feat(typescript): support 'override' properties in classes

docs/CHANGELOG.md

@@ -48,6 +48,7 @@ Semantic Versioning.
   * Assigning to a class now reports [E0003][] ("cannot assign to class").
   * Definite assignment assertions (`!` after a variable name in `let` or `var`)
     is now supported.
+  * `override` is now supported in classes.
   * Abstract constructor types (such as `abstract new () => C`) are now
     supported.
   * `export class { m(); }` in a .d.ts file no longer falsely reports [E0172][]

po/messages.pot

@@ -1433,6 +1433,10 @@ msgstr ""
 msgid "this required parameter appears after the optional parameter"
 msgstr ""
 
+#: src/quick-lint-js/diag/diagnostic-metadata-generated.cpp
+msgid "override properties are not allowed in interfaces"
+msgstr ""
+
 #: src/quick-lint-js/diag/diagnostic-metadata-generated.cpp
 msgid "integer cannot be represented and will be rounded to '{1}'"
 msgstr ""

src/quick-lint-js/diag/diagnostic-metadata-generated.cpp

@@ -3741,6 +3741,20 @@ const QLJS_CONSTINIT Diagnostic_Info all_diagnostic_infos[] = {
       },
     },
 
+    // Diag_Override_Property_Not_Allowed_In_Interface
+    {
+      .code = 449,
+      .severity = Diagnostic_Severity::error,
+      .message_formats = {
+        QLJS_TRANSLATABLE("override properties are not allowed in interfaces"),
+      },
+      .message_args = {
+        {
+          Diagnostic_Message_Arg_Info(offsetof(Diag_Override_Property_Not_Allowed_In_Interface, override_keyword), Diagnostic_Arg_Type::source_code_span),
+        },
+      },
+    },
+
     // Diag_Integer_Literal_Will_Lose_Precision
     {
       .code = 212,

src/quick-lint-js/diag/diagnostic-metadata-generated.h

@@ -260,6 +260,7 @@ namespace quick_lint_js {
   QLJS_DIAG_TYPE_NAME(Diag_Optional_Arrow_Parameter_With_Type_Annotation_Requires_Parentheses) \
   QLJS_DIAG_TYPE_NAME(Diag_Optional_Parameter_Cannot_Have_Initializer) \
   QLJS_DIAG_TYPE_NAME(Diag_Optional_Parameter_Cannot_Be_Followed_By_Required_Parameter) \
+  QLJS_DIAG_TYPE_NAME(Diag_Override_Property_Not_Allowed_In_Interface) \
   QLJS_DIAG_TYPE_NAME(Diag_Integer_Literal_Will_Lose_Precision) \
   QLJS_DIAG_TYPE_NAME(Diag_Parameter_Decorator_In_Abstract_Method) \
   QLJS_DIAG_TYPE_NAME(Diag_Parameter_Decorator_In_Declare_Class) \
@@ -469,7 +470,7 @@ namespace quick_lint_js {
   /* END */
 // clang-format on
 
-inline constexpr int Diag_Type_Count = 455;
+inline constexpr int Diag_Type_Count = 456;
 
 extern const Diagnostic_Info all_diagnostic_infos[Diag_Type_Count];
 }

src/quick-lint-js/diag/diagnostic-types-2.h

@@ -1924,6 +1924,13 @@ struct Diag_Optional_Parameter_Cannot_Be_Followed_By_Required_Parameter {
   Source_Code_Span required_parameter;
 };
 
+struct Diag_Override_Property_Not_Allowed_In_Interface {
+  [[qljs::diag("E0449", Diagnostic_Severity::error)]]  //
+  [[qljs::message("override properties are not allowed in interfaces",
+                  ARG(override_keyword))]]  //
+  Source_Code_Span override_keyword;
+};
+
 struct Diag_Integer_Literal_Will_Lose_Precision {
   [[qljs::diag("E0212", Diagnostic_Severity::warning)]]  //
   [[qljs::message("integer cannot be represented and will be rounded to '{1}'",

