Look at transitive imports when checking for @_predatesConcurrency imports

Author: DougGregor

lib/Sema/TypeCheckConcurrency.cpp

@@ -20,6 +20,7 @@
 #include "swift/Strings.h"
 #include "swift/AST/ASTWalker.h"
 #include "swift/AST/GenericEnvironment.h"
+#include "swift/AST/ImportCache.h"
 #include "swift/AST/Initializer.h"
 #include "swift/AST/ParameterList.h"
 #include "swift/AST/ProtocolConformance.h"
@@ -686,11 +687,23 @@ static Optional<AttributedImport<ImportedModule>> findImportFor(
   if (!fromSourceFile)
     return None;
 
+  // Look to see if the owning module was directly imported.
   for (const auto &import : fromSourceFile->getImports()) {
     if (import.module.importedModule == nominalModule)
       return import;
   }
 
+  // Now look for transitive imports.
+  auto &importCache = nominal->getASTContext().getImportCache();
+  for (const auto &import : fromSourceFile->getImports()) {
+    auto &importSet = importCache.getImportSet(import.module.importedModule);
+    for (const auto &transitive : importSet.getTransitiveImports()) {
+      if (transitive.importedModule == nominalModule) {
+        return import;
+      }
+    }
+  }
+
   return None;
 }
 

test/ClangImporter/predates_concurrency_import_swift6.swift

@@ -0,0 +1,17 @@
+// RUN: %empty-directory(%t)
+
+// FIXME: BEGIN -enable-source-import hackaround
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck -I %S/Inputs/custom-modules %s -verify -swift-version 6
+
+// REQUIRES: objc_interop
+// REQUIRES: concurrency
+// REQUIRES: asserts
+
+@_predatesConcurrency import Foundation
+
+func acceptSendable<T: Sendable>(_: T) { }
+
+func useSendable(ns: NSString) {
+  // Note: warning below is downgraded due to @_predatesConcurrency
+  acceptSendable(ns) // expected-warning{{type 'NSString' does not conform to the 'Sendable' protocol}}
+}