Handle macro expansion args in placeholder expansion

Update `ExpandEditorPlaceholdersToLiteralClosures` and
`CallToTrailingClosures` such that they can handle macro expansion
exprs and decls. This unfortunately requires changing them such that
they take a `Syntax` input and output to satisfy the conformance to
`SyntaxRefactoringProvider`, but that seems preferable to making the
refactoring types themselves generic.

If in the future we decide to expose `CallLikeSyntax` as a public
protocol, we could decide to expose additional generic `refactor`
overloads here. However it's not clear there's enough clients of
these APIs to motivate doing that in this PR.

Author: hamishknight

Release Notes/602.md

@@ -54,7 +54,13 @@
   - Pull Request: https://github.com/swiftlang/swift-syntax/pull/3028
   - Migration steps: Use `AttributeSyntax.Arguments.argumentList(LabeledExprListSyntax)` instead.
   - Notes: Removed cases from `AttributeSyntax.Arguments`: `token(TokenSyntax)`, `string(StringLiteralExprSyntax)`, `conventionArguments(ConventionAttributeArgumentsSyntax)`, `conventionWitnessMethodArguments(ConventionWitnessMethodAttributeArgumentsSyntax)`, `opaqueReturnTypeOfAttributeArguments(OpaqueReturnTypeOfAttributeArgumentsSyntax)`, `exposeAttributeArguments(ExposeAttributeArgumentsSyntax)`, `underscorePrivateAttributeArguments(UnderscorePrivateAttributeArgumentsSyntax)`, and `unavailableFromAsyncArguments(UnavailableFromAsyncAttributeArgumentsSyntax)`. Removed Syntax kinds: `ConventionAttributeArgumentsSyntax`, `ConventionWitnessMethodAttributeArgumentsSyntax`, `OpaqueReturnTypeOfAttributeArgumentsSyntax`, `ExposeAttributeArgumentsSyntax`, `UnderscorePrivateAttributeArgumentsSyntax`, and `UnavailableFromAsyncAttributeArgumentsSyntax`.
-,
+
+- `ExpandEditorPlaceholdersToLiteralClosures` & `CallToTrailingClosures` now take a `Syntax` parameter
+  - Description: These refactorings now take an arbitrary `Syntax` and return a `Syntax?`. If a non-function-like syntax node is passed, `nil` is returned. The previous `FunctionCallExprSyntax` overloads are deprecated.
+  - Pull Request: https://github.com/swiftlang/swift-syntax/pull/3092
+  - Migration steps: Insert a `Syntax(...)` initializer call for the argument, and cast the result with `.as(...)` if necessary.
+  - Notes: This allows the refactorings to correctly handle macro expansion expressions and declarations.
+
 ## Template
 
 - *Affected API or two word description*

Sources/SwiftRefactor/CMakeLists.txt

@@ -8,6 +8,7 @@
 
 add_swift_syntax_library(SwiftRefactor
   AddSeparatorsToIntegerLiteral.swift
+  CallLikeSyntax.swift
   CallToTrailingClosures.swift
   ConvertComputedPropertyToStored.swift
   ConvertComputedPropertyToZeroParameterFunction.swift

Sources/SwiftRefactor/CallLikeSyntax.swift

@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 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
+//
+//===----------------------------------------------------------------------===//
+
+#if compiler(>=6)
+public import SwiftSyntax
+#else
+import SwiftSyntax
+#endif
+
+// TODO: We ought to consider exposing this as a public syntax protocol.
+@_spi(Testing) public protocol CallLikeSyntax: SyntaxProtocol {
+  var arguments: LabeledExprListSyntax { get set }
+  var leftParen: TokenSyntax? { get set }
+  var rightParen: TokenSyntax? { get set }
+  var trailingClosure: ClosureExprSyntax? { get set }
+  var additionalTrailingClosures: MultipleTrailingClosureElementListSyntax { get set }
+}
+@_spi(Testing) extension FunctionCallExprSyntax: CallLikeSyntax {}
+@_spi(Testing) extension MacroExpansionExprSyntax: CallLikeSyntax {}
+@_spi(Testing) extension MacroExpansionDeclSyntax: CallLikeSyntax {}
+
+extension SyntaxProtocol {
+  @_spi(Testing) public func asProtocol(_: CallLikeSyntax.Protocol) -> (any CallLikeSyntax)? {
+    Syntax(self).asProtocol(SyntaxProtocol.self) as? CallLikeSyntax
+  }
+}

