Moved NodeInitRule into a separate file

Author: natikgadzhi

CodeGeneration/Sources/SyntaxSupport/Node.swift

@@ -63,7 +63,8 @@ public class Node {
     return kind.varOrCaseName
   }
 
-  /// List of convenience initializer rules for this node.
+  /// List of convenience initializer rules for this node. CodeGeneration will
+  /// generate a convenience initializer for each rule.
   public let rules: [NodeInitRule]
 
   /// If this is a layout node, return a view of the node that provides access
@@ -127,10 +128,6 @@ public class Node {
     self.nameForDiagnostics = nameForDiagnostics
     self.documentation = docCommentTrivia(from: documentation)
     self.parserFunction = parserFunction
-
-
-    // FIXME: We should validate rules and check that all referenced children
-    // elements in fact exist on that node.
     self.rules = rules
 
     let childrenWithUnexpected: [Child]
@@ -391,8 +388,3 @@ fileprivate extension Child {
 fileprivate extension Node {
 
 }
-
-public struct NodeInitRule {
-  public let nonOptionalChildName: String
-  public let childDefaultValues: [String: Token]
-}

CodeGeneration/Sources/SyntaxSupport/NodeInitRule.swift

@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import Foundation
+import SwiftSyntax
+
+/// A rule that describes convenienve initialization rules for a ``Node``.
+///
+/// When generating syntax nodes, SwiftSyntax will make additional
+/// convenience initializer for each rule that a Node has.
+///
+/// The convenience initializer will take a non-optional parameter
+/// `nonOptionalChildName`, and when a non-optional value is passed, it'll call
+/// the full memberwise initializer with the provided `childDefaultValues`.
+///
+/// For example, when initializing an `EnumCaseParameterSyntax`, the convenience
+/// initializer will take a non-optional `firstName` parameter, and when it's
+/// passed, it'll call the full memberwise initializer with
+/// `colon = .colonToken()`.
+public struct NodeInitRule {
+  /// The name of the parameter that is required to be present for
+  /// this conveniece initializer rule to apply.
+  public let nonOptionalChildName: String
+
+  /// A dicrionary of parameter names to their respective default values
+  /// to apply when the `nonOptionalChildName` is passed as concrete value.
+  public let childDefaultValues: [String: Token]
+}