fix(parser): reparse all statements with await identifier in unambiguous mode

crates/oxc_parser/src/js/expression.rs

@@ -66,6 +66,10 @@ impl<'a> ParserImpl<'a> {
         if !kind.is_identifier_reference(false, false) {
             return self.unexpected();
         }
+        // Track await identifier for potential reparsing in unambiguous mode
+        if kind == Kind::Await && !self.ctx.has_await() {
+            self.state.encountered_await_identifier = true;
+        }
         self.check_identifier(kind, self.ctx);
         let (span, name) = self.parse_identifier_kind(Kind::Ident);
         self.ast.identifier_reference(span, name)

crates/oxc_parser/src/js/statement.rs

@@ -44,7 +44,7 @@ impl<'a> ParserImpl<'a> {
 
         // Check if we need to track potential await reparsing.
         // This is only needed in unambiguous mode at top level when not in await context.
-        let track_await_reparse =
+        let mut track_await_reparse =
             is_top_level && self.source_type.is_unambiguous() && !self.ctx.has_await();
 
         let mut expecting_directives = true;
@@ -53,19 +53,29 @@ impl<'a> ParserImpl<'a> {
                 break;
             }
 
-            // In unambiguous mode, check if this statement might need reparsing.
-            // We need to track statements where `await` is followed by `/` on the same line,
-            // because if ESM is detected later, we need to reparse them.
-            let checkpoint = if track_await_reparse && self.needs_await_reparse_tracking() {
+            // Once ESM syntax is detected, enable await context for remaining statements
+            // and stop tracking (we'll reparse earlier statements at the end)
+            if track_await_reparse && self.module_record_builder.has_module_syntax() {
+                track_await_reparse = false;
+                self.ctx = self.ctx.and_await(true);
+            }
+
+            // Take checkpoint for every statement when tracking await reparse.
+            // We reset the flag and only store the checkpoint if an await identifier
+            // was actually encountered during parsing.
+            let checkpoint = if track_await_reparse {
+                self.state.encountered_await_identifier = false;
                 Some((statements.len(), self.checkpoint()))
             } else {
                 None
             };
 
             let stmt = self.parse_statement_list_item(stmt_ctx);
 
-            // If we took a checkpoint and this might need reparsing, store it.
-            if let Some((stmt_index, checkpoint)) = checkpoint {
+            // Store checkpoint only if await identifier was encountered
+            if let Some((stmt_index, checkpoint)) = checkpoint
+                && self.state.encountered_await_identifier
+            {
                 self.state.potential_await_reparse.push((stmt_index, checkpoint));
             }
 
@@ -94,20 +104,6 @@ impl<'a> ParserImpl<'a> {
         (directives, statements)
     }
 
-    /// Check if the current position might need await reparse tracking.
-    /// Returns true if we're at `await` followed by `/` on the same line.
-    fn needs_await_reparse_tracking(&mut self) -> bool {
-        if !self.at(Kind::Await) {
-            return false;
-        }
-        // Check if the next token is `/` on the same line
-        self.lookahead(|p| {
-            p.bump_any(); // bump `await`
-            let token = p.cur_token();
-            token.kind() == Kind::Slash && !token.is_on_new_line()
-        })
-    }
-
     /// `StatementListItem`[Yield, Await, Return] :
     ///     Statement[?Yield, ?Await, ?Return]
     ///     Declaration[?Yield, ?Await]

crates/oxc_parser/src/state.rs

@@ -20,13 +20,17 @@ pub struct ParserState<'a> {
 
     /// Statements that may need reparsing when `sourceType` is `unambiguous`.
     ///
-    /// In unambiguous mode, we initially parse top-level `await / ...` as
-    /// `await / 0 / u` (identifier divided by something). But if ESM syntax
-    /// is detected later, we need to reparse these as `await /0/u` (await
-    /// expression with regex).
+    /// In unambiguous mode, we initially parse top-level `await ...` as
+    /// `await(...)` (identifier/function call). But if ESM syntax is detected
+    /// later, we need to reparse these as await expressions.
     ///
     /// Each entry contains: (statement_index, checkpoint_before_statement)
     pub potential_await_reparse: Vec<(usize, ParserCheckpoint<'a>)>,
+
+    /// Flag to track if an `await` identifier was encountered during statement parsing.
+    /// Used to determine if a statement needs to be stored for potential reparsing
+    /// in unambiguous mode.
+    pub encountered_await_identifier: bool,
 }
 
