[FIR] Fix handling of type parameters in FIR mangling

#KT-57429 Fixed

compiler/fir/fir2ir/jvm-backend/src/org/jetbrains/kotlin/fir/backend/jvm/FirJvmMangleComputer.kt

@@ -33,28 +33,6 @@ class FirJvmMangleComputer(
     override fun copy(newMode: MangleMode): FirJvmMangleComputer =
         FirJvmMangleComputer(builder, newMode)
 
-    // FIXME this implementation causes the mangler to deliver different result than IR mangler. Consider using base method instead
-    override fun getEffectiveParent(typeParameter: ConeTypeParameterLookupTag): FirMemberDeclaration = typeParameter.symbol.fir.run {
-
-        fun FirTypeParameter.sameAs(other: FirTypeParameter) =
-            this === other ||
-                    (name == other.name && bounds.size == other.bounds.size &&
-                            bounds.zip(other.bounds).all { it.first.coneType == it.second.coneType })
-
-        for (parent in typeParameterContainers) {
-            if (parent.typeParameters.any { this.sameAs(it.symbol.fir) }) {
-                return parent
-            }
-            if (parent is FirCallableDeclaration) {
-                val overriddenFir = parent.originalForSubstitutionOverride
-                if (overriddenFir is FirTypeParametersOwner && overriddenFir.typeParameters.any { this.sameAs(it) }) {
-                    return parent
-                }
-            }
-        }
-        throw IllegalStateException("Should not be here!")
-    }
-
     private inner class JvmVisitor : Visitor() {
         override fun visitField(field: FirField) {
             if (field is FirJavaField) {

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/FirMangleComputer.kt

@@ -12,7 +12,6 @@ import org.jetbrains.kotlin.backend.common.serialization.mangle.collectForMangle
 import org.jetbrains.kotlin.fir.*
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.declarations.synthetic.FirSyntheticPropertyAccessor
-import org.jetbrains.kotlin.fir.declarations.utils.isExpect
 import org.jetbrains.kotlin.fir.declarations.utils.isStatic
 import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
 import org.jetbrains.kotlin.fir.resolve.providers.symbolProvider
@@ -108,8 +107,17 @@ open class FirMangleComputer(
     override fun isUnit(type: ConeKotlinType) = type.isUnit
 
     @OptIn(SymbolInternals::class)
-    override fun getEffectiveParent(typeParameter: ConeTypeParameterLookupTag): FirMemberDeclaration = typeParameter.symbol.fir.run {
-        this.containingDeclarationSymbol.fir as FirMemberDeclaration
+    override fun getEffectiveParent(typeParameter: ConeTypeParameterLookupTag): FirMemberDeclaration =
+        typeParameter.symbol.containingDeclarationSymbol.fir as FirMemberDeclaration
+
+    override fun getContainerIndex(parent: FirMemberDeclaration): Int {
+        // If a type parameter is declared in a java method, typeParameterContainers will contain the enhanced declaration,
+        // but parent will be the non-enhanced version.
+        // To work around this, we additionally compare declarations using their callable IDs.
+        val callableId = (parent as? FirCallableDeclaration)?.symbol?.callableId
+        return typeParameterContainers.indexOfFirst {
+            it == parent || it is FirCallableDeclaration && it.symbol.callableId == callableId
+        }
     }
 
     override fun renderDeclaration(declaration: FirDeclaration) = declaration.render()
@@ -279,4 +287,4 @@ open class FirMangleComputer(
             }
         }
     }
-}
+}