Add private-property-in-object support (#11372)

https://github.com/tc39/proposal-private-fields-in-in

Co-Authored-By: Nicolò Ribaudo <nicolo.ribaudo@gmail.com>
Co-Authored-By: Huáng Jùnliàng <jlhwung@gmail.com>

packages/babel-cli/test/fixtures/babel/--copy-files with ignore in babelignore/options.json

@@ -1,9 +1,3 @@
 {
-  "args": [
+  "args": ["src", "--out-dir", "lib", "--copy-files", "--verbose"]
-    "src",
-    "--out-dir",
-    "lib",
-    "--copy-files",
-    "--verbose"
-  ]
 }

packages/babel-cli/test/fixtures/babel/--copy-files with ignore in babelrc/options.json

@@ -1,9 +1,3 @@
 {
-  "args": [
+  "args": ["src", "--out-dir", "lib", "--copy-files", "--verbose"]
-    "src",
-    "--out-dir",
-    "lib",
-    "--copy-files",
-    "--verbose"
-  ]
 }

packages/babel-cli/test/fixtures/babel/--minified/options.json

@@ -1,3 +1,9 @@
 {
-  "args": ["--out-file", "script2.js", "--no-comments", "--minified", "script.js"]
+  "args": [
+    "--out-file",
+    "script2.js",
+    "--no-comments",
+    "--minified",
+    "script.js"
+  ]
 }

packages/babel-helper-create-class-features-plugin/src/features.js

@@ -5,6 +5,7 @@ export const FEATURES = Object.freeze({
   fields: 1 << 1,
   privateMethods: 1 << 2,
   decorators: 1 << 3,
+  privateIn: 1 << 4,
 });
 
 // We can't use a symbol because this needs to always be the same, even if
@@ -28,6 +29,39 @@ export function enableFeature(file, feature, loose) {
     file.set(featuresKey, file.get(featuresKey) | feature);
     if (loose) file.set(looseKey, file.get(looseKey) | feature);
   }
+
+  if (
+    hasFeature(file, FEATURES.fields) &&
+    hasFeature(file, FEATURES.privateMethods) &&
+    isLoose(file, FEATURES.fields) !== isLoose(file, FEATURES.privateMethods)
+  ) {
+    throw new Error(
+      "'loose' mode configuration must be the same for both @babel/plugin-proposal-class-properties " +
+        "and @babel/plugin-proposal-private-methods",
+    );
+  }
+
+  if (
+    hasFeature(file, FEATURES.fields) &&
+    hasFeature(file, FEATURES.privateIn) &&
+    isLoose(file, FEATURES.fields) !== isLoose(file, FEATURES.privateIn)
+  ) {
+    throw new Error(
+      "'loose' mode configuration must be the same for both @babel/plugin-proposal-class-properties " +
+        "and @babel/plugin-proposal-private-property-in-object",
+    );
+  }
+
+  if (
+    hasFeature(file, FEATURES.privateMethods) &&
+    hasFeature(file, FEATURES.privateIn) &&
+    isLoose(file, FEATURES.privateMethods) !== isLoose(file, FEATURES.privateIn)
+  ) {
+    throw new Error(
+      "'loose' mode configuration must be the same for both @babel/plugin-proposal-private-methods " +
+        "and @babel/plugin-proposal-private-property-in-object",
+    );
+  }
 }
 
 function hasFeature(file, feature) {
@@ -69,15 +103,18 @@ export function verifyUsedFeatures(path, file) {
   }
 
   if (
-    hasFeature(file, FEATURES.privateMethods) &&
+    path.isPrivateName() &&
-    hasFeature(file, FEATURES.fields) &&
+    path.parentPath.isBinaryExpression({
-    isLoose(file, FEATURES.privateMethods) !== isLoose(file, FEATURES.fields)
+      operator: "in",
+      left: path.node,
+    })
   ) {
+    if (!hasFeature(file, FEATURES.privateIn)) {
       throw path.buildCodeFrameError(
-      "'loose' mode configuration must be the same for both @babel/plugin-proposal-class-properties " +
+        "Private property in checks are not enabled.",
-        "and @babel/plugin-proposal-private-methods",
       );
     }
+  }
 
   if (path.isProperty()) {
     if (!hasFeature(file, FEATURES.fields)) {

packages/babel-helper-create-class-features-plugin/src/fields.js

@@ -70,16 +70,9 @@ export function buildPrivateNamesNodes(privateNamesMap, loose, state) {
 // Traverses the class scope, handling private name references. If an inner
 // class redeclares the same private name, it will hand off traversal to the
 // restricted visitor (which doesn't traverse the inner class's inner scope).
-const privateNameVisitor = {
+function privateNameVisitorFactory(visitor) {
-  PrivateName(path) {
+  const privateNameVisitor = {
-    const { privateNamesMap } = this;
+    ...visitor,
-    const { node, parentPath } = path;
-
-    if (!parentPath.isMemberExpression({ property: node })) return;
-    if (!privateNamesMap.has(node.id.name)) return;
-
-    this.handle(parentPath);
-  },
 
     Class(path) {
       const { privateNamesMap } = this;
@@ -103,7 +96,7 @@ const privateNameVisitor = {
       // This class redeclares some private field. We need to process the outer
       // environment with access to all the outer privates, then we can process
       // the inner environment with only the still-visible outer privates.
-    path.get("body").traverse(privateNameNestedVisitor, {
+      path.get("body").traverse(nestedVisitor, {
         ...this,
         redeclared,
       });
@@ -116,23 +109,65 @@ const privateNameVisitor = {
       // Features visitor, which'll process the redeclared privates.
       path.skipKey("body");
     },
-};
+  };
 
