[class] Fix ClassScope::LookupPrivateName to walk scope chain

private name was not found in the current scope. Outer private names
were sometimes coincidentally correctly resolved if the innermost
ClassScope does not need to allocate a context and does not have a
ScopeInfo.

ClassScope: :LookupPrivateName was not walking the scope chain when a
Change-Id: I18937e6cdf2ad4ae15825b11762fbec7a1358145
Bug: v8:9635
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1761547Reviewed-by: Sathya Gunasekaran  <gsathya@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63295}

src/ast/scopes.cc

@@ -2469,7 +2469,9 @@ Variable* ClassScope::LookupPrivateName(VariableProxy* proxy) {
     if (var == nullptr && !class_scope->scope_info_.is_null()) {
       var = class_scope->LookupPrivateNameInScopeInfo(proxy->raw_name());
     }
-    return var;
+    if (var != nullptr) {
+      return var;
+    }
   }
   return nullptr;
 }

test/test262/local-tests/test/language/expressions/class/elements/private-field-on-nested-class.js

+// This file was procedurally generated from the following sources:
+// - src/class-elements/private-field-on-nested-class.case
+// - src/class-elements/default/cls-expr.template
+/*---
+description: PrivateName CallExpression usage (private field) (field definitions in a class expression)
+esid: prod-FieldDefinition
+features: [class-fields-private, class-fields-public, class]
+flags: [generated]
+info: |
+    Updated Productions
+
+    CallExpression[Yield, Await]:
+      CoverCallExpressionAndAsyncArrowHead[?Yield, ?Await]
+      SuperCall[?Yield, ?Await]
+      CallExpression[?Yield, ?Await]Arguments[?Yield, ?Await]
+      CallExpression[?Yield, ?Await][Expression[+In, ?Yield, ?Await]]
+      CallExpression[?Yield, ?Await].IdentifierName
+      CallExpression[?Yield, ?Await]TemplateLiteral[?Yield, ?Await]
+      CallExpression[?Yield, ?Await].PrivateName
+
+---*/
+
+
+var C = class {
+  #outer = 'test262';
+
+  B_withoutPrivateField = class {
+    method(o) {
+      return o.#outer;
+    }
+  }
+
+  B_withPrivateField = class {
+    #inner = 42;
+    method(o) {
+      return o.#outer;
+    }
+  }
+}
+
+let c = new C();
+let innerB1 = new c.B_withoutPrivateField();
+assert.sameValue(innerB1.method(c), 'test262');
+let innerB2 = new c.B_withPrivateField();
+assert.sameValue(innerB2.method(c), 'test262');

test/test262/local-tests/test/language/statements/class/elements/private-field-on-nested-class.js

+// This file was procedurally generated from the following sources:
+// - src/class-elements/private-field-on-nested-class.case
+// - src/class-elements/default/cls-decl.template
+/*---
+description: PrivateName CallExpression usage (private field) (field definitions in a class declaration)
+esid: prod-FieldDefinition
+features: [class-fields-private, class-fields-public, class]
+flags: [generated]
+info: |
+    Updated Productions
+
+    CallExpression[Yield, Await]:
+      CoverCallExpressionAndAsyncArrowHead[?Yield, ?Await]
+      SuperCall[?Yield, ?Await]
+      CallExpression[?Yield, ?Await]Arguments[?Yield, ?Await]
+      CallExpression[?Yield, ?Await][Expression[+In, ?Yield, ?Await]]
+      CallExpression[?Yield, ?Await].IdentifierName
+      CallExpression[?Yield, ?Await]TemplateLiteral[?Yield, ?Await]
+      CallExpression[?Yield, ?Await].PrivateName
+
+---*/
+
+
+class C {
+  #outer = 'test262';
+
+  B_withoutPrivateField = class {
+    method(o) {
+      return o.#outer;
+    }
+  }
+
+  B_withPrivateField = class {
+    #inner = 42;
+    method(o) {
+      return o.#outer;
+    }
+  }
+}
+
+let c = new C();
+let innerB1 = new c.B_withoutPrivateField();
+assert.sameValue(innerB1.method(c), 'test262');
+let innerB2 = new c.B_withPrivateField();
+assert.sameValue(innerB2.method(c), 'test262');