 impl ParserState<'_> {
@@ -36,6 +40,7 @@ impl ParserState<'_> {
             cover_initialized_name: FxHashMap::default(),
             trailing_commas: FxHashMap::default(),
             potential_await_reparse: Vec::new(),
+            encountered_await_identifier: false,
         }
     }
 }

tasks/coverage/misc/pass/unambiguous-await-call.js

@@ -0,0 +1,2 @@
+// In unambiguous mode with ESM syntax, `await (...)` should parse as await expression
+await (async function () { })(); export {}

tasks/coverage/misc/pass/unambiguous-await-in-declaration.js

@@ -0,0 +1,2 @@
+// In unambiguous mode with ESM syntax, await in declarations should parse as await expression
+const x = await (async function () { })(); export {}

tasks/coverage/snapshots/codegen_misc.snap

@@ -1,3 +1,3 @@
 codegen_misc Summary:
-AST Parsed     : 59/59 (100.00%)
-Positive Passed: 59/59 (100.00%)
+AST Parsed     : 61/61 (100.00%)
+Positive Passed: 61/61 (100.00%)

tasks/coverage/snapshots/formatter_misc.snap

@@ -1,3 +1,3 @@
 formatter_misc Summary:
-AST Parsed     : 59/59 (100.00%)
-Positive Passed: 59/59 (100.00%)
+AST Parsed     : 61/61 (100.00%)
+Positive Passed: 61/61 (100.00%)

tasks/coverage/snapshots/parser_misc.snap

@@ -1,6 +1,6 @@
 parser_misc Summary:
-AST Parsed     : 59/59 (100.00%)
-Positive Passed: 59/59 (100.00%)
+AST Parsed     : 61/61 (100.00%)
+Positive Passed: 61/61 (100.00%)
 Negative Passed: 130/130 (100.00%)
 
   × Cannot assign to 'arguments' in strict mode

tasks/coverage/snapshots/parser_typescript.snap

@@ -19688,109 +19688,14 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/statements/Va
    ·            ╰── `as` expected
    ╰────
 
-  × The keyword 'await' is reserved
-   ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.1.ts:4:1]
+  × Parenthesized expressions may not have a trailing comma.
+   ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.1.ts:4:9]
  3 │ // reparse call as invalid await should error
  4 │ await (1,);
-   · ─────
- 5 │ await <number, string>(1);
-   ╰────
-
-  × The keyword 'await' is reserved
-   ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.1.ts:5:1]
- 4 │ await (1,);
+   ·         ─
  5 │ await <number, string>(1);
-   · ─────
- 6 │ 
    ╰────
-
-  × The keyword 'await' is reserved
-   ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.1.ts:8:1]
- 7 │ // reparse tagged template as invalid await should error
- 8 │ await <number, string> ``;
-   · ─────
- 9 │ 
-   ╰────
-
-  × The keyword 'await' is reserved
-    ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.1.ts:11:17]
- 10 │ // reparse class extends clause should fail
- 11 │ class C extends await<string> {
-    ·                 ─────
- 12 │ }
-    ╰────
-
-  × The keyword 'await' is reserved
-    ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.1.ts:15:3]
- 14 │ // await in class decorators should fail
- 15 │ @(await)
-    ·   ─────
- 16 │ class C1 {}
-    ╰────
-
-  × The keyword 'await' is reserved
-    ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.1.ts:18:2]
- 17 │ 
- 18 │ @await(x)
-    ·  ─────
- 19 │ class C2 {}
-    ╰────
-
-  × The keyword 'await' is reserved
-    ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.1.ts:21:2]
- 20 │ 
- 21 │ @await
-    ·  ─────
- 22 │ class C3 {}
-    ╰────
-
-  × The keyword 'await' is reserved
-    ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.1.ts:26:6]
- 25 │ class C4 {
- 26 │     @await
-    ·      ─────
- 27 │     ["foo"]() {}
-    ╰────
-
-  × The keyword 'await' is reserved
-    ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.1.ts:30:6]
- 29 │ class C5 {
- 30 │     @await(1)
-    ·      ─────
- 31 │     ["foo"]() {}
-    ╰────
-
-  × The keyword 'await' is reserved
-    ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.1.ts:34:7]
- 33 │ class C6 {
- 34 │     @(await)
-    ·       ─────
- 35 │     ["foo"]() {}
-    ╰────
-
-  × The keyword 'await' is reserved
-    ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.1.ts:40:14]
- 39 │ class C7 {
- 40 │     method1(@await [x]) {}
-    ·              ─────
- 41 │     method2(@await(1) [x]) {}
-    ╰────
-
-  × The keyword 'await' is reserved
-    ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.1.ts:41:14]
- 40 │     method1(@await [x]) {}
- 41 │     method2(@await(1) [x]) {}
-    ·              ─────
- 42 │     method3(@(await) [x]) {}
-    ╰────
-
-  × The keyword 'await' is reserved
-    ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.1.ts:42:15]
- 41 │     method2(@await(1) [x]) {}
- 42 │     method3(@(await) [x]) {}
-    ·               ─────
- 43 │ }
-    ╰────
+  help: Remove the trailing comma here
 
