Suggest stub stored properties where possible

beccadax · beccadax · commit 0cfda873b603 · 2025-04-09T16:48:41.000-07:00
When generating a stub fix-it for a protocol conformance or implementation extension, Swift will now evaluate whether the context allows the declaration of stored properties and, if so, will suggest one. It will also use the `let` keyword instead of `var` if the property has no setter.
diff --git a/include/swift/AST/PrintOptions.h b/include/swift/AST/PrintOptions.h
@@ -143,6 +143,9 @@ struct PrintOptions {
   /// Whether to print *any* accessors on properties.
   bool PrintPropertyAccessors = true;
 
+  /// Use \c let for a read-only computed property.
+  bool InferPropertyIntroducerFromAccessors = false;
+
   /// Whether to print *any* accessors on subscript.
   bool PrintSubscriptAccessors = true;
 
diff --git a/lib/AST/ASTPrinter.cpp b/lib/AST/ASTPrinter.cpp
@@ -3940,11 +3940,18 @@ void PrintAST::visitVarDecl(VarDecl *decl) {
   if (decl->isStatic() && Options.PrintStaticKeyword)
     printStaticKeyword(decl->getCorrectStaticSpelling());
   if (decl->getKind() == DeclKind::Var || Options.PrintParameterSpecifiers) {
+    // If InferPropertyIntroducerFromAccessors is set, turn all read-only
+    // properties to `let`.
+    auto introducer = decl->getIntroducer();
+    if (Options.InferPropertyIntroducerFromAccessors &&
+          !cast<VarDecl>(decl)->isSettable(nullptr))
+      introducer = VarDecl::Introducer::Let;
+
     // Map all non-let specifiers to 'var'.  This is not correct, but
     // SourceKit relies on this for info about parameter decls.
     
     Printer.printIntroducerKeyword(
-      decl->getIntroducer() == VarDecl::Introducer::Let ? "let" : "var",
+      introducer == VarDecl::Introducer::Let ? "let" : "var",
       Options, " ");
   }
   printContextIfNeeded(decl);
diff --git a/lib/Sema/TypeCheckProtocol.cpp b/lib/Sema/TypeCheckProtocol.cpp
@@ -3706,7 +3706,10 @@ bool swift::
 printRequirementStub(ValueDecl *Requirement, DeclContext *Adopter,
                      Type AdopterTy, SourceLoc TypeLoc, raw_ostream &OS,
                      bool withExplicitObjCAttr) {
-  if (isa<ConstructorDecl>(Requirement)) {
+  // We sometimes use this for @implementation extensions too.
+  bool forProtocol = isa<ProtocolDecl>(Requirement->getDeclContext());
+
+  if (isa<ConstructorDecl>(Requirement) && forProtocol) {
     if (auto CD = Adopter->getSelfClassDecl()) {
       if (!CD->isSemanticallyFinal() && isa<ExtensionDecl>(Adopter)) {
         // In this case, user should mark class as 'final' or define
@@ -3774,7 +3777,7 @@ printRequirementStub(ValueDecl *Requirement, DeclContext *Adopter,
 
     Printer << "\n";
   } else {
-    if (isa<ConstructorDecl>(Requirement)) {
+    if (isa<ConstructorDecl>(Requirement) && forProtocol) {
       if (auto CD = Adopter->getSelfClassDecl()) {
         if (!CD->isFinal()) {
           Printer << "required ";
@@ -3809,9 +3812,12 @@ printRequirementStub(ValueDecl *Requirement, DeclContext *Adopter,
     };
     Options.setBaseType(AdopterTy);
     Options.CurrentModule = Adopter->getParentModule();
-    if (isa<NominalTypeDecl>(Adopter)) {
-      // Create a variable declaration instead of a computed property in
-      // nominal types...
+
+    // Can the conforming declaration declare a stored property?
+    auto ImplementedAdopter = Adopter->getImplementedObjCContext();
+    if (isa<NominalTypeDecl>(ImplementedAdopter) &&
+          (!isa<EnumDecl>(ImplementedAdopter) || Requirement->isStatic())) {
+      // Create a variable declaration instead of a computed property...
       Options.PrintPropertyAccessors = false;
 
