Update freestanding macro protocols to use generics

Author: DougGregor

Sources/_SwiftSyntaxMacros/MacroProtocols/CodeItemMacro.swift

@@ -13,8 +13,8 @@ import SwiftSyntax
 public protocol CodeItemMacro: FreestandingMacro {
   /// Expand a macro described by the given freestanding macro expansion
   /// declaration within the given context to produce a set of declarations.
-  static func expansion(
+  static func expansion<Context: MacroExpansionContext>(
     of node: MacroExpansionDeclSyntax,
-    in context: any MacroExpansionContext
+    in context: Context
   ) throws -> [CodeBlockItemSyntax]
 }

Sources/_SwiftSyntaxMacros/MacroProtocols/DeclarationMacro.swift

@@ -13,9 +13,11 @@ import SwiftSyntax
 public protocol DeclarationMacro: FreestandingMacro {
   /// Expand a macro described by the given freestanding macro expansion
   /// declaration within the given context to produce a set of declarations.
-  static func expansion(
+  static func expansion<
+    Context: MacroExpansionContext
+  >(
     of node: MacroExpansionDeclSyntax,
-    in context: any MacroExpansionContext
+    in context: Context
   ) throws -> [DeclSyntax]
 }
 

Tests/SwiftSyntaxMacrosTest/MacroSystemTests.swift

@@ -198,9 +198,9 @@ extension SimpleDiagnosticMessage: FixItMessage {
 }
 
 public struct ErrorMacro: DeclarationMacro {
-  public static func expansion(
+  public static func expansion<Context: MacroExpansionContext>(
     of node: MacroExpansionDeclSyntax,
-    in context: any MacroExpansionContext
+    in context: Context
   ) throws -> [DeclSyntax] {
     guard let firstElement = node.argumentList.first,
       let stringLiteral = firstElement.expression
@@ -227,9 +227,9 @@ public struct ErrorMacro: DeclarationMacro {
 }
 
 struct DefineBitwidthNumberedStructsMacro: DeclarationMacro {
-  static func expansion(
+  static func expansion<Context: MacroExpansionContext>(
     of node: MacroExpansionDeclSyntax,
-    in context: any MacroExpansionContext
+    in context: Context
   ) throws -> [DeclSyntax] {
     guard let firstElement = node.argumentList.first,
       let stringLiteral = firstElement.expression