From 5a7a782da2e842f20d39f18e0ec3e9f2558ba3e0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicol=C3=B2=20Ribaudo?= <nicolo.ribaudo@gmail.com>
Date: Wed, 21 Apr 2021 18:03:42 +0200
Subject: [PATCH] Add private brand checks to `shippedProposals` (#13176)

---
 packages/babel-compat-data/data/plugins.json   |  3 +++
 .../scripts/data/plugin-features.js            |  2 ++
 .../scripts/download-compat-table.sh           |  2 +-
 .../babel-preset-env/data/shipped-proposals.js |  2 ++
 packages/babel-preset-env/package.json         |  2 ++
 .../babel-preset-env/src/available-plugins.js  |  5 +++++
 packages/babel-preset-env/src/index.js         |  2 --
 .../stdout.txt                                 |  1 +
 .../entry-corejs2-shippedProposals/stdout.txt  |  1 +
 .../entry-corejs3-all-chrome-71/stdout.txt     |  1 +
 .../debug-babel-7/entry-corejs3-all/stdout.txt |  1 +
 .../entry-corejs3-babel-polyfill/stdout.txt    |  1 +
 .../entry-corejs3-es-chrome-71/stdout.txt      |  1 +
 .../stdout.txt                                 |  1 +
 .../entry-corejs3-es-proposals/stdout.txt      |  1 +
 .../debug-babel-7/entry-corejs3-es/stdout.txt  |  1 +
 .../stdout.txt                                 |  1 +
 .../entry-corejs3-runtime-only/stdout.txt      |  1 +
 .../stdout.txt                                 |  1 +
 .../entry-corejs3-specific-entries/stdout.txt  |  1 +
 .../entry-corejs3-stable-chrome-71/stdout.txt  |  1 +
 .../stdout.txt                                 |  1 +
 .../entry-corejs3-stable/stdout.txt            |  1 +
 .../entry-corejs3-stage-chrome-71/stdout.txt   |  1 +
 .../entry-corejs3-stage/stdout.txt             |  1 +
 .../entry-corejs3-web-chrome-71/stdout.txt     |  1 +
 .../debug-babel-7/entry-corejs3-web/stdout.txt |  1 +
 .../stdout.txt                                 |  1 +
 .../shippedProposals-chrome-80/stdout.txt      |  1 +
 .../shippedProposals-chrome-84/stdout.txt      |  1 +
 .../stdout.txt                                 |  1 +
 .../stdout.txt                                 |  1 +
 .../stdout.txt                                 |  1 +
 .../stdout.txt                                 |  1 +
 .../stdout.txt                                 |  1 +
 .../entry-corejs2-shippedProposals/stdout.txt  |  1 +
 .../entry-corejs3-all-chrome-71/stdout.txt     |  1 +
 .../debug/entry-corejs3-all/stdout.txt         |  1 +
 .../entry-corejs3-babel-polyfill/stdout.txt    |  1 +
 .../entry-corejs3-es-chrome-71/stdout.txt      |  1 +
 .../stdout.txt                                 |  1 +
 .../entry-corejs3-es-proposals/stdout.txt      |  1 +
 .../fixtures/debug/entry-corejs3-es/stdout.txt |  1 +
 .../stdout.txt                                 |  1 +
 .../entry-corejs3-runtime-only/stdout.txt      |  1 +
 .../stdout.txt                                 |  1 +
 .../entry-corejs3-specific-entries/stdout.txt  |  1 +
 .../entry-corejs3-stable-chrome-71/stdout.txt  |  1 +
 .../stdout.txt                                 |  1 +
 .../debug/entry-corejs3-stable/stdout.txt      |  1 +
 .../entry-corejs3-stage-chrome-71/stdout.txt   |  1 +
 .../debug/entry-corejs3-stage/stdout.txt       |  1 +
 .../entry-corejs3-web-chrome-71/stdout.txt     |  1 +
 .../debug/entry-corejs3-web/stdout.txt         |  1 +
 .../stdout.txt                                 |  1 +
 .../shippedProposals-chrome-80/stdout.txt      |  1 +
 .../shippedProposals-chrome-84/stdout.txt      |  1 +
 .../stdout.txt                                 |  1 +
 .../stdout.txt                                 |  1 +
 .../stdout.txt                                 |  1 +
 .../stdout.txt                                 |  1 +
 .../methods-loose-preset-not-loose/stderr.txt  |  6 +++++-
 .../stderr.txt                                 |  4 ++++
 .../stderr.txt                                 |  4 ++++
 .../stderr.txt                                 |  6 +++++-
 .../stderr.txt                                 |  6 +++++-
 .../class-static-block-chrome-90/input.js      |  5 -----
 .../class-static-block-chrome-90/output.js     |  5 -----
 .../class-static-block-chrome-91/input.js      |  5 -----
 .../class-static-block-chrome-91/output.js     |  5 -----
 .../class-static-block-firefox-70/input.js     |  5 -----
 .../class-static-block-firefox-70/output.js    |  8 --------
 .../new-class-features-chrome-90/input.js      |  7 +++++++
 .../options.json                               |  0
 .../new-class-features-chrome-90/output.js     |  8 ++++++++
 .../new-class-features-chrome-91/input.js      |  7 +++++++
 .../options.json                               |  0
 .../new-class-features-chrome-91/output.js     |  6 ++++++
