[FIR] Report conflicts for data class generated members

^KT-59880

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

@@ -63,7 +63,7 @@ private fun FirBasedSymbol<*>.isCollectable(): Boolean {
     return when (this) {
         // - see tests with `fun () {}`.
         // you can't redeclare something that has no name.
-        is FirNamedFunctionSymbol -> source?.kind !is KtFakeSourceElementKind && name != SpecialNames.NO_NAME_PROVIDED
+        is FirNamedFunctionSymbol -> isCollectableAccordingToSource && name != SpecialNames.NO_NAME_PROVIDED
         is FirRegularClassSymbol -> name != SpecialNames.NO_NAME_PROVIDED
         // - see testEnumValuesValueOf.
         // it generates a static function that has
@@ -76,6 +76,9 @@ private fun FirBasedSymbol<*>.isCollectable(): Boolean {
     }
 }
 
+private val FirNamedFunctionSymbol.isCollectableAccordingToSource: Boolean
+    get() = source?.kind !is KtFakeSourceElementKind || source?.kind == KtFakeSourceElementKind.DataClassGeneratedMembers
+
 private val FirBasedSymbol<*>.resolvedStatus
     get() = when (this) {
         is FirCallableSymbol<*> -> resolvedStatus