Improve PCH handling (#136)

src/Compiler/Module.cpp

@@ -97,33 +97,16 @@ std::string scanModuleName(CompilationParams& params) {
 }
 
 std::expected<ModuleInfo, std::string> scanModule(CompilationParams& params) {
-    struct ModuleCollector : public clang::PPCallbacks {
-        ModuleInfo& info;
-
-        ModuleCollector(ModuleInfo& info) : info(info) {}
-
-        void moduleImport(clang::SourceLocation importLoc,
-                          clang::ModuleIdPath path,
-                          const clang::Module* imported) override {
-            assert(path.size() == 1);
-            info.mods.emplace_back(path[0].first->getName());
-        }
-    };
-
     ModuleInfo info;
-    clang::PreprocessOnlyAction action;
-    auto instance = impl::createInstance(params);
-
-    if(!action.BeginSourceFile(*instance, instance->getFrontendOpts().Inputs[0])) {
-        return std::unexpected("Failed to begin source file");
+    auto AST = preprocess(params);
+    if(!AST) {
+        return std::unexpected(AST.error());
     }
 
-    auto& pp = instance->getPreprocessor();
+    auto&& pp = AST->pp();
 
-    pp.addPPCallbacks(std::make_unique<ModuleCollector>(info));
-
-    if(auto error = action.Execute()) {
-        return std::unexpected(std::format("{}", error));
+    for(auto& import: AST->directives()[AST->getInterestedFile()].imports) {
+        info.mods.emplace_back(import.name);
     }
 
     if(pp.isInNamedModule()) {