 .../new-class-features-firefox-70/input.js     |  7 +++++++
 .../options.json                               |  0
 .../new-class-features-firefox-70/output.js    | 18 ++++++++++++++++++
 yarn.lock                                      |  4 +++-
 82 files changed, 148 insertions(+), 40 deletions(-)
 create mode 100644 packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-and-methods-loose-preset-not-loose/stderr.txt
 create mode 100644 packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-and-methods-not-loose-preset-loose/stderr.txt
 delete mode 100644 packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-90/input.js
 delete mode 100644 packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-90/output.js
 delete mode 100644 packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-91/input.js
 delete mode 100644 packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-91/output.js
 delete mode 100644 packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-firefox-70/input.js
 delete mode 100644 packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-firefox-70/output.js
 create mode 100644 packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-90/input.js
 rename packages/babel-preset-env/test/fixtures/shipped-proposals/{class-static-block-chrome-90 => new-class-features-chrome-90}/options.json (100%)
 create mode 100644 packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-90/output.js
 create mode 100644 packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-91/input.js
 rename packages/babel-preset-env/test/fixtures/shipped-proposals/{class-static-block-chrome-91 => new-class-features-chrome-91}/options.json (100%)
 create mode 100644 packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-91/output.js
 create mode 100644 packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-firefox-70/input.js
 rename packages/babel-preset-env/test/fixtures/shipped-proposals/{class-static-block-firefox-70 => new-class-features-firefox-70}/options.json (100%)
 create mode 100644 packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-firefox-70/output.js

diff --git a/packages/babel-compat-data/data/plugins.json b/packages/babel-compat-data/data/plugins.json
index 691587999e..7c60c3bb53 100644
--- a/packages/babel-compat-data/data/plugins.json
+++ b/packages/babel-compat-data/data/plugins.json
@@ -2,6 +2,9 @@
   "proposal-class-static-block": {
     "chrome": "91"
   },
+  "proposal-private-property-in-object": {
+    "chrome": "91"
+  },
   "proposal-class-properties": {
     "chrome": "74",
     "opera": "62",
diff --git a/packages/babel-compat-data/scripts/data/plugin-features.js b/packages/babel-compat-data/scripts/data/plugin-features.js
index ca3deb5b23..49c687f1bf 100644
--- a/packages/babel-compat-data/scripts/data/plugin-features.js
+++ b/packages/babel-compat-data/scripts/data/plugin-features.js
@@ -136,6 +136,8 @@ const es2021 = {
 
 const shippedProposal = {
   "proposal-class-static-block": "Class static initialization blocks",
+  "proposal-private-property-in-object":
+    "Ergonomic brand checks for private fields",
   "proposal-class-properties": {
     features: [
       "static class fields",
diff --git a/packages/babel-compat-data/scripts/download-compat-table.sh b/packages/babel-compat-data/scripts/download-compat-table.sh
index 53793a1fe9..8db31ddeaf 100755
--- a/packages/babel-compat-data/scripts/download-compat-table.sh
+++ b/packages/babel-compat-data/scripts/download-compat-table.sh
@@ -1,7 +1,7 @@
 #!/bin/bash
 set -e
 
-COMPAT_TABLE_COMMIT=ca2d70e305bc3295ade6b06a1c33a929db1ccacf
+COMPAT_TABLE_COMMIT=bcf74805f08ef13371ebe3aa36030bed4cd9a902
 GIT_HEAD=build/compat-table/.git/HEAD
 
 if [ -d "build/compat-table" ]; then
diff --git a/packages/babel-preset-env/data/shipped-proposals.js b/packages/babel-preset-env/data/shipped-proposals.js
index 96f531b55b..43f92047d4 100644
--- a/packages/babel-preset-env/data/shipped-proposals.js
+++ b/packages/babel-preset-env/data/shipped-proposals.js
@@ -6,6 +6,7 @@ const proposalPlugins = new Set([
   "proposal-class-properties",
   "proposal-private-methods",
   "proposal-class-static-block",
+  "proposal-private-property-in-object",
 ]);
 
 // use intermediary object to enforce alphabetical key order
@@ -21,6 +22,7 @@ const pluginSyntaxObject = {
   "proposal-optional-chaining": "syntax-optional-chaining",
   // note: we don't have syntax-private-methods
   "proposal-private-methods": "syntax-class-properties",
+  "proposal-private-property-in-object": "syntax-private-property-in-object",
