[swiftSyntax] Make SourceLength a struct

Author: ahoppen

tools/SwiftSyntax/RawSyntax.swift

@@ -36,6 +36,15 @@ extension ByteTreeUserInfoKey {
     ByteTreeUserInfoKey(rawValue: "SwiftSyntax.RawSyntax.OmittedNodeLookup")
 }
 
+/// Box a value type into a reference type
+class Box<T> {
+  let value: T
+
+  init(_ value: T) {
+    self.value = value
+  }
+}
+
 /// A ID that uniquely identifies a syntax node and stays stable across multiple
 /// incremental parses
 public struct SyntaxNodeId: Hashable, Codable {
@@ -84,11 +93,11 @@ struct RawSyntax: Codable {
   /// incremental parses
   let id: SyntaxNodeId
 
-  var _contentLength = AtomicCache<SourceLength>()
+  var _contentLength = AtomicCache<Box<SourceLength>>()
 
   /// The length of this node excluding its leading and trailing trivia
   var contentLength: SourceLength {
-    return _contentLength.value() {
+    return _contentLength.value({
       switch data {
       case .node(kind: _, layout: let layout):
         let firstElementIndex = layout.firstIndex(where: { $0 != nil })
@@ -109,11 +118,11 @@ struct RawSyntax: Codable {
             contentLength += element.trailingTriviaLength
           }
         }
-        return contentLength
+        return Box(contentLength)
       case .token(kind: let kind, leadingTrivia: _, trailingTrivia: _):
-        return SourceLength(of: kind.text)
+        return Box(SourceLength(of: kind.text))
       }
-    }
+    }).value
   }
 
   init(kind: SyntaxKind, layout: [RawSyntax?], presence: SourcePresence,

tools/SwiftSyntax/SourceLength.swift

@@ -13,7 +13,7 @@
 /// The length a syntax node spans in the source code. From any AbsolutePosition
 /// you reach a node's end location by either adding its UTF-8 length or by
 /// inserting `lines` newlines and then moving `columns` columns to the right.
-public final class SourceLength {
+public struct SourceLength {
   public let newlines: Int
   public let columnsAtLastLine: Int
   public let utf8Length: Int
@@ -90,4 +90,4 @@ extension AbsolutePosition {
   public static func +=(lhs: inout AbsolutePosition, rhs: SourceLength) {
     lhs = lhs + rhs
   }
-}
+}

tools/SwiftSyntax/SyntaxData.swift

@@ -18,14 +18,6 @@ import Foundation
 /// exposed to clients.
 typealias NodeIdentifier = [Int]
 
-/// Box a value type into a reference type
-fileprivate class Box<T> {
-  let value: T
-
-  init(_ value: T) {
-    self.value = value
-  }
-}
 
 /// SyntaxData is the underlying storage for each Syntax node.
 /// It's modelled as an array that stores and caches a SyntaxData for each raw