A Identifier declare bug founded in Node.Js REPL

[SmildWind]

• Version:
• Platform:
• Subsystem:

What steps will reproduce the bug?

when I use node.Js REPL in windows 10 os,I type code like this in commandLine :

node // Welcome to Node.js v14.11.0.
let a =b // "Uncaught ReferenceError: b is not defined"
let a = "helloWorld" // Uncaught SyntaxError: Identifier 'a' has already been declared
a = "helloWorld" // Uncaught ReferenceError: Cannot access 'a' before initialization`

and Then I could'n use "a" forever... util I restart node.JS REPL

How often does it reproduce? Is there a required condition?

I test the node_v12.18.4 and node_v14.11.0 , and both of them has this bug.

[insomnia-dreams-official]

Reproduce the same bug on unbuntu 18.04 and node.js 14.9.0
`
Welcome to Node.js v14.9.0.

let a = b
Uncaught ReferenceError: b is not defined
a = 1
Uncaught ReferenceError: Cannot access 'a' before initialization
let a
Uncaught SyntaxError: Identifier 'a' has already been declared
a = 1
Uncaught ReferenceError: Cannot access 'a' before initialization
let a = 1
Uncaught SyntaxError: Identifier 'a' has already been declared

`

[devsnek]

Duplicate of #8309