Remove dead code flagged by Periphery

Prune unused symbols the scan flagged and enforce `periphery scan --strict` in CI.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: RISCfuture

.github/workflows/periphery.yml

@@ -15,4 +15,4 @@ jobs:
       - name: Install Periphery
         run: brew install peripheryapp/periphery/periphery
       - name: Run Periphery
-        run: periphery scan
+        run: periphery scan --strict

.periphery.yml

@@ -1 +1,5 @@
 retain_public: true
+retain_assign_only_properties: true
+external_test_case_classes:
+  - QuickSpec
+  - AsyncSpec

Sources/SwiftNASR/Downloaders/Downloader.swift

@@ -94,6 +94,7 @@ extension Downloader {
     }
   }
 
+  // periphery:ignore - default protocol implementation; always provided by conformers
   func load(withProgress progressHandler: @Sendable (Progress) -> Void = { _ in }) throws
     -> Distribution
   {

Sources/SwiftNASR/Models/Records/ARTCC.swift

@@ -98,11 +98,6 @@ public struct ARTCC: ParentRecord {
   /// Fields that per-field remarks can be associated with.
   public enum Field: String, RemarkField {
     case alternateName, stateCode, location
-
-    static let fieldOrder: [Self?] = [
-      nil, nil, nil, nil, .alternateName, nil, nil, .stateCode,
-      .stateCode, .location, .location, .location, .location, nil, nil
-    ]
   }
 
   // MARK: - Classes
@@ -144,15 +139,6 @@ public struct ARTCC: ParentRecord {
     /// Fields that per-field remarks can be associated with.
     public enum Field: String, RemarkField {
       case altitude, associatedAirportCode
-
-      static let fieldOrder: [Self?] = [
-        nil, nil, nil, nil, nil, .altitude, nil, nil,
-        .associatedAirportCode, .associatedAirportCode,
-        .associatedAirportCode, .associatedAirportCode,
-        .associatedAirportCode, .associatedAirportCode,
-        .associatedAirportCode, .associatedAirportCode,
-        .associatedAirportCode
-      ]
     }
 
     enum CodingKeys: String, CodingKey {

Sources/SwiftNASR/Models/Records/Airway.swift

@@ -26,8 +26,6 @@ public struct Airway: ParentRecord {
   /// General remarks about the entire airway.
   public internal(set) var remarks = [String]()
 
-  weak var data: NASRData?
-
   public var id: String { "\(designation)\(type.rawValue)" }
 
   // MARK: - Nested Types

Sources/SwiftNASR/NASRData.swift

@@ -112,14 +112,7 @@ public actor NASRData {
   }
 
   /// Airways loaded by SwiftNASR.
-  public var airways: [Airway]? {
-    didSet {
-      guard airways != nil else { return }
-      for airwayIndex in 0..<airways!.count {
-        airways![airwayIndex].data = self
-      }
-    }
-  }
+  public var airways: [Airway]?
 
   /// ILS facilities loaded by SwiftNASR.
   public var ILSFacilities: [ILS]? {
@@ -586,15 +579,6 @@ extension WeatherStation {
   }
 }
 
-extension Airway {
-
-  /// Resolves the ARTCC for a segment by its ID.
-  func resolveARTCC(_ artccID: String?) async -> ARTCC? {
-    guard let artccID else { return nil }
-    return await data?.ARTCCs?.first { $0.code == artccID }
-  }
-}
-
 extension ILS {
 
   /// The airport where this ILS is located.

Sources/SwiftNASR/Parsers/ByteParsing/ASCII.swift

@@ -1,6 +1,9 @@
+// periphery:ignore:all
 /// Named ASCII byte constants for use in byte-level parsing.
 ///
 /// Using named constants instead of inline literals improves readability and reduces errors.
+/// This is a deliberately complete reference table covering the printable ASCII range, so
+/// individual unused entries are retained for coherence.
 @usableFromInline
 enum ASCII {
   // Control characters

Sources/SwiftNASR/Parsers/ByteParsing/ByteTransformer.swift

@@ -17,11 +17,6 @@ struct ByteTransformer {
     self.fields = fields
   }
 
-  /// Parses a frequency from bytes to kHz.
-  static func parseFrequency(_ bytes: ByteSlice) -> UInt? {
-    bytes.parseFrequencyKHz()
-  }
-
   /// Parses a frequency string to kHz.
   static func parseFrequency(_ string: String) -> UInt? {
     Array(string.utf8)[...].parseFrequencyKHz()

Sources/SwiftNASR/Parsers/CSV/CSVTransformer.swift

@@ -68,51 +68,6 @@ struct TransformedRow {
 struct CSVTransformer {
   // MARK: - Type Properties
 
-  static var yearOnly: DateFormatter {
-    let df = DateFormatter()
-    df.dateFormat = "yyyy"
-    df.timeZone = zulu
-    return df
-  }
-  static var monthYear: DateFormatter {
-    let df = DateFormatter()
-    df.dateFormat = "MM/yyyy"
-    df.timeZone = zulu
-    return df
-  }
-  static var monthDayYear: DateFormatter {
-    let df = DateFormatter()
-    df.dateFormat = "MMddyyyy"
-    df.timeZone = zulu
-    return df
-  }
-  static var monthDayYearSlash: DateFormatter {
-    let df = DateFormatter()
-    df.dateFormat = "MM/dd/yyyy"
-    df.timeZone = zulu
-    return df
-  }
-  // CSV date formats (FAA CSV uses yyyy/MM/dd and yyyy/MM)
-  static var yearMonthDaySlash: DateFormatter {
-    let df = DateFormatter()
-    df.dateFormat = "yyyy/MM/dd"
-    df.timeZone = zulu
-    return df
-  }
-  static var yearMonthSlash: DateFormatter {
-    let df = DateFormatter()
-    df.dateFormat = "yyyy/MM"
-    df.timeZone = zulu
-    return df
-  }
-  static var dayMonthYear: DateFormatter {
-    let df = DateFormatter()
-    df.dateFormat = "dd MMM yyyy"
-    df.locale = Locale(identifier: "en_US_POSIX")
-    df.timeZone = zulu
-    return df
-  }
-
   private static let ddmmssParser = DDMMSSParser()
 
   // MARK: - Instance Properties

Sources/SwiftNASR/Parsers/FixedWidthParser/FixedWidthNoRecordIDParser.swift

@@ -16,6 +16,7 @@ extension FixedWidthNoRecordIDParser {
     try parseValues(slices)
   }
 
+  // periphery:ignore - abstract requirement; subclasses must provide an implementation
   @available(*, unavailable)
   func finish(data _: NASRData) {
     fatalError("must be implemented by subclasses")