TypeError yields unusable variable

[john-aws]

• Version: v12.16.1
• Platform: OS X 10.14.6
• Subsystem:

What steps will reproduce the bug?

$ node
Welcome to Node.js v12.16.1.
Type ".help" for more information.
> let m = Map();
Uncaught TypeError: Constructor Map requires 'new'
    at Map (<anonymous>)
> m
Uncaught ReferenceError: m is not defined
> let m = new Map();
Uncaught SyntaxError: Identifier 'm' has already been declared
> m = new Map();
Uncaught ReferenceError: m is not defined
> delete m
false
> m = 2
Uncaught ReferenceError: m is not defined

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

100%

What is the expected behavior?

It appears that m is declared, but not defined. Why am I unable to initialize it at this point using m = 2 or m = new Map()?

[addaleax]

Duplicate of #8441 #8376 #8309 #16520 #14092 #32288 (and probably more) – basically, this is how the JS spec works, unfortunately.

V8 is working on a REPL mode that is going to allow us to work around this issue, see the comments in #32288 for more details.

[john-aws]

Thank you for the speedy response. I totally sympathize with you and the team when it comes to implementing the dark corners of the language spec and thanks for all your efforts.