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• Would you like to work on a fix?

How are you using Babel?

Other (Next.js, Gatsby, vue-cli, ...)

Input code

switch ( x ) { default : let x { ; } ; }

Configuration file name

No response

Configuration

No response

Current and expected behavior

In the input code, ReferenceError is expected but the transpiled code terminates without any error.

$ node input.js
output.js:1: ReferenceError: x is not defined
switch ( x ) { default : let x ; }
         ^
ReferenceError: x is not defined
    at output.js:1:10

$ node output.js # no error

Environment

Reproductions on Babel's own REPL

Possible solution

It might be possible to solve this issue by changing var x into var _x.

Additional context

No response