Sources/SwiftRefactor/CallToTrailingClosures.swift

@@ -50,19 +50,41 @@ public struct CallToTrailingClosures: SyntaxRefactoringProvider {
     }
   }
 
+  public typealias Input = Syntax
+  public typealias Output = Syntax
+
+  /// Apply the refactoring to a given syntax node. If either a
+  /// non-function-like syntax node is passed, or the refactoring fails,
+  /// `nil` is returned.
   // TODO: Rather than returning nil, we should consider throwing errors with
   // appropriate messages instead.
+  public static func refactor(
+    syntax: Syntax,
+    in context: Context = Context()
+  ) -> Syntax? {
+    guard let call = syntax.asProtocol(CallLikeSyntax.self) else { return nil }
+    return Syntax(fromProtocol: _refactor(syntax: call, in: context))
+  }
+
+  @available(*, deprecated, message: "Pass a Syntax argument instead of FunctionCallExprSyntax")
   public static func refactor(
     syntax call: FunctionCallExprSyntax,
     in context: Context = Context()
   ) -> FunctionCallExprSyntax? {
+    _refactor(syntax: call, in: context)
+  }
+
+  internal static func _refactor<C: CallLikeSyntax>(
+    syntax call: C,
+    in context: Context = Context()
+  ) -> C? {
     let converted = call.convertToTrailingClosures(from: context.startAtArgument)
-    return converted?.formatted().as(FunctionCallExprSyntax.self)
+    return converted?.formatted().as(C.self)
   }
 }
 
-extension FunctionCallExprSyntax {
-  fileprivate func convertToTrailingClosures(from startAtArgument: Int) -> FunctionCallExprSyntax? {
+extension CallLikeSyntax {
+  fileprivate func convertToTrailingClosures(from startAtArgument: Int) -> Self? {
     guard trailingClosure == nil, additionalTrailingClosures.isEmpty, leftParen != nil, rightParen != nil else {
       // Already have trailing closures
       return nil

Sources/SwiftRefactor/ExpandEditorPlaceholder.swift

@@ -180,7 +180,7 @@ public struct ExpandEditorPlaceholder: EditRefactoringProvider {
       placeholder.baseName.isEditorPlaceholder,
       let arg = placeholder.parent?.as(LabeledExprSyntax.self),
       let argList = arg.parent?.as(LabeledExprListSyntax.self),
-      let call = argList.parent?.as(FunctionCallExprSyntax.self),
+      let call = argList.parent?.asProtocol(CallLikeSyntax.self),
       let expandedClosures = ExpandEditorPlaceholdersToLiteralClosures.expandClosurePlaceholders(
         in: call,
         ifIncluded: arg,
@@ -266,6 +266,26 @@ public struct ExpandEditorPlaceholdersToLiteralClosures: SyntaxRefactoringProvid
     }
   }
 