       // ...but a non-mutating setter requirement will force us into a
@@ -3822,6 +3828,11 @@ printRequirementStub(ValueDecl *Requirement, DeclContext *Adopter,
           if (const auto Set = VD->getOpaqueAccessor(AccessorKind::Set))
             if (Set->getAttrs().hasAttribute<NonMutatingAttr>())
               Options.PrintPropertyAccessors = true;
+
+      // If we're not printing the accessors, make them affect the introducer
+      // instead.
+      Options.InferPropertyIntroducerFromAccessors =
+          !Options.PrintPropertyAccessors;
     }
     Requirement->print(Printer, Options);
     Printer << "\n";
diff --git a/test/Sema/fixits-derived-conformances.swift b/test/Sema/fixits-derived-conformances.swift
@@ -17,5 +17,5 @@ extension GenericStruct: @retroactive Equatable { }
 
 extension Enum: @retroactive CaseIterable { }
 // expected-error@-1 {{extension outside of file declaring enum 'Enum' prevents automatic synthesis of 'allCases' for protocol 'CaseIterable'}}
-// expected-note@-2 {{add stubs for conformance}}{{44-44=\n    public static var allCases: [Enum]\n}}
+// expected-note@-2 {{add stubs for conformance}}{{44-44=\n    public static let allCases: [Enum]\n}}
 
diff --git a/test/decl/ext/Inputs/objc_implementation.h b/test/decl/ext/Inputs/objc_implementation.h
@@ -85,6 +85,10 @@
 @property int categoryPropertyFromHeader2;
 @property int categoryPropertyFromHeader3;
 @property int categoryPropertyFromHeader4;
+@property int categoryPropertyFromHeader5;
+
+@property (readonly) int categoryReadonlyPropertyFromHeader1;
+
 
 @end
 
diff --git a/test/decl/ext/objc_implementation.swift b/test/decl/ext/objc_implementation.swift
@@ -17,7 +17,7 @@ protocol EmptySwiftProto {}
   // FIXME: give better diagnostic expected-note@-8 {{missing instance method 'method(fromHeader3:)'}} {{none}}
   // expected-note@-9 {{missing instance method 'extensionMethod(fromHeader2:)'}} {{none}}
   // expected-note@-10 {{missing property 'readonlyPropertyFromHeader7'}}
-  // expected-note@-11 {{add stubs for missing '@implementation' requirements}} {{77-77=\n    @objc(methodFromHeader3:)\n    open func method(fromHeader3 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(methodFromHeader4:)\n    open func method(fromHeader4 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(propertyFromHeader7)\n    open var propertyFromHeader7: Int32 {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n\n    @objc(propertyFromHeader8)\n    open var propertyFromHeader8: Int32 {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n\n    @objc(propertyFromHeader9)\n    open var propertyFromHeader9: Int32 {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n\n    @objc(readonlyPropertyFromHeader7)\n    open var readonlyPropertyFromHeader7: Int32 {\n        <#code#>\n    \}\n\n    @objc(extensionMethodFromHeader2:)\n    open func extensionMethod(fromHeader2 param: Int32) {\n        <#code#>\n    \}\n}}
+  // expected-note@-11 {{add stubs for missing '@implementation' requirements}} {{77-77=\n    @objc(methodFromHeader3:)\n    open func method(fromHeader3 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(methodFromHeader4:)\n    open func method(fromHeader4 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(propertyFromHeader7)\n    open var propertyFromHeader7: Int32\n\n    @objc(propertyFromHeader8)\n    open var propertyFromHeader8: Int32\n\n    @objc(propertyFromHeader9)\n    open var propertyFromHeader9: Int32\n\n    @objc(readonlyPropertyFromHeader7)\n    open let readonlyPropertyFromHeader7: Int32\n\n    @objc(extensionMethodFromHeader2:)\n    open func extensionMethod(fromHeader2 param: Int32) {\n        <#code#>\n    \}\n}}
 
   func method(fromHeader1: CInt) {
     // OK, provides an implementation for the header's method.
@@ -241,7 +241,9 @@ protocol EmptySwiftProto {}
   // expected-error@-1 {{extension for category 'PresentAdditions' does not provide all required implementations}}
   // expected-note@-2 {{missing instance method 'categoryMethod(fromHeader4:)'}} {{none}}
   // FIXME: give better diagnostic expected-note@-3 {{missing instance method 'categoryMethod(fromHeader3:)'}} {{none}}
-  // expected-note@-4 {{add stubs for missing '@implementation' requirements}} {{62-62=\n    @objc(categoryMethodFromHeader3:)\n    open func categoryMethod(fromHeader3 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(categoryMethodFromHeader4:)\n    open func categoryMethod(fromHeader4 param: Int32) {\n        <#code#>\n    \}\n}}
+  // expected-note@-4 {{missing property 'categoryPropertyFromHeader5'}} {{none}}
+  // expected-note@-5 {{missing property 'categoryReadonlyPropertyFromHeader1'}} {{none}}
+  // expected-note@-6 {{add stubs for missing '@implementation' requirements}} {{62-62=\n    @objc(categoryMethodFromHeader3:)\n    open func categoryMethod(fromHeader3 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(categoryMethodFromHeader4:)\n    open func categoryMethod(fromHeader4 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(categoryPropertyFromHeader5)\n    open var categoryPropertyFromHeader5: Int32 {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n\n    @objc(categoryReadonlyPropertyFromHeader1)\n    open var categoryReadonlyPropertyFromHeader1: Int32 {\n        <#code#>\n    \}\n}}
 
