Replace with calls with in-place mutation; clean up helpers.

Sources/SwiftFormat/Core/LegacyTriviaBehavior.swift

@@ -18,15 +18,14 @@ private final class LegacyTriviaBehaviorRewriter: SyntaxRewriter {
   override func visit(_ token: TokenSyntax) -> TokenSyntax {
     var token = token
     if let pendingLeadingTrivia = pendingLeadingTrivia {
-      token = token.with(\.leadingTrivia, pendingLeadingTrivia + token.leadingTrivia)
+      token.leadingTrivia = pendingLeadingTrivia + token.leadingTrivia
       self.pendingLeadingTrivia = nil
     }
     if token.nextToken(viewMode: .sourceAccurate) != nil,
       let firstIndexToMove = token.trailingTrivia.firstIndex(where: shouldTriviaPieceBeMoved)
     {
       pendingLeadingTrivia = Trivia(pieces: Array(token.trailingTrivia[firstIndexToMove...]))
-      token =
-        token.with(\.trailingTrivia, Trivia(pieces: Array(token.trailingTrivia[..<firstIndexToMove])))
+      token.trailingTrivia = Trivia(pieces: Array(token.trailingTrivia[..<firstIndexToMove]))
     }
     return token
   }

Sources/SwiftFormat/Core/ModifierListSyntax+Convenience.swift

@@ -13,15 +13,6 @@
 import SwiftSyntax
 
 extension DeclModifierListSyntax {
-
-  func has(modifier: String) -> Bool {
-    return contains { $0.name.text == modifier }
-  }
-
-  func has(modifier: TokenKind) -> Bool {
-    return contains { $0.name.tokenKind == modifier }
-  }
-
   /// Returns the declaration's access level modifier, if present.
   var accessLevelModifier: DeclModifierSyntax? {
     for modifier in self {
@@ -35,41 +26,33 @@ extension DeclModifierListSyntax {
     return nil
   }
 
-  /// Returns modifier list without the given modifier.
-  func remove(name: String) -> DeclModifierListSyntax {
-    return filter { $0.name.text != name }
+  /// Returns true if the modifier list contains any of the keywords in the given set.
+  func contains(anyOf keywords: Set<Keyword>) -> Bool {
+    return contains {
+      switch $0.name.tokenKind {
+      case .keyword(let keyword): return keywords.contains(keyword)
+      default: return false
+      }
+    }
   }
 
-  /// Returns a formatted declaration modifier token with the given name.
-  func createModifierToken(name: String) -> DeclModifierSyntax {
-    let id = TokenSyntax.identifier(name, trailingTrivia: .spaces(1))
-    let newModifier = DeclModifierSyntax(name: id, detail: nil)
-    return newModifier
+  /// Removes any of the modifiers in the given set from the modifier list, mutating it in-place.
+  mutating func remove(anyOf keywords: Set<Keyword>) {
+    self = filter {
+      switch $0.name.tokenKind {
+      case .keyword(let keyword): return !keywords.contains(keyword)
+      default: return true
+      }
+    }
   }
 
-  /// Inserts the given modifier into the list at a specific index.
-  ///
-  /// If the modifier is being inserted at the front of the list, the current front element's
-  /// leading trivia will be moved to the new element to preserve any leading comments and newlines.
-  mutating func triviaPreservingInsert(
-    _ modifier: DeclModifierSyntax, at index: SyntaxChildrenIndex
-  ) {
-    var modifier = modifier
-    modifier.trailingTrivia = [.spaces(1)]
-
-    guard index == self.startIndex else {
-      self.insert(modifier, at: index)
-      return
-    }
-    guard var firstMod = first, let firstTok = firstMod.firstToken(viewMode: .sourceAccurate) else {
-      self.insert(modifier, at: index)
-      return
+  /// Returns a copy of the modifier list with any of the modifiers in the given set removed.
+  func removing(anyOf keywords: Set<Keyword>) -> DeclModifierListSyntax {
+    return filter {
+      switch $0.name.tokenKind {
+      case .keyword(let keyword): return !keywords.contains(keyword)
+      default: return true
+      }
     }
-
-    modifier.leadingTrivia = firstTok.leadingTrivia
-    firstMod.leadingTrivia = []
-    firstMod.trailingTrivia = [.spaces(1)]
-    self[self.startIndex] = firstMod
-    self.insert(modifier, at: self.startIndex)
   }
 }