+  public typealias Input = Syntax
+  public typealias Output = Syntax
+
+  /// Apply the refactoring to a given syntax node. If either a
+  /// non-function-like syntax node is passed, or the refactoring fails,
+  /// `nil` is returned.
+  public static func refactor(
+    syntax: Syntax,
+    in context: Context = Context()
+  ) -> Syntax? {
+    guard let call = syntax.asProtocol(CallLikeSyntax.self) else { return nil }
+    let expanded = Self.expandClosurePlaceholders(
+      in: call,
+      ifIncluded: nil,
+      context: context
+    )
+    return Syntax(fromProtocol: expanded)
+  }
+
+  @available(*, deprecated, message: "Pass a Syntax argument instead of FunctionCallExprSyntax")
   public static func refactor(
     syntax call: FunctionCallExprSyntax,
     in context: Context = Context()
@@ -282,11 +302,11 @@ public struct ExpandEditorPlaceholdersToLiteralClosures: SyntaxRefactoringProvid
   /// closure, then return a replacement of this call with one that uses
   /// closures based on the function types provided by each editor placeholder.
   /// Otherwise return nil.
-  fileprivate static func expandClosurePlaceholders(
-    in call: FunctionCallExprSyntax,
+  fileprivate static func expandClosurePlaceholders<C: CallLikeSyntax>(
+    in call: C,
     ifIncluded arg: LabeledExprSyntax?,
     context: Context
-  ) -> FunctionCallExprSyntax? {
+  ) -> C? {
     switch context.format {
     case let .custom(formatter, allowNestedPlaceholders: allowNesting):
       let expanded = call.expandClosurePlaceholders(
@@ -305,11 +325,7 @@ public struct ExpandEditorPlaceholdersToLiteralClosures: SyntaxRefactoringProvid
       let callToTrailingContext = CallToTrailingClosures.Context(
         startAtArgument: call.arguments.count - expanded.numClosures
       )
-      guard let trailing = CallToTrailingClosures.refactor(syntax: expanded.expr, in: callToTrailingContext) else {
-        return nil
-      }
-
-      return trailing
+      return CallToTrailingClosures._refactor(syntax: expanded.expr, in: callToTrailingContext)
     }
   }
 }
@@ -382,7 +398,7 @@ extension TupleTypeElementSyntax {
   }
 }
 
-extension FunctionCallExprSyntax {
+extension CallLikeSyntax {
   /// If the given argument is `nil` or one of the last arguments that are all
   /// function-typed placeholders and this call doesn't have a trailing
   /// closure, then return a replacement of this call with one that uses
@@ -393,7 +409,7 @@ extension FunctionCallExprSyntax {
     indentationWidth: Trivia? = nil,
     customFormat: BasicFormat? = nil,
     allowNestedPlaceholders: Bool = false
-  ) -> (expr: FunctionCallExprSyntax, numClosures: Int)? {
+  ) -> (expr: Self, numClosures: Int)? {
     var includedArg = false
     var argsToExpand = 0
     for arg in arguments.reversed() {

Tests/SwiftRefactorTest/ExpandEditorPlaceholderTests.swift

@@ -451,6 +451,58 @@ final class ExpandEditorPlaceholderTests: XCTestCase {
       format: .testCustom()
     )
   }
+
+  func testMacroTrailingClosureExpansion1() throws {
+    try assertRefactorPlaceholderToken(
+      "#foo(\(closurePlaceholder), \(intPlaceholder))",
+      expected: """
+        {
+            \(voidPlaceholder)
+        }
+        """
+    )
+  }
+
+  func testMacroTrailingClosureExpansion2() throws {
+    let call = "#foo(fn: \(closureWithArgPlaceholder))"
+    let expanded = """
+      #foo { someInt in
+          \(stringPlaceholder)
+      }
+      """
+
+    try assertRefactorPlaceholderCall(call, expected: expanded)
+    try assertExpandEditorPlaceholdersToClosures(call, expected: expanded)
+  }
+
+  func testMacroTrailingClosureExpansion3() throws {
+    let call = "#foo(fn1: \(closurePlaceholder), fn2: \(closureWithArgPlaceholder))"
+    let expanded = """
+      #foo {
+          \(voidPlaceholder)
+      } fn2: { someInt in
+          \(stringPlaceholder)
+      }
+      """
+
+    try assertRefactorPlaceholderCall(call, expected: expanded)
+    try assertExpandEditorPlaceholdersToClosures(call, expected: expanded)
+  }
+
+  func testMacroTrailingClosureExpansion4() throws {
+    try assertExpandEditorPlaceholdersToClosures(
+      decl: """
+        #foo(fn1: \(closurePlaceholder), fn2: \(closurePlaceholder))
+        """,
+      expected: """
+        #foo {
+            \(voidPlaceholder)
+        } fn2: {
+            \(voidPlaceholder)
+        }
+        """
+    )
+  }
 }
 