   "proposal-unicode-property-regex": null,
 };
 
diff --git a/packages/babel-preset-env/package.json b/packages/babel-preset-env/package.json
index 8714f22560..fce3b84fbe 100644
--- a/packages/babel-preset-env/package.json
+++ b/packages/babel-preset-env/package.json
@@ -34,6 +34,7 @@
     "@babel/plugin-proposal-optional-catch-binding": "workspace:^7.13.8",
     "@babel/plugin-proposal-optional-chaining": "workspace:^7.13.12",
     "@babel/plugin-proposal-private-methods": "workspace:^7.13.0",
+    "@babel/plugin-proposal-private-property-in-object": "workspace:^7.13.0",
     "@babel/plugin-proposal-unicode-property-regex": "workspace:^7.12.13",
     "@babel/plugin-syntax-async-generators": "^7.8.4",
     "@babel/plugin-syntax-class-properties": "workspace:^7.12.13",
@@ -47,6 +48,7 @@
     "@babel/plugin-syntax-object-rest-spread": "^7.8.3",
     "@babel/plugin-syntax-optional-catch-binding": "^7.8.3",
     "@babel/plugin-syntax-optional-chaining": "^7.8.3",
+    "@babel/plugin-syntax-private-property-in-object": "workspace:^7.13.0",
     "@babel/plugin-syntax-top-level-await": "workspace:^7.12.13",
     "@babel/plugin-transform-arrow-functions": "workspace:^7.13.0",
     "@babel/plugin-transform-async-to-generator": "workspace:^7.13.0",
diff --git a/packages/babel-preset-env/src/available-plugins.js b/packages/babel-preset-env/src/available-plugins.js
index e55cc27deb..d7fb70a939 100644
--- a/packages/babel-preset-env/src/available-plugins.js
+++ b/packages/babel-preset-env/src/available-plugins.js
@@ -13,6 +13,7 @@ import syntaxNumericSeparator from "@babel/plugin-syntax-numeric-separator";
 import syntaxObjectRestSpread from "@babel/plugin-syntax-object-rest-spread";
 import syntaxOptionalCatchBinding from "@babel/plugin-syntax-optional-catch-binding";
 import syntaxOptionalChaining from "@babel/plugin-syntax-optional-chaining";
+import syntaxPrivatePropertyInObject from "@babel/plugin-syntax-private-property-in-object";
 import syntaxTopLevelAwait from "@babel/plugin-syntax-top-level-await";
 import proposalAsyncGeneratorFunctions from "@babel/plugin-proposal-async-generator-functions";
 import proposalClassProperties from "@babel/plugin-proposal-class-properties";
@@ -27,6 +28,7 @@ import proposalObjectRestSpread from "@babel/plugin-proposal-object-rest-spread"
 import proposalOptionalCatchBinding from "@babel/plugin-proposal-optional-catch-binding";
 import proposalOptionalChaining from "@babel/plugin-proposal-optional-chaining";
 import proposalPrivateMethods from "@babel/plugin-proposal-private-methods";
+import proposalPrivatePropertyInObject from "@babel/plugin-proposal-private-property-in-object";
 import proposalUnicodePropertyRegex from "@babel/plugin-proposal-unicode-property-regex";
 import transformAsyncToGenerator from "@babel/plugin-transform-async-to-generator";
 import transformArrowFunctions from "@babel/plugin-transform-arrow-functions";
@@ -93,6 +95,7 @@ export default {
   "proposal-optional-catch-binding": () => proposalOptionalCatchBinding,
   "proposal-optional-chaining": () => proposalOptionalChaining,
   "proposal-private-methods": () => proposalPrivateMethods,
+  "proposal-private-property-in-object": () => proposalPrivatePropertyInObject,
   "proposal-unicode-property-regex": () => proposalUnicodePropertyRegex,
   "syntax-async-generators": () => syntaxAsyncGenerators,
   "syntax-class-properties": () => syntaxClassProperties,
@@ -106,6 +109,7 @@ export default {
   "syntax-object-rest-spread": () => syntaxObjectRestSpread,
   "syntax-optional-catch-binding": () => syntaxOptionalCatchBinding,
   "syntax-optional-chaining": () => syntaxOptionalChaining,
+  "syntax-private-property-in-object": () => syntaxPrivatePropertyInObject,
   "syntax-top-level-await": () => syntaxTopLevelAwait,
   "transform-arrow-functions": () => transformArrowFunctions,
   "transform-async-to-generator": () => transformAsyncToGenerator,
@@ -145,4 +149,5 @@ export default {
 
 export const minVersions = {
   "proposal-class-static-block": "7.12.0",
+  "proposal-private-property-in-object": "7.10.0",
 };
diff --git a/packages/babel-preset-env/src/index.js b/packages/babel-preset-env/src/index.js
index e6c083a03e..bb6634b218 100644
--- a/packages/babel-preset-env/src/index.js
+++ b/packages/babel-preset-env/src/index.js
@@ -394,8 +394,6 @@ option \`forceAllTransforms: true\` instead.
       if (
         pluginName === "proposal-class-properties" ||
         pluginName === "proposal-private-methods" ||
-        // This is not included in preset-env yet, but let's keep it here so we
-        // don't forget about it in the future.
