Fix annex B block function hoisting semantics (#12512)

packages/babel-plugin-transform-block-scoping/src/index.js

@@ -338,6 +338,18 @@ const loopVisitor = {
   },
 };
 
+function isStrict(path) {
+  return !!path.find(({ node }) => {
+    if (t.isProgram(node)) {
+      if (node.sourceType === "module") return true;
+    } else if (!t.isBlockStatement(node)) return false;
+
+    return node.directives.some(
+      directive => directive.value.value === "use strict",
+    );
+  });
+}
+
 class BlockScoping {
   constructor(
     loopPath?: NodePath,
@@ -486,7 +498,10 @@ class BlockScoping {
           const parentBinding = scope.parent.getOwnBinding(key);
           if (
             binding.kind === "hoisted" &&
-            (!parentBinding || isVar(parentBinding.path.parent))
+            !binding.path.node.async &&
+            !binding.path.node.generator &&
+            (!parentBinding || isVar(parentBinding.path.parent)) &&
+            !isStrict(binding.path.parentPath)
           ) {
             continue;
           }

packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-async-generator/input.js

@@ -0,0 +1,16 @@
+// NOTE: When compiling async generators,
+// we run the async-generator-functions transform
+// as soon as in Program:enter, so when the block-scoping plugin
+// runs it has already been transpiled to a plain function.
+// The functions is thus visible to the outer scope.
+// This is a bug.
+
+if (true) {
+  async function* run() {
+    return true;
+  }
+}
+
+function test() {
+  return run();
+}

packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-async-generator/output.js

@@ -0,0 +1,15 @@
+// NOTE: When compiling async generators,
+// we run the async-generator-functions transform
+// as soon as in Program:enter, so when the block-scoping plugin
+// runs it has already been transpiled to a plain function.
+// The functions is thus visible to the outer scope.
+// This is a bug.
+if (true) {
+  var _run = async function* () {
+    return true;
+  };
+}
+
+function test() {
+  return run();
+}

packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-async/input.js

@@ -0,0 +1,9 @@
+if (true) {
+  async function run() {
+    return true;
+  }
+}
+
+function test() {
+  return run();
+}

packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-async/options.json

@@ -0,0 +1,7 @@
+{
+  "plugins": [
+    "transform-block-scoping",
+    "transform-block-scoped-functions",
+    "transform-async-to-generator"
+  ]
+}

packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-async/output.js

@@ -0,0 +1,19 @@
+function asyncGeneratorStep(gen, resolve, reject, _next, _throw, key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(_next, _throw); } }
+
+function _asyncToGenerator(fn) { return function () { var self = this, args = arguments; return new Promise(function (resolve, reject) { var gen = fn.apply(self, args); function _next(value) { asyncGeneratorStep(gen, resolve, reject, _next, _throw, "next", value); } function _throw(err) { asyncGeneratorStep(gen, resolve, reject, _next, _throw, "throw", err); } _next(undefined); }); }; }
+
+if (true) {
+  var _run = /*#__PURE__*/function () {
+    var _ref = _asyncToGenerator(function* () {
+      return true;
+    });
+
+    return function _run() {
+      return _ref.apply(this, arguments);
+    };
+  }();
+}
+
+function test() {
+  return run();
+}

packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-generator/input.js

@@ -0,0 +1,9 @@
+if (true) {
+  function* run() {
+    return true;
+  }
+}
+
+function test() {
+  return run();
+}

packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-generator/options.json

@@ -0,0 +1,7 @@
+{
+  "plugins": [
+    "transform-block-scoping",
+    "transform-block-scoped-functions",
+    "transform-regenerator"
+  ]
+}

packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-generator/output.js

@@ -0,0 +1,20 @@
+if (true) {
+  var _run = /*#__PURE__*/regeneratorRuntime.mark(function _callee() {
+    return regeneratorRuntime.wrap(function _callee$(_context) {
+      while (1) {
+        switch (_context.prev = _context.next) {
+          case 0:
+            return _context.abrupt("return", true);
+
+          case 1:
+          case "end":
+            return _context.stop();
+        }
+      }
+    }, _callee);
+  });
+}
+
+function test() {
+  return run();
+}

packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-module/input.mjs

@@ -0,0 +1,9 @@
+if (true) {
+  function run() {
+    return true;
+  }
+}
+
+function test() {
+  return run();
+}

packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-module/output.mjs

@@ -0,0 +1,9 @@
+if (true) {
+  var _run = function () {
+    return true;
+  };
+}
+
+function test() {
+  return run();
+}

packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-strict/input.js

@@ -0,0 +1,11 @@
+"use strict";
+
+if (true) {
+  function run() {
+    return true;
+  }
+}
+
+function test() {
+  return run();
+}

packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10046-strict/output.js

@@ -0,0 +1,11 @@
+"use strict";
+
+if (true) {
+  var _run = function () {
+    return true;
+  };
+}
+
+function test() {
+  return run();
+}