Disallow private name in object elements and TS type elements

packages/babel-parser/src/parser/expression.js

@@ -606,7 +606,7 @@ export default class ExpressionParser extends LValParser {
         ? this.parseExpression()
         : optional
         ? this.parseIdentifier(true)
-        : this.parseMaybePrivateName();
+        : this.parseMaybePrivateName(true);
       node.computed = computed;
 
       if (node.property.type === "PrivateName") {
@@ -1131,11 +1131,19 @@ export default class ExpressionParser extends LValParser {
     return this.finishNode(node, "BooleanLiteral");
   }
 
-  parseMaybePrivateName(): N.PrivateName | N.Identifier {
+  parseMaybePrivateName(
+    isPrivateNameAllowed: boolean,
+  ): N.PrivateName | N.Identifier {
     const isPrivate = this.match(tt.hash);
 
     if (isPrivate) {
       this.expectOnePlugin(["classPrivateProperties", "classPrivateMethods"]);
+      if (!isPrivateNameAllowed) {
+        this.raise(
+          this.state.pos,
+          "Private names can only be used as the name of a class element (i.e. class C { #p = 42; #m() {} } )\n or a property of member expression (i.e. this.#p).",
+        );
+      }
       const node = this.startNode();
       this.next();
       this.assertNoSpace("Unexpected space between # and identifier");
@@ -1596,12 +1604,12 @@ export default class ExpressionParser extends LValParser {
     }
 
     const containsEsc = this.state.containsEsc;
-    this.parsePropertyName(prop);
+    this.parsePropertyName(prop, /* isPrivateNameAllowed */ false);
 
     if (!isPattern && !containsEsc && !isGenerator && this.isAsyncProp(prop)) {
       isAsync = true;
       isGenerator = this.eat(tt.star);
-      this.parsePropertyName(prop);
+      this.parsePropertyName(prop, /* isPrivateNameAllowed */ false);
     } else {
       isAsync = false;
     }
@@ -1688,7 +1696,7 @@ export default class ExpressionParser extends LValParser {
     if (!containsEsc && this.isGetterOrSetterMethod(prop, isPattern)) {
       if (isGenerator || isAsync) this.unexpected();
       prop.kind = prop.key.name;
-      this.parsePropertyName(prop);
+      this.parsePropertyName(prop, /* isPrivateNameAllowed */ false);
       this.parseMethod(
         prop,
         /* isGenerator */ false,
@@ -1780,6 +1788,7 @@ export default class ExpressionParser extends LValParser {
 
   parsePropertyName(
     prop: N.ObjectOrClassMember | N.ClassMember | N.TsNamedTypeElementBase,
+    isPrivateNameAllowed: boolean,
   ): N.Expression | N.Identifier {
     if (this.eat(tt.bracketL)) {
       (prop: $FlowSubtype<N.ObjectOrClassMember>).computed = true;
@@ -1792,7 +1801,7 @@ export default class ExpressionParser extends LValParser {
       (prop: $FlowFixMe).key =
         this.match(tt.num) || this.match(tt.string) || this.match(tt.bigint)
           ? this.parseExprAtom()
-          : this.parseMaybePrivateName();
+          : this.parseMaybePrivateName(isPrivateNameAllowed);
 
       if (prop.key.type !== "PrivateName") {
         // ClassPrivateProperty is never computed, so we don't assign in that case.

packages/babel-parser/src/parser/statement.js

@@ -1474,7 +1474,7 @@ export default class StatementParser extends ExpressionParser {
   }
 
   parseClassPropertyName(member: N.ClassMember): N.Expression | N.Identifier {
-    const key = this.parsePropertyName(member);
+    const key = this.parsePropertyName(member, /* isPrivateNameAllowed */ true);
 
     if (
       !member.computed &&

packages/babel-parser/src/plugins/flow.js

@@ -2266,9 +2266,10 @@ export default (superClass: Class<Parser>): Class<Parser> =>
 
     parsePropertyName(
       node: N.ObjectOrClassMember | N.ClassMember | N.TsNamedTypeElementBase,
+      isPrivateNameAllowed: boolean,
     ): N.Identifier {
       const variance = this.flowParseVariance();
-      const key = super.parsePropertyName(node);
+      const key = super.parsePropertyName(node, isPrivateNameAllowed);
       // $FlowIgnore ("variance" not defined on TsNamedTypeElementBase)
       node.variance = variance;
       return key;

packages/babel-parser/src/plugins/typescript/index.js

@@ -507,7 +507,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         return idx;
       }
 
-      this.parsePropertyName(node);
+      this.parsePropertyName(node, /* isPrivateNameAllowed */ false);
       return this.tsParsePropertyOrMethodSignature(node, readonly);
     }
 

packages/babel-parser/test/fixtures/experimental/class-private-properties/invalid-destructuring-arguments/input.js

@@ -0,0 +1,4 @@
+class C {
+  #x = 1;
+  #p = ({ #x: x }) => {}
+}

packages/babel-parser/test/fixtures/experimental/class-private-properties/invalid-destructuring-arguments/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["classPrivateProperties"]
+}