src/quick-lint-js/fe/parse-class.cpp

@@ -359,6 +359,7 @@ void Parser::parse_and_visit_class_or_interface_member(
         case Token_Type::kw_async:
         case Token_Type::kw_declare:
         case Token_Type::kw_function:
+        case Token_Type::kw_override:
         case Token_Type::kw_private:
         case Token_Type::kw_protected:
         case Token_Type::kw_public:
@@ -1178,12 +1179,14 @@ void Parser::parse_and_visit_class_or_interface_member(
       error_if_decorator_not_first();
       error_if_abstract_with_decorator();
       error_if_abstract_or_static_after_accessor();
+      error_if_override_in_wrong_order();
       error_if_conflicting_modifiers();
       error_if_readonly_in_not_typescript();
       error_if_declare_in_not_typescript();
       error_if_declare_in_interface();
       error_if_declare_of_private_identifier(field_name);
       error_if_declare_field_with_assignment_assertion();
+      error_if_override_in_interface();
       error_if_accessor_in_interface();
       error_if_static_in_interface();
       error_if_static_abstract();
@@ -1204,6 +1207,8 @@ void Parser::parse_and_visit_class_or_interface_member(
       error_if_access_specifier_not_first_in_method();
       error_if_decorator_not_first();
       error_if_abstract_with_decorator();
+      error_if_override_in_wrong_order();
+      error_if_override_in_interface();
       error_if_static_in_interface();
       error_if_static_abstract();
       error_if_optional_in_not_typescript();
@@ -1554,6 +1559,7 @@ void Parser::parse_and_visit_class_or_interface_member(
         check_if_access_specifier_precedes_given_modifiers(
             Span<const Token_Type>({
                 Token_Type::kw_accessor,
+                Token_Type::kw_override,
                 Token_Type::kw_readonly,
                 Token_Type::kw_static,
             }));
@@ -1564,8 +1570,9 @@ void Parser::parse_and_visit_class_or_interface_member(
       if (p->options_.typescript && !modifiers.empty()) {
         check_if_access_specifier_precedes_given_modifiers(
             Span<const Token_Type>({
-                Token_Type::kw_static,
                 Token_Type::kw_async,
+                Token_Type::kw_override,
+                Token_Type::kw_static,
             }));
       }
     }
@@ -1640,6 +1647,44 @@ void Parser::parse_and_visit_class_or_interface_member(
                 });
           }
         }
+
+        if (const Modifier *override_modifier =
+                this->find_modifier(Token_Type::kw_override)) {
+          if (override_modifier > accessor_modifier) {
+            p->diag_reporter_->report(
+                Diag_Class_Modifier_Must_Preceed_Other_Modifier{
+                    .expected_first_modifier = override_modifier->span,
+                    .expected_second_modifier = accessor_modifier->span,
+                });
+          }
+        }
+      }
+    }
+
+    void error_if_override_in_wrong_order() {
+      if (const Modifier *override_modifier =
+              this->find_modifier(Token_Type::kw_override)) {
+        if (const Modifier *static_modifier =
+                this->find_modifier(Token_Type::kw_static)) {
+          if (static_modifier > override_modifier) {
+            p->diag_reporter_->report(
+                Diag_Class_Modifier_Must_Preceed_Other_Modifier{
+                    .expected_first_modifier = static_modifier->span,
+                    .expected_second_modifier = override_modifier->span,
+                });
+          }
+        }
+
+        if (const Modifier *abstract_modifier =
+                this->find_modifier(Token_Type::kw_abstract)) {
+          if (abstract_modifier > override_modifier) {
+            p->diag_reporter_->report(
+                Diag_Class_Modifier_Must_Preceed_Other_Modifier{
+                    .expected_first_modifier = abstract_modifier->span,
+                    .expected_second_modifier = override_modifier->span,
+                });
+          }
+        }
       }
     }
 
@@ -1686,6 +1731,18 @@ void Parser::parse_and_visit_class_or_interface_member(
       }
     }
 