-// Traverses the outer portion of a class, without touching the class's inner
+  // Traverses the outer portion of a class, without touching the class's inner
-// scope, for private names.
+  // scope, for private names.
-const privateNameNestedVisitor = traverse.visitors.merge([
+  const nestedVisitor = traverse.visitors.merge([
     {
-    PrivateName(path) {
+      ...visitor,
-      const { redeclared } = this;
-      const { name } = path.node.id;
-      if (redeclared.includes(name)) path.skip();
-    },
-  },
-  {
-    PrivateName: privateNameVisitor.PrivateName,
     },
     environmentVisitor,
-]);
+  ]);
+
+  return privateNameVisitor;
+}
+
+const privateNameVisitor = privateNameVisitorFactory({
+  PrivateName(path) {
+    const { privateNamesMap, redeclared } = this;
+    const { node, parentPath } = path;
+
+    if (!parentPath.isMemberExpression({ property: node })) return;
+
+    const { name } = node.id;
+    if (!privateNamesMap.has(name)) return;
+    if (redeclared && redeclared.includes(name)) return;
+
+    this.handle(parentPath);
+  },
+});
+
+const privateInVisitor = privateNameVisitorFactory({
+  BinaryExpression(path) {
+    const { operator, left, right } = path.node;
+    if (operator !== "in") return;
+    if (!path.get("left").isPrivateName()) return;
+
+    const { loose, privateNamesMap, redeclared } = this;
+    const { name } = left.id;
+
+    if (!privateNamesMap.has(name)) return;
+    if (redeclared && redeclared.includes(name)) return;
+
+    if (loose) {
+      const { id } = privateNamesMap.get(name);
+      path.replaceWith(template.expression.ast`
+        Object.prototype.hasOwnProperty.call(${right}, ${id})
+      `);
+      return;
+    }
+
+    const { id, static: isStatic } = privateNamesMap.get(name);
+
+    if (isStatic) {
+      path.replaceWith(template.expression.ast`${right} === ${this.classRef}`);
+      return;
+    }
+
+    path.replaceWith(template.expression.ast`${id}.has(${right})`);
+  },
+});
 
 const privateNameHandlerSpec = {
   memoise(member, count) {
@@ -306,6 +341,12 @@ export function transformPrivateNamesUsage(
       ...privateNameHandlerSpec,
     });
   }
+  body.traverse(privateInVisitor, {
+    privateNamesMap,
+    classRef: ref,
+    file: state,
+    loose,
+  });
 }
 
 function buildPrivateFieldInitLoose(ref, prop, privateNamesMap) {

packages/babel-helper-create-class-features-plugin/test/fixtures/plugin-proposal-decorators/ignore-abstract-methods/options.json

@@ -1,7 +1,5 @@
 {
-  "presets": [
+  "presets": [["typescript"]],
-    ["typescript"]
-  ],
   "plugins": [
     ["proposal-decorators", { "decoratorsBeforeExport": true }],
     ["proposal-class-properties"]

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

@@ -27,6 +27,7 @@ import {
   isReservedWord,
   isStrictReservedWord,
   isStrictBindReservedWord,
+  isIdentifierStart,
 } from "../util/identifier";
 import type { Pos, Position } from "../util/location";
 import * as charCodes from "charcodes";
@@ -1148,6 +1149,26 @@ export default class ExpressionParser extends LValParser {
           this.registerTopicReference();
           return this.finishNode(node, "PipelinePrimaryTopicReference");
         }
+
+        const nextCh = this.input.codePointAt(this.state.end);
+        if (isIdentifierStart(nextCh) || nextCh === charCodes.backslash) {
+          const start = this.state.start;
+          // $FlowIgnore It'll either parse a PrivateName or throw.
+          node = (this.parseMaybePrivateName(true): N.PrivateName);
+          if (this.match(tt._in)) {
+            this.expectPlugin("privateIn");
+            this.classScope.usePrivateName(node.id.name, node.start);
+          } else if (this.hasPlugin("privateIn")) {
+            this.raise(
+              this.state.start,
+              Errors.PrivateInExpectedIn,
+              node.id.name,
+            );
+          } else {
+            throw this.unexpected(start);
+          }
+          return node;
+        }
       }
       // fall through
       default:

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

@@ -130,6 +130,8 @@ export const Errors = Object.freeze({
     "Topic reference was used in a lexical context without topic binding",
   PrimaryTopicRequiresSmartPipeline:
     "Primary Topic Reference found but pipelineOperator not passed 'smart' for 'proposal' option.",
+  PrivateInExpectedIn:
+    "Private names are only allowed in property accesses (`obj.#%0`) or in `in` expressions (`#%0 in obj`)",
   PrivateNameRedeclaration: "Duplicate private name #%0",
   RecordExpressionBarIncorrectEndSyntaxType:
     "Record expressions ending with '|}' are only allowed when the 'syntaxType' option of the 'recordAndTuple' plugin is set to 'bar'",

packages/babel-parser/test/fixtures/es2020/nullish-coalescing-operator/with-pipeline/options.json

@@ -1,5 +1,3 @@
 {
-  "plugins": [
+  "plugins": [["pipelineOperator", { "proposal": "minimal" }]]
-    ["pipelineOperator", { "proposal": "minimal" }]
-  ]
 }

packages/babel-parser/test/fixtures/experimental/_no-plugin/private-in/input.js

@@ -0,0 +1,7 @@
+class Point {
+  #x = 1;
+  #y = 2;
+  static isPoint(obj) {
+    return #x in obj && #y in obj;
+  }
+}

packages/babel-parser/test/fixtures/experimental/_no-plugin/private-in/options.json

@@ -0,0 +1,6 @@
+{
+  "plugins": [
+    "classPrivateProperties"
+  ],
+  "throws": "This experimental syntax requires enabling the parser plugin: 'privateIn' (5:14)"
+}

packages/babel-parser/test/fixtures/experimental/class-private-methods/asi-failure-generator/options.json

@@ -1,4 +1,7 @@
 {
   "throws": "Unexpected token (3:3)",
-  "plugins": ["classProperties", "classPrivateMethods"]
+  "plugins": [
+    "classProperties",
+    "classPrivateMethods"
+  ]
 }

packages/babel-parser/test/fixtures/experimental/class-private-properties/failure-shorthand/options.json

@@ -1,4 +1,6 @@
 {
   "throws": "Unexpected token (4:11)",
-  "plugins": ["classPrivateProperties"]
+  "plugins": [
+    "classPrivateProperties"
+  ]
 }

packages/babel-parser/test/fixtures/experimental/pipeline-operator/proposal-smart-error,-unbound-topic,-simple/options.json

@@ -1,4 +1,11 @@
 {
-  "plugins": [["pipelineOperator", { "proposal": "smart" }]],
+  "plugins": [
+    [
+      "pipelineOperator",
+      {
+        "proposal": "smart"
+      }
+    ]
+  ],
   "throws": "Unexpected token (1:4)"
 }

packages/babel-parser/test/fixtures/experimental/private-in/private-binary-expression-left/input.js

@@ -0,0 +1,6 @@
+class Foo {
+  #x = 1;
+  test() {
+    #x + 1;
+  }
+}

packages/babel-parser/test/fixtures/experimental/private-in/private-binary-expression-left/options.json

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

packages/babel-parser/test/fixtures/experimental/private-in/private-binary-expression-left/output.json

