[SwiftSyntaxCodeActions] Moved syntactic code actions into a new module

Sources/SwiftSyntaxCodeActions/ConvertCommentToDocComment.swift

@@ -0,0 +1,85 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2026 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
+//
+//===----------------------------------------------------------------------===//
+
+@_spi(SourceKitLSP) import LanguageServerProtocol
+internal import SourceKitLSP
+import SwiftRefactor
+import SwiftSyntax
+
+/// Syntactic code action provider to convert line comments and block comments
+/// preceding a declaration into doc comments.
+struct ConvertCommentToDocComment: SyntaxRefactoringProvider {
+  static func refactor(syntax: DeclSyntax, in context: Void) throws -> DeclSyntax {
+    let newTrivia = Trivia(
+      pieces: syntax.leadingTrivia.map { piece in
+        switch piece {
+        case let .lineComment(text):
+          return .docLineComment("/" + text)
+        case let .blockComment(text):
+          return .docBlockComment("/**" + text.dropFirst(2))
+        default:
+          return piece
+        }
+      }
+    )
+    return syntax.with(\.leadingTrivia, newTrivia)
+  }
+}
+
+extension ConvertCommentToDocComment: SyntaxRefactoringCodeActionProvider {
+  static let title = "Convert Comment to Doc Comment"
+
+  static func nodeToRefactor(in scope: SyntaxCodeActionScope) -> DeclSyntax? {
+    let cursorPosition = scope.snapshot.absolutePosition(of: scope.request.range.lowerBound)
+    guard let token = scope.file.token(at: cursorPosition) else {
+      return nil
+    }
+    guard cursorIsInsideConvertibleComment(token: token, cursorPosition: cursorPosition) else {
+      return nil
+    }
+    guard
+      let declaration = Syntax(token).findParentOfSelf(
+        ofType: DeclSyntax.self,
+        stoppingIf: { $0.kind == .codeBlockItem || $0.kind == .memberBlockItem }
+      )
+    else { return nil }
+
+    guard let firstToken = declaration.firstToken(viewMode: .sourceAccurate),
+      firstToken.id == token.id
+    else { return nil }
+
+    return declaration
+  }
+
+  private static func cursorIsInsideConvertibleComment(
+    token: TokenSyntax,
+    cursorPosition: AbsolutePosition
+  ) -> Bool {
+    var offset = token.position
+    for piece in token.leadingTrivia {
+      let pieceStart = offset
+      let pieceEnd = offset + piece.sourceLength
+      switch piece {
+      case .blockComment,
+        .lineComment:
+        if pieceStart <= cursorPosition && cursorPosition < pieceEnd {
+          return true
+        }
+
+      default:
+        break
+      }
+      offset = pieceEnd
+    }
+    return false
+  }
+}