         pluginName === "proposal-private-property-in-object"
       ) {
         return [
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs2-shippedProposals-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs2-shippedProposals-chrome-71/stdout.txt
index 3a09cdfdf0..4af2511633 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs2-shippedProposals-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs2-shippedProposals-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs2-shippedProposals/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs2-shippedProposals/stdout.txt
index d501bfc1fe..93cec117ed 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs2-shippedProposals/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs2-shippedProposals/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-all-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-all-chrome-71/stdout.txt
index 77289e9ab9..958e75dcfb 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-all-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-all-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-all/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-all/stdout.txt
index 318d328c72..349d8cd1c4 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-all/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-all/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-babel-polyfill/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-babel-polyfill/stdout.txt
index 5dd03a627f..508a267c46 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-babel-polyfill/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-babel-polyfill/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-es-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-es-chrome-71/stdout.txt
index f96c3848b1..1ac2dde624 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-es-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-es-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-es-proposals-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-es-proposals-chrome-71/stdout.txt
index e7ba66cd36..ffaed0f7f5 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-es-proposals-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-es-proposals-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-es-proposals/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-es-proposals/stdout.txt
index 1328e0db79..2e86cc88d8 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-es-proposals/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-es-proposals/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-es/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-es/stdout.txt
index aed2fa1fab..1c2f3e34d7 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-es/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-es/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-runtime-only-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-runtime-only-chrome-71/stdout.txt
index 07769ffcb4..12c006098f 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-runtime-only-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-runtime-only-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-runtime-only/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-runtime-only/stdout.txt
index 0cd29b4f92..bcaf2b9968 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-runtime-only/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-runtime-only/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-specific-entries-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-specific-entries-chrome-71/stdout.txt
index a6fd6d2963..b808eb47fd 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-specific-entries-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-specific-entries-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-specific-entries/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-specific-entries/stdout.txt
index ba80ac716d..2e1d4a283c 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-specific-entries/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-specific-entries/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stable-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stable-chrome-71/stdout.txt
index 21fc079d1b..7a35910e8f 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stable-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stable-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stable-samsung-8.2/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stable-samsung-8.2/stdout.txt
index f8314e71a3..c2193ff7de 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stable-samsung-8.2/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stable-samsung-8.2/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { samsung }
+  proposal-private-property-in-object { samsung }
   proposal-class-properties { samsung }
   proposal-private-methods { samsung }
   proposal-numeric-separator { samsung < 11 }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stable/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stable/stdout.txt
index 57fed1f3ee..2bf51a3dbe 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stable/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stable/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stage-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stage-chrome-71/stdout.txt
index 2875f45685..31bd6fb4df 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stage-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stage-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stage/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stage/stdout.txt
index 5bc6800eaa..27480b80a3 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stage/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-stage/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-web-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-web-chrome-71/stdout.txt
index 6075ed9143..72085bb032 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-web-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-web-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-web/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-web/stdout.txt
index a20e766fc6..53617e7ff8 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-web/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-corejs3-web/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-no-corejs-shippedProposals/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-no-corejs-shippedProposals/stdout.txt
index 05b0129fa6..9a5f98e41c 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-no-corejs-shippedProposals/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/entry-no-corejs-shippedProposals/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/shippedProposals-chrome-80/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/shippedProposals-chrome-80/stdout.txt
index d4d9db78cf..9c8b3e4a45 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/shippedProposals-chrome-80/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/shippedProposals-chrome-80/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   syntax-numeric-separator
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/shippedProposals-chrome-84/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/shippedProposals-chrome-84/stdout.txt
index dcdf235ab5..d5ac3a7cb1 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/shippedProposals-chrome-84/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/shippedProposals-chrome-84/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   syntax-class-properties
   syntax-numeric-separator
   proposal-logical-assignment-operators { chrome < 85 }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/usage-corejs2-shippedProposals-1/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/usage-corejs2-shippedProposals-1/stdout.txt
index 4b1e5d5190..18944ea30e 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/usage-corejs2-shippedProposals-1/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/usage-corejs2-shippedProposals-1/stdout.txt
@@ -11,6 +11,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91, firefox, ie }
+  proposal-private-property-in-object { chrome < 91, firefox, ie }
   proposal-class-properties { chrome < 84, firefox, ie }
   proposal-private-methods { chrome < 84, firefox, ie }