@@ -0,0 +1,105 @@
+{
+  "type": "File",
+  "start":0,"end":50,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+  "errors": [
+    "SyntaxError: Private names are only allowed in property accesses (`obj.#x`) or in `in` expressions (`#x in obj`) (4:7)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":50,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":50,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":6,"end":9,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":9},"identifierName":"Foo"},
+          "name": "Foo"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start":10,"end":50,"loc":{"start":{"line":1,"column":10},"end":{"line":6,"column":1}},
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start":14,"end":21,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":9}},
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start":14,"end":16,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":4}},
+                "id": {
+                  "type": "Identifier",
+                  "start":15,"end":16,"loc":{"start":{"line":2,"column":3},"end":{"line":2,"column":4},"identifierName":"x"},
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start":19,"end":20,"loc":{"start":{"line":2,"column":7},"end":{"line":2,"column":8}},
+                "extra": {
+                  "rawValue": 1,
+                  "raw": "1"
+                },
+                "value": 1
+              }
+            },
+            {
+              "type": "ClassMethod",
+              "start":24,"end":48,"loc":{"start":{"line":3,"column":2},"end":{"line":5,"column":3}},
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":24,"end":28,"loc":{"start":{"line":3,"column":2},"end":{"line":3,"column":6},"identifierName":"test"},
+                "name": "test"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":31,"end":48,"loc":{"start":{"line":3,"column":9},"end":{"line":5,"column":3}},
+                "body": [
+                  {
+                    "type": "ExpressionStatement",
+                    "start":37,"end":44,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":11}},
+                    "expression": {
+                      "type": "BinaryExpression",
+                      "start":37,"end":43,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":10}},
+                      "left": {
+                        "type": "PrivateName",
+                        "start":37,"end":39,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":6}},
+                        "id": {
+                          "type": "Identifier",
+                          "start":38,"end":39,"loc":{"start":{"line":4,"column":5},"end":{"line":4,"column":6},"identifierName":"x"},
+                          "name": "x"
+                        }
+                      },
+                      "operator": "+",
+                      "right": {
+                        "type": "NumericLiteral",
+                        "start":42,"end":43,"loc":{"start":{"line":4,"column":9},"end":{"line":4,"column":10}},
+                        "extra": {
+                          "rawValue": 1,
+                          "raw": "1"
+                        },
+                        "value": 1
+                      }
+                    }
+                  }
+                ],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/private-in/private-binary-expression-right/input.js

@@ -0,0 +1,6 @@
+class Foo {
+  #x = 1;
+  test() {
+    1 + #x;
+  }
+}

packages/babel-parser/test/fixtures/experimental/private-in/private-binary-expression-right/options.json

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

packages/babel-parser/test/fixtures/experimental/private-in/private-binary-expression-right/output.json

@@ -0,0 +1,105 @@
+{
+  "type": "File",
+  "start":0,"end":50,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+  "errors": [
+    "SyntaxError: Private names are only allowed in property accesses (`obj.#x`) or in `in` expressions (`#x in obj`) (4:10)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":50,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":50,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":6,"end":9,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":9},"identifierName":"Foo"},
+          "name": "Foo"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start":10,"end":50,"loc":{"start":{"line":1,"column":10},"end":{"line":6,"column":1}},
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start":14,"end":21,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":9}},
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start":14,"end":16,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":4}},
+                "id": {
+                  "type": "Identifier",
+                  "start":15,"end":16,"loc":{"start":{"line":2,"column":3},"end":{"line":2,"column":4},"identifierName":"x"},
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start":19,"end":20,"loc":{"start":{"line":2,"column":7},"end":{"line":2,"column":8}},
+                "extra": {
+                  "rawValue": 1,
+                  "raw": "1"
+                },
+                "value": 1
+              }
+            },
+            {
+              "type": "ClassMethod",
+              "start":24,"end":48,"loc":{"start":{"line":3,"column":2},"end":{"line":5,"column":3}},
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":24,"end":28,"loc":{"start":{"line":3,"column":2},"end":{"line":3,"column":6},"identifierName":"test"},
+                "name": "test"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":31,"end":48,"loc":{"start":{"line":3,"column":9},"end":{"line":5,"column":3}},
+                "body": [
+                  {
+                    "type": "ExpressionStatement",
+                    "start":37,"end":44,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":11}},
+                    "expression": {
+                      "type": "BinaryExpression",
+                      "start":37,"end":43,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":10}},
+                      "left": {
+                        "type": "NumericLiteral",
+                        "start":37,"end":38,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":5}},
+                        "extra": {
+                          "rawValue": 1,
+                          "raw": "1"
+                        },
+                        "value": 1
+                      },
+                      "operator": "+",
+                      "right": {
+                        "type": "PrivateName",
+                        "start":41,"end":43,"loc":{"start":{"line":4,"column":8},"end":{"line":4,"column":10}},
+                        "id": {
+                          "type": "Identifier",
+                          "start":42,"end":43,"loc":{"start":{"line":4,"column":9},"end":{"line":4,"column":10},"identifierName":"x"},
+                          "name": "x"
+                        }
+                      }
+                    }
+                  }
+                ],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/private-in/private-expression/input.js

@@ -0,0 +1,6 @@
+class Foo {
+  #x = 1;
+  test() {
+    #x;
+  }
+}

packages/babel-parser/test/fixtures/experimental/private-in/private-expression/options.json

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

packages/babel-parser/test/fixtures/experimental/private-in/private-expression/output.json

@@ -0,0 +1,91 @@
+{
+  "type": "File",
+  "start":0,"end":46,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+  "errors": [
+    "SyntaxError: Private names are only allowed in property accesses (`obj.#x`) or in `in` expressions (`#x in obj`) (4:6)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":46,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":46,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":6,"end":9,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":9},"identifierName":"Foo"},
+          "name": "Foo"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start":10,"end":46,"loc":{"start":{"line":1,"column":10},"end":{"line":6,"column":1}},
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start":14,"end":21,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":9}},
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start":14,"end":16,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":4}},
+                "id": {
+                  "type": "Identifier",
+                  "start":15,"end":16,"loc":{"start":{"line":2,"column":3},"end":{"line":2,"column":4},"identifierName":"x"},
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start":19,"end":20,"loc":{"start":{"line":2,"column":7},"end":{"line":2,"column":8}},
+                "extra": {
+                  "rawValue": 1,
+                  "raw": "1"
+                },
+                "value": 1
+              }
+            },
+            {
+              "type": "ClassMethod",
+              "start":24,"end":44,"loc":{"start":{"line":3,"column":2},"end":{"line":5,"column":3}},
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":24,"end":28,"loc":{"start":{"line":3,"column":2},"end":{"line":3,"column":6},"identifierName":"test"},
+                "name": "test"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":31,"end":44,"loc":{"start":{"line":3,"column":9},"end":{"line":5,"column":3}},
+                "body": [
+                  {
+                    "type": "ExpressionStatement",
+                    "start":37,"end":40,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":7}},
+                    "expression": {
+                      "type": "PrivateName",
+                      "start":37,"end":39,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":6}},
+                      "id": {
+                        "type": "Identifier",
+                        "start":38,"end":39,"loc":{"start":{"line":4,"column":5},"end":{"line":4,"column":6},"identifierName":"x"},
+                        "name": "x"
+                      }
+                    }
+                  }
+                ],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/private-in/private-in-class-heritage/input.js

