Update param scope values when expanding parameters.

packages/babel-plugin-transform-es2015-parameters/src/index.js

@@ -15,8 +15,13 @@ export default function() {
           path.arrowFunctionToExpression();
         }
 
-        convertFunctionRest(path);
-        convertFunctionParams(path);
+        const convertedRest = convertFunctionRest(path);
+        const convertedParams = convertFunctionParams(path);
+
+        if (convertedRest || convertedParams) {
+          // Manually reprocess this scope to ensure that the moved params are updated.
+          path.scope.crawl();
+        }
       },
     },
   };

packages/babel-plugin-transform-es2015-parameters/src/params.js

@@ -96,7 +96,7 @@ export default function convertFunctionParams(path) {
     }
   }
 
-  if (body.length === 0) return;
+  if (body.length === 0) return false;
 
   // we need to cut off all trailing parameters
   if (firstOptionalIndex !== null) {
@@ -112,4 +112,6 @@ export default function convertFunctionParams(path) {
   } else {
     path.get("body").unshiftContainer("body", body);
   }
+
+  return true;
 }

packages/babel-plugin-transform-es2015-parameters/src/rest.js

@@ -222,7 +222,7 @@ function optimiseLengthGetter(path, argsId, offset) {
 
 export default function convertFunctionRest(path) {
   const { node, scope } = path;
-  if (!hasRest(node)) return;
+  if (!hasRest(node)) return false;
 
   const rest = node.params.pop().argument;
 
@@ -273,7 +273,7 @@ export default function convertFunctionRest(path) {
           path.replaceWith(argsId);
       }
     }
-    return;
+    return true;
   }
 
   state.references = state.references.concat(
@@ -338,4 +338,6 @@ export default function convertFunctionRest(path) {
 
     target.insertBefore(loop);
   }
+
+  return true;
 }