[AST] TypeWrappers: Always allow attributes that come from swiftinterfaces

Since type wrapper attributes could be applied to protocols and
the protocol types could be used as existential values, it's not
always possible to wrap all uses of feature into `#if $TypeWrappers`
block so let's allow use of attributes if they come from a Swift
interface file.

Author: xedin

include/swift/AST/TypeCheckRequests.h

@@ -3762,23 +3762,6 @@ class GetTypeWrapperInitializer
   bool isCached() const { return true; }
 };
 
-/// Check whether this is a protocol that has a type wrapper attribute
-/// or one of its dependencies does.
-class UsesTypeWrapperFeature
-    : public SimpleRequest<UsesTypeWrapperFeature, bool(NominalTypeDecl *),
-                           RequestFlags::Cached> {
-public:
-  using SimpleRequest::SimpleRequest;
-
-private:
-  friend SimpleRequest;
-
-  bool evaluate(Evaluator &evaluator, NominalTypeDecl *) const;
-
-public:
-  bool isCached() const { return true; }
-};
-
 /// Find the definition of a given macro.
 class MacroDefinitionRequest
     : public SimpleRequest<MacroDefinitionRequest,

include/swift/AST/TypeCheckerTypeIDZone.def

@@ -443,9 +443,6 @@ SWIFT_REQUEST(TypeChecker, ContinueTargetRequest,
 SWIFT_REQUEST(TypeChecker, GetTypeWrapperInitializer,
               ConstructorDecl *(NominalTypeDecl *),
               Cached, NoLocationInfo)
-SWIFT_REQUEST(TypeChecker, UsesTypeWrapperFeature,
-              bool(NominalTypeDecl *),
-              Cached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, MacroDefinitionRequest,
               MacroDefinition(MacroDecl *),
               Cached, NoLocationInfo)

lib/AST/ASTPrinter.cpp

@@ -2949,19 +2949,7 @@ static bool usesFeatureSpecializeAttributeWithAvailability(Decl *decl) {
 }
 
 static bool usesFeatureTypeWrappers(Decl *decl) {
-  NullablePtr<NominalTypeDecl> typeDecl;
-
-  if (auto *extension = dyn_cast<ExtensionDecl>(decl)) {
-    typeDecl = extension->getExtendedNominal();
-  } else {
-    typeDecl = dyn_cast<NominalTypeDecl>(decl);
-  }
-
-  if (!typeDecl)
-    return false;
-
-  return evaluateOrDefault(decl->getASTContext().evaluator,
-                           UsesTypeWrapperFeature{typeDecl.get()}, false);
+  return false;
 }
 
 static bool usesFeatureRuntimeDiscoverableAttrs(Decl *decl) {

lib/AST/TypeWrapper.cpp

@@ -44,53 +44,3 @@ bool VarDecl::isTypeWrapperLocalStorageForInitializer() const {
   }
   return false;
 }
-
-bool UsesTypeWrapperFeature::evaluate(Evaluator &evaluator,
-                                      NominalTypeDecl *decl) const {
-  // This is a type wrapper type.
-  if (decl->getAttrs().hasAttribute<TypeWrapperAttr>())
-    return true;
-
-  // This is a type wrapped type.
-  if (decl->hasTypeWrapper())
-    return true;
-
-  // This type could be depending on a type wrapper feature
-  // indirectly by conforming to a protocol with a type
-  // wrapper attribute. To determine that we need to walk
-  // protocol dependency chains and check each one.
-
-  auto &ctx = decl->getASTContext();
-
-  auto usesTypeWrapperFeature = [&](ProtocolDecl *protocol) {
-    return evaluateOrDefault(ctx.evaluator, UsesTypeWrapperFeature{protocol},
-                             false);
-  };
-
-  for (unsigned i : indices(decl->getInherited())) {
-    auto inheritedType = evaluateOrDefault(
-        ctx.evaluator,
-        InheritedTypeRequest{decl, i, TypeResolutionStage::Interface}, Type());
-
-    if (!(inheritedType && inheritedType->isConstraintType()))
-      continue;
-
-    if (auto *protocol =
-        dyn_cast_or_null<ProtocolDecl>(inheritedType->getAnyNominal())) {
-      if (usesTypeWrapperFeature(protocol))
-        return true;
-    }
-
-    if (auto composition = inheritedType->getAs<ProtocolCompositionType>()) {
-      for (auto member : composition->getMembers()) {
-        if (auto *protocol =
-                dyn_cast_or_null<ProtocolDecl>(member->getAnyNominal())) {
-          if (usesTypeWrapperFeature(protocol))
-            return true;
-        }
-      }
-    }
-  }
-
-  return false;
-}

lib/Sema/TypeCheckAttr.cpp

@@ -3826,7 +3826,16 @@ void AttributeChecker::visitPropertyWrapperAttr(PropertyWrapperAttr *attr) {
 }
 
 void AttributeChecker::visitTypeWrapperAttr(TypeWrapperAttr *attr) {
-  if (!Ctx.LangOpts.hasFeature(Feature::TypeWrappers)) {
+  auto isEnabled = [&]() {
+    if (Ctx.LangOpts.hasFeature(Feature::TypeWrappers))
+      return true;
+
+    // Accept attributes that come from swiftinterface files.
+    auto *parentSF = D->getDeclContext()->getParentSourceFile();
+    return parentSF && parentSF->Kind == SourceFileKind::Interface;
+  };
+
+  if (!isEnabled()) {
     diagnose(attr->getLocation(), diag::type_wrappers_are_experimental);
     attr->setInvalid();
     return;