fix(typescript): don't error on type: (a?, ...b) => ReturnType

quick-lint · Oct 14, 2023 · 2cd0a23 · 2cd0a23
1 parent f022b8d
commit 2cd0a23
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Showing 3 changed files with 10 additions and 1 deletion.
diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
@@ -51,6 +51,8 @@ Semantic Versioning.
     [E0034][] ("redeclaration of variable").
   * A namespace with the same name as an interface or type alias no longer
     falsely reports [E0034][] ("redeclaration of variable").
+  * `(a?, ...b) => ReturnType` in a TypeScript type no longer falsely reports
+    [E0379][] ("optional parameter cannot be followed by a required parameter").
   * Nested `module` declarations no longer falsely report [E0361][]. E0361's
     message has been changed:
     * Before: "module with string name is only allowed at the top level"

diff --git a/src/quick-lint-js/fe/parse-statement.cpp b/src/quick-lint-js/fe/parse-statement.cpp
@@ -2494,7 +2494,8 @@ void Parser::parse_and_visit_function_parameters(
            parameter->child_0()->kind() == Expression_Kind::Optional)) {
         previous_optional_span = parameter->span();
       } else {
-        if (previous_optional_span.has_value()) {
+        if (previous_optional_span.has_value() &&
+            parameter->kind() != Expression_Kind::Spread) {
           this->diag_reporter_->report(
               Diag_Optional_Parameter_Cannot_Be_Followed_By_Required_Parameter{
                   .optional_parameter = *previous_optional_span,

diff --git a/test/test-parse-typescript-function.cpp b/test/test-parse-typescript-function.cpp
@@ -757,6 +757,12 @@ TEST_F(Test_Parse_TypeScript_Function, optional_parameter_in_function_type) {
   }
 }
 
+TEST_F(Test_Parse_TypeScript_Function,
+       optional_parameter_followed_by_rest_parameter_is_allowed) {
+  test_parse_and_visit_typescript_type_expression(
+      u8"(param1?, ...rest) => ReturnType"_sv, no_diags, typescript_options);
+}
+
 TEST_F(Test_Parse_TypeScript_Function,
        optional_parameter_followed_by_required) {
   test_parse_and_visit_typescript_type_expression(