quick-lint · msharipov · Mar 14, 2024 · Mar 14, 2024 · Mar 14, 2024 · Mar 16, 2024
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
@@ -2429,6 +2429,10 @@ msgstr ""
 msgid "function 'let' call may be confused for destructuring; remove parentheses to declare a variable"
 msgstr ""
 
+#: src/quick-lint-js/diag/diagnostic-metadata-generated.cpp
+msgid "invalid syntax; missing parentheses around '{0}'"
+msgstr ""
+
 #: test/test-diagnostic-formatter.cpp
 #: test/test-vim-qflist-json-diag-reporter.cpp
 msgid "something happened"

diff --git a/src/quick-lint-js/diag/diagnostic-metadata-generated.cpp b/src/quick-lint-js/diag/diagnostic-metadata-generated.cpp
@@ -6975,6 +6975,20 @@ const QLJS_CONSTINIT Diagnostic_Info all_diagnostic_infos[] = {
         },
       },
     },
+
+    // Diag_Invalid_Operator_Directly_After_Postfix
+    {
+      .code = 721,
+      .severity = Diagnostic_Severity::error,
+      .message_formats = {
+        QLJS_TRANSLATABLE("invalid syntax; missing parentheses around '{0}'"),
+      },
+      .message_args = {
+        {
+          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
@@ -476,10 +476,11 @@ namespace quick_lint_js {
   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_Confusing_Let_Call) \
+  QLJS_DIAG_TYPE_NAME(Diag_Invalid_Operator_Directly_After_Postfix) \
   /* END */
 // clang-format on
 
-inline constexpr int Diag_Type_Count = 465;
+inline constexpr int Diag_Type_Count = 466;
 
 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
@@ -3628,6 +3628,12 @@ struct Diag_Confusing_Let_Call {
   Source_Code_Span let_function_call;
 };
 
+struct Diag_Invalid_Operator_Directly_After_Postfix {
+  [[qljs::diag("E0721", Diagnostic_Severity::error)]]  //
+  [[qljs::message("invalid syntax; missing parentheses around '{0}'",
+                  ARG(postfix_expression))]]  //
+  Source_Code_Span postfix_expression;
+};
 }
 QLJS_WARNING_POP
 

diff --git a/src/quick-lint-js/fe/parse-expression.cpp b/src/quick-lint-js/fe/parse-expression.cpp
@@ -1898,6 +1898,14 @@ 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
@@ -365,7 +365,8 @@ const Translation_Table translation_data = {
         {47, 43, 47, 54, 35, 38},            //
         {31, 39, 32, 33, 28, 27},            //
         {34, 15, 43, 40, 37, 33},            //
-        {39, 51, 50, 40, 38, 39},            //
+        {0, 0, 0, 0, 0, 39},                 //
+        {39, 51, 50, 40, 38, 49},            //
         {57, 72, 67, 55, 0, 41},             //
         {0, 0, 0, 58, 0, 50},                //
         {0, 0, 0, 22, 0, 19},                //
@@ -2240,6 +2241,7 @@ 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"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
@@ -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 = 609;
-constexpr std::size_t translation_table_string_table_size = 82687;
+constexpr std::uint16_t translation_table_mapping_table_size = 610;
+constexpr std::size_t translation_table_string_table_size = 82736;
 constexpr std::size_t translation_table_locale_table_size = 35;
 
 QLJS_CONSTEVAL std::uint16_t translation_table_const_look_up(
@@ -380,6 +380,7 @@ 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,
           "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
@@ -27,7 +27,7 @@ struct Translated_String {
 };
 
 // clang-format off
-inline const Translated_String test_translation_table[608] = {
+inline const Translated_String test_translation_table[609] = {
     {
         "\"global-groups\" entries must be strings"_translatable,
         u8"\"global-groups\" entries must be strings",
@@ -3922,6 +3922,17 @@ inline const Translated_String test_translation_table[608] = {
             u8"ogiltigt l\u00e5neuttryck i objektliteral",
         },
     },
+    {
+        "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}'",
+        },
+    },
     {
         "keywords cannot contain escape sequences"_translatable,
         u8"keywords cannot contain escape sequences",

diff --git a/test/test-parse-warning.cpp b/test/test-parse-warning.cpp
@@ -538,6 +538,21 @@ TEST_F(Test_Parse_Warning, warn_on_confusing_let_use) {
   test_parse_and_visit_statement(u8"let.prop({x} = y);"_sv, no_diags);
   test_parse_and_visit_statement(u8"let (x = y);"_sv, no_diags);
 }
+
+TEST_F(Test_Parse_Warning, invalid_operator_directly_after_postfix) {
+  test_parse_and_visit_expression(
+      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++.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);
+}
 }
 }