   proposal-numeric-separator { chrome < 75, firefox < 70, ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/usage-corejs2-shippedProposals-2/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/usage-corejs2-shippedProposals-2/stdout.txt
index f8c122d311..f151202e10 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/usage-corejs2-shippedProposals-2/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/usage-corejs2-shippedProposals-2/stdout.txt
@@ -11,6 +11,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91, firefox, ie }
+  proposal-private-property-in-object { chrome < 91, firefox, ie }
   proposal-class-properties { chrome < 84, firefox, ie }
   proposal-private-methods { chrome < 84, firefox, ie }
   proposal-numeric-separator { chrome < 75, firefox < 70, ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/usage-corejs3-shippedProposals-1/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/usage-corejs3-shippedProposals-1/stdout.txt
index 6382df362e..b8f57b58b7 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/usage-corejs3-shippedProposals-1/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/usage-corejs3-shippedProposals-1/stdout.txt
@@ -11,6 +11,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91, firefox, ie }
+  proposal-private-property-in-object { chrome < 91, firefox, ie }
   proposal-class-properties { chrome < 84, firefox, ie }
   proposal-private-methods { chrome < 84, firefox, ie }
   proposal-numeric-separator { chrome < 75, firefox < 70, ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug-babel-7/usage-corejs3-shippedProposals-2/stdout.txt b/packages/babel-preset-env/test/fixtures/debug-babel-7/usage-corejs3-shippedProposals-2/stdout.txt
index 392519960d..3fdc2a1bda 100644
--- a/packages/babel-preset-env/test/fixtures/debug-babel-7/usage-corejs3-shippedProposals-2/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug-babel-7/usage-corejs3-shippedProposals-2/stdout.txt
@@ -11,6 +11,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91, firefox, ie }
+  proposal-private-property-in-object { chrome < 91, firefox, ie }
   proposal-class-properties { chrome < 84, firefox, ie }
   proposal-private-methods { chrome < 84, firefox, ie }
   proposal-numeric-separator { chrome < 75, firefox < 70, ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs2-shippedProposals-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs2-shippedProposals-chrome-71/stdout.txt
index b1a3ffb905..e928f6277d 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs2-shippedProposals-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs2-shippedProposals-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs2-shippedProposals/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs2-shippedProposals/stdout.txt
index 99be3a5df3..e36a14f077 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs2-shippedProposals/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs2-shippedProposals/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-all-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-all-chrome-71/stdout.txt
index d1b82e2ad6..6fffa4b913 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-all-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-all-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-all/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-all/stdout.txt
index 7901694de2..bce49b559a 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-all/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-all/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-babel-polyfill/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-babel-polyfill/stdout.txt
index 18dd722656..ee6b4d9fb6 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-babel-polyfill/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-babel-polyfill/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es-chrome-71/stdout.txt
index a2ceded625..0220f19070 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es-proposals-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es-proposals-chrome-71/stdout.txt
index 5bdede8137..71c74afd46 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es-proposals-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es-proposals-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es-proposals/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es-proposals/stdout.txt
index 03ef9fd230..461c3cfc71 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es-proposals/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es-proposals/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es/stdout.txt
index 0b482ee835..b63af9d26c 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-es/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-runtime-only-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-runtime-only-chrome-71/stdout.txt
index db8e43d642..4f2ac405ec 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-runtime-only-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-runtime-only-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-runtime-only/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-runtime-only/stdout.txt
index 50a939baec..bb650165a2 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-runtime-only/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-runtime-only/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-specific-entries-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-specific-entries-chrome-71/stdout.txt
index 42f6b7b4cc..bbf63c9685 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-specific-entries-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-specific-entries-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-specific-entries/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-specific-entries/stdout.txt
index d167c4dc24..9e727e8b28 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-specific-entries/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-specific-entries/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stable-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stable-chrome-71/stdout.txt
index 900f91a824..56ab137952 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stable-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stable-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stable-samsung-8.2/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stable-samsung-8.2/stdout.txt
index 95c730254e..bbe014d7f9 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stable-samsung-8.2/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stable-samsung-8.2/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { samsung }
+  proposal-private-property-in-object { samsung }
   proposal-class-properties { samsung }
   proposal-private-methods { samsung }
   proposal-numeric-separator { samsung < 11 }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stable/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stable/stdout.txt
index cbc58e06d1..bfcbcddf7e 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stable/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stable/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stage-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stage-chrome-71/stdout.txt
index 87fab870f1..4741dd6a3a 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stage-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stage-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stage/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stage/stdout.txt
index 1daa69cfc3..7cea354bda 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stage/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-stage/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-web-chrome-71/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-web-chrome-71/stdout.txt
index bed42c549d..57c4755987 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-web-chrome-71/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-web-chrome-71/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   proposal-numeric-separator { chrome < 75 }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-web/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-web/stdout.txt
index a2c948e73c..96aaa680a7 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-web/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-corejs3-web/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug/entry-no-corejs-shippedProposals/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/entry-no-corejs-shippedProposals/stdout.txt
