feat(fe): add new diagnostic E0721

This diagnostic reports an error when `.` or `?.` directly follows `++` or `--`. Error message recommends adding parentheses around the postfix expression. This closes issue quick-lint#1208. quick-lint#1208
msharipov · Mar 14, 2024 · 73049dd · 73049dd
1 parent 313e1cf
commit 73049dd
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diff --git a/docs/errors/E0721.md b/docs/errors/E0721.md
@@ -0,0 +1,18 @@
+# E0721: invalid syntax; missing parentheses around postfix expression
+
+In JavaScript, putting a `.` or a `?.` directly following a postfix increment
+or decrement is a syntax error:
+
+```javascript
+let x = 3;
+console.log(x++.toString());  // Invalid syntax
+console.log(x--?.constructor);  // Invalid syntax
+```
+
+Add parentheses around the postfix expression to resolve this:
+
+```javascript
+let x = 3;
+console.log((x++).toString());
+console.log((x--)?.constructor);
+```
diff --git a/po/messages.pot b/po/messages.pot
@@ -2418,7 +2418,7 @@ msgid "namespace alias cannot use 'import type'"
 msgstr ""
 
 #: src/quick-lint-js/diag/diagnostic-metadata-generated.cpp
-msgid "invalid syntax; missing parentheses around {0}"
+msgid "invalid syntax; missing parentheses around '{0}'"
 msgstr ""
 
 #: test/test-diagnostic-formatter.cpp

diff --git a/src/quick-lint-js/diag/diagnostic-metadata-generated.cpp b/src/quick-lint-js/diag/diagnostic-metadata-generated.cpp
@@ -6930,16 +6930,16 @@ const QLJS_CONSTINIT Diagnostic_Info all_diagnostic_infos[] = {
       },
     },
 
-    // Diag_To_String_After_Increment
+    // Diag_Invalid_Operator_Directly_After_Postfix
     {
       .code = 721,
       .severity = Diagnostic_Severity::error,
       .message_formats = {
-        QLJS_TRANSLATABLE("invalid syntax; missing parentheses around {0}"),
+        QLJS_TRANSLATABLE("invalid syntax; missing parentheses around '{0}'"),
       },
       .message_args = {
         {
-          Diagnostic_Message_Arg_Info(offsetof(Diag_To_String_After_Increment, increment), Diagnostic_Arg_Type::source_code_span),
+          Diagnostic_Message_Arg_Info(offsetof(Diag_Invalid_Operator_Directly_After_Postfix, postfix_expression), Diagnostic_Arg_Type::source_code_span),
         },
       },
     },

diff --git a/src/quick-lint-js/diag/diagnostic-metadata-generated.h b/src/quick-lint-js/diag/diagnostic-metadata-generated.h
@@ -473,7 +473,7 @@ namespace quick_lint_js {
   QLJS_DIAG_TYPE_NAME(Diag_Multiple_Export_Defaults) \
   QLJS_DIAG_TYPE_NAME(Diag_Unintuitive_Bitshift_Precedence) \
   QLJS_DIAG_TYPE_NAME(Diag_TypeScript_Namespace_Alias_Cannot_Use_Import_Type) \
-  QLJS_DIAG_TYPE_NAME(Diag_To_String_After_Increment) \
+  QLJS_DIAG_TYPE_NAME(Diag_Invalid_Operator_Directly_After_Postfix) \
   /* END */
 // clang-format on
 

diff --git a/src/quick-lint-js/diag/diagnostic-types-2.h b/src/quick-lint-js/diag/diagnostic-types-2.h
@@ -3531,9 +3531,6 @@ struct Diag_Variable_Assigned_To_Self_Is_Noop {
   Source_Code_Span assignment_statement;
 };
 
-
-
-
 struct Diag_Xor_Used_As_Exponentiation {
   [[qljs::diag("E0710", Diagnostic_Severity::warning)]]  //
   [[qljs::message("'^' is the XOR operator; to exponentiate, use '**' instead",
@@ -3603,9 +3600,9 @@ struct Diag_TypeScript_Namespace_Alias_Cannot_Use_Import_Type {
   Source_Code_Span type_keyword;
 };
 
-struct Diag_To_String_After_Postfix {
+struct Diag_Invalid_Operator_Directly_After_Postfix {
   [[qljs::diag("E0721", Diagnostic_Severity::error)]]  //
-  [[qljs::message("invalid syntax; missing parentheses around {0}",
+  [[qljs::message("invalid syntax; missing parentheses around '{0}'",
                   ARG(postfix_expression))]]  //
   Source_Code_Span postfix_expression;
 };

diff --git a/src/quick-lint-js/fe/parse-expression.cpp b/src/quick-lint-js/fe/parse-expression.cpp
@@ -1896,6 +1896,14 @@ Expression* Parser::parse_expression_remainder(Parse_Visitor_Base& v,
       binary_builder.replace_last(
           this->make_expression<Expression::RW_Unary_Suffix>(
               binary_builder.last_expression(), operator_span));
+      Token_Type next_type = this->peek().type;
+      if (next_type == Token_Type::dot ||
+          next_type == Token_Type::question_dot) {
+        this->diag_reporter_->report(
+            Diag_Invalid_Operator_Directly_After_Postfix{
+                .postfix_expression =
+                    binary_builder.last_expression()->span()});
+      }
     }
     goto next;
 

