[clang] Allow generating module interfaces with parsing errors

clang/include/clang/Serialization/ASTWriter.h

@@ -997,13 +997,15 @@ class CXX20ModulesGenerator : public PCHGenerator {
   virtual Module *getEmittingModule(ASTContext &Ctx) override;
 
   CXX20ModulesGenerator(Preprocessor &PP, InMemoryModuleCache &ModuleCache,
-                        StringRef OutputFile, bool GeneratingReducedBMI);
+                        StringRef OutputFile, bool GeneratingReducedBMI,
+                        bool AllowASTWithErrors);
 
 public:
   CXX20ModulesGenerator(Preprocessor &PP, InMemoryModuleCache &ModuleCache,
-                        StringRef OutputFile)
+                        StringRef OutputFile, bool AllowASTWithErrors = false)
       : CXX20ModulesGenerator(PP, ModuleCache, OutputFile,
-                              /*GeneratingReducedBMI=*/false) {}
+                              /*GeneratingReducedBMI=*/false,
+                              AllowASTWithErrors) {}
 
   void HandleTranslationUnit(ASTContext &Ctx) override;
 };
@@ -1013,9 +1015,10 @@ class ReducedBMIGenerator : public CXX20ModulesGenerator {
 
 public:
   ReducedBMIGenerator(Preprocessor &PP, InMemoryModuleCache &ModuleCache,
-                      StringRef OutputFile)
+                      StringRef OutputFile, bool AllowASTWithErrors = false)
       : CXX20ModulesGenerator(PP, ModuleCache, OutputFile,
-                              /*GeneratingReducedBMI=*/true) {}
+                              /*GeneratingReducedBMI=*/true,
+                              AllowASTWithErrors) {}
 };
 
 /// If we can elide the definition of \param D in reduced BMI.

clang/lib/Frontend/FrontendActions.cpp

@@ -279,12 +279,14 @@ GenerateModuleInterfaceAction::CreateASTConsumer(CompilerInstance &CI,
       !CI.getFrontendOpts().ModuleOutputPath.empty()) {
     Consumers.push_back(std::make_unique<ReducedBMIGenerator>(
         CI.getPreprocessor(), CI.getModuleCache(),
-        CI.getFrontendOpts().ModuleOutputPath));
+        CI.getFrontendOpts().ModuleOutputPath,
+        +CI.getFrontendOpts().AllowPCMWithCompilerErrors));
   }
 
   Consumers.push_back(std::make_unique<CXX20ModulesGenerator>(
       CI.getPreprocessor(), CI.getModuleCache(),
-      CI.getFrontendOpts().OutputFile));
+      CI.getFrontendOpts().OutputFile,
+      +CI.getFrontendOpts().AllowPCMWithCompilerErrors));
 
   return std::make_unique<MultiplexConsumer>(std::move(Consumers));
 }

clang/lib/Serialization/GeneratePCH.cpp

@@ -102,12 +102,13 @@ void PCHGenerator::anchor() {}
 CXX20ModulesGenerator::CXX20ModulesGenerator(Preprocessor &PP,
                                              InMemoryModuleCache &ModuleCache,
                                              StringRef OutputFile,
-                                             bool GeneratingReducedBMI)
+                                             bool GeneratingReducedBMI,
+                                             bool AllowASTWithErrors)
     : PCHGenerator(
           PP, ModuleCache, OutputFile, llvm::StringRef(),
           std::make_shared<PCHBuffer>(),
           /*Extensions=*/ArrayRef<std::shared_ptr<ModuleFileExtension>>(),
-          /*AllowASTWithErrors*/ false, /*IncludeTimestamps=*/false,
+          AllowASTWithErrors, /*IncludeTimestamps=*/false,
           /*BuildingImplicitModule=*/false, /*ShouldCacheASTInMemory=*/false,
           GeneratingReducedBMI) {}
 

clang/test/Modules/pcm-with-errors.cpp

@@ -0,0 +1,26 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: cd %t
+
+// RUN: %clang_cc1 -std=c++23 m.cppm -emit-module-interface -o m.pcm -fallow-pcm-with-compiler-errors -verify
+// RUN: %clang_cc1 -std=c++23 main.cpp -fmodule-file=m=m.pcm -verify -fallow-pcm-with-compiler-errors -verify
+
+// RUN: %clang_cc1 -std=c++23 m.cppm -fmodules-reduced-bmi -emit-module-interface -o m.pcm -fallow-pcm-with-compiler-errors -verify
+// RUN: %clang_cc1 -std=c++23 main.cpp -fmodule-file=m=m.pcm -verify -fallow-pcm-with-compiler-errors -verify
+
+//--- m.cppm
+export module m;
+
+export int f() {
+  return 0;
+}
+
+export struct Foo {
+  __Int bar; // expected-error {{unknown type name '__Int'}}
+};
+
+//--- main.cpp
+// expected-no-diagnostics
+import m; // ok
+
+static_assert(__is_same(decltype(f), int())); // ok