fix(parser): parse escaped class field names after initializers (#28061)

The Babel class-field fixtures added in #28057 use escaped `in` and `instanceof` names after an initializer. Oxc consumes these names as binary operators and rejects valid class members.

Stop binary-expression parsing at these escaped names after a newline so ASI can end the initializer and class-member parsing can consume the name. Preserve escaped-keyword diagnostics for same-line operator expressions and after ASI, with diagnostic fixtures for both newline cases.

crates/oxc_parser/src/js/expression.rs

@@ -83,6 +83,9 @@ impl<'a, C: Config> ParserImpl<'a, C> {
         // allow `await` and `yield`, let semantic analysis report error
         let kind = self.cur_kind();
         if !kind.is_identifier_reference(false, false) {
+            if self.cur_token().escaped() && matches!(kind, Kind::In | Kind::Instanceof) {
+                return self.fatal_error(diagnostics::escaped_keyword(self.cur_token().span()));
+            }
             return self.unexpected();
         }
         // Track await identifier for potential reparsing in unambiguous mode
@@ -1350,6 +1353,13 @@ impl<'a, C: Config> ParserImpl<'a, C> {
                 break;
             }
 
+            if matches!(kind, Kind::In | Kind::Instanceof)
+                && self.cur_token().escaped()
+                && self.cur_token().is_on_new_line()
+            {
+                break;
+            }
+
             if matches!(kind, Kind::As | Kind::Satisfies) {
                 if self.cur_token().is_on_new_line() {
                     break;

tasks/coverage/misc/fail/escaped-in-after-newline.js

@@ -0,0 +1,2 @@
+a
+\u{69}n b;

tasks/coverage/misc/fail/escaped-instanceof-after-newline.js

@@ -0,0 +1,2 @@
+a
+\u{69}nstanceof b;

tasks/coverage/snapshots/formatter_babel.snap

@@ -2,7 +2,7 @@ commit: a56fe4a4
 
 formatter_babel Summary:
 AST Parsed     : 2280/2280 (100.00%)
-Positive Passed: 2271/2280 (99.61%)
+Positive Passed: 2269/2280 (99.52%)
 Mismatch: tasks/coverage/babel/packages/babel-parser/test/fixtures/annex-b/enabled/1.1-html-comments-close-let-declaration/input.js
 
 Mismatch: tasks/coverage/babel/packages/babel-parser/test/fixtures/annex-b/enabled/1.1-html-comments-close-let-declaration-cr/input.js
@@ -21,3 +21,7 @@ Mismatch: tasks/coverage/babel/packages/babel-parser/test/fixtures/comments/basi
 
 Mismatch: tasks/coverage/babel/packages/babel-parser/test/fixtures/comments/basic/sequence-expression/input.js
 
+Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/es2022/class-properties/escaped-in-after-initializer/input.js
+Cannot assign to this expression
+Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/class/escaped-in-after-initializer/input.ts
+Cannot assign to this expression

tasks/coverage/snapshots/lexer_misc.snap

@@ -1,3 +1,3 @@
 lexer_misc Summary:
-AST Parsed     : 367/367 (100.00%)
-Positive Passed: 367/367 (100.00%)
+AST Parsed     : 369/369 (100.00%)
+Positive Passed: 369/369 (100.00%)

tasks/coverage/snapshots/parser_babel.snap

@@ -1,8 +1,8 @@
 commit: a56fe4a4
 
 parser_babel Summary:
-AST Parsed     : 2278/2280 (99.91%)
-Positive Passed: 2259/2280 (99.08%)
+AST Parsed     : 2280/2280 (100.00%)
+Positive Passed: 2260/2280 (99.12%)
 Negative Passed: 1789/1804 (99.17%)
 Expect Syntax Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/cast/unparenthesized-assert-and-assign/input.ts
 
@@ -63,25 +63,6 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/annex-
    ·                   ╰── `g` has already been declared here
    ╰────
 
-Fatal error: tasks/coverage/babel/packages/babel-parser/test/fixtures/es2022/class-properties/escaped-in-after-initializer/input.js
-
-  × Keywords cannot contain escape characters
-   ╭─[babel/packages/babel-parser/test/fixtures/es2022/class-properties/escaped-in-after-initializer/input.js:3:3]
- 2 │   x = 1
- 3 │   \u{69}n
-   ·   ───────
- 4 │   y = a
-   ╰────
-
-  × Cannot assign to this expression
-   ╭─[babel/packages/babel-parser/test/fixtures/es2022/class-properties/escaped-in-after-initializer/input.js:2:7]
- 1 │     class C {
- 2 │ ╭─▶   x = 1
- 3 │ │     \u{69}n
- 4 │ ╰─▶   y = a
- 5 │       \u{69}nstanceof
-   ╰────
-
 Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/estree/class-private-method/typescript-invalid-abstract/input.ts
 
