FIR checker: simplify isExpect|isExternal checks

Those resolve information are different from modality/visibility, which
could have conflicting modifiers.

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

@@ -36,22 +36,18 @@ private inline fun isInsideSpecificClass(
 
 internal fun FirMemberDeclaration.isEffectivelyExpect(
     containingClass: FirRegularClass?,
-    modifierList: FirModifierList? = null,
     context: CheckerContext,
 ): Boolean {
-    val isExpect = this.isExpect || modifierList?.modifiers?.any { it.token == KtTokens.EXPECT_KEYWORD } == true
-    if (isExpect) return true
+    if (this.isExpect) return true
 
     return containingClass != null && isInsideExpectClass(containingClass, context)
 }
 
 internal fun FirMemberDeclaration.isEffectivelyExternal(
     containingClass: FirRegularClass?,
-    modifierList: FirModifierList? = null,
     context: CheckerContext,
 ): Boolean {
-    val isExternal = this.isExternal || modifierList?.modifiers?.any { it.token == KtTokens.EXTERNAL_KEYWORD } == true
-    if (isExternal) return true
+    if (this.isExternal) return true
 
     // NB: [MemberDescriptor.isEffectivelyExternal] checks property accessors for property and vice versa.
     // But, raw FIR creation already did such upward/downward propagation of modifiers.
@@ -63,11 +59,10 @@ internal fun FirMemberDeclaration.isEffectivelyExternal(
 internal fun checkExpectDeclarationVisibilityAndBody(
     declaration: FirMemberDeclaration,
     source: FirSourceElement,
-    modifierList: FirModifierList?,
     reporter: DiagnosticReporter,
     context: CheckerContext
 ) {
-    if (declaration.isExpect || modifierList?.modifiers?.any { it.token == KtTokens.EXPECT_KEYWORD } == true) {
+    if (declaration.isExpect) {
         if (Visibilities.isPrivate(declaration.visibility)) {
             reporter.reportOn(source, FirErrors.EXPECTED_PRIVATE_DECLARATION, context)
         }
@@ -116,7 +111,7 @@ private fun checkPropertyInitializer(
         }
     }
 
-    val isExpect = property.isEffectivelyExpect(containingClass, modifierList, context)
+    val isExpect = property.isEffectivelyExpect(containingClass, context)
 
     when {
         property.initializer != null -> {
@@ -150,7 +145,7 @@ private fun checkPropertyInitializer(
             }
         }
         else -> {
-            val isExternal = property.isEffectivelyExternal(containingClass, modifierList, context)
+            val isExternal = property.isEffectivelyExternal(containingClass, context)
             if (backingFieldRequired && !inInterface && !property.isLateInit && !isExpect && !isInitialized && !isExternal) {
                 property.source?.let {
                     if (property.receiverTypeRef != null && !property.hasAccessorImplementation) {

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

@@ -50,7 +50,6 @@ object FirMemberFunctionsChecker : FirRegularClassChecker() {
         }
         val isInsideExpectClass = isInsideExpectClass(containingDeclaration, context)
         val hasOpenModifier = modifierList?.modifiers?.any { it.token == KtTokens.OPEN_KEYWORD } == true
-        val isExternal = function.isExternal || modifierList?.modifiers?.any { it.token == KtTokens.EXTERNAL_KEYWORD } == true
         if (!function.hasBody) {
             if (containingDeclaration.isInterface) {
                 if (Visibilities.isPrivate(function.visibility)) {
@@ -59,11 +58,11 @@ object FirMemberFunctionsChecker : FirRegularClassChecker() {
                 if (!isInsideExpectClass && !hasAbstractModifier && hasOpenModifier) {
                     reporter.reportOn(source, FirErrors.REDUNDANT_OPEN_IN_INTERFACE, context)
                 }
-            } else if (!isInsideExpectClass && !hasAbstractModifier && !isExternal) {
+            } else if (!isInsideExpectClass && !hasAbstractModifier && !function.isExternal) {
                 reporter.reportOn(source, FirErrors.NON_ABSTRACT_FUNCTION_WITH_NO_BODY, function, context)
             }
         }
 
-        checkExpectDeclarationVisibilityAndBody(function, source, modifierList, reporter, context)
+        checkExpectDeclarationVisibilityAndBody(function, source, reporter, context)
     }
 }

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

@@ -149,7 +149,7 @@ object FirMemberPropertiesChecker : FirRegularClassChecker() {
         val modifierList = with(FirModifierList) { property.source.getModifierList() }
 
         checkProperty(containingDeclaration, property, modifierList, isInitialized, reporter, context)
-        checkExpectDeclarationVisibilityAndBody(property, source, modifierList, reporter, context)
+        checkExpectDeclarationVisibilityAndBody(property, source, reporter, context)
 
         val hasAbstractModifier = modifierList?.modifiers?.any { it.token == KtTokens.ABSTRACT_KEYWORD } == true
         val isAbstract = property.isAbstract || hasAbstractModifier

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

@@ -30,12 +30,11 @@ object FirTopLevelFunctionsChecker : FirFileChecker() {
         // So, our source of truth should be the full modifier list retrieved from the source.
         val modifierList = with(FirModifierList) { source.getModifierList() }
         if (modifierList?.modifiers?.any { it.token == KtTokens.ABSTRACT_KEYWORD } == true) return
-        if (function.isExternal || modifierList?.modifiers?.any { it.token == KtTokens.EXTERNAL_KEYWORD } == true) return
-        val isExpect = function.isExpect || modifierList?.modifiers?.any { it.token == KtTokens.EXPECT_KEYWORD } == true
-        if (!function.hasBody && !isExpect) {
+        if (function.isExternal) return
+        if (!function.hasBody && !function.isExpect) {
             reporter.reportOn(source, FirErrors.NON_MEMBER_FUNCTION_NO_BODY, function, context)
         }
 
-        checkExpectDeclarationVisibilityAndBody(function, source, modifierList, reporter, context)
+        checkExpectDeclarationVisibilityAndBody(function, source, reporter, context)
     }
 }

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

@@ -29,6 +29,6 @@ object FirTopLevelPropertiesChecker : FirFileChecker() {
         val modifierList = with(FirModifierList) { source.getModifierList() }
 
         checkProperty(null, property, modifierList, property.initializer != null, reporter, context)
-        checkExpectDeclarationVisibilityAndBody(property, source, modifierList, reporter, context)
+        checkExpectDeclarationVisibilityAndBody(property, source, reporter, context)
     }
 }