fix(parser): reset auto-accessor initializer context (#25384)

## Summary

- Align auto-accessor initializer parsing with class-field initializer grammar.
- Add regressions for `in` in a `for` initializer and disallowed inherited `await`/`yield` contexts.

## Root cause

The auto-accessor path only enabled `new.target`. It therefore inherited outer `~In`, `Await`, and `Yield` grammar contexts: `a in b` could not parse in a `for` initializer, while `await` and `yield` could incorrectly parse from enclosing async/generator functions. The fix applies the same `In | NewTarget` addition and `Yield | Await` removal already used for class fields, while retaining AssignmentExpression parsing.

## References

- [ECMAScript `FieldDefinition` grammar](https://tc39.es/ecma262/#prod-FieldDefinition)
- [ECMAScript `Initializer` grammar](https://tc39.es/ecma262/#prod-Initializer)
- [TC39 decorators proposal: class auto-accessors](https://github.com/tc39/proposal-decorators#introduction)

crates/oxc_parser/src/js/class.rs

@@ -418,9 +418,12 @@ impl<'a, C: Config> ParserImpl<'a, C> {
         decorators: ArenaVec<'a, Decorator<'a>>,
     ) -> ClassElement<'a> {
         let type_annotation = if self.is_ts { self.parse_ts_type_annotation() } else { None };
-        // `new.target` is allowed in a class accessor field initializer.
         let value = self.eat(Kind::Eq).then(|| {
-            self.context_add(Context::NewTarget, Self::parse_assignment_expression_or_higher)
+            self.context(
+                Context::In | Context::NewTarget,
+                Context::Yield | Context::Await,
+                Self::parse_assignment_expression_or_higher,
+            )
         });
         self.asi();
         let r#type = if modifiers.contains(ModifierKind::Abstract) {

tasks/coverage/misc/fail/auto-accessor-initializer-await.js

@@ -0,0 +1,5 @@
+async function f() {
+  class C {
+    accessor x = await 1;
+  }
+}

tasks/coverage/misc/fail/auto-accessor-initializer-yield.js

@@ -0,0 +1,5 @@
+function* f() {
+  class C {
+    accessor x = yield 1;
+  }
+}

tasks/coverage/misc/pass/auto-accessor-initializer-context.js

@@ -0,0 +1,7 @@
+for (
+  class C {
+    field = a in b;
+    accessor x = a in b;
+  };
+  ;
+) {}

tasks/coverage/snapshots/codegen_misc.snap

@@ -1,3 +1,3 @@
 codegen_misc Summary:
-AST Parsed     : 75/75 (100.00%)
-Positive Passed: 75/75 (100.00%)
+AST Parsed     : 76/76 (100.00%)
+Positive Passed: 76/76 (100.00%)

tasks/coverage/snapshots/formatter_misc.snap

@@ -1,3 +1,3 @@
 formatter_misc Summary:
-AST Parsed     : 75/75 (100.00%)
-Positive Passed: 75/75 (100.00%)
+AST Parsed     : 76/76 (100.00%)
+Positive Passed: 76/76 (100.00%)

tasks/coverage/snapshots/parser_misc.snap

@@ -1,7 +1,7 @@
 parser_misc Summary:
-AST Parsed     : 75/75 (100.00%)
-Positive Passed: 75/75 (100.00%)
-Negative Passed: 156/156 (100.00%)
+AST Parsed     : 76/76 (100.00%)
+Positive Passed: 76/76 (100.00%)
+Negative Passed: 158/158 (100.00%)
 
   × Cannot assign to 'arguments' in strict mode
    ╭─[misc/fail/arguments-eval-ambient.ts:2:13]
@@ -136,6 +136,24 @@ Negative Passed: 156/156 (100.00%)
     ╰────
   note: Classes are always strict mode code
 
+  × `await` is only allowed within async functions and at the top levels of modules
+   ╭─[misc/fail/auto-accessor-initializer-await.js:3:18]
+ 2 │   class C {
+ 3 │     accessor x = await 1;
+   ·                  ─────
+ 4 │   }
+   ╰────
+  help: Either remove this `await` or add the `async` keyword to the enclosing function
+
+  × A 'yield' expression is only allowed in a generator body.
+   ╭─[misc/fail/auto-accessor-initializer-yield.js:3:18]
+ 2 │   class C {
+ 3 │     accessor x = yield 1;
+   ·                  ─────
+ 4 │   }
+   ╰────
+  help: Either remove this `yield` or change the enclosing function to a generator function (`function*`)
+
   × Cannot use await in class static initialization block
    ╭─[misc/fail/await-expr-in-block-in-class-static-block.mjs:4:7]
  3 │     {

tasks/coverage/snapshots/semantic_misc.snap

@@ -1,6 +1,6 @@
 semantic_misc Summary:
-AST Parsed     : 75/75 (100.00%)
-Positive Passed: 71/75 (94.67%)
+AST Parsed     : 76/76 (100.00%)
+Positive Passed: 72/76 (94.74%)
 semantic Error: tasks/coverage/misc/pass/declare-let-private.ts
 Bindings mismatch:
 after transform: ScopeId(0): ["private"]

tasks/coverage/snapshots/transformer_misc.snap

@@ -1,3 +1,3 @@
 transformer_misc Summary:
-AST Parsed     : 75/75 (100.00%)
-Positive Passed: 75/75 (100.00%)
+AST Parsed     : 76/76 (100.00%)
+Positive Passed: 76/76 (100.00%)