refactor(semantic): add strict mode in scope flags for class definiti…

…ons (#4156)

related: #4142 (comment)

Although we called `enter_node(Class)`, that doesn't mean we're in the `class` scope. It causes our must to visit decorators before `enter_node`.

Let's look at this case. It causes a syntax error if we don't visit decorators before `enter_node`
```js
// This file was procedurally generated from the following sources:
// - src/decorator/decorator-call-expr-identifier-reference-yield.case
// - src/decorator/syntax/valid/cls-expr-decorators-valid-syntax.template
/*---
description: Decorator @ DecoratorCallExpression (Valid syntax for decorator on class expression)
esid: prod-ClassExpression
features: [class, decorators]
flags: [generated, noStrict]
info: |
    ClassExpression[Yield, Await] :
      DecoratorList[?Yield, ?Await]opt class BindingIdentifier[?Yield, ?Await]opt ClassTail[?Yield, ?Await]

    DecoratorList[Yield, Await] :
      DecoratorList[?Yield, ?Await]opt Decorator[?Yield, ?Await]

    Decorator[Yield, Await] :
      @ DecoratorMemberExpression[?Yield, ?Await]
      @ DecoratorParenthesizedExpression[?Yield, ?Await]
      @ DecoratorCallExpression[?Yield, ?Await]

    ...

    DecoratorCallExpression[Yield, Await] :
      DecoratorMemberExpression[?Yield, ?Await] Arguments[?Yield, ?Await]

    DecoratorMemberExpression[Yield, Await] :
      IdentifierReference[?Yield, ?Await]
      DecoratorMemberExpression[?Yield, ?Await] . IdentifierName
      DecoratorMemberExpression[?Yield, ?Await] . PrivateIdentifier

    IdentifierReference[Yield, Await] :
      [~Yield] yield
      ...

---*/
function decorator() {
  return () => {};
}
var yield = decorator;

var C = @yield() class {};

```
Errors:
```shell
  × The keyword 'yield' is reserved
    ╭─[language/statements/class/decorator/syntax/valid/decorator-call-expr-identifier-reference-yield.js:45:2]
 44 │
 45 │ @yield() class C {}
    ·  ─────
    ╰────
```

The changed code makes more sense. Only if we call `enter_scope` for class, the flags will contain `StrictMode`. Also, we can get the exact `flags` of the `scope` in the `class` at the transformer

For example:

```
class A {
   B() {
       // Before: flags is `Function`
      //  After: flags is `Function | StrictMode`
   }
}
```

The regression tests will be fixed in follow-up PRs

crates/oxc_semantic/src/builder.rs

@@ -269,7 +269,6 @@ impl<'a> SemanticBuilder<'a> {
 
     pub fn strict_mode(&self) -> bool {
         self.current_scope_flags().is_strict_mode()
-            || self.current_node_flags.contains(NodeFlags::Class)
     }
 
     pub fn set_function_node_flag(&mut self, flag: NodeFlags) {
@@ -432,6 +431,12 @@ impl<'a> Visit<'a> for SemanticBuilder<'a> {
             if flags.contains(ScopeFlags::Top) { None } else { Some(self.current_scope_id) };
 
         let mut flags = flags;
+
+        if !flags.is_strict_mode() && self.current_node_flags.has_class() {
+            // NOTE A class definition is always strict mode code.
+            flags |= ScopeFlags::StrictMode;
+        };
+
         if let Some(parent_scope_id) = parent_scope_id {
             flags = self.scope.get_new_scope_flags(flags, parent_scope_id);
         }

tasks/coverage/parser_test262.snap

@@ -2,60 +2,12 @@ commit: a1587416
 
 parser_test262 Summary:
 AST Parsed     : 45859/45859 (100.00%)
-Positive Passed: 45853/45859 (99.99%)
+Positive Passed: 45859/45859 (100.00%)
 Negative Passed: 3925/3929 (99.90%)
 Expect Syntax Error: "language/import/import-assertions/json-invalid.js"
 Expect Syntax Error: "language/import/import-assertions/json-named-bindings.js"
 Expect Syntax Error: "language/import/import-attributes/json-invalid.js"
 Expect Syntax Error: "language/import/import-attributes/json-named-bindings.js"
-Expect to Parse: "language/expressions/class/decorator/syntax/valid/decorator-call-expr-identifier-reference-yield.js"
-
-  × The keyword 'yield' is reserved
-    ╭─[language/expressions/class/decorator/syntax/valid/decorator-call-expr-identifier-reference-yield.js:44:10]
- 43 │ 
- 44 │ var C = @yield() class {};
-    ·          ─────
-    ╰────
-Expect to Parse: "language/expressions/class/decorator/syntax/valid/decorator-member-expr-identifier-reference-yield.js"
-
-  × The keyword 'yield' is reserved
-    ╭─[language/expressions/class/decorator/syntax/valid/decorator-member-expr-identifier-reference-yield.js:33:10]
- 32 │ 
- 33 │ var C = @yield class {};
-    ·          ─────
-    ╰────
-Expect to Parse: "language/expressions/class/decorator/syntax/valid/decorator-parenthesized-expr-identifier-reference-yield.js"
-
-  × The keyword 'yield' is reserved
-    ╭─[language/expressions/class/decorator/syntax/valid/decorator-parenthesized-expr-identifier-reference-yield.js:51:11]
- 50 │ 
- 51 │ var C = @(yield) class {};
-    ·           ─────
-    ╰────
-Expect to Parse: "language/statements/class/decorator/syntax/valid/decorator-call-expr-identifier-reference-yield.js"
-
-  × The keyword 'yield' is reserved
-    ╭─[language/statements/class/decorator/syntax/valid/decorator-call-expr-identifier-reference-yield.js:45:2]
- 44 │ 
- 45 │ @yield() class C {}
-    ·  ─────
-    ╰────
-Expect to Parse: "language/statements/class/decorator/syntax/valid/decorator-member-expr-identifier-reference-yield.js"
-
-  × The keyword 'yield' is reserved
-    ╭─[language/statements/class/decorator/syntax/valid/decorator-member-expr-identifier-reference-yield.js:34:2]
- 33 │ 
- 34 │ @yield class C {}
-    ·  ─────
-    ╰────
-Expect to Parse: "language/statements/class/decorator/syntax/valid/decorator-parenthesized-expr-identifier-reference-yield.js"
-
-  × The keyword 'yield' is reserved
-    ╭─[language/statements/class/decorator/syntax/valid/decorator-parenthesized-expr-identifier-reference-yield.js:52:3]
- 51 │ 
- 52 │ @(yield) class C {}
-    ·   ─────
-    ╰────
 
   × '0'-prefixed octal literals and octal escape sequences are deprecated
     ╭─[annexB/language/expressions/template-literal/legacy-octal-escape-sequence-strict.js:18:4]