[Observation] Switch Observable to be a non-marker protocol

lib/Macros/Sources/ObservationMacros/Extensions.swift

@@ -58,7 +58,7 @@ extension VariableDeclSyntax {
       guard let decl = accessor.as(AccessorDeclSyntax.self) else {
         return nil
       }
-      if predicate(decl.accessorKind.tokenKind) {
+      if predicate(decl.accessorSpecifier.tokenKind) {
         return decl
       } else {
         return nil
@@ -85,7 +85,7 @@ extension VariableDeclSyntax {
 
 
   var isImmutable: Bool {
-    return bindingKeyword.tokenKind == .keyword(.let)
+    return bindingSpecifier.tokenKind == .keyword(.let)
   }
 
   func isEquivalent(to other: VariableDeclSyntax) -> Bool {
@@ -198,9 +198,9 @@ extension FunctionDeclSyntax {
   var signatureStandin: SignatureStandin {
     var parameters = [String]()
     for parameter in signature.input.parameterList {
-      parameters.append(parameter.firstName.text + ":" + (parameter.type.genericSubstitution(genericParameterClause?.genericParameterList) ?? "" ))
+      parameters.append(parameter.firstName.text + ":" + (parameter.type.genericSubstitution(genericParameterClause?.parameters) ?? "" ))
     }
-    let returnType = signature.output?.returnType.genericSubstitution(genericParameterClause?.genericParameterList) ?? "Void"
+    let returnType = signature.output?.returnType.genericSubstitution(genericParameterClause?.parameters) ?? "Void"
     return SignatureStandin(isInstance: isInstance, identifier: identifier.text, parameters: parameters, returnType: returnType)
   }
 

lib/Macros/Sources/ObservationMacros/ObservableMacro.swift

@@ -71,7 +71,7 @@ public struct ObservableMacro {
   static var ignoredAttribute: AttributeSyntax {
     AttributeSyntax(
       leadingTrivia: .space,
-      atSignToken: .atSignToken(),
+      atSign: .atSignToken(),
       attributeName: SimpleTypeIdentifierSyntax(name: .identifier(ignoredMacroName)),
       trailingTrivia: .space
     )
@@ -173,12 +173,14 @@ extension PatternBindingListSyntax {
 }
 
 extension VariableDeclSyntax {
-    func privatePrefixed(_ prefix: String, addingAttribute attribute: AttributeSyntax) -> VariableDeclSyntax {
-    VariableDeclSyntax(
+  func privatePrefixed(_ prefix: String, addingAttribute attribute: AttributeSyntax) -> VariableDeclSyntax {
+    let newAttributes = AttributeListSyntax(
+      (attributes.map(Array.init) ?? []) + [.attribute(attribute)])
+    return VariableDeclSyntax(
       leadingTrivia: leadingTrivia,
-      attributes: attributes?.appending(.attribute(attribute)) ?? [.attribute(attribute)],
+      attributes: newAttributes,
       modifiers: modifiers?.privatePrefixed(prefix) ?? ModifierListSyntax(keyword: .private),
-      bindingKeyword: TokenSyntax(bindingKeyword.tokenKind, leadingTrivia: .space, trailingTrivia: .space, presence: .present),
+      bindingSpecifier: TokenSyntax(bindingSpecifier.tokenKind, leadingTrivia: .space, trailingTrivia: .space, presence: .present),
       bindings: bindings.privatePrefixed(prefix),
       trailingTrivia: trailingTrivia
     )
@@ -265,30 +267,27 @@ extension ObservableMacro: MemberAttributeMacro {
   }
 }
 
-extension ObservableMacro: ConformanceMacro {
-  public static func expansion<Declaration: DeclGroupSyntax, Context: MacroExpansionContext>(
+extension ObservableMacro: ExtensionMacro {
+  public static func expansion(
     of node: AttributeSyntax,
-    providingConformancesOf declaration: Declaration,
-    in context: Context
-  ) throws -> [(TypeSyntax, GenericWhereClauseSyntax?)] {
-    let inheritanceList: InheritedTypeListSyntax?
-    if let classDecl = declaration.as(ClassDeclSyntax.self) {
-      inheritanceList = classDecl.inheritanceClause?.inheritedTypeCollection
-    } else if let structDecl = declaration.as(StructDeclSyntax.self) {
-      inheritanceList = structDecl.inheritanceClause?.inheritedTypeCollection
-    } else {
-      inheritanceList = nil
-    }
-
-    if let inheritanceList {
-      for inheritance in inheritanceList {
-        if inheritance.typeName.identifier == ObservableMacro.conformanceName {
-          return []
-        }
-      }
+    attachedTo declaration: some DeclGroupSyntax,
+    providingExtensionsOf type: some TypeSyntaxProtocol,
+    conformingTo protocols: [TypeSyntax],
+    in context: some MacroExpansionContext
+  ) throws -> [ExtensionDeclSyntax] {
+    // This method can be called twice - first with an empty `protocols` when
+    // no conformance is needed, and second with a `MissingTypeSyntax` instance.
+    if protocols.isEmpty {
+      return []
     }
-
-    return [(ObservableMacro.observableConformanceType, nil)]
+
+    let decl: DeclSyntax = """
+      extension \(raw: type.trimmedDescription): \(raw: qualifiedConformanceName) {}
+      """
+
+    return [
+      decl.cast(ExtensionDeclSyntax.self)
+    ]
   }
 }
 