@@ -0,0 +1,6 @@
+class Foo {
+  #x = 1;
+  test() {
+    class X extends (#x in {}) {};
+  }
+}

packages/babel-parser/test/fixtures/experimental/private-in/private-in-class-heritage/options.json

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

packages/babel-parser/test/fixtures/experimental/private-in/private-in-class-heritage/output.json

@@ -0,0 +1,116 @@
+{
+  "type": "File",
+  "start":0,"end":73,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":73,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":73,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":6,"end":9,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":9},"identifierName":"Foo"},
+          "name": "Foo"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start":10,"end":73,"loc":{"start":{"line":1,"column":10},"end":{"line":6,"column":1}},
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start":14,"end":21,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":9}},
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start":14,"end":16,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":4}},
+                "id": {
+                  "type": "Identifier",
+                  "start":15,"end":16,"loc":{"start":{"line":2,"column":3},"end":{"line":2,"column":4},"identifierName":"x"},
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start":19,"end":20,"loc":{"start":{"line":2,"column":7},"end":{"line":2,"column":8}},
+                "extra": {
+                  "rawValue": 1,
+                  "raw": "1"
+                },
+                "value": 1
+              }
+            },
+            {
+              "type": "ClassMethod",
+              "start":24,"end":71,"loc":{"start":{"line":3,"column":2},"end":{"line":5,"column":3}},
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":24,"end":28,"loc":{"start":{"line":3,"column":2},"end":{"line":3,"column":6},"identifierName":"test"},
+                "name": "test"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":31,"end":71,"loc":{"start":{"line":3,"column":9},"end":{"line":5,"column":3}},
+                "body": [
+                  {
+                    "type": "ClassDeclaration",
+                    "start":37,"end":66,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":33}},
+                    "id": {
+                      "type": "Identifier",
+                      "start":43,"end":44,"loc":{"start":{"line":4,"column":10},"end":{"line":4,"column":11},"identifierName":"X"},
+                      "name": "X"
+                    },
+                    "superClass": {
+                      "type": "BinaryExpression",
+                      "start":54,"end":62,"loc":{"start":{"line":4,"column":21},"end":{"line":4,"column":29}},
+                      "left": {
+                        "type": "PrivateName",
+                        "start":54,"end":56,"loc":{"start":{"line":4,"column":21},"end":{"line":4,"column":23}},
+                        "id": {
+                          "type": "Identifier",
+                          "start":55,"end":56,"loc":{"start":{"line":4,"column":22},"end":{"line":4,"column":23},"identifierName":"x"},
+                          "name": "x"
+                        }
+                      },
+                      "operator": "in",
+                      "right": {
+                        "type": "ObjectExpression",
+                        "start":60,"end":62,"loc":{"start":{"line":4,"column":27},"end":{"line":4,"column":29}},
+                        "properties": []
+                      },
+                      "extra": {
+                        "parenthesized": true,
+                        "parenStart": 53
+                      }
+                    },
+                    "body": {
+                      "type": "ClassBody",
+                      "start":64,"end":66,"loc":{"start":{"line":4,"column":31},"end":{"line":4,"column":33}},
+                      "body": []
+                    }
+                  },
+                  {
+                    "type": "EmptyStatement",
+                    "start":66,"end":67,"loc":{"start":{"line":4,"column":33},"end":{"line":4,"column":34}}
+                  }
+                ],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/private-in/private-in-escaped-sequence/input.js

@@ -0,0 +1,6 @@
+class Foo {
+  #\u{61} = 1;
+  test() {
+    #\u{61} in {};
+  }
+}

packages/babel-parser/test/fixtures/experimental/private-in/private-in-escaped-sequence/options.json

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

packages/babel-parser/test/fixtures/experimental/private-in/private-in-escaped-sequence/output.json

@@ -0,0 +1,98 @@
+{
+  "type": "File",
+  "start":0,"end":62,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":62,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":62,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":6,"end":9,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":9},"identifierName":"Foo"},
+          "name": "Foo"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start":10,"end":62,"loc":{"start":{"line":1,"column":10},"end":{"line":6,"column":1}},
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start":14,"end":26,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":14}},
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start":14,"end":21,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":9}},
+                "id": {
+                  "type": "Identifier",
+                  "start":15,"end":21,"loc":{"start":{"line":2,"column":3},"end":{"line":2,"column":9},"identifierName":"a"},
+                  "name": "a"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start":24,"end":25,"loc":{"start":{"line":2,"column":12},"end":{"line":2,"column":13}},
+                "extra": {
+                  "rawValue": 1,
+                  "raw": "1"
+                },
+                "value": 1
+              }
+            },
+            {
+              "type": "ClassMethod",
+              "start":29,"end":60,"loc":{"start":{"line":3,"column":2},"end":{"line":5,"column":3}},
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":29,"end":33,"loc":{"start":{"line":3,"column":2},"end":{"line":3,"column":6},"identifierName":"test"},
+                "name": "test"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":36,"end":60,"loc":{"start":{"line":3,"column":9},"end":{"line":5,"column":3}},
+                "body": [
+                  {
+                    "type": "ExpressionStatement",
+                    "start":42,"end":56,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":18}},
+                    "expression": {
+                      "type": "BinaryExpression",
+                      "start":42,"end":55,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":17}},
+                      "left": {
+                        "type": "PrivateName",
+                        "start":42,"end":49,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":11}},
+                        "id": {
+                          "type": "Identifier",
+                          "start":43,"end":49,"loc":{"start":{"line":4,"column":5},"end":{"line":4,"column":11},"identifierName":"a"},
+                          "name": "a"
+                        }
+                      },
+                      "operator": "in",
+                      "right": {
+                        "type": "ObjectExpression",
+                        "start":53,"end":55,"loc":{"start":{"line":4,"column":15},"end":{"line":4,"column":17}},
+                        "properties": []
+                      }
+                    }
+                  }
+                ],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/private-in/private-in-parenthesized/input.js

@@ -0,0 +1,6 @@
+class Foo {
+  #x = 1;
+  test() {
+    (#x) in {};
+  }
+}

packages/babel-parser/test/fixtures/experimental/private-in/private-in-parenthesized/options.json

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

packages/babel-parser/test/fixtures/experimental/private-in/private-in-parenthesized/output.json