   func method(fromHeader3: CInt) {
     // FIXME: should emit expected-DISABLED-error@-1 {{instance method 'method(fromHeader3:)' should be implemented in extension for main class interface, not category 'PresentAdditions'}}
diff --git a/test/decl/ext/objc_implementation_class_extension.swift b/test/decl/ext/objc_implementation_class_extension.swift
@@ -11,7 +11,7 @@
   // expected-note@-5 {{missing property 'otherModuleExtensionPropertyFromHeader2'}} {{none}}
   // expected-note@-6 {{missing instance method 'extensionMethod(fromHeader2:)'}} {{none}}
   // expected-note@-7 {{missing property 'extensionPropertyFromHeader2'}} {{none}}
-  // expected-note@-8 {{add stubs for missing '@implementation' requirements}} {{43-43=\n    @objc(methodFromHeader2:)\n    open func method(fromHeader2 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(propertyFromHeader2)\n    open var propertyFromHeader2: Int32 {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n\n    @objc(otherModuleExtensionMethodFromHeader2:)\n    open func otherModuleExtensionMethod(fromHeader2 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(otherModuleExtensionPropertyFromHeader2)\n    open var otherModuleExtensionPropertyFromHeader2: Int32 {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n\n    @objc(extensionMethodFromHeader2:)\n    open func extensionMethod(fromHeader2 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(extensionPropertyFromHeader2)\n    open var extensionPropertyFromHeader2: Int32 {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n}}
+  // expected-note@-8 {{add stubs for missing '@implementation' requirements}} {{43-43=\n    @objc(methodFromHeader2:)\n    open func method(fromHeader2 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(propertyFromHeader2)\n    open var propertyFromHeader2: Int32\n\n    @objc(otherModuleExtensionMethodFromHeader2:)\n    open func otherModuleExtensionMethod(fromHeader2 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(otherModuleExtensionPropertyFromHeader2)\n    open var otherModuleExtensionPropertyFromHeader2: Int32\n\n    @objc(extensionMethodFromHeader2:)\n    open func extensionMethod(fromHeader2 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(extensionPropertyFromHeader2)\n    open var extensionPropertyFromHeader2: Int32\n}}
 
   @objc func method(fromHeader1: CInt) {}
   @objc private func method(fromHeader2: CInt) {}
diff --git a/test/decl/ext/objc_implementation_conflicts.swift b/test/decl/ext/objc_implementation_conflicts.swift
@@ -231,6 +231,17 @@ import objc_implementation_private
     get { return 1 }
     set {}
   }
+
+  @objc var categoryPropertyFromHeader5: CInt {
+    // OK, provides an implementation with a computed property
+    get { return 1 }
+    set {}
+  }
+
+  @objc var categoryReadonlyPropertyFromHeader1: CInt {
+    // OK, provides an implementation with a computed property
+    get { return 1 }
+  }
 }
 
