Merge pull request #72023 from beccadax/lazy-objc-workaround

Add workaround flag for lazy import-as-member

Author: beccadax

include/swift/AST/ClangModuleLoader.h

@@ -144,6 +144,7 @@ class ClangModuleLoader : public ModuleLoader {
   virtual clang::Sema &getClangSema() const = 0;
   virtual const clang::CompilerInstance &getClangInstance() const = 0;
   virtual void printStatistics() const = 0;
+  virtual void dumpSwiftLookupTables() const = 0;
 
   /// Returns the module that contains imports and declarations from all loaded
   /// Objective-C header files.

include/swift/Basic/LangOptions.h

@@ -380,6 +380,11 @@ namespace swift {
     /// Enable experimental eager Clang module diagnostics.
     bool EnableExperimentalEagerClangModuleDiagnostics = false;
 
+    /// Force ClangImporter's import-as-member extensions to load thier members
+    /// immediately, bypassing their SwiftLookupTables. This emulates an
+    /// implementation quirk of previous compilers.
+    bool DisableNamedLazyImportAsMemberLoading = false;
+
     /// Enable inference of Sendable conformances for public types.
     bool EnableInferPublicSendable = false;
 

include/swift/ClangImporter/ClangImporter.h

@@ -538,7 +538,7 @@ class ClangImporter final : public ClangModuleLoader {
   void printStatistics() const override;
 
   /// Dump Swift lookup tables.
-  void dumpSwiftLookupTables();
+  void dumpSwiftLookupTables() const override;
 
   /// Given the path of a Clang module, collect the names of all its submodules.
   /// Calling this function does not load the module.

include/swift/Frontend/FrontendOptions.h

@@ -280,6 +280,10 @@ class FrontendOptions {
   /// termination.
   bool PrintClangStats = false;
 
+  /// Indicates whether or not the Clang importer should dump lookup tables
+  /// upon termination.
+  bool DumpClangLookupTables = false;
+
   /// Indicates whether standard help should be shown.
   bool PrintHelp = false;
 

include/swift/Option/FrontendOptions.td

@@ -372,7 +372,13 @@ def debug_constraints_on_line_EQ : Joined<["-"], "debug-constraints-on-line=">,
   Alias<debug_constraints_on_line>;
 
 def disable_named_lazy_member_loading : Flag<["-"], "disable-named-lazy-member-loading">,
-  HelpText<"Disable per-name lazy member loading">;
+  HelpText<"Disable per-name lazy member loading (obsolete)">;
+
+def disable_named_lazy_import_as_member_loading :
+  Flag<["-"], "disable-named-lazy-import-as-member-loading">,
+  HelpText<"Import all of a type's import-as-member globals together, as Swift "
+           "5.10 and earlier did; temporary workaround for modules that are "
+           "sensitive to this change">;
 
 def dump_requirement_machine : Flag<["-"], "dump-requirement-machine">,
   HelpText<"Enables dumping rewrite systems from the generics implementation">;
@@ -580,6 +586,10 @@ def stack_promotion_limit : Separate<["-"], "stack-promotion-limit">,
 def dump_clang_diagnostics : Flag<["-"], "dump-clang-diagnostics">,
   HelpText<"Dump Clang diagnostics to stderr">;
 
+def dump_clang_lookup_tables : Flag<["-"], "dump-clang-lookup-tables">,
+  HelpText<"Dump the importer's Swift-name-to-Clang-name lookup tables to "
+           "stderr">;
+
 def disable_modules_validate_system_headers : Flag<["-"], "disable-modules-validate-system-headers">,
   HelpText<"Disable validating system headers in the Clang importer">;
 

lib/AST/NameLookup.cpp

@@ -1487,10 +1487,25 @@ void MemberLookupTable::addMembers(DeclRange members) {
   }
 }
 
+static bool shouldLoadMembersImmediately(ExtensionDecl *ext) {
+  assert(ext->hasLazyMembers());
+  if (ext->wasDeserialized() || ext->hasClangNode())
+    return false;
+
+  // This extension is lazy but is not deserialized or backed by a clang node,
+  // so it's a ClangImporter extension containing import-as-member globals.
+  // Historically, Swift forced these extensions to load their members
+  // immediately, bypassing the module's SwiftLookupTable. Using the
+  // SwiftLookupTable *ought* to work the same, but in practice it sometimes
+  // gives different results when a header is not properly modularized. Provide
+  // a flag to temporarily re-enable the old behavior.
+  return ext->getASTContext().LangOpts.DisableNamedLazyImportAsMemberLoading;
+}
+
 void MemberLookupTable::addExtension(ExtensionDecl *ext) {
   // If we can lazy-load this extension, only take the members we've loaded
   // so far.
-  if (ext->hasLazyMembers()) {
+  if (ext->hasLazyMembers() && !shouldLoadMembersImmediately(ext)) {
     addMembers(ext->getCurrentMembersWithoutLoading());
     clearLazilyCompleteCache();
     clearLazilyCompleteForMacroExpansionCache();

lib/ClangImporter/ClangImporter.cpp

@@ -6269,7 +6269,7 @@ EffectiveClangContext ClangImporter::Implementation::getEffectiveClangContext(
   return EffectiveClangContext();
 }
 
-void ClangImporter::dumpSwiftLookupTables() {
+void ClangImporter::dumpSwiftLookupTables() const {
   Impl.dumpSwiftLookupTables();
 }
 

lib/Frontend/ArgsToFrontendOptionsConverter.cpp

@@ -170,6 +170,8 @@ bool ArgsToFrontendOptionsConverter::convert(
   computeDebugTimeOptions();
   computeTBDOptions();
 
+  Opts.DumpClangLookupTables |= Args.hasArg(OPT_dump_clang_lookup_tables);
+
   Opts.CheckOnoneSupportCompleteness = Args.hasArg(OPT_check_onone_completeness);
 
   Opts.ParseStdlib |= Args.hasArg(OPT_parse_stdlib);

lib/Frontend/CompilerInvocation.cpp

@@ -626,6 +626,9 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
       !Args.hasArg(OPT_disable_experimental_clang_importer_diagnostics) &&
       Args.hasArg(OPT_enable_experimental_eager_clang_module_diagnostics);
 
+  Opts.DisableNamedLazyImportAsMemberLoading |=
+      Args.hasArg(OPT_disable_named_lazy_import_as_member_loading);
+
   Opts.DisableImplicitConcurrencyModuleImport |=
     Args.hasArg(OPT_disable_implicit_concurrency_module_import);
 

lib/FrontendTool/FrontendTool.cpp

@@ -1117,6 +1117,9 @@ static void performEndOfPipelineActions(CompilerInstance &Instance) {
   if (auto *stats = ctx.Stats)
     countASTStats(*stats, Instance);
 
+  if (opts.DumpClangLookupTables && ctx.getClangModuleLoader())
+    ctx.getClangModuleLoader()->dumpSwiftLookupTables();
+
   // Report mangling stats if there was no error.
   if (!ctx.hadError())
     Mangle::printManglingStats();