feat(typescript): improve diagnostic on '<<' in extends clause

The following TypeScript code is legal: class C<T> {} new C<<T>() => null>(); interface I<T> {} class D implements I< <T>() => null> {} interface I2 extends I< <T>() => null> {} But the following is not: interface I<T> {} class D implements I<<T>() => null> {} interface I2 extends I<<T>() => null> {} Report a nice diagnostic on the erroneous '<<' in these cases to help the programmer write correct TypeScript code.
quick-lint · Dec 12, 2023 · 64bfe94 · 64bfe94
1 parent b76c649
commit 64bfe94
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Showing 11 changed files with 113 additions and 5 deletions.
diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
@@ -27,6 +27,8 @@ Semantic Versioning.
     conditional expression with a function in the truthy branch.
     (`cond ? (t) : param => body` continues to be parsed as a conditional
     expression with a function in the falsy branch.)
+  * Using `<<` in an interface's `extends` clause or a class's `implements`
+    clause now reports [E0429][] instead of misleading diagnostics.
 
 ### Fixed
 
@@ -1318,6 +1320,7 @@ Beta release.
 [E0398]: https://quick-lint-js.com/errors/E0398/
 [E0426]: https://quick-lint-js.com/errors/E0426/
 [E0427]: https://quick-lint-js.com/errors/E0427/
+[E0429]: https://quick-lint-js.com/errors/E0429/
 [E0450]: https://quick-lint-js.com/errors/E0450/
 [E0451]: https://quick-lint-js.com/errors/E0451/
 [E0452]: https://quick-lint-js.com/errors/E0452/

diff --git a/po/messages.pot b/po/messages.pot
@@ -1537,6 +1537,10 @@ msgstr ""
 msgid "interfaces cannot contain static blocks"
 msgstr ""
 
+#: src/quick-lint-js/diag/diagnostic-metadata-generated.cpp
+msgid "space is required between '<' and '<' inside 'extends' clause"
+msgstr ""
+
 #: src/quick-lint-js/diag/diagnostic-metadata-generated.cpp
 msgid "'declare class' cannot contain static block"
 msgstr ""

diff --git a/src/quick-lint-js/diag/diagnostic-metadata-generated.cpp b/src/quick-lint-js/diag/diagnostic-metadata-generated.cpp
@@ -4573,6 +4573,20 @@ const QLJS_CONSTINIT Diagnostic_Info all_diagnostic_infos[] = {
       },
     },
 
+    // Diag_TypeScript_Generic_Less_Less_Not_Split
+    {
+      .code = 429,
+      .severity = Diagnostic_Severity::error,
+      .message_formats = {
+        QLJS_TRANSLATABLE("space is required between '<' and '<' inside 'extends' clause"),
+      },
+      .message_args = {
+        {
+          Diagnostic_Message_Arg_Info(offsetof(Diag_TypeScript_Generic_Less_Less_Not_Split, expected_space), Diagnostic_Arg_Type::source_code_span),
+        },
+      },
+    },
+
     // Diag_TypeScript_Declare_Class_Cannot_Contain_Static_Block_Statement
     {
       .code = 332,

diff --git a/src/quick-lint-js/diag/diagnostic-metadata-generated.h b/src/quick-lint-js/diag/diagnostic-metadata-generated.h
@@ -315,6 +315,7 @@ namespace quick_lint_js {
   QLJS_DIAG_TYPE_NAME(Diag_TypeScript_Inline_Type_Export_Not_Allowed_In_Type_Only_Export) \
   QLJS_DIAG_TYPE_NAME(Diag_TypeScript_Inline_Type_Import_Not_Allowed_In_Type_Only_Import) \
   QLJS_DIAG_TYPE_NAME(Diag_TypeScript_Interfaces_Cannot_Contain_Static_Blocks) \
+  QLJS_DIAG_TYPE_NAME(Diag_TypeScript_Generic_Less_Less_Not_Split) \
   QLJS_DIAG_TYPE_NAME(Diag_TypeScript_Declare_Class_Cannot_Contain_Static_Block_Statement) \
   QLJS_DIAG_TYPE_NAME(Diag_TypeScript_Declare_Field_Not_Allowed_In_JavaScript) \
   QLJS_DIAG_TYPE_NAME(Diag_TypeScript_Declare_Field_Cannot_Use_Private_Identifier) \
@@ -450,7 +451,7 @@ namespace quick_lint_js {
   /* END */
 // clang-format on
 
