[PackageInterface] Fix isInterfacePackageEffectivelyPublic.

ValueDecl::isInterfacePackageEffectivelyPublic is used to check if a package decl in
interface file can be skipped for typecheck; if the decl is inlinable and in public or
private interface, it should be allowed to skip. This PR adds a missing check which
looks up the Interface source kind.

Resolves rdar://135388095

Author: elsh

lib/AST/Decl.cpp

@@ -4219,18 +4219,27 @@ bool ValueDecl::isUsableFromInline() const {
 }
 
 bool ValueDecl::isInterfacePackageEffectivelyPublic() const {
-  // If a package decl has a @usableFromInline (or other inlinable)
-  // attribute, and is defined in a module built from interface, it
-  // can be referenced by another module that imports it even though
-  // the defining interface module does not have package-name (such
-  // as public or private interface); in such case, the decl is treated
-  // as public and access checks in sema are skipped.
-  // We might need to add another check here to ensure the interface
-  // was part of the same package before the package-name was removed.
-  return getFormalAccess() == AccessLevel::Package &&
-         isUsableFromInline() &&
-         getModuleContext()->getPackageName().empty() &&
-         getModuleContext()->isBuiltFromInterface();
+  // A package decl with @usableFromInline (or other inlinable
+  // attributes) is essentially public, and can be printed in
+  // public (or private) interface file without package-name;
+  // it can be referenced by another module (without package-name)
+  // importing such interface module.
+  auto isCandidate = getFormalAccess() == AccessLevel::Package &&
+                     isUsableFromInline() &&
+                     getModuleContext()->getPackageName().empty();
+  if (!isCandidate)
+    return false;
+
+  // Treat the decl as public (1) if it's contained in an interface
+  // file, e.g. when running -typecheck-module-from-interface or
+  // -compile-module-from-interface.
+  isCandidate = false;
+  if (auto srcFile = getDeclContext()->getParentSourceFile()) {
+    isCandidate = srcFile->Kind == SourceFileKind::Interface;
+  }
+  // Or (2) if the decl being referenced in a client file is defined
+  // in an interface module.
+  return isCandidate || getModuleContext()->isBuiltFromInterface();
 }
 
 bool ValueDecl::shouldHideFromEditor() const {
@@ -4512,9 +4521,9 @@ getAccessScopeForFormalAccess(const ValueDecl *VD,
     if (!pkg) {
       if (VD->isInterfacePackageEffectivelyPublic())
         return AccessScope::getPublic();
-      // Instead of reporting and failing early, return the scope of resultDC to
-      // allow continuation (should still non-zero exit later if in script mode)
-      return AccessScope(resultDC);
+
+      // If reached here, should be treated as internal.
+      return AccessScope(resultDC->getParentModule());
     } else {
       return AccessScope(pkg);
     }

test/ModuleInterface/package_interface_disable_package_name.swift

@@ -17,14 +17,21 @@
 
 // CHECK-PUBLIC-NOT: -package-name foopkg
 // CHECK-PUBLIC-NOT: -package-name barpkg
+// CHECK-PUBLIC-NOT: pkgVar
 // CHECK-PRIVATE-NOT: -package-name foopkg
 // CHECK-PRIVATE-NOT: -package-name barpkg
+// CHECK-PRIVATE-NOT: pkgVar
 // CHECK-PACKAGE-NOT: -package-name foopkg
 
 // CHECK-PUBLIC:  -enable-library-evolution -swift-version 6 -module-name Bar
 // CHECK-PRIVATE:  -enable-library-evolution -swift-version 6 -module-name Bar
 // CHECK-PACKAGE:  -enable-library-evolution -swift-version 6 -module-name Bar -package-name barpkg
 
+/// Typechecking interface files (without package-name in non-package interface) should succeed.
+// RUN: %target-swift-frontend -typecheck-module-from-interface %t/Bar.swiftinterface
+// RUN: %target-swift-frontend -typecheck-module-from-interface %t/Bar.private.swiftinterface -module-name Bar
+// RUN: %target-swift-frontend -typecheck-module-from-interface %t/Bar.package.swiftinterface -module-name Bar
+
 /// Verify building modules from non-package interfaces succeeds without the package-name flag.
 // RUN: %target-swift-frontend -compile-module-from-interface %t/Bar.swiftinterface -o %t/Bar.swiftmodule -module-name Bar
 // RUN: %target-swift-frontend -typecheck %t/Use.swift -I %t -verify
@@ -71,8 +78,13 @@
 // RUN: %target-swift-frontend -typecheck %t/Use.swift -I %t -package-name barpkg -experimental-package-interface-load -verify
 
 //--- Bar.swift
-public struct PubStruct {}
+public struct PubStruct {
+  public var pubVar: Int
+  package var pkgVar: Int
+}
+
 @_spi(bar) public struct SPIStruct {}
+
 package struct PkgStruct {}
 
 @usableFromInline