FIR resolve: add nested companion scope #KT-24095 Fixed

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirTypeResolveTransformer.kt

@@ -70,6 +70,12 @@ open class FirTypeResolveTransformer : FirTransformer<Nothing?>() {
         resolveSuperTypesAndExpansions(klass)
 
         scope.scopes += FirNestedClassifierScope(classId, klass.session)
+        val companionObjects = klass.declarations.filterIsInstance<FirClass>().filter { it.isCompanion }
+        for (companionObject in companionObjects) {
+            val companionId = ClassId(packageFqName, classLikeName.child(companionObject.name), false)
+            scope.scopes += FirNestedClassifierScope(companionId, klass.session)
+        }
+
         val superTypeScopes = lookupSuperTypes(klass).map { FirNestedClassifierScope(it, klass.session) }
         scope.scopes.addAll(superTypeScopes)
         val result = super.transformClass(klass, data)

compiler/testData/fir/resolve/companion.kt

@@ -0,0 +1,17 @@
+package test
+
+abstract class Some {
+    companion object {
+        class InCompanion
+    }
+
+    abstract val x: InCompanion
+}
+
+abstract class Another {
+    companion object NamedCompanion {
+        class InCompanion
+    }
+
+    abstract val x: InCompanion
+}

compiler/testData/fir/resolve/companion.txt

@@ -0,0 +1,23 @@
+FILE: companion.kt
+    public? abstract class Some {
+        public? final companion object Companion {
+            public? final class InCompanion {
+            }
+
+        }
+
+        public? abstract property x(val): R|test/Some.Companion.InCompanion|
+            public? get(): R|test/Some.Companion.InCompanion|
+
+    }
+    public? abstract class Another {
+        public? final companion object NamedCompanion {
+            public? final class InCompanion {
+            }
+
+        }
+
+        public? abstract property x(val): R|test/Another.NamedCompanion.InCompanion|
+            public? get(): R|test/Another.NamedCompanion.InCompanion|
+
+    }

compiler/tests/org/jetbrains/kotlin/fir/FirResolveTestCaseGenerated.java

@@ -29,6 +29,12 @@ public class FirResolveTestCaseGenerated extends AbstractFirResolveTestCase {
         KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/fir/resolve"), Pattern.compile("^([^.]+)\\.kt$"), TargetBackend.ANY, true, "stdlib");
     }
 
+    @TestMetadata("companion.kt")
+    public void testCompanion() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/fir/resolve/companion.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("derivedClass.kt")
     public void testDerivedClass() throws Exception {
         runTest("compiler/testData/fir/resolve/derivedClass.kt");