index 6bd31f22f5..2684419386 100644
--- a/packages/babel-preset-env/test/fixtures/debug/entry-no-corejs-shippedProposals/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/entry-no-corejs-shippedProposals/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { ie }
+  proposal-private-property-in-object { ie }
   proposal-class-properties { ie }
   proposal-private-methods { ie }
   proposal-numeric-separator { ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug/shippedProposals-chrome-80/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/shippedProposals-chrome-80/stdout.txt
index d4d9db78cf..9c8b3e4a45 100644
--- a/packages/babel-preset-env/test/fixtures/debug/shippedProposals-chrome-80/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/shippedProposals-chrome-80/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   proposal-class-properties { chrome < 84 }
   proposal-private-methods { chrome < 84 }
   syntax-numeric-separator
diff --git a/packages/babel-preset-env/test/fixtures/debug/shippedProposals-chrome-84/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/shippedProposals-chrome-84/stdout.txt
index dcdf235ab5..d5ac3a7cb1 100644
--- a/packages/babel-preset-env/test/fixtures/debug/shippedProposals-chrome-84/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/shippedProposals-chrome-84/stdout.txt
@@ -9,6 +9,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91 }
+  proposal-private-property-in-object { chrome < 91 }
   syntax-class-properties
   syntax-numeric-separator
   proposal-logical-assignment-operators { chrome < 85 }
diff --git a/packages/babel-preset-env/test/fixtures/debug/usage-corejs2-shippedProposals-1/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/usage-corejs2-shippedProposals-1/stdout.txt
index 5776ff9d0b..62a6693710 100644
--- a/packages/babel-preset-env/test/fixtures/debug/usage-corejs2-shippedProposals-1/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/usage-corejs2-shippedProposals-1/stdout.txt
@@ -11,6 +11,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91, firefox, ie }
+  proposal-private-property-in-object { chrome < 91, firefox, ie }
   proposal-class-properties { chrome < 84, firefox, ie }
   proposal-private-methods { chrome < 84, firefox, ie }
   proposal-numeric-separator { chrome < 75, firefox < 70, ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug/usage-corejs2-shippedProposals-2/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/usage-corejs2-shippedProposals-2/stdout.txt
index 03be5fbb6f..953b73860f 100644
--- a/packages/babel-preset-env/test/fixtures/debug/usage-corejs2-shippedProposals-2/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/usage-corejs2-shippedProposals-2/stdout.txt
@@ -11,6 +11,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91, firefox, ie }
+  proposal-private-property-in-object { chrome < 91, firefox, ie }
   proposal-class-properties { chrome < 84, firefox, ie }
   proposal-private-methods { chrome < 84, firefox, ie }
   proposal-numeric-separator { chrome < 75, firefox < 70, ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug/usage-corejs3-shippedProposals-1/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/usage-corejs3-shippedProposals-1/stdout.txt
index 7521b8ae98..0c84d12875 100644
--- a/packages/babel-preset-env/test/fixtures/debug/usage-corejs3-shippedProposals-1/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/usage-corejs3-shippedProposals-1/stdout.txt
@@ -11,6 +11,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91, firefox, ie }
+  proposal-private-property-in-object { chrome < 91, firefox, ie }
   proposal-class-properties { chrome < 84, firefox, ie }
   proposal-private-methods { chrome < 84, firefox, ie }
   proposal-numeric-separator { chrome < 75, firefox < 70, ie }
diff --git a/packages/babel-preset-env/test/fixtures/debug/usage-corejs3-shippedProposals-2/stdout.txt b/packages/babel-preset-env/test/fixtures/debug/usage-corejs3-shippedProposals-2/stdout.txt
index d2290f9e64..49f039b853 100644
--- a/packages/babel-preset-env/test/fixtures/debug/usage-corejs3-shippedProposals-2/stdout.txt
+++ b/packages/babel-preset-env/test/fixtures/debug/usage-corejs3-shippedProposals-2/stdout.txt
@@ -11,6 +11,7 @@ Using modules transform: auto
 
 Using plugins:
   proposal-class-static-block { chrome < 91, firefox, ie }
+  proposal-private-property-in-object { chrome < 91, firefox, ie }
   proposal-class-properties { chrome < 84, firefox, ie }
   proposal-private-methods { chrome < 84, firefox, ie }
   proposal-numeric-separator { chrome < 75, firefox < 70, ie }
diff --git a/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/methods-loose-preset-not-loose/stderr.txt b/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/methods-loose-preset-not-loose/stderr.txt
index 90fafc7e53..637316b477 100644
--- a/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/methods-loose-preset-not-loose/stderr.txt
+++ b/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/methods-loose-preset-not-loose/stderr.txt
@@ -1,4 +1,8 @@
-Though the "loose" option was set to "false" in your @babel/preset-env config, it will not be used for @babel/plugin-proposal-class-properties since the "loose" mode option was set to "true" for @babel/plugin-proposal-private-methods.
+Though the "loose" option was set to "false" in your @babel/preset-env config, it will not be used for @babel/plugin-proposal-private-private-property-in-object since the "loose" mode option was set to "true" for @babel/plugin-proposal-private-methods.
+The "loose" option must be the same for @babel/plugin-proposal-class-properties, @babel/plugin-proposal-private-methods and @babel/plugin-proposal-private-property-in-object (when they are enabled): you can silence this warning by explicitly adding
+	["@babel/plugin-proposal-private-private-property-in-object", { "loose": true }]
+to the "plugins" section of your Babel config.
+Though the "loose" option was set to "false" in your @babel/preset-env config, it will not be used for @babel/plugin-proposal-class-properties since the "loose" mode option was set to "true" for @babel/plugin-proposal-private-private-property-in-object.
 The "loose" option must be the same for @babel/plugin-proposal-class-properties, @babel/plugin-proposal-private-methods and @babel/plugin-proposal-private-property-in-object (when they are enabled): you can silence this warning by explicitly adding
 	["@babel/plugin-proposal-class-properties", { "loose": true }]
 to the "plugins" section of your Babel config.
diff --git a/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-and-methods-loose-preset-not-loose/stderr.txt b/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-and-methods-loose-preset-not-loose/stderr.txt
new file mode 100644
index 0000000000..1e9c2f53b2
--- /dev/null
+++ b/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-and-methods-loose-preset-not-loose/stderr.txt
@@ -0,0 +1,4 @@
+Though the "loose" option was set to "false" in your @babel/preset-env config, it will not be used for @babel/plugin-proposal-private-private-property-in-object since the "loose" mode option was set to "true" for @babel/plugin-proposal-private-methods.
+The "loose" option must be the same for @babel/plugin-proposal-class-properties, @babel/plugin-proposal-private-methods and @babel/plugin-proposal-private-property-in-object (when they are enabled): you can silence this warning by explicitly adding
+	["@babel/plugin-proposal-private-private-property-in-object", { "loose": true }]
+to the "plugins" section of your Babel config.
diff --git a/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-and-methods-not-loose-preset-loose/stderr.txt b/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-and-methods-not-loose-preset-loose/stderr.txt
new file mode 100644
index 0000000000..1022c38841
--- /dev/null
+++ b/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-and-methods-not-loose-preset-loose/stderr.txt
@@ -0,0 +1,4 @@
+Though the "loose" option was set to "true" in your @babel/preset-env config, it will not be used for @babel/plugin-proposal-private-private-property-in-object since the "loose" mode option was set to "false" for @babel/plugin-proposal-private-methods.
