[cfe] Cleanup declaration and encoding for SourceFactoryBuilder

Change-Id: I3af44198c4e61da39d08e3954b61b7fb3ad9c135
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/416962
Reviewed-by: Jens Johansen <[email protected]>
Commit-Queue: Johnni Winther <[email protected]>

Author: johnniwinther

pkg/front_end/lib/src/fragment/factory/body_builder_context.dart

@@ -0,0 +1,113 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:kernel/ast.dart';
+import 'package:kernel/transformations/flags.dart';
+
+import '../../base/identifiers.dart';
+import '../../base/local_scope.dart';
+import '../../builder/formal_parameter_builder.dart';
+import '../../builder/type_builder.dart';
+import '../../kernel/body_builder_context.dart';
+import '../../source/source_factory_builder.dart';
+import 'declaration.dart';
+
+class FactoryBodyBuilderContext extends BodyBuilderContext {
+  final SourceFactoryBuilder _builder;
+
+  final FactoryDeclaration _declaration;
+
+  final Member _member;
+
+  FactoryBodyBuilderContext(this._builder, this._declaration, this._member)
+      : super(_builder.libraryBuilder, _builder.declarationBuilder,
+            isDeclarationInstanceMember: _builder.isDeclarationInstanceMember);
+
+  @override
+  VariableDeclaration getFormalParameter(int index) {
+    return _declaration.getFormalParameter(index);
+  }
+
+  @override
+  VariableDeclaration? getTearOffParameter(int index) {
+    return _declaration.getTearOffParameter(index);
+  }
+
+  @override
+  TypeBuilder get returnType => _declaration.returnType;
+
+  @override
+  // Coverage-ignore(suite): Not run.
+  List<FormalParameterBuilder>? get formals => _declaration.formals;
+
+  @override
+  LocalScope computeFormalParameterInitializerScope(LocalScope parent) {
+    /// Initializer formals or super parameters cannot occur in getters so
+    /// we don't need to create a new scope.
+    return parent;
+  }
+
+  @override
+  FormalParameterBuilder? getFormalParameterByName(Identifier name) {
+    return _declaration.getFormal(name);
+  }
+
+  @override
+  int get memberNameLength => _builder.name.length;
+
+  @override
+  FunctionNode get function {
+    return _declaration.function;
+  }
+
+  @override
+  // Coverage-ignore(suite): Not run.
+  bool get isFactory => true;
+
+  @override
+  // Coverage-ignore(suite): Not run.
+  bool get isNativeMethod {
+    return _declaration.isNative;
+  }
+
+  @override
+  bool get isExternalFunction {
+    return _declaration.isExternal;
+  }
+
+  @override
+  bool get isSetter => false;
+
+  @override
+  int get memberNameOffset => _declaration.fileOffset;
+
+  @override
+  // Coverage-ignore(suite): Not run.
+  void registerSuperCall() {
+    _member.transformerFlags |= TransformerFlag.superCalls;
+  }
+
+  @override
+  void registerFunctionBody(Statement body) {
+    _declaration.setBody(body);
+  }
+
+  @override
+  void setAsyncModifier(AsyncMarker asyncModifier) {
+    _declaration.setAsyncModifier(asyncModifier);
+  }
+
+  @override
+  bool get isRedirectingFactory => _declaration.redirectionTarget != null;
+
+  @override
+  DartType get returnTypeContext {
+    return _declaration.function.returnType;
+  }
+
+  @override
+  String get redirectingFactoryTargetName {
+    return _declaration.redirectionTarget!.fullNameForErrors;
+  }
+}