileAgainstJvmAbiTestGenerated extends AbstractLegacyCompi
         runTest("plugins/jvm-abi-gen/testData/compile/privateOnlyConstructors/");
     }
 
+    @TestMetadata("privateValueClassConstructor")
+    public void testPrivateValueClassConstructor() throws Exception {
+        runTest("plugins/jvm-abi-gen/testData/compile/privateValueClassConstructor/");
+    }
+
     @TestMetadata("topLevel")
     public void testTopLevel() throws Exception {
         runTest("plugins/jvm-abi-gen/testData/compile/topLevel/");

plugins/jvm-abi-gen/testData/compile/privateValueClassConstructor/app/app.kt

@@ -0,0 +1,7 @@
+package app
+
+import lib.*
+
+fun runAppAndReturnOk(): String {
+    return A.a().b()
+}

plugins/jvm-abi-gen/testData/compile/privateValueClassConstructor/lib/lib.kt

@@ -0,0 +1,7 @@
+package lib
+
+@JvmInline
+value class A private constructor(val value: String) {
+    companion object { fun a() = A("OK") }
+    inline fun b() = value
+}