+The "loose" option must be the same for @babel/plugin-proposal-class-properties, @babel/plugin-proposal-private-methods and @babel/plugin-proposal-private-property-in-object (when they are enabled): you can silence this warning by explicitly adding
+	["@babel/plugin-proposal-private-private-property-in-object", { "loose": false }]
+to the "plugins" section of your Babel config.
diff --git a/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-loose-preset-not-loose/stderr.txt b/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-loose-preset-not-loose/stderr.txt
index 68b6ffd194..4e1891bf44 100644
--- a/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-loose-preset-not-loose/stderr.txt
+++ b/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-loose-preset-not-loose/stderr.txt
@@ -1,4 +1,8 @@
-Though the "loose" option was set to "false" in your @babel/preset-env config, it will not be used for @babel/plugin-proposal-private-methods since the "loose" mode option was set to "true" for @babel/plugin-proposal-class-properties.
+Though the "loose" option was set to "false" in your @babel/preset-env config, it will not be used for @babel/plugin-proposal-private-private-property-in-object since the "loose" mode option was set to "true" for @babel/plugin-proposal-class-properties.
+The "loose" option must be the same for @babel/plugin-proposal-class-properties, @babel/plugin-proposal-private-methods and @babel/plugin-proposal-private-property-in-object (when they are enabled): you can silence this warning by explicitly adding
+	["@babel/plugin-proposal-private-private-property-in-object", { "loose": true }]
+to the "plugins" section of your Babel config.
+Though the "loose" option was set to "false" in your @babel/preset-env config, it will not be used for @babel/plugin-proposal-private-methods since the "loose" mode option was set to "true" for @babel/plugin-proposal-private-private-property-in-object.
 The "loose" option must be the same for @babel/plugin-proposal-class-properties, @babel/plugin-proposal-private-methods and @babel/plugin-proposal-private-property-in-object (when they are enabled): you can silence this warning by explicitly adding
 	["@babel/plugin-proposal-private-methods", { "loose": true }]
 to the "plugins" section of your Babel config.
diff --git a/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-not-loose-preset-loose/stderr.txt b/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-not-loose-preset-loose/stderr.txt
index 69f2a4eda4..c7b671d4ee 100644
--- a/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-not-loose-preset-loose/stderr.txt
+++ b/packages/babel-preset-env/test/fixtures/loose-class-features-precedence/properties-not-loose-preset-loose/stderr.txt
@@ -1,4 +1,8 @@
-Though the "loose" option was set to "true" in your @babel/preset-env config, it will not be used for @babel/plugin-proposal-private-methods since the "loose" mode option was set to "false" for @babel/plugin-proposal-class-properties.
+Though the "loose" option was set to "true" in your @babel/preset-env config, it will not be used for @babel/plugin-proposal-private-private-property-in-object since the "loose" mode option was set to "false" for @babel/plugin-proposal-class-properties.
+The "loose" option must be the same for @babel/plugin-proposal-class-properties, @babel/plugin-proposal-private-methods and @babel/plugin-proposal-private-property-in-object (when they are enabled): you can silence this warning by explicitly adding
+	["@babel/plugin-proposal-private-private-property-in-object", { "loose": false }]
+to the "plugins" section of your Babel config.
+Though the "loose" option was set to "true" in your @babel/preset-env config, it will not be used for @babel/plugin-proposal-private-methods since the "loose" mode option was set to "false" for @babel/plugin-proposal-private-private-property-in-object.
 The "loose" option must be the same for @babel/plugin-proposal-class-properties, @babel/plugin-proposal-private-methods and @babel/plugin-proposal-private-property-in-object (when they are enabled): you can silence this warning by explicitly adding
 	["@babel/plugin-proposal-private-methods", { "loose": false }]
 to the "plugins" section of your Babel config.
