[FIR] Make reporting of local class diagnostics more consistent with K1

It would be nice to report more appropriate diagnostics at the
corresponding places, but right now it's more important to
fix greenness-redness problems. Plus, this is already how K1 works.

^KT-59900 Fixed

compiler/fir/analysis-tests/testData/resolve/cfg/innerClassInAnonymousObject.kt

@@ -1,7 +1,7 @@
 // !DUMP_CFG
 
 val x = object {
-    class Nested {
+    <!NESTED_CLASS_NOT_ALLOWED!>class Nested<!> {
         fun foo() {}
     }
 }

compiler/fir/analysis-tests/testData/resolve/diagnostics/localEntitytNotAllowed.kt

@@ -8,16 +8,16 @@ object A {
     val a = object : Any() {
         <!LOCAL_OBJECT_NOT_ALLOWED!>object D<!> {
             <!LOCAL_OBJECT_NOT_ALLOWED!>object G<!>
-            <!LOCAL_INTERFACE_NOT_ALLOWED, NESTED_CLASS_NOT_ALLOWED!>interface Z<!>
+            <!NESTED_CLASS_NOT_ALLOWED!>interface Z<!>
         }
 
-        <!LOCAL_INTERFACE_NOT_ALLOWED!>interface Y<!>
+        <!NESTED_CLASS_NOT_ALLOWED!>interface Y<!>
     }
 
     fun b() {
         <!LOCAL_OBJECT_NOT_ALLOWED!>object E<!> {
             <!LOCAL_OBJECT_NOT_ALLOWED!>object F<!>
-            <!LOCAL_INTERFACE_NOT_ALLOWED, NESTED_CLASS_NOT_ALLOWED!>interface M<!>
+            <!NESTED_CLASS_NOT_ALLOWED!>interface M<!>
         }
 
         <!LOCAL_INTERFACE_NOT_ALLOWED!>interface N<!>
@@ -25,7 +25,7 @@ object A {
         val c = object : Any() {
             val t = "test"
 
-            <!LOCAL_INTERFACE_NOT_ALLOWED!>interface U<!>
+            <!NESTED_CLASS_NOT_ALLOWED!>interface U<!>
         }
     }
 }

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirLocalEntityNotAllowedChecker.kt

@@ -11,6 +11,7 @@ import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
 import org.jetbrains.kotlin.diagnostics.DiagnosticReporter
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
 import org.jetbrains.kotlin.diagnostics.reportOn
+import org.jetbrains.kotlin.fir.declarations.FirClass
 import org.jetbrains.kotlin.fir.declarations.FirRegularClass
 import org.jetbrains.kotlin.fir.declarations.utils.isCompanion
 import org.jetbrains.kotlin.fir.declarations.utils.visibility
@@ -21,10 +22,12 @@ object FirLocalEntityNotAllowedChecker : FirRegularClassChecker() {
             return
         }
 
+        val container = context.containingDeclarations.lastOrNull()
+
         when {
             declaration.classKind == ClassKind.OBJECT && !declaration.isCompanion ->
                 reporter.reportOn(declaration.source, FirErrors.LOCAL_OBJECT_NOT_ALLOWED, declaration.name, context)
-            declaration.classKind == ClassKind.INTERFACE ->
+            declaration.classKind == ClassKind.INTERFACE && container !is FirClass ->
                 reporter.reportOn(declaration.source, FirErrors.LOCAL_INTERFACE_NOT_ALLOWED, declaration.name, context)
             else -> {
             }

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirNestedClassChecker.kt

@@ -6,12 +6,13 @@
 package org.jetbrains.kotlin.fir.analysis.checkers.declaration
 
 import org.jetbrains.kotlin.descriptors.ClassKind
+import org.jetbrains.kotlin.descriptors.EffectiveVisibility
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
 import org.jetbrains.kotlin.diagnostics.DiagnosticReporter
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.NESTED_CLASS_NOT_ALLOWED
 import org.jetbrains.kotlin.diagnostics.reportOn
-import org.jetbrains.kotlin.fir.declarations.FirClass
+import org.jetbrains.kotlin.fir.declarations.*
-import org.jetbrains.kotlin.fir.declarations.FirRegularClass
+import org.jetbrains.kotlin.fir.declarations.utils.effectiveVisibility
 import org.jetbrains.kotlin.fir.declarations.utils.isCompanion
 import org.jetbrains.kotlin.fir.declarations.utils.isInner
 import org.jetbrains.kotlin.fir.declarations.utils.isLocal
@@ -22,25 +23,24 @@ object FirNestedClassChecker : FirRegularClassChecker() {
     override fun check(declaration: FirRegularClass, context: CheckerContext, reporter: DiagnosticReporter) {
         // Local enums / objects / companion objects are handled with different diagnostic codes.
         if ((declaration.classKind.isSingleton || declaration.classKind == ClassKind.ENUM_CLASS) && declaration.isLocal) return
-        val containingDeclaration = context.containingDeclarations.lastOrNull() ?: return
+        val containingDeclaration = context.containingDeclarations.lastOrNull() as? FirClass ?: return
 
