Add string interpolation for FunctionParameterClauseSyntax

Author: kimdv

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/SwiftParser/generated/LayoutNodes+Parsable.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)
+      """
+    )
+  }
+}