[FIR] Introduce memberDeclarationNameOrNull

compiler/fir/checkers/checkers.js/src/org/jetbrains/kotlin/fir/analysis/js/checkers/FirJsStableName.kt

@@ -8,10 +8,8 @@ package org.jetbrains.kotlin.fir.analysis.js.checkers
 import org.jetbrains.kotlin.descriptors.Visibilities
 import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.analysis.checkers.getContainingClassSymbol
-import org.jetbrains.kotlin.fir.declarations.FirMemberDeclaration
 import org.jetbrains.kotlin.fir.declarations.utils.*
 import org.jetbrains.kotlin.fir.symbols.FirBasedSymbol
-import org.jetbrains.kotlin.fir.symbols.SymbolInternals
 import org.jetbrains.kotlin.fir.symbols.impl.*
 
 internal data class FirJsStableName(
@@ -40,7 +38,6 @@ internal data class FirJsStableName(
             }
         }
 
-        @OptIn(SymbolInternals::class)
         fun createStableNameOrNull(symbol: FirBasedSymbol<*>, session: FirSession): FirJsStableName? {
             val jsName = symbol.getJsName(session)
             if (jsName != null) {
@@ -70,7 +67,7 @@ internal data class FirJsStableName(
                 //  - FirJsStableName.shouldClashBeCaughtByCommonFrontendCheck().
                 hasPublicName(symbol, session)
             ) {
-                val name = (symbol.fir as? FirMemberDeclaration)?.nameOrSpecialName?.identifierOrNullIfSpecial
+                val name = symbol.memberDeclarationNameOrNull?.identifierOrNullIfSpecial
                 if (name != null) {
                     return FirJsStableName(name, symbol, !hasStableNameInJavaScript, symbol.isPresentInGeneratedCode(session))
                 }

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/coneDiagnosticToFirDiagnostic.kt

@@ -31,7 +31,6 @@ import org.jetbrains.kotlin.fir.resolve.inference.model.ConeExpectedTypeConstrai
 import org.jetbrains.kotlin.fir.resolve.inference.model.ConeLambdaArgumentConstraintPosition
 import org.jetbrains.kotlin.fir.symbols.ConeTypeParameterLookupTag
 import org.jetbrains.kotlin.fir.symbols.FirBasedSymbol
-import org.jetbrains.kotlin.fir.symbols.SymbolInternals
 import org.jetbrains.kotlin.fir.symbols.impl.FirCallableSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirClassLikeSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirNamedFunctionSymbol
@@ -318,11 +317,11 @@ private fun mapInapplicableCandidateError(
 
             is TypeVariableAsExplicitReceiver -> {
                 val typeParameter = rootCause.typeParameter
-                @OptIn(SymbolInternals::class)
                 FirErrors.BUILDER_INFERENCE_STUB_RECEIVER.createOn(
                     rootCause.explicitReceiver.source,
                     typeParameter.symbol.name,
-                    (typeParameter.symbol.containingDeclarationSymbol.fir as FirMemberDeclaration).nameOrSpecialName
+                    typeParameter.symbol.containingDeclarationSymbol.memberDeclarationNameOrNull
+                        ?: error("containingDeclarationSymbol must have been a member declaration")
                 )
             }
 
@@ -541,8 +540,8 @@ private fun ConstraintSystemError.toDiagnostic(
             FirErrors.BUILDER_INFERENCE_MULTI_LAMBDA_RESTRICTION.createOn(
                 anonymous.source ?: source,
                 typeParameterSymbol.name,
-                @OptIn(SymbolInternals::class)
-                (typeParameterSymbol.containingDeclarationSymbol.fir as FirMemberDeclaration).nameOrSpecialName
+                typeParameterSymbol.containingDeclarationSymbol.memberDeclarationNameOrNull
+                    ?: error("containingDeclarationSymbol must have been a member declaration")
             )
         }
 

compiler/fir/tree/src/org/jetbrains/kotlin/fir/declarations/utils/FirDeclarationUtil.kt

@@ -6,8 +6,8 @@
 package org.jetbrains.kotlin.fir.declarations.utils
 
 import org.jetbrains.kotlin.fir.declarations.*
-import org.jetbrains.kotlin.fir.symbols.impl.FirConstructorSymbol
-import org.jetbrains.kotlin.fir.symbols.impl.FirNamedFunctionSymbol
+import org.jetbrains.kotlin.fir.symbols.FirBasedSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.*
 import org.jetbrains.kotlin.fir.types.ConeClassLikeType
 import org.jetbrains.kotlin.fir.types.coneTypeSafe
 import org.jetbrains.kotlin.fir.types.isNullableAny
@@ -49,14 +49,14 @@ val FirDeclaration.isNonLocal
 
 val FirCallableDeclaration.isExtension get() = receiverParameter != null
 
+val FirBasedSymbol<*>.memberDeclarationNameOrNull: Name?
+    // Accessing `fir` is ok, because `nameOrSpecialName` only accesses names
+    get() = (fir as? FirMemberDeclaration)?.nameOrSpecialName
+
 val FirMemberDeclaration.nameOrSpecialName: Name
     get() = when (this) {
-        is FirCallableDeclaration ->
-            this.symbol.callableId.callableName
-        is FirClass ->
-            this.classId.shortClassName
-        is FirTypeAlias ->
-            this.name
+        is FirCallableDeclaration -> symbol.callableId.callableName
+        is FirClassLikeDeclaration -> classId.shortClassName
     }
 
 val FirNamedFunctionSymbol.isMethodOfAny: Boolean