From 289c533aadb4ee5d6a7ef2a740c4d38cd7b6cc59 Mon Sep 17 00:00:00 2001
From: Cameron Martin <cameron_martin@shelter.org.uk>
Date: Tue, 27 Nov 2018 17:27:21 +0000
Subject: [PATCH 1/2] [@babel/traverse]: Fixed type of path when using enter &
 exit visitor.

---
 types/babel__traverse/babel__traverse-tests.ts | 8 ++++++--
 types/babel__traverse/index.d.ts               | 2 +-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/types/babel__traverse/babel__traverse-tests.ts b/types/babel__traverse/babel__traverse-tests.ts
index 5b4fbbef5f..974831dbca 100644
--- a/types/babel__traverse/babel__traverse-tests.ts
+++ b/types/babel__traverse/babel__traverse-tests.ts
@@ -4,10 +4,14 @@ import * as t from "@babel/types";
 // Examples from: https://github.com/thejameskyle/babel-handbook/blob/master/translations/en/plugin-handbook.md
 const MyVisitor: Visitor = {
     Identifier: {
-        enter() {
+        enter(path) {
+            // $ExpectType NodePath<Identifier>
+            path;
             console.log("Entered!");
         },
-        exit() {
+        exit(path) {
+            // $ExpectType NodePath<Identifier>
+            path;
             console.log("Exited!");
         }
     }
diff --git a/types/babel__traverse/index.d.ts b/types/babel__traverse/index.d.ts
index 465a60464f..740f5f4429 100644
--- a/types/babel__traverse/index.d.ts
+++ b/types/babel__traverse/index.d.ts
@@ -142,7 +142,7 @@ export type Visitor<S = Node> = VisitNodeObject<Node> & {
     [P in Node["type"]]?: VisitNode<S, Extract<Node, { type: P; }>>;
 };
 
-export type VisitNode<T, P> = VisitNodeFunction<T, P> | VisitNodeObject<T>;
+export type VisitNode<T, P> = VisitNodeFunction<T, P> | VisitNodeObject<P>;
 
 export type VisitNodeFunction<T, P> = (this: T, path: NodePath<P>, state: any) => void;
 

From 0226045de5e8db79594af54dbab3f5b77b972d3c Mon Sep 17 00:00:00 2001
From: Cameron Martin <cameronmartin123@gmail.com>
Date: Tue, 27 Nov 2018 20:42:30 +0000
Subject: [PATCH 2/2] Implemented all changes outlined in the comments in pull
 request #30862.

---
 .../babel__traverse/babel__traverse-tests.ts  | 37 +++++++++++++++++++
 types/babel__traverse/index.d.ts              | 14 +++----
 2 files changed, 44 insertions(+), 7 deletions(-)

diff --git a/types/babel__traverse/babel__traverse-tests.ts b/types/babel__traverse/babel__traverse-tests.ts
index 974831dbca..772b392b63 100644
--- a/types/babel__traverse/babel__traverse-tests.ts
+++ b/types/babel__traverse/babel__traverse-tests.ts
@@ -112,3 +112,40 @@ const BindingKindTest: Visitor = {
         // kind === 'anythingElse';
     },
 };
+
+interface SomeVisitorState { someState: string; }
+
+const VisitorStateTest: Visitor<SomeVisitorState> = {
+    enter(path, state) {
+        // $ExpectType SomeVisitorState
+        state;
+        // $ExpectType SomeVisitorState
+        this;
+    },
+    exit(path, state) {
+        // $ExpectType SomeVisitorState
+        state;
+        // $ExpectType SomeVisitorState
+        this;
+    },
+    Identifier(path, state) {
+        // $ExpectType SomeVisitorState
+        state;
+        // $ExpectType SomeVisitorState
+        this;
+    },
+    FunctionDeclaration: {
+        enter(path, state) {
+            // $ExpectType SomeVisitorState
+            state;
+            // $ExpectType SomeVisitorState
+            this;
+        },
+        exit(path, state) {
+            // $ExpectType SomeVisitorState
+            state;
+            // $ExpectType SomeVisitorState
+            this;
+        }
+    }
+};
diff --git a/types/babel__traverse/index.d.ts b/types/babel__traverse/index.d.ts
index 740f5f4429..a0a3730057 100644
--- a/types/babel__traverse/index.d.ts
+++ b/types/babel__traverse/index.d.ts
@@ -138,17 +138,17 @@ export class Binding {
     constantViolations: NodePath[];
 }
 
-export type Visitor<S = Node> = VisitNodeObject<Node> & {
-    [P in Node["type"]]?: VisitNode<S, Extract<Node, { type: P; }>>;
+export type Visitor<S = {}> = VisitNodeObject<S, Node> & {
+    [Type in Node["type"]]?: VisitNode<S, Extract<Node, { type: Type; }>>;
 };
 
-export type VisitNode<T, P> = VisitNodeFunction<T, P> | VisitNodeObject<P>;
+export type VisitNode<S, P> = VisitNodeFunction<S, P> | VisitNodeObject<S, P>;
 
-export type VisitNodeFunction<T, P> = (this: T, path: NodePath<P>, state: any) => void;
+export type VisitNodeFunction<S, P> = (this: S, path: NodePath<P>, state: S) => void;
 
-export interface VisitNodeObject<T> {
-    enter?(path: NodePath<T>, state: any): void;
-    exit?(path: NodePath<T>, state: any): void;
+export interface VisitNodeObject<S, P> {
+    enter?: VisitNodeFunction<S, P>;
+    exit?: VisitNodeFunction<S, P>;
 }
 
 export class NodePath<T = Node> {