 @objc class SwiftClass {}
diff --git a/test/decl/ext/objc_implementation_early_adopter.swift b/test/decl/ext/objc_implementation_early_adopter.swift
@@ -17,7 +17,7 @@ protocol EmptySwiftProto {}
   // FIXME: give better diagnostic expected-note@-8 {{missing instance method 'method(fromHeader3:)'}} {{none}}
   // expected-note@-9 {{missing instance method 'extensionMethod(fromHeader2:)'}} {{none}}
   // expected-note@-10 {{missing property 'readonlyPropertyFromHeader7'}}
-  // expected-note@-11 {{add stubs for missing '@implementation' requirements}} {{76-76=\n    @objc(methodFromHeader3:)\n    open func method(fromHeader3 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(methodFromHeader4:)\n    open func method(fromHeader4 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(propertyFromHeader7)\n    open var propertyFromHeader7: Int32 {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n\n    @objc(propertyFromHeader8)\n    open var propertyFromHeader8: Int32 {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n\n    @objc(propertyFromHeader9)\n    open var propertyFromHeader9: Int32 {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n\n    @objc(readonlyPropertyFromHeader7)\n    open var readonlyPropertyFromHeader7: Int32 {\n        <#code#>\n    \}\n\n    @objc(extensionMethodFromHeader2:)\n    open func extensionMethod(fromHeader2 param: Int32) {\n        <#code#>\n    \}\n}}
+  // expected-note@-11 {{add stubs for missing '@implementation' requirements}} {{76-76=\n    @objc(methodFromHeader3:)\n    open func method(fromHeader3 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(methodFromHeader4:)\n    open func method(fromHeader4 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(propertyFromHeader7)\n    open var propertyFromHeader7: Int32\n\n    @objc(propertyFromHeader8)\n    open var propertyFromHeader8: Int32\n\n    @objc(propertyFromHeader9)\n    open var propertyFromHeader9: Int32\n\n    @objc(readonlyPropertyFromHeader7)\n    open let readonlyPropertyFromHeader7: Int32\n\n    @objc(extensionMethodFromHeader2:)\n    open func extensionMethod(fromHeader2 param: Int32) {\n        <#code#>\n    \}\n}}
 
   func method(fromHeader1: CInt) {
     // OK, provides an implementation for the header's method.
@@ -241,7 +241,9 @@ protocol EmptySwiftProto {}
   // expected-warning@-1 {{extension for category 'PresentAdditions' does not provide all required implementations; this will become an error after adopting '@implementation'}}
   // expected-note@-2 {{missing instance method 'categoryMethod(fromHeader4:)'}} {{none}}
   // FIXME: give better diagnostic expected-note@-3 {{missing instance method 'categoryMethod(fromHeader3:)'}} {{none}}
-  // expected-note@-4 {{add stubs for missing '@implementation' requirements}} {{61-61=\n    @objc(categoryMethodFromHeader3:)\n    open func categoryMethod(fromHeader3 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(categoryMethodFromHeader4:)\n    open func categoryMethod(fromHeader4 param: Int32) {\n        <#code#>\n    \}\n}}
+  // expected-note@-4 {{missing property 'categoryPropertyFromHeader5'}} {{none}}
+  // expected-note@-5 {{missing property 'categoryReadonlyPropertyFromHeader1'}} {{none}}
+  // expected-note@-6 {{add stubs for missing '@implementation' requirements}} {{61-61=\n    @objc(categoryMethodFromHeader3:)\n    open func categoryMethod(fromHeader3 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(categoryMethodFromHeader4:)\n    open func categoryMethod(fromHeader4 param: Int32) {\n        <#code#>\n    \}\n\n    @objc(categoryPropertyFromHeader5)\n    open var categoryPropertyFromHeader5: Int32 {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n\n    @objc(categoryReadonlyPropertyFromHeader1)\n    open var categoryReadonlyPropertyFromHeader1: Int32 {\n        <#code#>\n    \}\n}}
 
   func method(fromHeader3: CInt) {
     // FIXME: should emit expected-DISABLED-error@-1 {{instance method 'method(fromHeader3:)' should be implemented in extension for main class interface, not category 'PresentAdditions'}}
diff --git a/test/decl/protocol/conforms/fixit_stub.swift b/test/decl/protocol/conforms/fixit_stub.swift
@@ -1,17 +1,20 @@
 // RUN: %target-typecheck-verify-swift
 
