From fa11361354d12375d327a2288dafbaafb42d0853 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hua=CC=81ng=20Ju=CC=80nlia=CC=80ng?= <i@jhuang.me>
Date: Fri, 7 Jun 2019 00:02:16 -0400
Subject: [PATCH] WIP: working on third test case

---
 .../babel-traverse/src/scope/lib/renamer.js   | 50 ++++++++++++++++++-
 1 file changed, 49 insertions(+), 1 deletion(-)

diff --git a/packages/babel-traverse/src/scope/lib/renamer.js b/packages/babel-traverse/src/scope/lib/renamer.js
index cdfd90819681..89dee46e76c1 100644
--- a/packages/babel-traverse/src/scope/lib/renamer.js
+++ b/packages/babel-traverse/src/scope/lib/renamer.js
@@ -29,6 +29,24 @@ const renameVisitor = {
   },
 };
 
+function isSafeBinding(scope, node) {
+  if (!scope.hasOwnBinding(node.name)) return true;
+  const { kind } = scope.getOwnBinding(node.name);
+  return kind === "param" || kind === "local";
+}
+
+const outerBindingVisitor = {
+  ReferencedIdentifier(path, state) {
+    const { node } = path;
+    if (node.name === state.oldName && !isSafeBinding(state.scope, node)) {
+      state.paramDefaultOuterBinding = true;
+      path.stop();
+    }
+  },
+  Scope(path) {
+    path.skip();
+  },
+};
 export default class Renamer {
   constructor(binding: Binding, oldName: string, newName: string) {
     this.newName = newName;
@@ -116,7 +134,37 @@ export default class Renamer {
       }
     }
 
-    scope.traverse(block || scope.block, renameVisitor, this);
+    const state = {
+      paramDefaultOuterBinding: false,
+      scope,
+      oldName,
+    };
+    if (scope.path.isFunction()) {
+      const params = scope.path.get("params");
+      for (let i = 0; i < params.length; i++) {
+        const param = params[i];
+        if (param.isAssignmentPattern()) {
+          const right = param.get("right");
+          if (!state.paramDefaultOuterBinding) {
+            if (
+              right.isIdentifier() &&
+              right.node.body.name === oldName &&
+              !isSafeBinding(scope, right.node.body)
+            ) {
+              state.paramDefaultOuterBinding = true;
+              break;
+            } else {
+              right.traverse(outerBindingVisitor, state);
+            }
+          }
+        }
+      }
+    }
+    if (state.paramDefaultOuterBinding) {
+      scope.traverse(block || scope.block.body, renameVisitor, this);
+    } else {
+      scope.traverse(block || scope.block, renameVisitor, this);
+    }
 
     if (!block) {
       scope.removeOwnBinding(oldName);