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 moving the trailing trivia of the variable declaration to the trailing trivia of 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

@@ -923,24 +923,34 @@ private class MacroApplication<Context: MacroExpansionContext>: SyntaxRewriter {
       return DeclSyntax(node)
     }
 
-    guard node.bindings.count == 1, let binding = node.bindings.first else {
+    guard node.bindings.count == 1 else {
       contextGenerator(Syntax(node)).addDiagnostics(
         from: MacroApplicationError.accessorMacroOnVariableWithMultipleBindings,
         node: node
       )
       return DeclSyntax(node)
     }
-
-    let expansion = expandAccessors(of: node, existingAccessors: binding.accessorBlock)
+    
+    let bindingKeyPath = \VariableDeclSyntax.bindings[node.bindings.startIndex]
+    let binding = node[keyPath: bindingKeyPath]
+    var expansion = expandAccessors(of: node, existingAccessors: binding.accessorBlock)
+    
     if expansion.accessors != binding.accessorBlock {
+      if binding.accessorBlock == nil {
+        // remove the trailing trivia of the variable declaration and move it
+        // to the trailing trivia of the left brace of the newly created accessor block
+        node[keyPath: bindingKeyPath].trailingTrivia = []
+        expansion.accessors?.leftBrace.trailingTrivia = binding.trailingTrivia
+      }
+
       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
+        node[keyPath: bindingKeyPath].accessorBlock = expansion.accessors?.with(\.leadingTrivia, [])
+        node[keyPath: bindingKeyPath].initializer = nil
       } else {
-        node.bindings[node.bindings.startIndex].accessorBlock = expansion.accessors
+        node[keyPath: bindingKeyPath].accessorBlock = expansion.accessors
       }
     }
 

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(
       """