 protocol Protocol1 {
-  func foo(arg1: Int, arg2: String) -> String // expected-note{{protocol requires function 'foo(arg1:arg2:)' with type '(Int, String) -> String'}}
-  func bar() throws -> String // expected-note{{protocol requires function 'bar()' with type '() throws -> String'}}
-  func generic<T>(t: T) // expected-note{{protocol requires function 'generic(t:)' with type '<T> (t: T) -> ()'}}
-  init(arg: Int) // expected-note{{protocol requires initializer 'init(arg:)' with type '(arg: Int)'}}
-  var baz: Int { get } // expected-note{{protocol requires property 'baz' with type 'Int'}}
-  var baz2: Int { get set } // expected-note{{protocol requires property 'baz2' with type 'Int'}}
-  subscript(arg: Int) -> String { get } //expected-note{{rotocol requires subscript with type '(Int) -> String'}}
-  subscript(arg1: Int, arg2: Int) -> String { get set } //expected-note{{protocol requires subscript with type '(Int, Int) -> String'}}
+  func foo(arg1: Int, arg2: String) -> String // expected-note 2{{protocol requires function 'foo(arg1:arg2:)' with type '(Int, String) -> String'}}
+  func bar() throws -> String // expected-note 2{{protocol requires function 'bar()' with type '() throws -> String'}}
+  func generic<T>(t: T) // expected-note 2{{protocol requires function 'generic(t:)' with type '<T> (t: T) -> ()'}}
+  init(arg: Int) // expected-note 2{{protocol requires initializer 'init(arg:)' with type '(arg: Int)'}}
+  var baz: Int { get } // expected-note 2{{protocol requires property 'baz' with type 'Int'}}
+  var baz2: Int { get set } // expected-note 2{{protocol requires property 'baz2' with type 'Int'}}
+  subscript(arg: Int) -> String { get } //expected-note 2{{rotocol requires subscript with type '(Int) -> String'}}
+  subscript(arg1: Int, arg2: Int) -> String { get set } //expected-note 2{{protocol requires subscript with type '(Int, Int) -> String'}}
+}
+
+class Adopter: Protocol1 { // expected-error{{type 'Adopter' does not conform to protocol 'Protocol1'}} expected-note {{add stubs for conformance}} {{27-27=\n    func foo(arg1: Int, arg2: String) -> String {\n        <#code#>\n    \}\n\n    func bar() throws -> String {\n        <#code#>\n    \}\n\n    func generic<T>(t: T) {\n        <#code#>\n    \}\n\n    required init(arg: Int) {\n        <#code#>\n    \}\n\n    let baz: Int\n\n    var baz2: Int\n\n    subscript(arg: Int) -> String {\n        <#code#>\n    \}\n\n    subscript(arg1: Int, arg2: Int) -> String {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n}}
 }
 
-class Adopter: Protocol1 { // expected-error{{type 'Adopter' does not conform to protocol 'Protocol1'}} expected-note {{add stubs for conformance}} {{27-27=\n    func foo(arg1: Int, arg2: String) -> String {\n        <#code#>\n    \}\n\n    func bar() throws -> String {\n        <#code#>\n    \}\n\n    func generic<T>(t: T) {\n        <#code#>\n    \}\n\n    required init(arg: Int) {\n        <#code#>\n    \}\n\n    var baz: Int\n\n    var baz2: Int\n\n    subscript(arg: Int) -> String {\n        <#code#>\n    \}\n\n    subscript(arg1: Int, arg2: Int) -> String {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n}}
+enum EnumAdopter: Protocol1 { // expected-error{{type 'EnumAdopter' does not conform to protocol 'Protocol1'}} expected-note {{add stubs for conformance}} {{30-30=\n    func foo(arg1: Int, arg2: String) -> String {\n        <#code#>\n    \}\n\n    func bar() throws -> String {\n        <#code#>\n    \}\n\n    func generic<T>(t: T) {\n        <#code#>\n    \}\n\n    init(arg: Int) {\n        <#code#>\n    \}\n\n    var baz: Int {\n        <#code#>\n    \}\n\n    var baz2: Int {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n\n    subscript(arg: Int) -> String {\n        <#code#>\n    \}\n\n    subscript(arg1: Int, arg2: Int) -> String {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n}}
 }
 
 
diff --git a/test/decl/protocol/fixits_missing_protocols_in_context.swift b/test/decl/protocol/fixits_missing_protocols_in_context.swift
@@ -13,7 +13,7 @@ class C {
   func assign() {
     p = self
     // expected-error@-1 {{cannot assign value of type 'C' to type '(any P)?'}}
-    // expected-note@-2 {{add missing conformance to 'P' to class 'C'}} {{-4:8-8=: P}} {{-4:10-10=\n    func method() {\n        <#code#>\n    \}\n\n    var property: Int\n}}
+    // expected-note@-2 {{add missing conformance to 'P' to class 'C'}} {{-4:8-8=: P}} {{-4:10-10=\n    func method() {\n        <#code#>\n    \}\n\n    let property: Int\n}}
   }
 }
 
@@ -25,7 +25,7 @@ class C1 {
   func assign() {
     p = self
     // expected-error@-1 {{cannot assign value of type 'C1' to type '(any P)?'}}
-    // expected-note@-2 {{add missing conformance to 'P' to class 'C1'}} {{-4:9-9=: P}} {{-4:11-11=\n    var property: Int\n}}
+    // expected-note@-2 {{add missing conformance to 'P' to class 'C1'}} {{-4:9-9=: P}} {{-4:11-11=\n    let property: Int\n}}
   }
 
   func method() {}
