[Property delegates] Diagnose too-restrictive 'value' and 'init(initialValue:)' .

The 'value' property and 'init(initialValue:)' initializer cannot have
more restrictive access than the property delegate itself. Diagnose
this.

Author: DougGregor

include/swift/AST/DiagnosticsSema.def

@@ -4326,6 +4326,11 @@ ERROR(property_with_delegate_conflict_attribute,none,
       "property %0 with a delegate cannot also be "
       "%select{lazy|@NSCopying|@NSManaged|weak|unowned|unmanaged}1",
       (DeclName, int))
+ERROR(property_delegate_type_requirement_not_accessible,none,
+      "%select{private|fileprivate|internal|public|open}0 %1 %2 cannot have "
+      "more restrictive access than its enclosing property delegate type %3 "
+      "(which is %select{private|fileprivate|internal|public|open}4)",
+      (AccessLevel, DescriptiveDeclKind, DeclName, Type, AccessLevel))
 
 #ifndef DIAG_NO_UNDEF
 # if defined(DIAG)

lib/Sema/TypeCheckPropertyDelegates.cpp

@@ -219,7 +219,8 @@ PropertyDelegateTypeInfoRequest::evaluate(
     nominal->lookupQualified(nominal, ctx.Id_value, NL_QualifiedDefault, decls);
     for (const auto &foundDecl : decls) {
       auto foundVar = dyn_cast<VarDecl>(foundDecl);
-      if (!foundVar || foundVar->isStatic())
+      if (!foundVar || foundVar->isStatic() ||
+          foundVar->getDeclContext() != nominal)
         continue;
 
       unwrapVars.push_back(foundVar);
@@ -247,6 +248,16 @@ PropertyDelegateTypeInfoRequest::evaluate(
     return PropertyDelegateTypeInfo();
   }
 
+  // The 'value' property must be as accessible as the nominal type.
+  if (result.unwrapProperty->getFormalAccess() < nominal->getFormalAccess()) {
+    auto var = result.unwrapProperty;
+    var->diagnose(diag::property_delegate_type_requirement_not_accessible,
+                  var->getFormalAccess(), var->getDescriptiveKind(),
+                  var->getFullName(), nominal->getDeclaredType(),
+                  nominal->getFormalAccess());
+    return PropertyDelegateTypeInfo();
+  }
+
   // Determine whether we have an init(initialValue:), and diagnose
   // ambiguities.
   {
@@ -257,7 +268,7 @@ PropertyDelegateTypeInfoRequest::evaluate(
     nominal->lookupQualified(nominal, initName, NL_QualifiedDefault, decls);
     for (const auto &decl : decls) {
       auto init = dyn_cast<ConstructorDecl>(decl);
-      if (!init)
+      if (!init || init->getDeclContext() != nominal)
         continue;
 
       initialValueInitializers.push_back(init);
@@ -267,9 +278,19 @@ PropertyDelegateTypeInfoRequest::evaluate(
     case 0:
       break;
 
-    case 1:
-      result.initialValueInit = initialValueInitializers.front();
+    case 1: {
+      // 'init(initialValue:)' must be as accessible as the nominal type.
+      auto init = initialValueInitializers.front();
+      if (init->getFormalAccess() < nominal->getFormalAccess()) {
+        init->diagnose(diag::property_delegate_type_requirement_not_accessible,
+                       init->getFormalAccess(), init->getDescriptiveKind(),
+                       init->getFullName(), nominal->getDeclaredType(),
+                       nominal->getFormalAccess());
+      } else {
+        result.initialValueInit = init;
+      }
       break;
+    }
 
     default:
       // Diagnose ambiguous init(initialValue:) initializers.

test/decl/var/property_delegates.swift

@@ -430,6 +430,20 @@ struct BadCombinations {
   unowned var z: C by Wrapper // expected-error{{property 'z' with a delegate cannot also be unowned}}
 }
 
+@propertyDelegate
+struct NonVisibleValueDelegate<Value> {
+  private var value: Value // expected-error{{private property 'value' cannot have more restrictive access than its enclosing property delegate type 'NonVisibleValueDelegate' (which is internal)}}
+}
+
+@propertyDelegate
+struct NonVisibleInitDelegate<Value> {
+  var value: Value
+
+  private init(initialValue: Value) { // expected-error{{private initializer 'init(initialValue:)' cannot have more restrictive access than its enclosing property delegate type 'NonVisibleInitDelegate' (which is internal)}}
+    self.value = initialValue
+  }
+}
+
 // ---------------------------------------------------------------------------
 // Explicitly-specified accessors
 // ---------------------------------------------------------------------------