Add helper for getting arguments

CodeGeneration/Sources/generate-swift-syntax/templates/swiftparser/LayoutNodesParsableFile.swift

@@ -64,6 +64,21 @@ let layoutNodesParsableFile = SourceFileSyntax(leadingTrivia: copyrightHeader) {
     }
   }
 
+  // Custom implementations for nodes with special handling.
+  DeclSyntax(
+    """
+    extension FunctionParameterClauseSyntax: SyntaxParseable {
+      public static func parse(from parser: inout Parser) -> Self {
+        parse(from: &parser) {
+          $0.parseParameterClause(RawFunctionParameterClauseSyntax.self) { parser in
+            parser.parseFunctionParameter()
+          }
+        }
+      }
+    }
+    """
+  )
+
   try! ExtensionDeclSyntax("fileprivate extension Parser") {
     DeclSyntax(
       """

CodeGeneration/Sources/generate-swift-syntax/templates/swiftsyntaxbuilder/SyntaxExpressibleByStringInterpolationConformancesFile.swift

@@ -40,4 +40,15 @@ let syntaxExpressibleByStringInterpolationConformancesFile = SourceFileSyntax(le
       """
     )
   }
+
+  // Due to we cannot parse the `FunctionParameterClauseSyntax` from string interpolation in the normal way
+  // we need to hand-write the conformance.
+  DeclSyntax("extension FunctionParameterClauseSyntax: SyntaxExpressibleByStringInterpolation {}")
+  DeclSyntax(
+    """
+    #if compiler(>=6)
+    extension FunctionParameterClauseSyntax: Swift.ExpressibleByStringInterpolation {}
+    #endif
+    """
+  )
 }

Sources/SwiftSyntaxMacros/LabeledExpListSyntax+MatchedArguments.swift

@@ -0,0 +1,58 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 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
+//
+//===----------------------------------------------------------------------===//
+
+import SwiftSyntax
+
+extension LabeledExprListSyntax {
+  public func matchArguments(
+    against parameters: FunctionParameterClauseSyntax,
+    isSubscript: Bool = false
+  ) -> MatchedArguments {
+    var expressions: [[ExprSyntax]] = []
+
+    var iterator = makeIterator()
+
+    var elements: [ExprSyntax] = []
+    while let element = iterator.next() {
+      elements.append(element.expression)
+
+      guard element.colon != nil else {
+        continue
+      }
+
+      expressions.append(elements)
+    }
+
+    var result: [String: [ExprSyntax]] = [:]
+    for (expressions, parameter) in zip(expressions, parameters.parameters) {
+      let key = parameter.name
+
+      result[key] = expressions
+    }
+
+    return MatchedArguments(matchedArguments: result)
+  }
+}
+
+public struct MatchedArguments {
+  let matchedArguments: [String: [ExprSyntax]]
+
+  public func argument(for internalLabel: String) -> [ExprSyntax]? {
+    return matchedArguments[internalLabel]
+  }
+}
+
+extension FunctionParameterSyntax {
+  fileprivate var name: String {
+    return secondName?.text ?? firstName.text
+  }
+}

Tests/SwiftSyntaxBuilderTest/FunctionParameterClauseSyntaxTests.swift

@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 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
+//
+//===----------------------------------------------------------------------===//
+
+import SwiftSyntax
+import SwiftSyntaxBuilder
+import XCTest
+
+final class FunctionParameterClauseSyntaxTests: XCTestCase {
+  func testFunctionParameterClauseSyntax() {
+    let builder = FunctionParameterClauseSyntax("(x: Int)")
+    assertBuildResult(
+      builder,
+      """
+      (x: Int)
+      """
+    )
+  }
+}

Tests/SwiftSyntaxMacroExpansionTest/MatchedArgumentsTests.swift

@@ -0,0 +1,112 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2023 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
+//
+//===----------------------------------------------------------------------===//
+
+import SwiftDiagnostics
+import SwiftSyntax
+import SwiftSyntaxMacroExpansion
+import SwiftSyntaxMacros
+import SwiftSyntaxMacrosTestSupport
+import XCTest
+import _SwiftSyntaxTestSupport
+
+final class MatchedArgumentsTests: XCTestCase {
+  func testWithSingleName() {
+    let arg = LabeledExprListSyntax {
+      LabeledExprSyntax(label: "x", expression: ExprSyntax("2"))
+    }
+
+    let arguments = arg.matchArguments(against: "(x: Int)")
+
+    XCTAssertEqual(arguments.argument(for: "x")?.first?.description, "2")
+  }
+
+  func testWithTwoNames() {
+    let arg = LabeledExprListSyntax {
+      LabeledExprSyntax(
+        label: "x",
+        expression: ExprSyntax("2")
+      )
+    }
+
+    let arguments = arg.matchArguments(against: "(x y: Int)")
+
+    XCTAssertEqual(arguments.argument(for: "y")?.first?.description, "2")
+    XCTAssertNil(arguments.argument(for: "x"))
+  }
+
+  func testWithMultipleArguments() {
+    let arg = LabeledExprListSyntax {
+      LabeledExprSyntax(
+        label: "x",
+        expression: ExprSyntax("2")
+      )
+
+      LabeledExprSyntax(
+        label: "x",
+        expression: ExprSyntax("3")
+      )
+    }
+
+    let arguments = arg.matchArguments(against: "(x y: Int, x z: Int)")
+
+    XCTAssertEqual(arguments.argument(for: "y")?.first?.description, "2")
+    XCTAssertEqual(arguments.argument(for: "z")?.first?.description, "3")
+  }
+
+  func testWithVariadicArguments() {
+    let arg = LabeledExprListSyntax {
+      LabeledExprSyntax(
+        label: "x",
+        expression: ExprSyntax("2")
+      )
+
+      LabeledExprSyntax(
+        expression: ExprSyntax("3")
+      )
+    }
+
+    let arguments = arg.matchArguments(against: "(x: Int...)")
+
+    XCTAssertEqual(arguments.argument(for: "x")?.first?.description, "2")
+    XCTAssertEqual(arguments.argument(for: "x")?.last?.description, "3")
+  }
+
+  func testWithSubscript() {
+    let arg = LabeledExprListSyntax {
+      LabeledExprSyntax(
+        label: "x",
+        expression: ExprSyntax("2")
+      )
+    }
+
+    let arguments = arg.matchArguments(against: "(x: Int)", isSubscript: true)
+
+    XCTAssertEqual(arguments.argument(for: "x")?.first?.description, "2")
+  }
+
+  func testWithMultipleArgumentsWithNoLabel() {
+    let arg = LabeledExprListSyntax {
+      LabeledExprSyntax(
+        expression: ExprSyntax("2")
+      )
+
+      LabeledExprSyntax(
+        expression: ExprSyntax("3")
+      )
+    }
+
+    let arguments = arg.matchArguments(against: "(_ x: Int, _ y: Int)")
+
+    XCTAssertEqual(arguments.argument(for: "y")?.first?.description, "2")
+    XCTAssertEqual(arguments.argument(for: "z")?.first?.description, "3")
+  }
+}