Fix shadow variables reassignment for block scoping in loops. (#6814)

packages/babel-plugin-transform-block-scoping/test/fixtures/exec/for-continuation-outer-reference.js

@@ -0,0 +1,13 @@
+let data = [true, false, false, true, false];
+
+for (let index = 0; index < data.length; index++) {
+    let item = data[index];
+    if (!item) {
+        data.splice(index, 1);
+        index--;
+        continue;
+    }
+    let fn = function () {item;};
+}
+
+assert(data.every(item => item));

packages/babel-plugin-transform-block-scoping/test/fixtures/general/wrap-closure-shadow-variables-reassignment/actual.js

@@ -0,0 +1,7 @@
+for (let index = 0; index < 10; index++) {
+    if (index % 2) {
+        index+=3;
+        continue;
+    }
+    let fn = function () {index;};
+}

packages/babel-plugin-transform-block-scoping/test/fixtures/general/wrap-closure-shadow-variables-reassignment/expected.js

@@ -0,0 +1,19 @@
+var _loop = function (_index) {
+  if (_index % 2) {
+    _index += 3;
+    index = _index;
+    return "continue";
+  }
+
+  var fn = function () {
+    _index;
+  };
+
+  index = _index;
+};
+
+for (var index = 0; index < 10; index++) {
+  var _ret = _loop(index);
+
+  if (_ret === "continue") continue;
+}