Refactor: add severity as explicit field for diagnostics

Each error type listed in error.h has a severity. The severity is
implicitly described by the first message. I think this is awkward.

Make the severity explicitly a separate field. This will let us replace
ERROR/WARNING/NOTE with a single MESSAGE macro in the future.

This commit should not change behavior.

Author: strager

src/buffering-error-reporter.cpp

@@ -21,7 +21,7 @@ struct buffering_error_reporter::impl {
     union underlying_error {
       explicit underlying_error() noexcept {}
 
-#define QLJS_ERROR_TYPE(name, code, struct_body, format)             \
+#define QLJS_ERROR_TYPE(name, code, severity, struct_body, format)   \
   ::quick_lint_js::name name;                                        \
   static_assert(std::is_trivially_copyable_v<::quick_lint_js::name>, \
                 #name " should be trivially copyable");
@@ -58,7 +58,7 @@ buffering_error_reporter::~buffering_error_reporter() = default;
 
 void buffering_error_reporter::report_impl(error_type type, void *error) {
   static constexpr unsigned char error_sizes[] = {
-#define QLJS_ERROR_TYPE(name, code, struct_body, format) \
+#define QLJS_ERROR_TYPE(name, code, severity, struct_body, format) \
   sizeof(::quick_lint_js::name),
       QLJS_X_ERROR_TYPES
 #undef QLJS_ERROR_TYPE

src/diagnostic.cpp

@@ -40,7 +40,9 @@ constexpr void strcpy(char* out, const char* in) noexcept {
 template <class Error>
 class diagnostic_info_builder {
  public:
-  constexpr explicit diagnostic_info_builder(const char* code) {
+  constexpr explicit diagnostic_info_builder(const char* code,
+                                             diagnostic_severity sev) {
+    this->info_.severity = sev;
     strcpy(this->info_.code, code);
   }
 
@@ -49,6 +51,16 @@ class diagnostic_info_builder {
   constexpr diagnostic_info_builder add(diagnostic_severity sev,
                                         const translatable_message& message,
                                         const Args&... arg_infos) {
+    if (this->current_message_index_ == 0) {
+      if (sev != this->info_.severity) {
+#if __cpp_constexpr >= 201907L && !defined(_MSC_VER)
+        // If you see an error with the following line, error.h contains a
+        // QLJS_ERROR_TYPE call with inconsistent diagnostic severities.
+        asm("");
+#endif
+      }
+    }
+
     diagnostic_message_info& message_info =
         this->info_.messages[this->current_message_index_++];
     message_info.format = message;
@@ -124,13 +136,14 @@ struct diagnostic_info_for_error;
 #define NOTE(message_format, ...) \
   .add(diagnostic_severity::note, message_format, MAKE_ARGS(__VA_ARGS__))
 
-#define QLJS_ERROR_TYPE(name, code, struct_body, format_call)                \
+#define QLJS_ERROR_TYPE(name, code, severity, struct_body, format_call)      \
   template <>                                                                \
   struct diagnostic_info_for_error<name> {                                   \
     using error_class = name;                                                \
                                                                              \
     static DIAGNOSTIC_CONSTEXPR_IF_POSSIBLE diagnostic_info get() noexcept { \
-      return diagnostic_info_builder<name>(code) format_call.build();        \
+      return diagnostic_info_builder<name>(code, severity)                   \
+          format_call.build();                                               \
     }                                                                        \
   };
 QLJS_X_ERROR_TYPES
@@ -139,7 +152,7 @@ QLJS_X_ERROR_TYPES
 
 DIAGNOSTIC_CONSTEXPR_IF_POSSIBLE const diagnostic_info
     all_diagnostic_infos[] = {
-#define QLJS_ERROR_TYPE(name, code, struct_body, format_call) \
+#define QLJS_ERROR_TYPE(name, code, severity, struct_body, format_call) \
   diagnostic_info_for_error<name>::get(),
         QLJS_X_ERROR_TYPES
 #undef QLJS_ERROR_TYPE

src/error-debug.cpp

@@ -8,8 +8,8 @@
 namespace quick_lint_js {
 std::ostream& operator<<(std::ostream& out, error_type type) {
   switch (type) {
-#define QLJS_ERROR_TYPE(name, code, struct_body, format_call) \
-  case error_type::name:                                      \
+#define QLJS_ERROR_TYPE(name, code, severity, struct_body, format_call) \
+  case error_type::name:                                                \
     return out << #name;
     QLJS_X_ERROR_TYPES
 #undef QLJS_ERROR_TYPE

src/quick-lint-js/diagnostic.h

@@ -48,6 +48,7 @@ struct diagnostic_message_info {
 
 struct diagnostic_info {
   char code[6];
+  diagnostic_severity severity QLJS_WORK_AROUND_GCC_BUG_105191;
   // If we support more than two infos (i.e. more than one note), the VS Code
   // plugin needs to be updated. See NOTE(multiple notes).
   diagnostic_message_info messages[2];

src/quick-lint-js/error-reporter.h

@@ -19,9 +19,9 @@ class error_reporter {
 
   virtual ~error_reporter() = default;
 
-#define QLJS_ERROR_TYPE(name, code, struct_body, format)   \
-  void report(name error) {                                \
-    this->report_impl(error_type_from_type<name>, &error); \
+#define QLJS_ERROR_TYPE(name, code, severity, struct_body, format) \
+  void report(name error) {                                        \
+    this->report_impl(error_type_from_type<name>, &error);         \
   }
   QLJS_X_ERROR_TYPES
 #undef QLJS_ERROR_TYPE