[AST] Add SPI information to public access scopes

Author: xymus

include/swift/AST/AccessScope.h

@@ -24,12 +24,16 @@ namespace swift {
 /// a particular declaration can be accessed.
 class AccessScope {
   /// The declaration context (if not public) along with a bit saying
-  /// whether this scope is private (or not).
+  /// whether this scope is private, SPI or not.
+  /// If the declaration context is set, the bit means that the scope is
+  /// private or not. If the declaration context is null, the bit means that
+  /// this scope is SPI or not.
   llvm::PointerIntPair<const DeclContext *, 1, bool> Value;
+
 public:
-  AccessScope(const DeclContext *DC, bool isPrivate = false);
+  AccessScope(const DeclContext *DC, bool isPrivate = false, bool isSPI = false);
 
-  static AccessScope getPublic() { return AccessScope(nullptr); }
+  static AccessScope getPublic(bool isSPI = false) { return AccessScope(nullptr, false, isSPI); }
 
   /// Check if private access is allowed. This is a lexical scope check in Swift
   /// 3 mode. In Swift 4 mode, declarations and extensions of the same type will
@@ -46,18 +50,24 @@ class AccessScope {
   }
 
   bool isPublic() const { return !Value.getPointer(); }
-  bool isPrivate() const { return Value.getInt(); }
+  bool isPrivate() const { return Value.getPointer() && Value.getInt(); }
   bool isFileScope() const;
   bool isInternal() const;
 
+  // Is this a public scope
+  bool isSPI() const { return !Value.getPointer() && Value.getInt(); }
+
   /// Returns true if this is a child scope of the specified other access scope.
   ///
   /// \see DeclContext::isChildContextOf
   bool isChildOf(AccessScope AS) const {
     if (!isPublic() && !AS.isPublic())
       return allowsPrivateAccess(getDeclContext(), AS.getDeclContext());
-    if (isPublic() && AS.isPublic())
+    if (isPublic() && AS.isPublic()) {
+      if (isSPI() != AS.isSPI())
+        return isSPI();
       return false;
+    }
     return AS.isPublic();
   }
 
@@ -76,6 +86,8 @@ class AccessScope {
   /// have common intersection, or None if scopes don't intersect.
   const Optional<AccessScope> intersectWith(AccessScope accessScope) const {
     if (hasEqualDeclContextWith(accessScope)) {
+      if (isSPI())
+        return *this;
       if (isPrivate())
         return *this;
       return accessScope;

lib/AST/DeclContext.cpp

@@ -954,14 +954,16 @@ getPrivateDeclContext(const DeclContext *DC, const SourceFile *useSF) {
   return lastExtension ? lastExtension : DC;
 }
 
-AccessScope::AccessScope(const DeclContext *DC, bool isPrivate)
-    : Value(DC, isPrivate) {
+AccessScope::AccessScope(const DeclContext *DC, bool isPrivate, bool isSPI)
+    : Value(DC, isPrivate || isSPI) {
   if (isPrivate) {
     DC = getPrivateDeclContext(DC, DC->getParentSourceFile());
     Value.setPointer(DC);
   }
   if (!DC || isa<ModuleDecl>(DC))
     assert(!isPrivate && "public or internal scope can't be private");
+  if (DC)
+    assert(!isSPI && "only public scopes can be SPI");
 }
 
 bool AccessScope::isFileScope() const {

lib/Sema/TypeCheckAccess.cpp

@@ -171,8 +171,6 @@ class TypeAccessScopeDiagnoser : private ASTWalker {
                                            AccessScope accessScope,
                                            const DeclContext *useDC,
                                            bool treatUsableFromInlineAsPublic) {
-    assert(!accessScope.isPublic() &&
-           "why would we need to find a public access scope?");
     if (TR == nullptr)
       return nullptr;
     TypeAccessScopeDiagnoser diagnoser(accessScope, useDC,