Fix Accessor Macros Attached to Properties With Trailing Comments

fixed the bug that trailing comments of a property would stay in place after macro expansion, commenting out the left brace of the newly created accessor block
- the bug affected only properties without an accessor block while having trailing line comments
- fixed by converting line comments/doc line comments into block comments/doc block comments
- trailing comments of the initializer will be transferred to its preceding token
added tests on properties with trailing comments and with/without an accessor block

Author: AppAppWorks

Sources/SwiftSyntaxMacroExpansion/MacroSystem.swift

@@ -933,6 +933,39 @@ private class MacroApplication<Context: MacroExpansionContext>: SyntaxRewriter {
 
     let expansion = expandAccessors(of: node, existingAccessors: binding.accessorBlock)
     if expansion.accessors != binding.accessorBlock {
+      if binding.accessorBlock == nil {
+        // convert line comments in the trailing trivia of a property without
+        // an accessor block that would comment out the left brace in the newly
+        // created accessor block
+
+        func convertTrivia(_ trivia: Trivia) -> [TriviaPiece] {
+          trivia.map { piece in
+            switch piece {
+            case let .lineComment(lineComment):
+              .blockComment("/*\(lineComment.dropFirst(2))*/")
+            case let .docLineComment(docLineComment):
+              .docBlockComment("/**\(docLineComment.dropFirst(3))*/")
+            default:
+              piece
+            }
+          }
+        }
+
+        let convertedPieces =
+          if let trailingTrivia = binding.initializer?.trailingTrivia {
+            // compensate the leading space truncated from the accessor block below
+            convertTrivia(trailingTrivia) + [.spaces(1)]
+          } else {
+            convertTrivia(binding.trailingTrivia)
+          }
+
+        if binding.typeAnnotation == nil {
+          node.bindings[node.bindings.startIndex].pattern.trailingTrivia = Trivia(pieces: convertedPieces)
+        } else {
+          node.bindings[node.bindings.startIndex].typeAnnotation?.trailingTrivia = Trivia(pieces: convertedPieces)
+        }
+      }
+
       if binding.initializer != nil, expansion.expandsGetSet {
         // The accessor block will have a leading space, but there will already be a
         // space between the variable and the to-be-removed initializer. Remove the

Tests/SwiftSyntaxMacroExpansionTest/AccessorMacroTests.swift

@@ -44,6 +44,95 @@ fileprivate struct ConstantOneGetter: AccessorMacro {
 final class AccessorMacroTests: XCTestCase {
   private let indentationWidth: Trivia = .spaces(2)
 
+  func testAccessorOnVariableDeclWithTrailingLineCommentAndNoAccessorBlock() {
+    assertMacroExpansion(
+      """
+      @constantOne
+      var x: Int // hello
+      """,
+      expandedSource: """
+        var x: Int /* hello*/ {
+          get {
+            return 1
+          }
+        }
+        """,
+      macros: ["constantOne": ConstantOneGetter.self],
+      indentationWidth: indentationWidth
+    )
+
+    assertMacroExpansion(
+      """
+      @constantOne
+      var x: Int /// hello
+      """,
+      expandedSource: """
+        var x: Int /** hello*/ {
+          get {
+            return 1
+          }
+        }
+        """,
+      macros: ["constantOne": ConstantOneGetter.self],
+      indentationWidth: indentationWidth
+    )
+
+    assertMacroExpansion(
+      """
+      @constantOne
+      var x: Int = 1 /// hello
+      """,
+      expandedSource: """
+        var x: Int /** hello*/ {
+          get {
+            return 1
+          }
+        }
+        """,
+      macros: ["constantOne": ConstantOneGetter.self],
+      indentationWidth: indentationWidth
+    )
+
+    assertMacroExpansion(
+      """
+      @constantOne
+      var x /// hello
+      """,
+      expandedSource: """
+        var x /** hello*/ {
+          get {
+            return 1
+          }
+        }
+        """,
+      macros: ["constantOne": ConstantOneGetter.self],
+      indentationWidth: indentationWidth
+    )
+  }
+
+  func testAccessorOnVariableDeclWithTrailingLineCommentAndAccessorBlock() {
+    assertMacroExpansion(
+      """
+      @constantOne
+      var x: Int { // hello
+        1
+      }
+      """,
+      expandedSource: """
+        var x: Int { // hello
+        get {
+            1
+        }
+          get {
+            return 1
+          }
+        }
+        """,
+      macros: ["constantOne": ConstantOneGetter.self],
+      indentationWidth: indentationWidth
+    )
+  }
+
   func testAccessorOnVariableDeclWithExistingGetter() {
     assertMacroExpansion(
       """