Merge pull request #27896 from AnthonyLatsis/proto-stubs-nonmutating-set

Sema: Print property accessors for non-mutating setter requirements

Author: jrose-apple

lib/Sema/TypeCheckProtocol.cpp

@@ -2627,13 +2627,13 @@ printRequirementStub(ValueDecl *Requirement, DeclContext *Adopter,
     Options.FunctionDefinitions = true;
     Options.PrintAccessorBodiesInProtocols = true;
 
+    bool AdopterIsClass = Adopter->getSelfClassDecl() != nullptr;
     // Skip 'mutating' only inside classes: mutating methods usually
     // don't have a sensible non-mutating implementation.
-    bool isClass = Adopter->getSelfClassDecl() != nullptr;
-    if (isClass)
+    if (AdopterIsClass)
       Options.ExcludeAttrList.push_back(DAK_Mutating);
     // 'nonmutating' is only meaningful on value type member accessors.
-    if (isClass || !isa<AbstractStorageDecl>(Requirement))
+    if (AdopterIsClass || !isa<AbstractStorageDecl>(Requirement))
       Options.ExcludeAttrList.push_back(DAK_NonMutating);
 
     // FIXME: Once we support move-only types, remove this if the
@@ -2650,10 +2650,19 @@ printRequirementStub(ValueDecl *Requirement, DeclContext *Adopter,
     };
     Options.setBaseType(AdopterTy);
     Options.CurrentModule = Adopter->getParentModule();
-    if (!isa<ExtensionDecl>(Adopter)) {
+    if (isa<NominalTypeDecl>(Adopter)) {
       // Create a variable declaration instead of a computed property in
-      // nominal types
+      // nominal types...
       Options.PrintPropertyAccessors = false;
+
+      // ...but a non-mutating setter requirement will force us into a
+      // computed property in non-class adopters; don't leave the user
+      // wondering why a conformance fails.
+      if (!AdopterIsClass)
+        if (const auto VD = dyn_cast<VarDecl>(Requirement))
+          if (const auto Set = VD->getAccessor(AccessorKind::Set))
+            if (Set->getAttrs().hasAttribute<NonMutatingAttr>())
+              Options.PrintPropertyAccessors = true;
     }
     Requirement->print(Printer, Options);
     Printer << "\n";

test/decl/protocol/conforms/fixit_stub_editor.swift

@@ -39,15 +39,15 @@ class C2 : P4 {} // expected-error{{type 'C2' does not conform to protocol 'P4'}
 //   in structs.
 // =============================================================================
 
-protocol LocalMutabilityProto {
-    mutating func foo()
-    subscript() -> Int { get nonmutating set }
+protocol MutabilityProto {
+  mutating func foo()
+  subscript() -> Int { get nonmutating set }
 }
 
-class Class1: LocalMutabilityProto { // expected-error{{type 'Class1' does not conform to protocol 'LocalMutabilityProto'}} expected-note{{do you want to add protocol stubs?}} {{37-37=\n    func foo() {\n        <#code#>\n    \}\n\n    subscript() -> Int {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n}}
+class Class1: MutabilityProto { // expected-error{{type 'Class1' does not conform to protocol 'MutabilityProto'}} expected-note{{do you want to add protocol stubs?}} {{32-32=\n    func foo() {\n        <#code#>\n    \}\n\n    subscript() -> Int {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n}}
 }
 
-struct Struct1: LocalMutabilityProto { // expected-error{{type 'Struct1' does not conform to protocol 'LocalMutabilityProto'}} expected-note{{do you want to add protocol stubs?}} {{39-39=\n    mutating func foo() {\n        <#code#>\n    \}\n\n    subscript() -> Int {\n        get {\n            <#code#>\n        \}\n        nonmutating set {\n            <#code#>\n        \}\n    \}\n}}
+struct Struct1: MutabilityProto { // expected-error{{type 'Struct1' does not conform to protocol 'MutabilityProto'}} expected-note{{do you want to add protocol stubs?}} {{34-34=\n    mutating func foo() {\n        <#code#>\n    \}\n\n    subscript() -> Int {\n        get {\n            <#code#>\n        \}\n        nonmutating set {\n            <#code#>\n        \}\n    \}\n}}
 }
 
 import fixit_stub_mutability_proto_module
@@ -57,3 +57,18 @@ class Class2: ExternalMutabilityProto { // expected-error{{type 'Class2' does no
 
 struct Struct2: ExternalMutabilityProto { // expected-error{{type 'Struct2' does not conform to protocol 'ExternalMutabilityProto'}} expected-note{{do you want to add protocol stubs?}} {{42-42=\n    mutating func foo() {\n        <#code#>\n    \}\n\n    subscript() -> Int {\n        mutating get {\n            <#code#>\n        \}\n        nonmutating set(newValue) {\n            <#code#>\n        \}\n    \}\n}}
 }
+
+protocol PropertyMutabilityProto {
+  var computed: Int { mutating get nonmutating set }
+  var stored: Int { mutating get set }
+}
+
+class Class3: PropertyMutabilityProto { // expected-error{{type 'Class3' does not conform to protocol 'PropertyMutabilityProto'}} expected-note{{do you want to add protocol stubs?}} {{40-40=\n    var computed: Int\n\n    var stored: Int\n}}
+}
+
+struct Struct3: PropertyMutabilityProto { // expected-error{{type 'Struct3' does not conform to protocol 'PropertyMutabilityProto'}} expected-note{{do you want to add protocol stubs?}} {{42-42=\n    var computed: Int {\n        mutating get {\n            <#code#>\n        \}\n        nonmutating set {\n            <#code#>\n        \}\n    \}\n\n    var stored: Int\n}}
+}
+
+class Class4 {}
+extension Class4: PropertyMutabilityProto { // expected-error{{type 'Class4' does not conform to protocol 'PropertyMutabilityProto'}} expected-note{{do you want to add protocol stubs?}} {{44-44=\n    var computed: Int {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n\n    var stored: Int {\n        get {\n            <#code#>\n        \}\n        set {\n            <#code#>\n        \}\n    \}\n}}
+}