-        when (containingDeclaration) {
+        // Since 1.3, enum entries can contain inner classes only.
-            is FirRegularClass -> {
+        // Companion objects are reported with code WRONG_MODIFIER_CONTAINING_DECLARATION instead
-                if (!declaration.isInner && (containingDeclaration.isInner || containingDeclaration.isLocal)) {
+        if (containingDeclaration.classKind == ClassKind.ENUM_ENTRY && !declaration.isInner && !declaration.isCompanion) {
-                    reporter.reportOn(declaration.source, NESTED_CLASS_NOT_ALLOWED, declaration.description, context)
+            reporter.reportOn(declaration.source, NESTED_CLASS_NOT_ALLOWED, declaration.description, context)
-                }
+            return
-            }
+        }
-            is FirClass -> {
+
-                // Since 1.3, enum entries can contain inner classes only.
+        val containerIsLocal = containingDeclaration.effectiveVisibility == EffectiveVisibility.Local
-                // Companion objects are reported with code WRONG_MODIFIER_CONTAINING_DECLARATION instead
+
-                if (containingDeclaration.classKind == ClassKind.ENUM_ENTRY && !declaration.isInner && !declaration.isCompanion) {
+        if (!declaration.isInner && (containingDeclaration.isInner || containerIsLocal || context.isInsideAnonymousObject)) {
-                    reporter.reportOn(declaration.source, NESTED_CLASS_NOT_ALLOWED, declaration.description, context)
+            reporter.reportOn(declaration.source, NESTED_CLASS_NOT_ALLOWED, declaration.description, context)
-                }
-            }
-            else -> {}
         }
     }
 
+    private val CheckerContext.isInsideAnonymousObject get() = containingDeclarations.any { it is FirAnonymousObject }
+
     // Note: here we don't differentiate anonymous object like in FE1.0
     // (org.jetbrains.kotlin.resolve.ModifiersChecker.DetailedClassKind) because this case has been ruled out in the first place.
     private val FirRegularClass.description: String

compiler/testData/diagnostics/tests/inner/innerClassInEnumEntryClass_lv12.fir.kt

@@ -6,7 +6,7 @@ enum class Enum {
 
         <!NESTED_CLASS_NOT_ALLOWED!>class TestNested<!>
 
-        <!LOCAL_INTERFACE_NOT_ALLOWED, NESTED_CLASS_NOT_ALLOWED!>interface TestInterface<!>
+        <!NESTED_CLASS_NOT_ALLOWED!>interface TestInterface<!>
 
         <!LOCAL_OBJECT_NOT_ALLOWED!>object TestObject<!>
 

compiler/testData/diagnostics/tests/inner/innerClassInEnumEntryClass_lv13.fir.kt

@@ -6,7 +6,7 @@ enum class Enum {
 
         <!NESTED_CLASS_NOT_ALLOWED!>class TestNested<!>
 
-        <!LOCAL_INTERFACE_NOT_ALLOWED, NESTED_CLASS_NOT_ALLOWED!>interface TestInterface<!>
+        <!NESTED_CLASS_NOT_ALLOWED!>interface TestInterface<!>
 
         <!LOCAL_OBJECT_NOT_ALLOWED!>object TestObject<!>
 

compiler/testData/diagnostics/tests/inner/kt6026.fir.kt

@@ -1,8 +0,0 @@
-// KT-6026 Exception on instantiating a nested class in an anonymous object
-
-val oo = object {
-    // Forbidden in KT-13510
-    class Nested
-
-    fun f1() = Nested(<!TOO_MANY_ARGUMENTS!>11<!>)
-}

compiler/testData/diagnostics/tests/inner/kt6026.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // KT-6026 Exception on instantiating a nested class in an anonymous object
 
 val oo = object {

compiler/testData/diagnostics/tests/localInterfaces.fir.kt

@@ -1,14 +0,0 @@
-// !DIAGNOSTICS: -UNUSED_VARIABLE
-
-fun foo() {
-    <!LOCAL_INTERFACE_NOT_ALLOWED!>interface a<!> {}
-    val b = object {
-        <!LOCAL_INTERFACE_NOT_ALLOWED!>interface c<!> {}
-    }
-    class A {
-        <!LOCAL_INTERFACE_NOT_ALLOWED, NESTED_CLASS_NOT_ALLOWED!>interface d<!> {}
-    }
-    val f = {
-        <!LOCAL_INTERFACE_NOT_ALLOWED!>interface e<!> {}
-    }
-}

compiler/testData/diagnostics/tests/localInterfaces.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_VARIABLE
 
 fun foo() {

compiler/testData/diagnostics/tests/objects/nestedClassInAnonymousObject.fir.kt

@@ -1,11 +0,0 @@
-class X {
-    val foo = object {
-        class Foo
-    }
-
-    fun test() {
-        object {
-            class Foo
-        }
-    }
-}

compiler/testData/diagnostics/tests/objects/nestedClassInAnonymousObject.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 class X {
     val foo = object {
         <!NESTED_CLASS_NOT_ALLOWED!>class Foo<!>