diff --git a/src/quick-lint-js/i18n/translation-table-generated.cpp b/src/quick-lint-js/i18n/translation-table-generated.cpp
@@ -364,7 +364,7 @@ const Translation_Table translation_data = {
         {31, 39, 32, 33, 28, 27},            //
         {34, 15, 43, 40, 37, 33},            //
         {0, 0, 0, 0, 0, 39},                 //
-        {39, 51, 50, 40, 38, 47},            //
+        {39, 51, 50, 40, 38, 49},            //
         {57, 72, 67, 55, 0, 41},             //
         {0, 0, 0, 58, 0, 50},                //
         {0, 0, 0, 22, 0, 19},                //
@@ -2236,7 +2236,7 @@ const Translation_Table translation_data = {
         u8"invalid function parameter\0"
         u8"invalid hex escape sequence: {0}\0"
         u8"invalid lone literal in object literal\0"
-        u8"invalid syntax; missing parentheses around {0}\0"
+        u8"invalid syntax; missing parentheses around '{0}'\0"
         u8"keywords cannot contain escape sequences\0"
         u8"label named 'await' not allowed in async function\0"
         u8"labelled statement\0"

diff --git a/src/quick-lint-js/i18n/translation-table-generated.h b/src/quick-lint-js/i18n/translation-table-generated.h
@@ -19,7 +19,7 @@ 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 = 607;
-constexpr std::size_t translation_table_string_table_size = 82488;
+constexpr std::size_t translation_table_string_table_size = 82490;
 constexpr std::size_t translation_table_locale_table_size = 35;
 
 QLJS_CONSTEVAL std::uint16_t translation_table_const_look_up(
@@ -378,7 +378,7 @@ QLJS_CONSTEVAL std::uint16_t translation_table_const_look_up(
           "invalid function parameter"sv,
           "invalid hex escape sequence: {0}"sv,
           "invalid lone literal in object literal"sv,
-          "invalid syntax; missing parentheses around {0}"sv,
+          "invalid syntax; missing parentheses around '{0}'"sv,
           "keywords cannot contain escape sequences"sv,
           "label named 'await' not allowed in async function"sv,
           "labelled statement"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
@@ -3901,14 +3901,14 @@ inline const Translated_String test_translation_table[606] = {
         },
     },
     {
-        "invalid syntax; missing parentheses around {0}"_translatable,
-        u8"invalid syntax; missing parentheses around {0}",
-        {
-            u8"invalid syntax; missing parentheses around {0}",
-            u8"invalid syntax; missing parentheses around {0}",
-            u8"invalid syntax; missing parentheses around {0}",
-            u8"invalid syntax; missing parentheses around {0}",
-            u8"invalid syntax; missing parentheses around {0}",
+        "invalid syntax; missing parentheses around '{0}'"_translatable,
+        u8"invalid syntax; missing parentheses around '{0}'",
+        {
+            u8"invalid syntax; missing parentheses around '{0}'",
+            u8"invalid syntax; missing parentheses around '{0}'",
+            u8"invalid syntax; missing parentheses around '{0}'",
+            u8"invalid syntax; missing parentheses around '{0}'",
+            u8"invalid syntax; missing parentheses around '{0}'",
         },
     },
     {

diff --git a/test/test-parse-warning.cpp b/test/test-parse-warning.cpp
@@ -507,13 +507,19 @@ TEST_F(Test_Parse_Warning, early_exit_does_not_trigger_fallthrough_warning) {
   }
 }
 
-TEST_F(Test_Parse_Warning, to_string_called_directly_after_postfix) {
+TEST_F(Test_Parse_Warning, invalid_operator_directly_after_postfix) {
   test_parse_and_visit_expression(
-      u8"x++.toString()"_sv, //
-      u8"^^^ Diag_To_String_After_Postfix"_diag);
+      u8"x++.toString()"_sv,  //
+      u8"^^^ Diag_Invalid_Operator_Directly_After_Postfix"_diag);
+  test_parse_and_visit_expression(u8"(x++).toString()"_sv, no_diags);
   test_parse_and_visit_expression(
-      u8"(x++).toString()"_sv,
-      no_diags);
+      u8"x++.constructor"_sv,  //
+      u8"^^^ Diag_Invalid_Operator_Directly_After_Postfix"_diag);
+  test_parse_and_visit_expression(u8"(x++).constructor"_sv, no_diags);
+  test_parse_and_visit_expression(
+      u8"x--?.constructor"_sv,  //
+      u8"^^^ Diag_Invalid_Operator_Directly_After_Postfix"_diag);
+  test_parse_and_visit_expression(u8"(x--)?.constructor"_sv, no_diags);
 }
 }
 }