From 2b1300bbfb2938b57eb9668f1df63da57c6c3b71 Mon Sep 17 00:00:00 2001
From: "Matthew \"strager\" Glazar" <strager.nds@gmail.com>
Date: Wed, 27 Dec 2023 03:50:49 -0500
Subject: [PATCH] fix(typescript): fix <42>x; and other cases being parsed as
 JSX

---
 src/quick-lint-js/fe/parse-expression.cpp     | 22 ++++++++++
 ...-parse-typescript-angle-type-assertion.cpp | 44 +++++++++++++++++++
 2 files changed, 66 insertions(+)

diff --git a/src/quick-lint-js/fe/parse-expression.cpp b/src/quick-lint-js/fe/parse-expression.cpp
index 05c75ee9b0..619453cafc 100644
--- a/src/quick-lint-js/fe/parse-expression.cpp
+++ b/src/quick-lint-js/fe/parse-expression.cpp
@@ -3606,7 +3606,29 @@ Expression* Parser::parse_jsx_or_typescript_generic_expression(
       }
       break;
 
+    // <readonly />        // JSX.
+    // <readonly T[]>expr  // Type assertion.
+    case Token_Type::kw_keyof:
+    case Token_Type::kw_this:
+    case Token_Type::kw_readonly:
+    case Token_Type::kw_typeof:
+    case Token_Type::kw_unique:
+    case Token_Type::number:
     default:
+      // For these uncommon cases, don't try hard to guess what the user
+      // meant.
+      this->lexer_.roll_back_transaction(std::move(transaction));
+      if (this->options_.jsx) {
+        return this->parse_jsx_expression(v);
+      } else {
+        return this->parse_typescript_angle_type_assertion_expression(
+            v, prec,
+            /*is_invalid_due_to_jsx_ambiguity=*/false);
+      }
+      break;
+
+    // <>hello<>  // JSX.
+    case Token_Type::greater:
       break;
     }
     this->lexer_.roll_back_transaction(std::move(transaction));
diff --git a/test/test-parse-typescript-angle-type-assertion.cpp b/test/test-parse-typescript-angle-type-assertion.cpp
index 0e3b42ee5c..052d3b7062 100644
--- a/test/test-parse-typescript-angle-type-assertion.cpp
+++ b/test/test-parse-typescript-angle-type-assertion.cpp
@@ -117,6 +117,8 @@ TEST_F(Test_Parse_TypeScript_Angle_Type_Assertion, angle_type_assertion) {
            u8"< & Type>(expr);"_sv,
            u8"<[Type]>(expr);"_sv,
            u8"<Type[]>(expr);"_sv,
+           u8"<readonly Type[]>(expr);"_sv,
+           u8"<keyof Type>(expr);"_sv,
            u8"<{k: Type}>(expr);"_sv,
        }) {
     SCOPED_TRACE(out_string8(code));
@@ -158,6 +160,48 @@ TEST_F(Test_Parse_TypeScript_Angle_Type_Assertion, angle_type_assertion) {
                           }));
   }
 
+  {
+    Spy_Visitor p = test_parse_and_visit_statement(
+        u8"<typeof v>expr;"_sv, no_diags, typescript_options);
+    EXPECT_THAT(p.visits, ElementsAreArray({
+                              "visit_enter_type_scope",  // <
+                              "visit_variable_use",      // v
+                              "visit_exit_type_scope",   // >
+                              "visit_variable_use",      // expr
+                          }));
+    EXPECT_THAT(p.variable_uses, ElementsAreArray({u8"v"_sv, u8"expr"_sv}));
+  }
+
+  {
+    Spy_Visitor p = test_parse_and_visit_statement(
+        u8"<unique symbol>expr;"_sv, no_diags, typescript_options);
+    EXPECT_THAT(p.visits, ElementsAreArray({
+                              "visit_enter_type_scope",  // <
+                              "visit_exit_type_scope",   // >
+                              "visit_variable_use",      // expr
+                          }));
+  }
+
+  {
+    Spy_Visitor p = test_parse_and_visit_statement(u8"<this>expr;"_sv, no_diags,
+                                                   typescript_options);
+    EXPECT_THAT(p.visits, ElementsAreArray({
+                              "visit_enter_type_scope",  // <
+                              "visit_exit_type_scope",   // >
+                              "visit_variable_use",      // expr
+                          }));
+  }
+
+  {
+    Spy_Visitor p = test_parse_and_visit_statement(u8"<42>expr;"_sv, no_diags,
+                                                   typescript_options);
+    EXPECT_THAT(p.visits, ElementsAreArray({
+                              "visit_enter_type_scope",  // <
+                              "visit_exit_type_scope",   // >
+                              "visit_variable_use",      // expr
+                          }));
+  }
+
   for (const String8& type :
        typescript_builtin_type_keywords | typescript_special_type_keywords) {
     Test_Parser p(concat(u8"<"_sv, type, u8">expr;"_sv), typescript_options);