@@ -0,0 +1,105 @@
+{
+  "type": "File",
+  "start":0,"end":54,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+  "errors": [
+    "SyntaxError: Private names are only allowed in property accesses (`obj.#x`) or in `in` expressions (`#x in obj`) (4:7)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":54,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":54,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":6,"end":9,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":9},"identifierName":"Foo"},
+          "name": "Foo"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start":10,"end":54,"loc":{"start":{"line":1,"column":10},"end":{"line":6,"column":1}},
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start":14,"end":21,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":9}},
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start":14,"end":16,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":4}},
+                "id": {
+                  "type": "Identifier",
+                  "start":15,"end":16,"loc":{"start":{"line":2,"column":3},"end":{"line":2,"column":4},"identifierName":"x"},
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start":19,"end":20,"loc":{"start":{"line":2,"column":7},"end":{"line":2,"column":8}},
+                "extra": {
+                  "rawValue": 1,
+                  "raw": "1"
+                },
+                "value": 1
+              }
+            },
+            {
+              "type": "ClassMethod",
+              "start":24,"end":52,"loc":{"start":{"line":3,"column":2},"end":{"line":5,"column":3}},
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":24,"end":28,"loc":{"start":{"line":3,"column":2},"end":{"line":3,"column":6},"identifierName":"test"},
+                "name": "test"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":31,"end":52,"loc":{"start":{"line":3,"column":9},"end":{"line":5,"column":3}},
+                "body": [
+                  {
+                    "type": "ExpressionStatement",
+                    "start":37,"end":48,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":15}},
+                    "expression": {
+                      "type": "BinaryExpression",
+                      "start":37,"end":47,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":14}},
+                      "left": {
+                        "type": "PrivateName",
+                        "start":38,"end":40,"loc":{"start":{"line":4,"column":5},"end":{"line":4,"column":7}},
+                        "id": {
+                          "type": "Identifier",
+                          "start":39,"end":40,"loc":{"start":{"line":4,"column":6},"end":{"line":4,"column":7},"identifierName":"x"},
+                          "name": "x"
+                        },
+                        "extra": {
+                          "parenthesized": true,
+                          "parenStart": 37
+                        }
+                      },
+                      "operator": "in",
+                      "right": {
+                        "type": "ObjectExpression",
+                        "start":45,"end":47,"loc":{"start":{"line":4,"column":12},"end":{"line":4,"column":14}},
+                        "properties": []
+                      }
+                    }
+                  }
+                ],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/private-in/private-in-without-field/input.js

@@ -0,0 +1,5 @@
+class Foo {
+  test() {
+    #x in {};
+  }
+}

packages/babel-parser/test/fixtures/experimental/private-in/private-in-without-field/options.json

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

packages/babel-parser/test/fixtures/experimental/private-in/private-in-without-field/output.json

@@ -0,0 +1,78 @@
+{
+  "type": "File",
+  "start":0,"end":42,"loc":{"start":{"line":1,"column":0},"end":{"line":5,"column":1}},
+  "errors": [
+    "SyntaxError: Private name #x is not defined (3:4)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":42,"loc":{"start":{"line":1,"column":0},"end":{"line":5,"column":1}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":42,"loc":{"start":{"line":1,"column":0},"end":{"line":5,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":6,"end":9,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":9},"identifierName":"Foo"},
+          "name": "Foo"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start":10,"end":42,"loc":{"start":{"line":1,"column":10},"end":{"line":5,"column":1}},
+          "body": [
+            {
+              "type": "ClassMethod",
+              "start":14,"end":40,"loc":{"start":{"line":2,"column":2},"end":{"line":4,"column":3}},
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":14,"end":18,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":6},"identifierName":"test"},
+                "name": "test"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":21,"end":40,"loc":{"start":{"line":2,"column":9},"end":{"line":4,"column":3}},
+                "body": [
+                  {
+                    "type": "ExpressionStatement",
+                    "start":27,"end":36,"loc":{"start":{"line":3,"column":4},"end":{"line":3,"column":13}},
+                    "expression": {
+                      "type": "BinaryExpression",
+                      "start":27,"end":35,"loc":{"start":{"line":3,"column":4},"end":{"line":3,"column":12}},
+                      "left": {
+                        "type": "PrivateName",
+                        "start":27,"end":29,"loc":{"start":{"line":3,"column":4},"end":{"line":3,"column":6}},
+                        "id": {
+                          "type": "Identifier",
+                          "start":28,"end":29,"loc":{"start":{"line":3,"column":5},"end":{"line":3,"column":6},"identifierName":"x"},
+                          "name": "x"
+                        }
+                      },
+                      "operator": "in",
+                      "right": {
+                        "type": "ObjectExpression",
+                        "start":33,"end":35,"loc":{"start":{"line":3,"column":10},"end":{"line":3,"column":12}},
+                        "properties": []
+                      }
+                    }
+                  }
+                ],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/experimental/private-in/private-in/input.js

@@ -0,0 +1,6 @@
+class Foo {
+  #x = 1;
+  test() {
+    #x in {};
+  }
+}

packages/babel-parser/test/fixtures/experimental/private-in/private-in/options.json

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

packages/babel-parser/test/fixtures/experimental/private-in/private-in/output.json

@@ -0,0 +1,98 @@
+{
+  "type": "File",
+  "start":0,"end":52,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":52,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":52,"loc":{"start":{"line":1,"column":0},"end":{"line":6,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":6,"end":9,"loc":{"start":{"line":1,"column":6},"end":{"line":1,"column":9},"identifierName":"Foo"},
+          "name": "Foo"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start":10,"end":52,"loc":{"start":{"line":1,"column":10},"end":{"line":6,"column":1}},
+          "body": [
+            {
+              "type": "ClassPrivateProperty",
+              "start":14,"end":21,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":9}},
+              "static": false,
+              "key": {
+                "type": "PrivateName",
+                "start":14,"end":16,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":4}},
+                "id": {
+                  "type": "Identifier",
+                  "start":15,"end":16,"loc":{"start":{"line":2,"column":3},"end":{"line":2,"column":4},"identifierName":"x"},
+                  "name": "x"
+                }
+              },
+              "value": {
+                "type": "NumericLiteral",
+                "start":19,"end":20,"loc":{"start":{"line":2,"column":7},"end":{"line":2,"column":8}},
+                "extra": {
+                  "rawValue": 1,
+                  "raw": "1"
+                },
+                "value": 1
+              }
+            },
+            {
+              "type": "ClassMethod",
+              "start":24,"end":50,"loc":{"start":{"line":3,"column":2},"end":{"line":5,"column":3}},
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":24,"end":28,"loc":{"start":{"line":3,"column":2},"end":{"line":3,"column":6},"identifierName":"test"},
+                "name": "test"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":31,"end":50,"loc":{"start":{"line":3,"column":9},"end":{"line":5,"column":3}},
+                "body": [
+                  {
+                    "type": "ExpressionStatement",
+                    "start":37,"end":46,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":13}},
+                    "expression": {
+                      "type": "BinaryExpression",
+                      "start":37,"end":45,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":12}},
+                      "left": {
+                        "type": "PrivateName",
+                        "start":37,"end":39,"loc":{"start":{"line":4,"column":4},"end":{"line":4,"column":6}},
+                        "id": {
+                          "type": "Identifier",
+                          "start":38,"end":39,"loc":{"start":{"line":4,"column":5},"end":{"line":4,"column":6},"identifierName":"x"},
+                          "name": "x"
+                        }
+                      },
+                      "operator": "in",
+                      "right": {
+                        "type": "ObjectExpression",
+                        "start":43,"end":45,"loc":{"start":{"line":4,"column":10},"end":{"line":4,"column":12}},
+                        "properties": []
+                      }
+                    }
+                  }
+                ],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/typings/babel-parser.d.ts