diff --git a/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-90/input.js b/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-90/input.js
deleted file mode 100644
index 11f7d7c96d..0000000000
--- a/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-90/input.js
+++ /dev/null
@@ -1,5 +0,0 @@
-class A {
-  static {
-    register(A);
-  }
-}
diff --git a/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-90/output.js b/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-90/output.js
deleted file mode 100644
index 53afe864cd..0000000000
--- a/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-90/output.js
+++ /dev/null
@@ -1,5 +0,0 @@
-class A {
-  static #_ = (() => {
-    register(A);
-  })();
-}
diff --git a/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-91/input.js b/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-91/input.js
deleted file mode 100644
index 11f7d7c96d..0000000000
--- a/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-91/input.js
+++ /dev/null
@@ -1,5 +0,0 @@
-class A {
-  static {
-    register(A);
-  }
-}
diff --git a/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-91/output.js b/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-91/output.js
deleted file mode 100644
index 11f7d7c96d..0000000000
--- a/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-91/output.js
+++ /dev/null
@@ -1,5 +0,0 @@
-class A {
-  static {
-    register(A);
-  }
-}
diff --git a/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-firefox-70/input.js b/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-firefox-70/input.js
deleted file mode 100644
index 11f7d7c96d..0000000000
--- a/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-firefox-70/input.js
+++ /dev/null
@@ -1,5 +0,0 @@
-class A {
-  static {
-    register(A);
-  }
-}
diff --git a/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-firefox-70/output.js b/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-firefox-70/output.js
deleted file mode 100644
index 6e4f4f2bcc..0000000000
--- a/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-firefox-70/output.js
+++ /dev/null
@@ -1,8 +0,0 @@
-class A {}
-
-var _ = {
-  writable: true,
-  value: (() => {
-    register(A);
-  })()
-};
diff --git a/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-90/input.js b/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-90/input.js
new file mode 100644
index 0000000000..d5bcaa3421
--- /dev/null
+++ b/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-90/input.js
@@ -0,0 +1,7 @@
+class A {
+  #foo;
+
+  static {
+    register(A, #foo in A);
+  }
+}
diff --git a/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-90/options.json b/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-90/options.json
similarity index 100%
rename from packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-90/options.json
rename to packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-90/options.json
diff --git a/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-90/output.js b/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-90/output.js
new file mode 100644
index 0000000000..ce3182dcfd
--- /dev/null
+++ b/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-90/output.js
@@ -0,0 +1,8 @@
+var _fooBrandCheck = new WeakSet();
+
+class A {
+  #foo = void _fooBrandCheck.add(this);
+  static #_ = (() => {
+    register(A, _fooBrandCheck.has(A));
+  })();
+}
diff --git a/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-91/input.js b/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-91/input.js
new file mode 100644
index 0000000000..d5bcaa3421
--- /dev/null
+++ b/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-91/input.js
@@ -0,0 +1,7 @@
+class A {
+  #foo;
+
+  static {
+    register(A, #foo in A);
+  }
+}
diff --git a/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-91/options.json b/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-91/options.json
similarity index 100%
rename from packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-chrome-91/options.json
rename to packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-91/options.json
diff --git a/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-91/output.js b/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-91/output.js
new file mode 100644
index 0000000000..49dd03d43a
--- /dev/null
+++ b/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-chrome-91/output.js
@@ -0,0 +1,6 @@
+class A {
+  #foo;
+  static {
+    register(A, #foo in A);
+  }
+}
diff --git a/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-firefox-70/input.js b/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-firefox-70/input.js
new file mode 100644
index 0000000000..d5bcaa3421
--- /dev/null
+++ b/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-firefox-70/input.js
@@ -0,0 +1,7 @@
+class A {
+  #foo;
+
+  static {
+    register(A, #foo in A);
+  }
+}
diff --git a/packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-firefox-70/options.json b/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-firefox-70/options.json
similarity index 100%
rename from packages/babel-preset-env/test/fixtures/shipped-proposals/class-static-block-firefox-70/options.json
rename to packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-firefox-70/options.json
diff --git a/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-firefox-70/output.js b/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-firefox-70/output.js
new file mode 100644
index 0000000000..c953ed1420
--- /dev/null
+++ b/packages/babel-preset-env/test/fixtures/shipped-proposals/new-class-features-firefox-70/output.js
@@ -0,0 +1,18 @@
+var _foo = new WeakMap();
+
+class A {
+  constructor() {
+    _foo.set(this, {
+      writable: true,
+      value: void 0
+    });
+  }
+
+}
+
+var _ = {
+  writable: true,
+  value: (() => {
+    register(A, _foo.has(A));
+  })()
+};
diff --git a/yarn.lock b/yarn.lock
index 2b38c04b21..620a5b0ca1 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1443,7 +1443,7 @@ __metadata:
   languageName: unknown
   linkType: soft
 
-"@babel/plugin-proposal-private-property-in-object@workspace:*, @babel/plugin-proposal-private-property-in-object@workspace:packages/babel-plugin-proposal-private-property-in-object":
+"@babel/plugin-proposal-private-property-in-object@workspace:*, @babel/plugin-proposal-private-property-in-object@workspace:^7.13.0, @babel/plugin-proposal-private-property-in-object@workspace:packages/babel-plugin-proposal-private-property-in-object":
   version: 0.0.0-use.local
   resolution: "@babel/plugin-proposal-private-property-in-object@workspace:packages/babel-plugin-proposal-private-property-in-object"
   dependencies:
@@ -3111,6 +3111,7 @@ __metadata:
     "@babel/plugin-proposal-optional-catch-binding": "workspace:^7.13.8"
     "@babel/plugin-proposal-optional-chaining": "workspace:^7.13.12"
     "@babel/plugin-proposal-private-methods": "workspace:^7.13.0"
+    "@babel/plugin-proposal-private-property-in-object": "workspace:^7.13.0"
     "@babel/plugin-proposal-unicode-property-regex": "workspace:^7.12.13"
     "@babel/plugin-syntax-async-generators": ^7.8.4
     "@babel/plugin-syntax-class-properties": "workspace:^7.12.13"
@@ -3124,6 +3125,7 @@ __metadata:
     "@babel/plugin-syntax-object-rest-spread": ^7.8.3
     "@babel/plugin-syntax-optional-catch-binding": ^7.8.3
     "@babel/plugin-syntax-optional-chaining": ^7.8.3
+    "@babel/plugin-syntax-private-property-in-object": "workspace:^7.13.0"
     "@babel/plugin-syntax-top-level-await": "workspace:^7.12.13"
     "@babel/plugin-transform-arrow-functions": "workspace:^7.13.0"
     "@babel/plugin-transform-async-to-generator": "workspace:^7.13.0"