+    void error_if_override_in_interface() {
+      if (is_interface) {
+        if (const Modifier *override_modifier =
+                find_modifier(Token_Type::kw_override)) {
+          p->diag_reporter_->report(
+              Diag_Override_Property_Not_Allowed_In_Interface{
+                  .override_keyword = override_modifier->span,
+              });
+        }
+      }
+    }
+
     void error_if_static_in_interface() {
       if (is_interface) {
         if (const Modifier *static_modifier =

src/quick-lint-js/i18n/translation-table-generated.cpp

@@ -490,6 +490,7 @@ const Translation_Table translation_data = {
         {0, 0, 0, 68, 0, 64},                //
         {0, 0, 0, 0, 0, 40},                 //
         {0, 0, 0, 0, 0, 34},                 //
+        {0, 0, 0, 0, 0, 50},                 //
         {0, 0, 0, 0, 0, 10},                 //
         {0, 0, 0, 0, 0, 51},                 //
         {0, 0, 0, 0, 0, 56},                 //
@@ -2354,6 +2355,7 @@ const Translation_Table translation_data = {
         u8"overload signature must match modifiers on this overload method\0"
         u8"overloaded function '{0}' declared here\0"
         u8"overloaded method is marked '{0}'\0"
+        u8"override properties are not allowed in interfaces\0"
         u8"parameter\0"
         u8"parameter decorator must be before other modifiers\0"
         u8"parameter decorators are not allowed in 'declare class'\0"

src/quick-lint-js/i18n/translation-table-generated.h

@@ -18,8 +18,8 @@ namespace quick_lint_js {
 using namespace std::literals::string_view_literals;
 
 constexpr std::uint32_t translation_table_locale_count = 5;
-constexpr std::uint16_t translation_table_mapping_table_size = 599;
-constexpr std::size_t translation_table_string_table_size = 82152;
+constexpr std::uint16_t translation_table_mapping_table_size = 600;
+constexpr std::size_t translation_table_string_table_size = 82202;
 constexpr std::size_t translation_table_locale_table_size = 35;
 
 QLJS_CONSTEVAL std::uint16_t translation_table_const_look_up(
@@ -504,6 +504,7 @@ QLJS_CONSTEVAL std::uint16_t translation_table_const_look_up(
           "overload signature must match modifiers on this overload method"sv,
           "overloaded function '{0}' declared here"sv,
           "overloaded method is marked '{0}'"sv,
+          "override properties are not allowed in interfaces"sv,
           "parameter"sv,
           "parameter decorator must be before other modifiers"sv,
           "parameter decorators are not allowed in 'declare class'"sv,

src/quick-lint-js/i18n/translation-table-test-generated.h

@@ -27,7 +27,7 @@ struct Translated_String {
 };
 
 // clang-format off
-inline const Translated_String test_translation_table[598] = {
+inline const Translated_String test_translation_table[599] = {
     {
         "\"global-groups\" entries must be strings"_translatable,
         u8"\"global-groups\" entries must be strings",
@@ -5286,6 +5286,17 @@ inline const Translated_String test_translation_table[598] = {
             u8"overloaded method is marked '{0}'",
         },
     },
+    {
+        "override properties are not allowed in interfaces"_translatable,
+        u8"override properties are not allowed in interfaces",
+        {
+            u8"override properties are not allowed in interfaces",
+            u8"override properties are not allowed in interfaces",
+            u8"override properties are not allowed in interfaces",
+            u8"override properties are not allowed in interfaces",
+            u8"override properties are not allowed in interfaces",
+        },
+    },
     {
         "parameter"_translatable,
         u8"parameter",