-inline constexpr int Diag_Type_Count = 436;
+inline constexpr int Diag_Type_Count = 437;
 
 extern const Diagnostic_Info all_diagnostic_infos[Diag_Type_Count];
 }

diff --git a/src/quick-lint-js/diag/diagnostic-types-2.h b/src/quick-lint-js/diag/diagnostic-types-2.h
@@ -2367,6 +2367,16 @@ struct Diag_TypeScript_Interfaces_Cannot_Contain_Static_Blocks {
   Source_Code_Span static_token;
 };
 
+struct Diag_TypeScript_Generic_Less_Less_Not_Split {
+  [[qljs::diag("E0429", Diagnostic_Severity::error)]]  //
+  // clang-format off
+  [[qljs::message("space is required between '<' and '<' inside 'extends' "
+                  "or 'implements' clause",
+                  ARG(expected_space))]]  //
+  // clang-format on
+  Source_Code_Span expected_space;
+};
+
 struct Diag_TypeScript_Declare_Class_Cannot_Contain_Static_Block_Statement {
   [[qljs::diag("E0332", Diagnostic_Severity::error)]]  //
   [[qljs::message("'declare class' cannot contain static block",

diff --git a/src/quick-lint-js/fe/parse-class.cpp b/src/quick-lint-js/fe/parse-class.cpp
@@ -2100,8 +2100,17 @@ void Parser::parse_and_visit_typescript_interface_reference(
     v.visit_variable_type_use(ident);
   }
 
-  if (this->peek().type == Token_Type::less) {
+  if (this->peek().type == Token_Type::less ||
+      this->peek().type == Token_Type::less_less) {
     // extends SomeType<Arg>
+    // extends SomeType< <T>() => ReturnType>
+    if (this->peek().type == Token_Type::less_less) {
+      // extends SomeType<<T>() => ReturnType>  // Invalid.
+      const Char8 *second_less = this->peek().begin + 1;
+      this->diag_reporter_->report(Diag_TypeScript_Generic_Less_Less_Not_Split{
+          .expected_space = Source_Code_Span::unit(second_less),
+      });
+    }
     this->parse_and_visit_typescript_generic_arguments(v);
   }
 }

diff --git a/src/quick-lint-js/i18n/translation-table-generated.cpp b/src/quick-lint-js/i18n/translation-table-generated.cpp
@@ -457,6 +457,7 @@ const Translation_Table translation_data = {
         {0, 0, 0, 0, 0, 9},                  //
         {11, 9, 0, 10, 0, 42},               //
         {0, 0, 0, 0, 0, 19},                 //
+        {0, 0, 0, 0, 0, 62},                 //
         {0, 0, 0, 0, 0, 19},                 //
         {0, 0, 0, 0, 0, 41},                 //
         {0, 0, 0, 0, 0, 25},                 //
@@ -2259,6 +2260,7 @@ const Translation_Table translation_data = {
         u8"see here\0"
         u8"semicolon is not allowed after decorators\0"
         u8"something happened\0"
+        u8"space is required between '<' and '<' inside 'extends' clause\0"
         u8"spread starts here\0"
         u8"spread tuple elements cannot be optional\0"
         u8"static block starts here\0"

diff --git a/src/quick-lint-js/i18n/translation-table-generated.h b/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 = 532;
-constexpr std::size_t translation_table_string_table_size = 80499;
+constexpr std::uint16_t translation_table_mapping_table_size = 533;
+constexpr std::size_t translation_table_string_table_size = 80561;
 constexpr std::size_t translation_table_locale_table_size = 35;
 
 QLJS_CONSTEVAL std::uint16_t translation_table_const_look_up(
@@ -471,6 +471,7 @@ QLJS_CONSTEVAL std::uint16_t translation_table_const_look_up(
           "see here"sv,
           "semicolon is not allowed after decorators"sv,
           "something happened"sv,
+          "space is required between '<' and '<' inside 'extends' clause"sv,
           "spread starts here"sv,
           "spread tuple elements cannot be optional"sv,
           "static block starts here"sv,

