fix(fe): fix fallthrough warning after returning switch

Author: strager

docs/CHANGELOG.md

@@ -68,6 +68,9 @@ Semantic Versioning.
 * `for await (async of []);` no longer falsely reports [E0082][] ("assigning to
   'async' in a for-of loop requires parentheses"). (`for (async of []);` still
   reports the diagnostic.)
+* A `return` statement inside a nested `switch` no longer falsely repots
+  [E0427][] ("missing 'break;' or '// fallthrough' comment between " "statement
+  and 'case'").
 * TypeScript support (still experimental):
   * Types named `await`, `implements`, `interface`, `let`, `package`, `private`,
     `protected`, `public`, `static`, and `yield` are now recognized in type

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

@@ -3071,12 +3071,15 @@ void Parser::parse_and_visit_switch(Parse_Visitor_Base &v) {
     case Token_Type::kw_throw:
     case Token_Type::kw_break:
     case Token_Type::kw_case:
+
     // Temporarily return true to omit diag with these statments
+    case Token_Type::kw_do:
+    case Token_Type::kw_for:
     case Token_Type::kw_if:
+    case Token_Type::kw_switch:
     case Token_Type::kw_try:
     case Token_Type::kw_while:
-    case Token_Type::kw_do:
-    case Token_Type::kw_for:
+    case Token_Type::kw_with:
     case Token_Type::left_curly:
       return true;
     default:

test/test-parse-warning.cpp

@@ -485,6 +485,30 @@ TEST_F(Test_Parse_Warning, Diag_Fallthrough_Without_Comment_In_Switch) {
       default:})"_sv,
       no_diags);
 }
+
+TEST_F(Test_Parse_Warning, early_exit_does_not_trigger_fallthrough_warning) {
+  for (String8_View exiting_code : {
+           u8"break;"_sv,
+           u8"continue;"_sv,
+           u8"do { return; } while (true);"_sv,
+           u8"for (;;) { return; }"_sv,
+           u8"if (false) { } else { return; }"_sv,
+           u8"if (true) { return; }"_sv,
+           u8"return x;"_sv,
+           u8"return;"_sv,
+           u8"switch (c) { default: return; }"_sv,
+           u8"throw err;"_sv,
+           u8"try { return; } catch (e) {}"_sv,
+           u8"while (true) { return; }"_sv,
+           u8"with (o) { return; }"_sv,
+           u8"{ return; }"_sv,
+       }) {
+    test_parse_and_visit_statement(
+        concat(u8"for (;;) { switch (a) { case 1: "_sv, exiting_code,
+               u8" default: break; } }"_sv),
+        no_diags);
+  }
+}
 }
 }