   × TS(18019): 'abstract' modifier cannot be used with a private identifier.
@@ -120,23 +101,33 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
  5 │     f();
    ╰────
 
-Fatal error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/class/escaped-in-after-initializer/input.ts
+Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/class/escaped-in-after-initializer/input.ts
 
-  × Keywords cannot contain escape characters
+  × Identifier `\u{69}n` has already been declared
    ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/escaped-in-after-initializer/input.ts:3:3]
  2 │   x = 1
  3 │   \u{69}n
-   ·   ───────
+   ·   ───┬───
+   ·      ╰── `\u{69}n` has already been declared here
  4 │   y = () => a
+ 5 │   \u{69}nstanceof
+ 6 │   z = 1
+ 7 │   \u{69}n() {}
+   ·   ───┬───
+   ·      ╰── It can not be redeclared here
+ 8 │   \u{69}n = 1
    ╰────
 
-  × Cannot assign to this expression
-   ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/escaped-in-after-initializer/input.ts:2:7]
- 1 │     class C {
- 2 │ ╭─▶   x = 1
- 3 │ │     \u{69}n
- 4 │ ╰─▶   y = () => a
- 5 │       \u{69}nstanceof
+  × Identifier `\u{69}n` has already been declared
+   ╭─[babel/packages/babel-parser/test/fixtures/typescript/class/escaped-in-after-initializer/input.ts:7:3]
+ 6 │   z = 1
+ 7 │   \u{69}n() {}
+   ·   ───┬───
+   ·      ╰── `\u{69}n` has already been declared here
+ 8 │   \u{69}n = 1
+   ·   ───┬───
+   ·      ╰── It can not be redeclared here
+ 9 │ }
    ╰────
 
 Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/class/members-with-modifier-names/input.ts

tasks/coverage/snapshots/parser_misc.snap

@@ -1,7 +1,7 @@
 parser_misc Summary:
 AST Parsed     : 114/114 (100.00%)
 Positive Passed: 114/114 (100.00%)
-Negative Passed: 255/255 (100.00%)
+Negative Passed: 257/257 (100.00%)
 
   × TS(1275): 'accessor' modifier can only appear on a property declaration.
    ╭─[misc/fail/accessor-modifier-abstract-method.ts:1:29]
@@ -573,6 +573,20 @@ Negative Passed: 255/255 (100.00%)
    ·        ───────────
    ╰────
 
+  × Keywords cannot contain escape characters
+   ╭─[misc/fail/escaped-in-after-newline.js:2:1]
+ 1 │ a
+ 2 │ \u{69}n b;
+   · ───────
+   ╰────
+
+  × Keywords cannot contain escape characters
+   ╭─[misc/fail/escaped-instanceof-after-newline.js:2:1]
+ 1 │ a
+ 2 │ \u{69}nstanceof b;
+   · ───────────────
+   ╰────
+
   × Keywords cannot contain escape characters
    ╭─[misc/fail/escaped-type-import.ts:1:8]
  1 │ import t\u0079pe Foo = require("m");

tasks/coverage/snapshots/semantic_babel.snap

@@ -2,7 +2,7 @@ commit: a56fe4a4
 
 semantic_babel Summary:
 AST Parsed     : 2280/2280 (100.00%)
-Positive Passed: 2185/2280 (95.83%)
+Positive Passed: 2186/2280 (95.88%)
 semantic Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/annex-b/enabled/1.1-html-comments-open-export-default-from/input.js
 Cannot use export statement outside a module
 
@@ -42,10 +42,6 @@ Symbol scope ID mismatch for "_await":
 after transform: SymbolId(3): ScopeId(2)
 rebuilt        : SymbolId(2): ScopeId(0)
 
-semantic Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/es2022/class-properties/escaped-in-after-initializer/input.js
-Keywords cannot contain escape characters
-Cannot assign to this expression
-
 semantic Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/es2026/async-explicit-resource-management/valid-for-using-binding-of-of/input.js
 Symbol reference IDs mismatch for "of":
 after transform: SymbolId(1): [ReferenceId(0)]
@@ -108,8 +104,8 @@ after transform: ["a"]
 rebuilt        : []
 
 semantic Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/class/escaped-in-after-initializer/input.ts
-Keywords cannot contain escape characters
-Cannot assign to this expression
+Identifier `\u{69}n` has already been declared
+Identifier `\u{69}n` has already been declared
 
 semantic Error: tasks/coverage/babel/packages/babel-parser/test/fixtures/typescript/class/get-generic/input.ts
 Bindings mismatch: