[FIR] Make FirFile.annotationsContainer nullable

Previously, when no file annotations were present, the FIR element
didn't have a source.
By making it nullable, it will only be created when appropriate and the
source will never be null.

#KT-55835

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

@@ -28,7 +28,7 @@ abstract class FirFile : FirDeclaration() {
     abstract override val moduleData: FirModuleData
     abstract override val origin: FirDeclarationOrigin
     abstract override val attributes: FirDeclarationAttributes
-    abstract val annotationsContainer: FirFileAnnotationsContainer
+    abstract val annotationsContainer: FirFileAnnotationsContainer?
     abstract val packageDirective: FirPackageDirective
     abstract val imports: List<FirImport>
     abstract val declarations: List<FirDeclaration>

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

@@ -43,7 +43,7 @@ class FirFileBuilder : FirAnnotationContainerBuilder {
     lateinit var moduleData: FirModuleData
     lateinit var origin: FirDeclarationOrigin
     var attributes: FirDeclarationAttributes = FirDeclarationAttributes()
-    lateinit var annotationsContainer: FirFileAnnotationsContainer
+    var annotationsContainer: FirFileAnnotationsContainer? = null
     lateinit var packageDirective: FirPackageDirective
     val imports: MutableList<FirImport> = mutableListOf()
     val declarations: MutableList<FirDeclaration> = mutableListOf()

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

@@ -39,7 +39,7 @@ internal class FirFileImpl(
     override val moduleData: FirModuleData,
     override val origin: FirDeclarationOrigin,
     override val attributes: FirDeclarationAttributes,
-    override var annotationsContainer: FirFileAnnotationsContainer,
+    override var annotationsContainer: FirFileAnnotationsContainer?,
     override var packageDirective: FirPackageDirective,
     override val imports: MutableList<FirImport>,
     override val declarations: MutableList<FirDeclaration>,
@@ -48,7 +48,7 @@ internal class FirFileImpl(
     override val sourceFileLinesMapping: KtSourceFileLinesMapping?,
     override val symbol: FirFileSymbol,
 ) : FirFile() {
-    override val annotations: List<FirAnnotation> get() = annotationsContainer.annotations
+    override val annotations: List<FirAnnotation> get() = annotationsContainer?.annotations ?: emptyList()
 
     init {
         symbol.bind(this)
@@ -57,7 +57,7 @@ internal class FirFileImpl(
     }
 
     override fun <R, D> acceptChildren(visitor: FirVisitor<R, D>, data: D) {
-        annotationsContainer.accept(visitor, data)
+        annotationsContainer?.accept(visitor, data)
         packageDirective.accept(visitor, data)
         imports.forEach { it.accept(visitor, data) }
         declarations.forEach { it.accept(visitor, data) }
@@ -76,7 +76,7 @@ internal class FirFileImpl(
     }
 
     override fun <D> transformAnnotationsContainer(transformer: FirTransformer<D>, data: D): FirFileImpl {
-        annotationsContainer = annotationsContainer.transform(transformer, data)
+        annotationsContainer = annotationsContainer?.transform(transformer, data)
         return this
     }
 

compiler/fir/tree/src/org/jetbrains/kotlin/fir/renderer/FirRenderer.kt

@@ -172,7 +172,7 @@ class FirRenderer(
             printer.println(file.name)
 
             printer.pushIndent()
-            visitFileAnnotationsContainer(file.annotationsContainer)
+            file.annotationsContainer?.let { visitFileAnnotationsContainer(it) }
             visitPackageDirective(file.packageDirective)
             file.imports.forEach { it.accept(this) }
             file.declarations.forEach { it.accept(this) }

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

@@ -41,6 +41,10 @@ object BuilderConfigurator : AbstractBuilderConfigurator<FirTreeBuilder>(FirTree
             fields from klass without listOf("symbol", "resolvePhase", "resolveState", "controlFlowGraphReference")
         }
 
+        builder(file) {
+            defaultNull("annotationsContainer")
+        }
+
         builder(regularClass) {
             parents += classBuilder
             parents += typeParameterRefsOwnerBuilder

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

@@ -609,7 +609,7 @@ object ImplementationConfigurator : AbstractFirTreeImplementationConfigurator()
 
         impl(file) {
             default("annotations") {
-                value = "annotationsContainer.annotations"
+                value = "annotationsContainer?.annotations ?: emptyList()"
                 withGetter = true
             }
         }

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

@@ -477,7 +477,7 @@ object NodeConfigurator : AbstractFieldConfigurator<FirTreeBuilder>(FirTreeBuild
         }
 
         file.configure {
-            +field("annotationsContainer", fileAnnotationsContainer).withTransform()
+            +field("annotationsContainer", fileAnnotationsContainer, nullable = true).withTransform()
             +field("packageDirective", packageDirective)
             +fieldList(import).withTransform()
             +declarations.withTransform()