   × Identifier expected. 'await' is a reserved word that cannot be used here.
    ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.10.ts:2:19]
@@ -19820,27 +19725,55 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/statements/Va
    ·        ─────
    ╰────
 
+  × Cannot use `await` as an identifier in an async context
+   ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.12.ts:5:8]
+ 4 │ // await disallowed in import=namespace when in a module
+ 5 │ import await = foo.await;
+   ·        ─────
+   ╰────
+
   × The keyword 'await' is reserved
    ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.12.ts:5:8]
  4 │ // await disallowed in import=namespace when in a module
  5 │ import await = foo.await;
    ·        ─────
    ╰────
 
+  × Cannot use `await` as an identifier in an async context
+   ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.2.ts:4:5]
+ 3 │ // reparse variable name as await should fail
+ 4 │ var await = 1;
+   ·     ─────
+   ╰────
+
   × The keyword 'await' is reserved
    ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.2.ts:4:5]
  3 │ // reparse variable name as await should fail
  4 │ var await = 1;
    ·     ─────
    ╰────
 
+  × Cannot use `await` as an identifier in an async context
+   ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.3.ts:4:6]
+ 3 │ // reparse binding pattern as await should fail
+ 4 │ var {await} = {await:1};
+   ·      ─────
+   ╰────
+
   × The keyword 'await' is reserved
    ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.3.ts:4:6]
  3 │ // reparse binding pattern as await should fail
  4 │ var {await} = {await:1};
    ·      ─────
    ╰────
 
+  × Cannot use `await` as an identifier in an async context
+   ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.4.ts:4:6]
+ 3 │ // reparse binding pattern as await should fail
+ 4 │ var [await] = [1];
+   ·      ─────
+   ╰────
+
   × The keyword 'await' is reserved
    ╭─[typescript/tests/cases/conformance/externalModules/topLevelAwaitErrors.4.ts:4:6]
  3 │ // reparse binding pattern as await should fail
@@ -24107,6 +24040,14 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/statements/Va
  3 │ }
    ╰────
 
+  × Cannot use `await` as an identifier in an async context
+   ╭─[typescript/tests/cases/conformance/salsa/plainJSBinderErrors.ts:3:7]
+ 2 │ export default 13
+ 3 │ const await = 1
+   ·       ─────
+ 4 │ const yield = 2
+   ╰────
+
   × Cannot use `await` as an identifier in an async context
    ╭─[typescript/tests/cases/conformance/salsa/plainJSBinderErrors.ts:6:11]
  5 │ async function f() {

tasks/coverage/snapshots/semantic_misc.snap

@@ -1,6 +1,6 @@
 semantic_misc Summary:
-AST Parsed     : 59/59 (100.00%)
-Positive Passed: 40/59 (67.80%)
+AST Parsed     : 61/61 (100.00%)
+Positive Passed: 42/61 (68.85%)
 semantic Error: tasks/coverage/misc/pass/declare-let-private.ts
 Bindings mismatch:
 after transform: ScopeId(0): ["private"]

tasks/coverage/snapshots/transformer_misc.snap

@@ -1,5 +1,5 @@
 transformer_misc Summary:
-AST Parsed     : 59/59 (100.00%)
-Positive Passed: 58/59 (98.31%)
+AST Parsed     : 61/61 (100.00%)
+Positive Passed: 60/61 (98.36%)
 Mismatch: tasks/coverage/misc/pass/babel-16776-s.js