[FIR] KT-54507: Report redundant for abstract interfaces

^KT-54507 Fixed

Merge-request: KT-MR-8490
Merged-by: Nikolay Lunyak <Nikolay.Lunyak@jetbrains.com>

compiler/fir/analysis-tests/testData/resolve/extendedCheckers/RedundantModalityModifierChecker.fir.txt

@@ -83,6 +83,9 @@ FILE: RedundantModalityModifierChecker.kt
         public open override val gav: R|kotlin/Int| = Int(13)
             public get(): R|kotlin/Int|
 
+        private final fun fan(): R|kotlin/Unit| {
+        }
+
     }
     public final class Final : R|kotlin/Any| {
         public constructor(): R|Final| {
@@ -136,3 +139,15 @@ FILE: RedundantModalityModifierChecker.kt
     }
     public open interface OpenInterface : R|kotlin/Any| {
     }
+    public final class FinalDerived2 : R|Base| {
+        public constructor(gav: R|kotlin/Int|): R|FinalDerived2| {
+            super<R|Base|>()
+        }
+
+        public final override val gav: R|kotlin/Int| = R|<local>/gav|
+            public get(): R|kotlin/Int|
+
+        public open override fun bar(): R|kotlin/Unit| {
+        }
+
+    }

compiler/fir/analysis-tests/testData/resolve/extendedCheckers/RedundantModalityModifierChecker.kt

@@ -55,6 +55,8 @@ open class OpenDerived : Base() {
     override final fun bar() {}
     // Redundant open
     override <!REDUNDANT_MODALITY_MODIFIER!>open<!> val gav = 13
+
+    private <!REDUNDANT_MODALITY_MODIFIER!>final<!> fun fan() {}
 }
 // Redundant final
 <!REDUNDANT_MODALITY_MODIFIER!>final<!> class Final
@@ -78,8 +80,12 @@ abstract class AbstractDerived2 : Interface {
     override <!REDUNDANT_MODALITY_MODIFIER!>open<!> val gav = 13
 }
 // Redundant abstract interface
-abstract interface AbstractInterface
+<!REDUNDANT_MODALITY_MODIFIER!>abstract<!> interface AbstractInterface
 // Redundant final object
 <!REDUNDANT_MODALITY_MODIFIER!>final<!> object FinalObject
 // Open interface
 <!REDUNDANT_MODIFIER_FOR_TARGET!>open<!> interface OpenInterface
+
+class FinalDerived2(override <!REDUNDANT_MODALITY_MODIFIER!>final<!> val gav: Int) : Base() {
+    override fun bar() {}
+}

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirHelpers.kt

@@ -34,7 +34,6 @@ import org.jetbrains.kotlin.fir.symbols.FirBasedSymbol
 import org.jetbrains.kotlin.fir.symbols.SymbolInternals
 import org.jetbrains.kotlin.fir.symbols.impl.*
 import org.jetbrains.kotlin.fir.types.*
-import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.name.*
 import org.jetbrains.kotlin.psi.KtParameter
 import org.jetbrains.kotlin.psi.KtParameter.VAL_VAR_TOKEN_SET
@@ -225,32 +224,23 @@ fun FirClass.modality(): Modality? {
  * returns implicit modality by FirMemberDeclaration<*>
  */
 fun FirMemberDeclaration.implicitModality(context: CheckerContext): Modality {
-    if (this is FirRegularClass && (this.classKind == ClassKind.CLASS || this.classKind == ClassKind.OBJECT)) {
-        if (this.classKind == ClassKind.INTERFACE) return Modality.ABSTRACT
-        return Modality.FINAL
-    }
-
-    val klass = context.findClosestClassOrObject() ?: return Modality.FINAL
-    val source = source ?: return Modality.FINAL
-    val tree = source.treeStructure
-    if (tree.overrideModifier(source.lighterASTNode) != null) {
-        val klassModalityTokenType = klass.source?.let { tree.modalityModifier(it.lighterASTNode)?.tokenType }
-        if (klassModalityTokenType == KtTokens.ABSTRACT_KEYWORD ||
-            klassModalityTokenType == KtTokens.OPEN_KEYWORD ||
-            klassModalityTokenType == KtTokens.SEALED_KEYWORD
-        ) {
-            return Modality.OPEN
+    if (this is FirRegularClass) {
+        return when (classKind) {
+            ClassKind.INTERFACE -> Modality.ABSTRACT
+            else -> Modality.FINAL
         }
     }
 
-    if (klass is FirRegularClass
-        && klass.classKind == ClassKind.INTERFACE
-        && tree.visibilityModifier(source.lighterASTNode)?.tokenType != KtTokens.PRIVATE_KEYWORD
-    ) {
-        return if (this.hasBody()) Modality.OPEN else Modality.ABSTRACT
-    }
+    val containingClass = context.findClosestClassOrObject() ?: return Modality.FINAL
 
-    return Modality.FINAL
+    return when {
+        isOverride && !containingClass.isFinal -> Modality.OPEN
+        containingClass.isInterface -> when {
+            hasBody() -> Modality.OPEN
+            else -> Modality.ABSTRACT
+        }
+        else -> Modality.FINAL
+    }
 }
 
 private fun FirDeclaration.hasBody(): Boolean = when (this) {

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extended/RedundantModalityModifierSyntaxChecker.kt

@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.fir.analysis.checkers.extended
 
 import org.jetbrains.kotlin.KtFakeSourceElementKind
+import org.jetbrains.kotlin.KtRealSourceElementKind
 import org.jetbrains.kotlin.KtSourceElement
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.Modality
@@ -19,13 +20,17 @@ import org.jetbrains.kotlin.diagnostics.reportOn
 import org.jetbrains.kotlin.fir.declarations.FirClass
 import org.jetbrains.kotlin.fir.declarations.FirDeclaration
 import org.jetbrains.kotlin.fir.declarations.FirMemberDeclaration
+import org.jetbrains.kotlin.fir.declarations.FirValueParameter
 import org.jetbrains.kotlin.fir.declarations.utils.modality
 import org.jetbrains.kotlin.psi.KtDeclaration
 
 object RedundantModalityModifierSyntaxChecker : FirDeclarationSyntaxChecker<FirDeclaration, KtDeclaration>() {
 
     override fun isApplicable(element: FirDeclaration, source: KtSourceElement): Boolean =
-        source.kind !is KtFakeSourceElementKind && element is FirMemberDeclaration
+        element.isMemberWithRealSource && element !is FirValueParameter
+                || element.source?.kind == KtFakeSourceElementKind.PropertyFromParameter
+
+    private val FirDeclaration.isMemberWithRealSource get() = this is FirMemberDeclaration && source?.kind is KtRealSourceElementKind
 
     override fun checkPsiOrLightTree(
         element: FirDeclaration,