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 transfering line comments from the trailing trivia of the variable binding to the left brace of the accessor block
added tests on properties with trailing comments and with/without an accessor block

Author: AppAppWorks

Sources/SwiftSyntaxMacroExpansion/MacroSystem.swift

@@ -931,17 +931,39 @@ private class MacroApplication<Context: MacroExpansionContext>: SyntaxRewriter {
       return DeclSyntax(node)
     }
 
-    let expansion = expandAccessors(of: node, existingAccessors: binding.accessorBlock)
+    var expansion = expandAccessors(of: node, existingAccessors: binding.accessorBlock)
     if expansion.accessors != binding.accessorBlock {
+      var newBinding = binding
+      if binding.accessorBlock == nil, let accessors = expansion.accessors {
+        // transfer all line comments from the trailing trivia of the binding pattern
+        // to the trailing trivia of the left brace of the newly created accessor block
+        var truncatedPieces = [TriviaPiece]()
+        var leftBraceTriviaPieces = accessors.leftBrace.trailingTrivia.pieces
+
+        for piece in binding.trailingTrivia {
+          switch piece {
+          case .lineComment, .docLineComment:
+            leftBraceTriviaPieces.append(piece)
+          default:
+            truncatedPieces.append(piece)
+          }
+        }
+
+        newBinding.trailingTrivia = Trivia(pieces: truncatedPieces)
+        expansion.accessors = accessors.with(\.leftBrace.trailingTrivia, Trivia(pieces: leftBraceTriviaPieces))
+      }
+
       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
         // leading trivia on the accessor block so we don't double up.
-        node.bindings[node.bindings.startIndex].accessorBlock = expansion.accessors?.with(\.leadingTrivia, [])
-        node.bindings[node.bindings.startIndex].initializer = nil
+        newBinding.accessorBlock = expansion.accessors?.with(\.leadingTrivia, [])
+        newBinding.initializer = nil
       } else {
-        node.bindings[node.bindings.startIndex].accessorBlock = expansion.accessors
+        newBinding.accessorBlock = expansion.accessors
       }
+
+      node.bindings[node.bindings.startIndex] = newBinding
     }
 
     return DeclSyntax(node)

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 /*1*/ // hello
+      """,
+      expandedSource: """
+        var x: Int /*1*/  {// 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 /*h*/ { // hello
+        1
+      }
+      """,
+      expandedSource: """
+        var x: Int /*h*/ { // hello
+        get {
+            1
+        }
+          get {
+            return 1
+          }
+        }
+        """,
+      macros: ["constantOne": ConstantOneGetter.self],
+      indentationWidth: indentationWidth
+    )
+  }
+
   func testAccessorOnVariableDeclWithExistingGetter() {
     assertMacroExpansion(
       """