@@ -123,6 +123,7 @@ export type ParserPlugin =
     'partialApplication' |
     'pipelineOperator' |
     'placeholders' |
+    'privateIn' |
     'throwExpressions' |
     'topLevelAwait' |
     'typescript' |

packages/babel-plugin-proposal-private-property-in-object/.npmignore

@@ -0,0 +1,3 @@
+src
+test
+*.log

packages/babel-plugin-proposal-private-property-in-object/README.md

@@ -0,0 +1,20 @@
+# @babel/plugin-proposal-private-property-in-object
+
+> This plugin transforms checks for a private property in an object
+
+See our website [@babel/plugin-proposal-private-property-in-object](https://babeljs.io/docs/en/next/babel-plugin-proposal-private-property-in-object.html) for more information.
+
+## Install
+
+Using npm:
+
+```sh
+npm install --save-dev
+@babel/plugin-proposal-private-property-in-object
+```
+
+or using yarn:
+
+```sh
+yarn add @babel/plugin-proposal-private-property-in-object --dev
+```

packages/babel-plugin-proposal-private-property-in-object/package.json

@@ -0,0 +1,25 @@
+{
+  "name": "@babel/plugin-proposal-private-property-in-object",
+  "version": "7.8.3",
+  "description": "This plugin transforms checks for a private property in an object",
+  "repository": "https://github.com/babel/babel/tree/master/packages/babel-plugin-proposal-private-property-in-object",
+  "license": "MIT",
+  "publishConfig": {
+    "access": "public"
+  },
+  "main": "lib/index.js",
+  "keywords": [
+    "babel-plugin"
+  ],
+  "dependencies": {
+    "@babel/helper-create-class-features-plugin": "^7.8.3",
+    "@babel/helper-plugin-utils": "^7.8.3"
+  },
+  "peerDependencies": {
+    "@babel/core": "^7.0.0-0"
+  },
+  "devDependencies": {
+    "@babel/core": "^7.8.3",
+    "@babel/helper-plugin-test-runner": "^7.8.3"
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/src/index.js

@@ -0,0 +1,22 @@
+/* eslint-disable @babel/development/plugin-name */
+
+import { declare } from "@babel/helper-plugin-utils";
+import {
+  createClassFeaturePlugin,
+  FEATURES,
+} from "@babel/helper-create-class-features-plugin";
+
+export default declare((api, options) => {
+  api.assertVersion(7);
+
+  return createClassFeaturePlugin({
+    name: "proposal-class-properties",
+
+    feature: FEATURES.privateIn,
+    loose: options.loose,
+
+    manipulateOptions(opts, parserOpts) {
+      parserOpts.plugins.push("privateIn");
+    },
+  });
+});

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/accessor/input.js

@@ -0,0 +1,7 @@
+class Foo {
+  get #foo() {}
+
+  test(other) {
+    return #foo in other;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/accessor/output.js

@@ -0,0 +1,23 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+    Object.defineProperty(this, _foo, {
+      get: _get_foo,
+      set: void 0
+    });
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test(other) {
+      return Object.prototype.hasOwnProperty.call(other, _foo);
+    }
+  }]);
+  return Foo;
+}();
+
+var _foo = babelHelpers.classPrivateFieldLooseKey("foo");
+
+var _get_foo = function () {};

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/field/input.js

@@ -0,0 +1,7 @@
+class Foo {
+  #foo = 1;
+
+  test(other) {
+    return #foo in other;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/field/output.js

@@ -0,0 +1,21 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+    Object.defineProperty(this, _foo, {
+      writable: true,
+      value: 1
+    });
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test(other) {
+      return Object.prototype.hasOwnProperty.call(other, _foo);
+    }
+  }]);
+  return Foo;
+}();
+
+var _foo = babelHelpers.classPrivateFieldLooseKey("foo");

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/method/input.js

@@ -0,0 +1,7 @@
+class Foo {
+  #foo() {}
+
+  test(other) {
+    return #foo in other;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/method/output.js

@@ -0,0 +1,22 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+    Object.defineProperty(this, _foo, {
+      value: _foo2
+    });
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test(other) {
+      return Object.prototype.hasOwnProperty.call(other, _foo);
+    }
+  }]);
+  return Foo;
+}();
+
+var _foo = babelHelpers.classPrivateFieldLooseKey("foo");
+
+var _foo2 = function _foo2() {};

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/native-classes/input.js

@@ -0,0 +1,12 @@
+class Foo {
+  static #foo = "foo";
+  #bar = "bar";
+
+  static test() {
+    return #foo in Foo;
+  }
+
+  test() {
+    return #bar in this;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/native-classes/options.json

@@ -0,0 +1,8 @@
+{
+  "plugins": [
+    ["external-helpers", { "helperVersion": "7.100.0" }],
+    "proposal-private-property-in-object",
+    "proposal-class-properties",
+    "proposal-private-methods"
+  ]
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/native-classes/output.js

@@ -0,0 +1,24 @@
+class Foo {
+  constructor() {
+    _bar.set(this, {
+      writable: true,
+      value: "bar"
+    });
+  }
+
+  static test() {
+    return Foo === Foo;
+  }
+
+  test() {
+    return _bar.has(this);
+  }
+
+}
+
+var _bar = new WeakMap();
+
+var _foo = {
+  writable: true,
+  value: "foo"
+};

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/nested-class-other-redeclared/input.js

@@ -0,0 +1,18 @@
+class Foo {
+  #foo = 1;
+  #bar = 1;
+
+  test() {
+    class Nested {
+      #bar = 2;
+
+      test() {
+        #foo in this;
+        #bar in this;
+      }
+    }
+
+    #foo in this;
+    #bar in this;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/nested-class-other-redeclared/output.js

