Improve PCH handling (#136)

include/Compiler/Compilation.h

@@ -45,15 +45,8 @@ struct CompilationParams {
     }
 };
 
-namespace impl {
-
-/// Create a compiler invocation from the given compilation parameters.
-std::unique_ptr<clang::CompilerInvocation> createInvocation(CompilationParams& params);
-
-/// Create a compiler instance from the given compilation parameters.
-std::unique_ptr<clang::CompilerInstance> createInstance(CompilationParams& params);
-
-}  // namespace impl
+/// Only preprocess ths source flie.
+std::expected<ASTInfo, std::string> preprocess(CompilationParams& params);
 
 /// Build AST from given file path and content. If pch or pcm provided, apply them to the compiler.
 /// Note this function will not check whether we need to update the PCH or PCM, caller should check

include/Compiler/Directive.h

@@ -115,12 +115,25 @@ struct Pragma {
     clang::SourceLocation loc;
 };
 
+struct Import {
+    /// The name of imported module.
+    std::string name;
+
+    /// The location of import keyword, may comes from macro expansion.
+    clang::SourceLocation location;
+
+    /// The locations of tokens that make up the token name, may comes
+    /// from macro expansion.
+    std::vector<clang::SourceLocation> name_locations;
+};
+
 struct Directive {
     std::vector<Include> includes;
     std::vector<HasInclude> hasIncludes;
     std::vector<Condition> conditions;
     std::vector<MacroRef> macros;
     std::vector<Pragma> pragmas;
+    std::vector<Import> imports;
 
     /// Tell preprocessor to collect directives information and store them in `directives`.
     static void attach(clang::Preprocessor& pp,