 fileprivate func assertRefactorPlaceholder(
@@ -489,7 +541,7 @@ fileprivate func assertRefactorPlaceholderCall(
   line: UInt = #line
 ) throws {
   var parser = Parser(expr)
-  let call = try XCTUnwrap(ExprSyntax.parse(from: &parser).as(FunctionCallExprSyntax.self), file: file, line: line)
+  let call = try XCTUnwrap(ExprSyntax.parse(from: &parser).asProtocol(CallLikeSyntax.self), file: file, line: line)
   let arg = call.arguments[call.arguments.index(at: placeholder)]
   let token: TokenSyntax = try XCTUnwrap(arg.expression.as(DeclReferenceExprSyntax.self), file: file, line: line)
     .baseName
@@ -513,7 +565,7 @@ fileprivate func assertRefactorPlaceholderToken(
   line: UInt = #line
 ) throws {
   var parser = Parser(expr)
-  let call = try XCTUnwrap(ExprSyntax.parse(from: &parser).as(FunctionCallExprSyntax.self), file: file, line: line)
+  let call = try XCTUnwrap(ExprSyntax.parse(from: &parser).asProtocol(CallLikeSyntax.self), file: file, line: line)
   let arg = call.arguments[call.arguments.index(at: placeholder)]
   let token: TokenSyntax = try XCTUnwrap(arg.expression.as(DeclReferenceExprSyntax.self), file: file, line: line)
     .baseName
@@ -529,15 +581,12 @@ fileprivate func assertRefactorPlaceholderToken(
 }
 
 fileprivate func assertExpandEditorPlaceholdersToClosures(
-  _ expr: String,
+  _ call: some CallLikeSyntax,
   expected: String,
   format: ExpandEditorPlaceholdersToLiteralClosures.Context.Format = .trailing(indentationWidth: nil),
   file: StaticString = #filePath,
   line: UInt = #line
 ) throws {
-  var parser = Parser(expr)
-  let call = try XCTUnwrap(ExprSyntax.parse(from: &parser).as(FunctionCallExprSyntax.self), file: file, line: line)
-
   try assertRefactor(
     call,
     context: ExpandEditorPlaceholdersToLiteralClosures.Context(format: format),
@@ -548,6 +597,42 @@ fileprivate func assertExpandEditorPlaceholdersToClosures(
   )
 }
 
+fileprivate func assertExpandEditorPlaceholdersToClosures(
+  _ expr: String,
+  expected: String,
+  format: ExpandEditorPlaceholdersToLiteralClosures.Context.Format = .trailing(indentationWidth: nil),
+  file: StaticString = #filePath,
+  line: UInt = #line
+) throws {
+  var parser = Parser(expr)
+  let call = try XCTUnwrap(ExprSyntax.parse(from: &parser).asProtocol(CallLikeSyntax.self), file: file, line: line)
+  try assertExpandEditorPlaceholdersToClosures(
+    call,
+    expected: expected,
+    format: format,
+    file: file,
+    line: line
+  )
+}
+
+fileprivate func assertExpandEditorPlaceholdersToClosures(
+  decl: String,
+  expected: String,
+  format: ExpandEditorPlaceholdersToLiteralClosures.Context.Format = .trailing(indentationWidth: nil),
+  file: StaticString = #filePath,
+  line: UInt = #line
+) throws {
+  var parser = Parser(decl)
+  let call = try XCTUnwrap(DeclSyntax.parse(from: &parser).asProtocol(CallLikeSyntax.self), file: file, line: line)
+  try assertExpandEditorPlaceholdersToClosures(
+    call,
+    expected: expected,
+    format: format,
+    file: file,
+    line: line
+  )
+}
+
 fileprivate extension ExpandEditorPlaceholdersToLiteralClosures.Context.Format {
   static func testCustom(indentationWidth: Trivia? = nil) -> Self {
     .custom(CustomClosureFormat(indentationWidth: indentationWidth), allowNestedPlaceholders: true)