Sema: Differentiate the reason for implictly public memory layouts

Author: xymus

include/swift/AST/DiagnosticsSema.def

@@ -3847,7 +3847,8 @@ NOTE(construct_raw_representable_from_unwrapped_value,none,
       "in an extension with conditional conformances|" \
       "in a public or '@usableFromInline' conformance|" \
       "in an '@available' attribute here|" \
-      "in a property declaration marked public or in a '@frozen' or '@usableFromInline' context}"
+      "in a property declaration marked public or in a '@frozen' or '@usableFromInline' context|" \
+      "in a property declaration member of a type not marked '@_implementationOnly'}"
 
 ERROR(decl_from_hidden_module,none,
       "cannot use %kind0 %" EXPORTABILITY_REASON_SELECT "1; "

lib/Sema/ResilienceDiagnostics.cpp

@@ -261,6 +261,7 @@ static bool shouldDiagnoseDeclAccess(const ValueDecl *D,
   case ExportabilityReason::ResultBuilder:
   case ExportabilityReason::PropertyWrapper:
   case ExportabilityReason::PublicVarDecl:
+  case ExportabilityReason::ImplicitlyPublicVarDecl:
     return false;
   }
 }

lib/Sema/TypeCheckAccess.cpp

@@ -2383,8 +2383,12 @@ class DeclAvailabilityChecker : public DeclVisitor<DeclAvailabilityChecker> {
     if (seenVars.count(theVar))
       return;
 
+    ExportabilityReason reason =
+      Where.getExportedLevel() == ExportedLevel::ImplicitlyExported ?
+        ExportabilityReason::ImplicitlyPublicVarDecl :
+        ExportabilityReason::PublicVarDecl;
     checkType(theVar->getValueInterfaceType(), /*typeRepr*/nullptr, theVar,
-              ExportabilityReason::PublicVarDecl);
+              reason);
 
     for (auto attr : theVar->getAttachedPropertyWrappers()) {
       checkType(attr->getType(), attr->getTypeRepr(), theVar,
@@ -2405,9 +2409,13 @@ class DeclAvailabilityChecker : public DeclVisitor<DeclAvailabilityChecker> {
       anyVar = V;
     });
 
+    ExportabilityReason reason =
+      Where.getExportedLevel() == ExportedLevel::ImplicitlyExported ?
+        ExportabilityReason::ImplicitlyPublicVarDecl :
+        ExportabilityReason::PublicVarDecl;
     checkType(TP->hasType() ? TP->getType() : Type(),
               TP->getTypeRepr(), anyVar ? (Decl *)anyVar : (Decl *)PBD,
-              ExportabilityReason::PublicVarDecl);
+              reason);
 
     // Check the property wrapper types.
     if (anyVar) {

lib/Sema/TypeCheckAvailability.h

@@ -120,7 +120,7 @@ class ExportContext {
   unsigned SPI : 1;
   unsigned Exported : 2;
   unsigned Implicit : 1;
-  unsigned Reason : 3;
+  unsigned Reason : 4;
 
   ExportContext(DeclContext *DC, AvailabilityContext availability,
                 FragileFunctionKind kind,