@@ -0,0 +1,49 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+    Object.defineProperty(this, _foo, {
+      writable: true,
+      value: 1
+    });
+    Object.defineProperty(this, _bar, {
+      writable: true,
+      value: 1
+    });
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test() {
+      let Nested = /*#__PURE__*/function () {
+        function Nested() {
+          babelHelpers.classCallCheck(this, Nested);
+          Object.defineProperty(this, _bar2, {
+            writable: true,
+            value: 2
+          });
+        }
+
+        babelHelpers.createClass(Nested, [{
+          key: "test",
+          value: function test() {
+            Object.prototype.hasOwnProperty.call(this, _foo);
+            Object.prototype.hasOwnProperty.call(this, _bar2);
+          }
+        }]);
+        return Nested;
+      }();
+
+      var _bar2 = babelHelpers.classPrivateFieldLooseKey("bar");
+
+      Object.prototype.hasOwnProperty.call(this, _foo);
+      Object.prototype.hasOwnProperty.call(this, _bar);
+    }
+  }]);
+  return Foo;
+}();
+
+var _foo = babelHelpers.classPrivateFieldLooseKey("foo");
+
+var _bar = babelHelpers.classPrivateFieldLooseKey("bar");

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/nested-class-redeclared/input.js

@@ -0,0 +1,15 @@
+class Foo {
+  #foo = 1;
+
+  test() {
+    class Nested {
+      #foo = 2;
+
+      test() {
+        #foo in this;
+      }
+    }
+
+    #foo in this;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/nested-class-redeclared/output.js

@@ -0,0 +1,41 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+    Object.defineProperty(this, _foo, {
+      writable: true,
+      value: 1
+    });
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test() {
+      let Nested = /*#__PURE__*/function () {
+        function Nested() {
+          babelHelpers.classCallCheck(this, Nested);
+          Object.defineProperty(this, _foo2, {
+            writable: true,
+            value: 2
+          });
+        }
+
+        babelHelpers.createClass(Nested, [{
+          key: "test",
+          value: function test() {
+            Object.prototype.hasOwnProperty.call(this, _foo2);
+          }
+        }]);
+        return Nested;
+      }();
+
+      var _foo2 = babelHelpers.classPrivateFieldLooseKey("foo");
+
+      Object.prototype.hasOwnProperty.call(this, _foo);
+    }
+  }]);
+  return Foo;
+}();
+
+var _foo = babelHelpers.classPrivateFieldLooseKey("foo");

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/nested-class/input.js

@@ -0,0 +1,13 @@
+class Foo {
+  #foo = 1;
+
+  test() {
+    class Nested {
+      test() {
+        #foo in this;
+      }
+    }
+
+    #foo in this;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/nested-class/output.js

@@ -0,0 +1,35 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+    Object.defineProperty(this, _foo, {
+      writable: true,
+      value: 1
+    });
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test() {
+      let Nested = /*#__PURE__*/function () {
+        function Nested() {
+          babelHelpers.classCallCheck(this, Nested);
+        }
+
+        babelHelpers.createClass(Nested, [{
+          key: "test",
+          value: function test() {
+            Object.prototype.hasOwnProperty.call(this, _foo);
+          }
+        }]);
+        return Nested;
+      }();
+
+      Object.prototype.hasOwnProperty.call(this, _foo);
+    }
+  }]);
+  return Foo;
+}();
+
+var _foo = babelHelpers.classPrivateFieldLooseKey("foo");

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/options.json

@@ -0,0 +1,9 @@
+{
+  "plugins": [
+    ["external-helpers", { "helperVersion": "7.100.0" }],
+    ["proposal-private-property-in-object", { "loose": true }],
+    ["proposal-class-properties", { "loose": true }],
+    ["proposal-private-methods", { "loose": true }],
+    "transform-classes"
+  ]
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/static-accessor/input.js

@@ -0,0 +1,7 @@
+class Foo {
+  static get #foo() {}
+
+  test(other) {
+    return #foo in other;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/static-accessor/output.js

@@ -0,0 +1,24 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test(other) {
+      return Object.prototype.hasOwnProperty.call(other, _foo);
+    }
+  }]);
+  return Foo;
+}();
+
+var _foo = babelHelpers.classPrivateFieldLooseKey("foo");
+
+var _get_foo = function () {};
+
+Object.defineProperty(Foo, _foo, {
+  get: _get_foo,
+  set: void 0
+});

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/static-field/input.js

@@ -0,0 +1,7 @@
+class Foo {
+  static #foo = 1;
+
+  test(other) {
+    return #foo in other;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/static-field/output.js

@@ -0,0 +1,22 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test(other) {
+      return Object.prototype.hasOwnProperty.call(other, _foo);
+    }
+  }]);
+  return Foo;
+}();
+
+var _foo = babelHelpers.classPrivateFieldLooseKey("foo");
+
+Object.defineProperty(Foo, _foo, {
+  writable: true,
+  value: 1
+});

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/static-method/input.js

@@ -0,0 +1,7 @@
+class Foo {
+  static #foo() {}
+
+  test(other) {
+    return #foo in other;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private-loose/static-method/output.js

@@ -0,0 +1,23 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test(other) {
+      return Object.prototype.hasOwnProperty.call(other, _foo);
+    }
+  }]);
+  return Foo;
+}();
+
+var _foo = babelHelpers.classPrivateFieldLooseKey("foo");
+
+var _foo2 = function _foo2() {};
+
+Object.defineProperty(Foo, _foo, {
+  value: _foo2
+});

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/accessor/input.js

@@ -0,0 +1,7 @@
+class Foo {
+  get #foo() {}
+
+  test(other) {
+    return #foo in other;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/accessor/output.js

@@ -0,0 +1,24 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+
+    _foo.set(this, {
+      get: _get_foo,
+      set: void 0
+    });
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test(other) {
+      return _foo.has(other);
+    }
+  }]);
+  return Foo;
+}();
+
+var _foo = new WeakMap();
+
+var _get_foo = function () {};

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/field/input.js

@@ -0,0 +1,7 @@
+class Foo {
+  #foo = 1;
+
+  test(other) {
+    return #foo in other;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/field/output.js

@@ -0,0 +1,22 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+
+    _foo.set(this, {
+      writable: true,
+      value: 1
+    });
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test(other) {
+      return _foo.has(other);
+    }
+  }]);
+  return Foo;
+}();
+
+var _foo = new WeakMap();

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/method/input.js

@@ -0,0 +1,7 @@
+class Foo {
+  #foo() {}
+
+  test(other) {
+    return #foo in other;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/method/output.js

