Sema: Fix superfluous error about private decls in internal memory layouts

Don't consider implicitly exposed memory layouts when checking for
usable from inline correctness. That check applies only to memory
layouts marked as exposed explicitly. Consider the implict state only at
the general availability checking.

Author: xymus

include/swift/AST/Decl.h

@@ -6727,7 +6727,10 @@ class VarDecl : public AbstractStorageDecl {
   ///
   /// From the standpoint of access control and exportability checking, this
   /// var will behave as if it was public, even if it is internal or private.
-  bool isLayoutExposedToClients() const;
+  ///
+  /// If \p applyImplicit, consider implicitly exposed layouts as well.
+  /// This applies to non-resilient modules.
+  bool isLayoutExposedToClients(bool applyImplicit = false) const;
 
   /// Is this a special debugger variable?
   bool isDebuggerVar() const { return Bits.VarDecl.IsDebuggerVar; }

lib/AST/Availability.cpp

@@ -1006,7 +1006,7 @@ bool swift::isExported(const ValueDecl *VD) {
 
   // Is this a stored property in a @frozen struct or class?
   if (auto *property = dyn_cast<VarDecl>(VD))
-    if (property->isLayoutExposedToClients())
+    if (property->isLayoutExposedToClients(/*applyImplicit=*/true))
       return true;
 
   return false;

lib/AST/Decl.cpp

@@ -2753,7 +2753,7 @@ bool VarDecl::isInitExposedToClients() const {
   return hasInitialValue() && isLayoutExposedToClients();
 }
 
-bool VarDecl::isLayoutExposedToClients() const {
+bool VarDecl::isLayoutExposedToClients(bool applyImplicit) const {
   auto parent = dyn_cast<NominalTypeDecl>(getDeclContext());
   if (!parent) return false;
   if (isStatic()) return false;
@@ -2763,9 +2763,11 @@ bool VarDecl::isLayoutExposedToClients() const {
     parent->getFormalAccessScope(/*useDC=*/nullptr,
                                  /*treatUsableFromInlineAsPublic=*/true);
 
-  // Resilient modules hide layouts by default.
-  if (!getASTContext().LangOpts.hasFeature(Feature::CheckImplementationOnly) ||
-      M->getResilienceStrategy() == ResilienceStrategy::Resilient) {
+  // Resilient modules and classes hide layouts by default.
+  bool layoutIsHiddenByDefault = !applyImplicit ||
+    !getASTContext().LangOpts.hasFeature(Feature::CheckImplementationOnly) ||
+    M->getResilienceStrategy() == ResilienceStrategy::Resilient;
+  if (layoutIsHiddenByDefault) {
     if (!nominalAccess.isPublic())
       return false;
 

test/Sema/hidden-memory-layout.swift

@@ -62,9 +62,11 @@ public struct ExposedLayoutPublic {
   public init() { fatalError() }
 }
 
+internal struct ExposedLayoutInternal {
+}
+
 private struct ExposedLayoutPrivate {
 // expected-note @-1 2 {{struct 'ExposedLayoutPrivate' is not '@usableFromInline' or public}}
-// expected-opt-in-note @-2 {{type declared here}}
   init() { fatalError() } // expected-note {{initializer 'init()' is not '@usableFromInline' or public}}
 }
 
@@ -74,7 +76,7 @@ private struct HiddenLayout {
 // expected-opt-in-note @-1 2 {{struct 'HiddenLayout' is not '@usableFromInline' or public}}
 // expected-opt-in-note @-2 1 {{initializer 'init()' is not '@usableFromInline' or public}}
 // expected-opt-in-note @-3 2 {{struct declared here}}
-// expected-opt-in-note @-4 {{type declared here}}
+// expected-opt-in-note @-4 {{struct declared here}}
 }
 #else
 private struct HiddenLayout {
@@ -163,12 +165,26 @@ public struct ExposedLayoutPublicUser {
   // expected-opt-in-error @-1 {{cannot use struct 'StructFromDirect' in a property declaration marked public or in a '@frozen' or '@usableFromInline' context; 'directs' has been imported as implementation-only}}
 
   private var a: ExposedLayoutPublic
+  private var aa: ExposedLayoutInternal
   private var b: ExposedLayoutPrivate
-  // expected-opt-in-error @-1 {{type referenced from a stored property in a '@frozen' struct must be '@usableFromInline' or public}}
 
   private var c: HiddenLayout
   // expected-opt-in-error @-1 {{cannot use struct 'HiddenLayout' in a property declaration marked public or in a '@frozen' or '@usableFromInline' context; it is a struct marked '@_implementationOnly'}}
-  // expected-opt-in-error @-2 {{type referenced from a stored property in a '@frozen' struct must be '@usableFromInline' or public}}
+
+  private func privateFunc(h: HiddenLayout) {}
+  // expected-embedded-opt-in-error @-1 {{struct 'HiddenLayout' cannot be used in an embedded function not marked '@_neverEmitIntoClient' because it is a struct marked '@_implementationOnly'}}
+}
+
+private struct ExposedLayoutInternalUser {
+
+  private var privateField: StructFromDirect
+  // expected-opt-in-error @-1 {{cannot use struct 'StructFromDirect' in a property declaration marked public or in a '@frozen' or '@usableFromInline' context; 'directs' has been imported as implementation-only}}
+
+  private var a: ExposedLayoutPublic
+  private var aa: ExposedLayoutInternal
+  private var b: ExposedLayoutPrivate
+  private var c: HiddenLayout
+  // expected-opt-in-error @-1 {{cannot use struct 'HiddenLayout' in a property declaration marked public or in a '@frozen' or '@usableFromInline' context; it is a struct marked '@_implementationOnly'}}
 
   private func privateFunc(h: HiddenLayout) {}
   // expected-embedded-opt-in-error @-1 {{struct 'HiddenLayout' cannot be used in an embedded function not marked '@_neverEmitIntoClient' because it is a struct marked '@_implementationOnly'}}
@@ -180,6 +196,7 @@ private struct ExposedLayoutPrivateUser {
   // expected-opt-in-error @-1 {{cannot use struct 'StructFromDirect' in a property declaration marked public or in a '@frozen' or '@usableFromInline' context; 'directs' has been imported as implementation-only}}
 
   private var a: ExposedLayoutPublic
+  private var aa: ExposedLayoutInternal
   private var b: ExposedLayoutPrivate
   private var c: HiddenLayout
   // expected-opt-in-error @-1 {{cannot use struct 'HiddenLayout' in a property declaration marked public or in a '@frozen' or '@usableFromInline' context; it is a struct marked '@_implementationOnly'}}
@@ -194,6 +211,7 @@ private struct HiddenLayoutUser {
   public var publicField: StructFromDirect
   private var privateField: StructFromDirect
   private var a: ExposedLayoutPublic
+  private var aa: ExposedLayoutInternal
   private var b: ExposedLayoutPrivate
   private var c: HiddenLayout