test/test-parse-typescript-class.cpp

@@ -1407,6 +1407,98 @@ TEST_F(Test_Parse_TypeScript_Class,
   }
 }
 
+TEST_F(Test_Parse_TypeScript_Class, override_property) {
+  {
+    Spy_Visitor p = test_parse_and_visit_module(
+        u8"class C extends B { override method() {} }"_sv, no_diags,
+        typescript_options);
+    EXPECT_THAT(p.visits, ElementsAreArray({
+                              "visit_enter_class_scope",          // C
+                              "visit_variable_use",               // B
+                              "visit_enter_class_scope_body",     // {
+                              "visit_enter_function_scope",       // method
+                              "visit_enter_function_scope_body",  // {
+                              "visit_exit_function_scope",        // }
+                              "visit_property_declaration",       // method
+                              "visit_exit_class_scope",           // }
+                              "visit_variable_declaration",       // C
+                              "visit_end_of_module",
+                          }));
+  }
+
+  {
+    Spy_Visitor p = test_parse_and_visit_module(
+        u8"class C extends B { override field; }"_sv, no_diags,
+        typescript_options);
+    EXPECT_THAT(p.visits, ElementsAreArray({
+                              "visit_enter_class_scope",       // C
+                              "visit_variable_use",            // B
+                              "visit_enter_class_scope_body",  // {
+                              "visit_property_declaration",    // field
+                              "visit_exit_class_scope",        // }
+                              "visit_variable_declaration",    // C
+                              "visit_end_of_module",
+                          }));
+  }
+
+  {
+    Spy_Visitor p = test_parse_and_visit_module(
+        u8"class C extends B { override accessor prop; }"_sv, no_diags,
+        typescript_options);
+    EXPECT_THAT(p.visits, ElementsAreArray({
+                              "visit_enter_class_scope",       // C
+                              "visit_variable_use",            // B
+                              "visit_enter_class_scope_body",  // {
+                              "visit_property_declaration",    // prop
+                              "visit_exit_class_scope",        // }
+                              "visit_variable_declaration",    // C
+                              "visit_end_of_module",
+                          }));
+  }
+
+  test_parse_and_visit_module(
+      u8"class C extends B { static override method() {} }"_sv, no_diags,
+      typescript_options);
+}
+
+TEST_F(Test_Parse_TypeScript_Class, override_keyword_order) {
+  test_parse_and_visit_module(
+      u8"class C extends B { override static method() {} }"_sv,  //
+      u8"                             ^^^^^^ Diag_Class_Modifier_Must_Preceed_Other_Modifier.expected_first_modifier\n"_diag  //
+      u8"                    ^^^^^^^^ .expected_second_modifier"_diag,
+      typescript_options);
+  test_parse_and_visit_module(
+      u8"class C extends B { accessor override prop; }"_sv,  //
+      u8"                             ^^^^^^^^ Diag_Class_Modifier_Must_Preceed_Other_Modifier.expected_first_modifier\n"_diag  //
+      u8"                    ^^^^^^^^ .expected_second_modifier"_diag,
+      typescript_options);
+  test_parse_and_visit_module(
+      u8"class C extends B { override public method() {} }"_sv,  //
+      u8"                             ^^^^^^ Diag_Access_Specifier_Must_Precede_Other_Modifiers.second_modifier\n"_diag  //
+      u8"                    ^^^^^^^^ .first_modifier"_diag,
+      typescript_options);
+  test_parse_and_visit_module(
+      u8"class C extends B { override public field; }"_sv,  //
+      u8"                             ^^^^^^ Diag_Access_Specifier_Must_Precede_Other_Modifiers.second_modifier\n"_diag  //
+      u8"                    ^^^^^^^^ .first_modifier"_diag,
+      typescript_options);
+  test_parse_and_visit_module(
+      u8"abstract class C extends B { override abstract field; }"_sv,  //
+      u8"                                      ^^^^^^^^ Diag_Class_Modifier_Must_Preceed_Other_Modifier.expected_first_modifier\n"_diag  //
+      u8"                             ^^^^^^^^ .expected_second_modifier"_diag,
+      typescript_options);
+}
+
+TEST_F(Test_Parse_TypeScript_Class,
+       override_method_prohibits_newline_after_override_keyword) {
+  {
+    Spy_Visitor p = test_parse_and_visit_statement(
+        u8"class C { override\n m() { } }"_sv, no_diags, typescript_options);
+    EXPECT_THAT(p.property_declarations,
+                ElementsAreArray({u8"override", u8"m"}));
+  }
+}
+
 TEST_F(Test_Parse_TypeScript_Class, accessor_field) {
   {
     Spy_Visitor p = test_parse_and_visit_statement(

test/test-parse-typescript-interface.cpp

@@ -1610,6 +1610,13 @@ TEST_F(Test_Parse_TypeScript_Interface,
                           }));
   }
 }
+
+TEST_F(Test_Parse_TypeScript_Interface, override_is_not_allowed) {
+  test_parse_and_visit_statement(
+      u8"interface I { override method(); }"_sv,
+      u8"              ^^^^^^^^ Diag_Override_Property_Not_Allowed_In_Interface"_diag,
+      typescript_options);
+}
 }
 }