@@ -0,0 +1,21 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+
+    _foo.add(this);
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test(other) {
+      return _foo.has(other);
+    }
+  }]);
+  return Foo;
+}();
+
+var _foo = new WeakSet();
+
+var _foo2 = function _foo2() {};

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/native-classes/input.js

@@ -0,0 +1,12 @@
+class Foo {
+  static #foo = "foo";
+  #bar = "bar";
+
+  static test() {
+    return #foo in Foo;
+  }
+
+  test() {
+    return #bar in this;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/native-classes/options.json

@@ -0,0 +1,8 @@
+{
+  "plugins": [
+    ["external-helpers", { "helperVersion": "7.100.0" }],
+    "proposal-private-property-in-object",
+    "proposal-class-properties",
+    "proposal-private-methods"
+  ]
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/native-classes/output.js

@@ -0,0 +1,24 @@
+class Foo {
+  constructor() {
+    _bar.set(this, {
+      writable: true,
+      value: "bar"
+    });
+  }
+
+  static test() {
+    return Foo === Foo;
+  }
+
+  test() {
+    return _bar.has(this);
+  }
+
+}
+
+var _bar = new WeakMap();
+
+var _foo = {
+  writable: true,
+  value: "foo"
+};

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/nested-class-other-redeclared/input.js

@@ -0,0 +1,18 @@
+class Foo {
+  #foo = 1;
+  #bar = 1;
+
+  test() {
+    class Nested {
+      #bar = 2;
+
+      test() {
+        #foo in this;
+        #bar in this;
+      }
+    }
+
+    #foo in this;
+    #bar in this;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/nested-class-other-redeclared/output.js

@@ -0,0 +1,54 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+
+    _foo.set(this, {
+      writable: true,
+      value: 1
+    });
+
+    _bar.set(this, {
+      writable: true,
+      value: 1
+    });
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test() {
+      let Nested = /*#__PURE__*/function () {
+        function Nested() {
+          babelHelpers.classCallCheck(this, Nested);
+
+          _bar2.set(this, {
+            writable: true,
+            value: 2
+          });
+        }
+
+        babelHelpers.createClass(Nested, [{
+          key: "test",
+          value: function test() {
+            _foo.has(this);
+
+            _bar2.has(this);
+          }
+        }]);
+        return Nested;
+      }();
+
+      var _bar2 = new WeakMap();
+
+      _foo.has(this);
+
+      _bar.has(this);
+    }
+  }]);
+  return Foo;
+}();
+
+var _foo = new WeakMap();
+
+var _bar = new WeakMap();

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/nested-class-redeclared/input.js

@@ -0,0 +1,15 @@
+class Foo {
+  #foo = 1;
+
+  test() {
+    class Nested {
+      #foo = 2;
+
+      test() {
+        #foo in this;
+      }
+    }
+
+    #foo in this;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/nested-class-redeclared/output.js

@@ -0,0 +1,43 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+
+    _foo.set(this, {
+      writable: true,
+      value: 1
+    });
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test() {
+      let Nested = /*#__PURE__*/function () {
+        function Nested() {
+          babelHelpers.classCallCheck(this, Nested);
+
+          _foo2.set(this, {
+            writable: true,
+            value: 2
+          });
+        }
+
+        babelHelpers.createClass(Nested, [{
+          key: "test",
+          value: function test() {
+            _foo2.has(this);
+          }
+        }]);
+        return Nested;
+      }();
+
+      var _foo2 = new WeakMap();
+
+      _foo.has(this);
+    }
+  }]);
+  return Foo;
+}();
+
+var _foo = new WeakMap();

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/nested-class/input.js

@@ -0,0 +1,13 @@
+class Foo {
+  #foo = 1;
+
+  test() {
+    class Nested {
+      test() {
+        #foo in this;
+      }
+    }
+
+    #foo in this;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/nested-class/output.js

@@ -0,0 +1,36 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+
+    _foo.set(this, {
+      writable: true,
+      value: 1
+    });
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test() {
+      let Nested = /*#__PURE__*/function () {
+        function Nested() {
+          babelHelpers.classCallCheck(this, Nested);
+        }
+
+        babelHelpers.createClass(Nested, [{
+          key: "test",
+          value: function test() {
+            _foo.has(this);
+          }
+        }]);
+        return Nested;
+      }();
+
+      _foo.has(this);
+    }
+  }]);
+  return Foo;
+}();
+
+var _foo = new WeakMap();

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/options.json

@@ -0,0 +1,9 @@
+{
+  "plugins": [
+    ["external-helpers", { "helperVersion": "7.100.0" }],
+    "proposal-private-property-in-object",
+    "proposal-class-properties",
+    "proposal-private-methods",
+    "transform-classes"
+  ]
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/static-accessor/input.js

@@ -0,0 +1,7 @@
+class Foo {
+  static get #foo() {}
+
+  test(other) {
+    return #foo in other;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/static-accessor/output.js

@@ -0,0 +1,22 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test(other) {
+      return other === Foo;
+    }
+  }]);
+  return Foo;
+}();
+
+var _get_foo = function () {};
+
+var _foo = {
+  get: _get_foo,
+  set: void 0
+};

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/static-field/input.js

@@ -0,0 +1,7 @@
+class Foo {
+  static #foo = 1;
+
+  test(other) {
+    return #foo in other;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/static-field/output.js

@@ -0,0 +1,20 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test(other) {
+      return other === Foo;
+    }
+  }]);
+  return Foo;
+}();
+
+var _foo = {
+  writable: true,
+  value: 1
+};

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/static-method/input.js

@@ -0,0 +1,7 @@
+class Foo {
+  static #foo() {}
+
+  test(other) {
+    return #foo in other;
+  }
+}

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/private/static-method/output.js

@@ -0,0 +1,17 @@
+let Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+  }
+
+  babelHelpers.createClass(Foo, [{
+    key: "test",
+    value: function test(other) {
+      return other === Foo;
+    }
+  }]);
+  return Foo;
+}();
+
+var _foo = function _foo() {};

packages/babel-plugin-proposal-private-property-in-object/test/index.js

@@ -0,0 +1,3 @@
+import runner from "@babel/helper-plugin-test-runner";
+
+runner(__dirname);

packages/babel-types/src/definitions/core.js

@@ -80,7 +80,15 @@ defineType("BinaryExpression", {
       validate: assertOneOf(...BINARY_OPERATORS),
     },
     left: {
-      validate: assertNodeType("Expression"),
+      validate: (function() {
+        const expression = assertNodeType("Expression");
+        const inOp = assertNodeType("Expression", "PrivateName");
+
+        return function(node, key, val) {
+          const validator = node.operator === "in" ? inOp : expression;
+          validator(node, key, val);
+        };
+      })(),
     },
     right: {
       validate: assertNodeType("Expression"),