stdlib/public/Observation/Sources/Observation/CMakeLists.txt

@@ -24,6 +24,7 @@ add_swift_target_library(swiftObservation ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} IS
   SWIFT_COMPILE_FLAGS
     ${SWIFT_STANDARD_LIBRARY_SWIFT_FLAGS}
     "-enable-experimental-feature" "Macros"
+    "-enable-experimental-feature" "ExtensionMacros"
     -Xfrontend -disable-implicit-string-processing-module-import
 
   C_COMPILE_FLAGS

stdlib/public/Observation/Sources/Observation/Observable.swift

@@ -18,7 +18,7 @@
 /// the ``Observation/Observable-swift.macro`` macro when adding observation
 /// support to a type.
 @available(SwiftStdlib 5.9, *)
-@_marker public protocol Observable { }
+public protocol Observable { }
 
 #if $Macros && hasAttribute(attached)
 
@@ -46,7 +46,7 @@
 @attached(member, names: named(_$observationRegistrar), named(access), named(withMutation), arbitrary)
 #endif
 @attached(memberAttribute)
-@attached(conformance)
+@attached(extension, conformances: Observable)
 public macro Observable() =
   #externalMacro(module: "ObservationMacros", type: "ObservableMacro")
 

test/stdlib/Observation/Observable.swift

@@ -1,9 +1,9 @@
 // REQUIRES: swift_swift_parser, executable_test
 
-// RUN: %target-run-simple-swift( -Xfrontend -disable-availability-checking -parse-as-library -enable-experimental-feature InitAccessors -enable-experimental-feature Macros -Xfrontend -plugin-path -Xfrontend %swift-host-lib-dir/plugins)
+// RUN: %target-run-simple-swift( -Xfrontend -disable-availability-checking -parse-as-library -enable-experimental-feature InitAccessors -enable-experimental-feature Macros -enable-experimental-feature ExtensionMacros -Xfrontend -plugin-path -Xfrontend %swift-host-lib-dir/plugins)
 
 // Run this test via the swift-plugin-server
-// RUN: %target-run-simple-swift( -Xfrontend -disable-availability-checking -parse-as-library -enable-experimental-feature InitAccessors -enable-experimental-feature Macros -Xfrontend -external-plugin-path -Xfrontend %swift-host-lib-dir/plugins#%swift-plugin-server)
+// RUN: %target-run-simple-swift( -Xfrontend -disable-availability-checking -parse-as-library -enable-experimental-feature InitAccessors -enable-experimental-feature Macros -enable-experimental-feature ExtensionMacros -Xfrontend -external-plugin-path -Xfrontend %swift-host-lib-dir/plugins#%swift-plugin-server)
 
 // Asserts is required for '-enable-experimental-feature InitAccessors'.
 // REQUIRES: asserts

test/stdlib/Observation/ObservableDidSetWillSet.swift

@@ -1,6 +1,6 @@
 // REQUIRES: swift_swift_parser, executable_test
 
-// RUN: %target-run-simple-swift( -Xfrontend -disable-availability-checking -enable-experimental-feature InitAccessors -enable-experimental-feature Macros -Xfrontend -plugin-path -Xfrontend %swift-host-lib-dir/plugins) | %FileCheck %s
+// RUN: %target-run-simple-swift( -Xfrontend -disable-availability-checking -enable-experimental-feature InitAccessors -enable-experimental-feature Macros -enable-experimental-feature ExtensionMacros -Xfrontend -plugin-path -Xfrontend %swift-host-lib-dir/plugins) | %FileCheck %s
 
 // Asserts is required for '-enable-experimental-feature InitAccessors'.
 // REQUIRES: asserts