diff --git a/src/quick-lint-js/i18n/translation-table-test-generated.h b/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[531] = {
+inline const Translated_String test_translation_table[532] = {
     {
         "\"global-groups\" entries must be strings"_translatable,
         u8"\"global-groups\" entries must be strings",
@@ -4923,6 +4923,17 @@ inline const Translated_String test_translation_table[531] = {
             u8"something happened",
         },
     },
+    {
+        "space is required between '<' and '<' inside 'extends' clause"_translatable,
+        u8"space is required between '<' and '<' inside 'extends' clause",
+        {
+            u8"space is required between '<' and '<' inside 'extends' clause",
+            u8"space is required between '<' and '<' inside 'extends' clause",
+            u8"space is required between '<' and '<' inside 'extends' clause",
+            u8"space is required between '<' and '<' inside 'extends' clause",
+            u8"space is required between '<' and '<' inside 'extends' clause",
+        },
+    },
     {
         "spread starts here"_translatable,
         u8"spread starts here",

diff --git a/test/test-parse-typescript-class.cpp b/test/test-parse-typescript-class.cpp
@@ -1546,6 +1546,33 @@ TEST_F(Test_Parse_TypeScript_Class, implement_multiple_things) {
               ElementsAreArray({u8"Apple", u8"Banana", u8"Carrot"}));
 }
 
+// TODO(#1114): Report the same diagnostic for 'extends'.
+TEST_F(Test_Parse_TypeScript_Class,
+       implements_generic_with_arrow_type_requires_space) {
+  {
+    Spy_Visitor p = test_parse_and_visit_module(
+        u8"class C implements I<<T>() => ReturnType<T>> {}"_sv,  //
+        u8"                     ` Diag_TypeScript_Generic_Less_Less_Not_Split"_diag,
+        typescript_options);
+    EXPECT_THAT(
+        p.variable_declarations,
+        ElementsAreArray({generic_param_decl(u8"T"), class_decl(u8"C")}));
+    EXPECT_THAT(p.variable_uses,
+                ElementsAreArray({u8"I", u8"ReturnType", u8"T"}));
+  }
+
+  {
+    Spy_Visitor p = test_parse_and_visit_module(
+        u8"class C implements I< <T>() => ReturnType<T>> {}"_sv, no_diags,
+        typescript_options);
+    EXPECT_THAT(
+        p.variable_declarations,
+        ElementsAreArray({generic_param_decl(u8"T"), class_decl(u8"C")}));
+    EXPECT_THAT(p.variable_uses,
+                ElementsAreArray({u8"I", u8"ReturnType", u8"T"}));
+  }
+}
+
 TEST_F(Test_Parse_TypeScript_Class, parameter_property_in_constructor) {
   {
     Spy_Visitor p = test_parse_and_visit_module(

diff --git a/test/test-parse-typescript-interface.cpp b/test/test-parse-typescript-interface.cpp
@@ -158,6 +158,32 @@ TEST_F(Test_Parse_TypeScript_Interface, extends_generic) {
   EXPECT_THAT(p.variable_uses, ElementsAreArray({u8"A", u8"B"}));
 }
 
+TEST_F(Test_Parse_TypeScript_Interface,
+       extends_generic_with_arrow_type_requires_space) {
+  {
+    Spy_Visitor p = test_parse_and_visit_module(
+        u8"interface I extends Base<<T>() => ReturnType<T>> {}"_sv,  //
+        u8"                         ` Diag_TypeScript_Generic_Less_Less_Not_Split"_diag,
+        typescript_options);
+    EXPECT_THAT(
+        p.variable_declarations,
+        ElementsAreArray({interface_decl(u8"I"), generic_param_decl(u8"T")}));
+    EXPECT_THAT(p.variable_uses,
+                ElementsAreArray({u8"Base", u8"ReturnType", u8"T"}));
+  }
+
+  {
+    Spy_Visitor p = test_parse_and_visit_module(
+        u8"interface I extends Base< <T>() => ReturnType<T>> {}"_sv, no_diags,
+        typescript_options);
+    EXPECT_THAT(
+        p.variable_declarations,
+        ElementsAreArray({interface_decl(u8"I"), generic_param_decl(u8"T")}));
+    EXPECT_THAT(p.variable_uses,
+                ElementsAreArray({u8"Base", u8"ReturnType", u8"T"}));
+  }
+}
+
 TEST_F(Test_Parse_TypeScript_Interface, unclosed_interface_statement) {
   {
     Spy_Visitor p = test_parse_and_visit_module(