[FIR] Make FirTypeParameter.containingDeclarationSymbol not null

Also fix initializing this property in all places

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/FirTypeParameter.kt

@@ -29,7 +29,7 @@ abstract class FirTypeParameter : FirTypeParameterRef, FirDeclaration() {
     abstract override val attributes: FirDeclarationAttributes
     abstract val name: Name
     abstract override val symbol: FirTypeParameterSymbol
-    abstract val containingDeclarationSymbol: FirBasedSymbol<*>?
+    abstract val containingDeclarationSymbol: FirBasedSymbol<*>
     abstract val variance: Variance
     abstract val isReified: Boolean
     abstract val bounds: List<FirTypeRef>

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/builder/FirTypeParameterBuilder.kt

@@ -37,7 +37,7 @@ class FirTypeParameterBuilder : FirAnnotationContainerBuilder {
     var attributes: FirDeclarationAttributes = FirDeclarationAttributes()
     lateinit var name: Name
     lateinit var symbol: FirTypeParameterSymbol
-    var containingDeclarationSymbol: FirBasedSymbol<*>? = null
+    lateinit var containingDeclarationSymbol: FirBasedSymbol<*>
     lateinit var variance: Variance
     var isReified: Boolean by kotlin.properties.Delegates.notNull<Boolean>()
     val bounds: MutableList<FirTypeRef> = mutableListOf()

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/declarations/impl/FirTypeParameterImpl.kt

@@ -33,7 +33,7 @@ internal class FirTypeParameterImpl(
     override val attributes: FirDeclarationAttributes,
     override val name: Name,
     override val symbol: FirTypeParameterSymbol,
-    override val containingDeclarationSymbol: FirBasedSymbol<*>?,
+    override val containingDeclarationSymbol: FirBasedSymbol<*>,
     override val variance: Variance,
     override val isReified: Boolean,
     override val bounds: MutableList<FirTypeRef>,

compiler/fir/tree/src/org/jetbrains/kotlin/fir/symbols/impl/FirTypeParameterSymbol.kt

@@ -37,7 +37,7 @@ class FirTypeParameterSymbol : FirClassifierSymbol<FirTypeParameter>() {
     val isReified: Boolean
         get() = fir.isReified
 
-    val containingDeclarationSymbol: FirBasedSymbol<*>?
+    val containingDeclarationSymbol: FirBasedSymbol<*>
         get() = fir.containingDeclarationSymbol
 }
 

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/NodeConfigurator.kt

@@ -294,7 +294,7 @@ object NodeConfigurator : AbstractFieldConfigurator<FirTreeBuilder>(FirTreeBuild
         typeParameter.configure {
             +name
             +symbol("FirTypeParameterSymbol")
-            +field("containingDeclarationSymbol", firBasedSymbolType, "*", nullable = true).apply {
+            +field("containingDeclarationSymbol", firBasedSymbolType, "*").apply {
                 withBindThis = false
             }
             +field(varianceType)