1 files changed, 39 insertions, 0 deletions
diff --git a/node_modules/@babel/preset-modules/src/plugins/transform-safari-block-shadowing/index.js b/node_modules/@babel/preset-modules/src/plugins/transform-safari-block-shadowing/index.js
new file mode 100644
index 00000000..f509c6b6
--- /dev/null
+++ b/node_modules/@babel/preset-modules/src/plugins/transform-safari-block-shadowing/index.js
@@ -0,0 +1,39 @@
+/**
+ * Fixes block-shadowed let/const bindings in Safari 10/11.
+ * https://kangax.github.io/compat-table/es6/#test-let_scope_shadow_resolution
+ */
+export default function({ types: t }) {
+  return {
+    name: "transform-safari-block-shadowing",
+    visitor: {
+      VariableDeclarator(path) {
+        // the issue only affects let and const bindings:
+        const kind = path.parent.kind;
+        if (kind !== "let" && kind !== "const") return;
+
+        // ignore non-block-scoped bindings:
+        const block = path.scope.block;
+        if (t.isFunction(block) || t.isProgram(block)) return;
+
+        const bindings = t.getOuterBindingIdentifiers(path.node.id);
+        for (const name of Object.keys(bindings)) {
+          let scope = path.scope;
+
+          // ignore parent bindings (note: impossible due to let/const?)
+          if (!scope.hasOwnBinding(name)) continue;
+
+          // check if shadowed within the nearest function/program boundary
+          while ((scope = scope.parent)) {
+            if (scope.hasOwnBinding(name)) {
+              path.scope.rename(name);
+              break;
+            }
+            if (t.isFunction(scope.block) || t.isProgram(scope.block)) {
+              break;
+            }
+          }
+        }
+      },
+    },
+  };
+}