Global this can be incorrect depending on input code context

[overlookmotel]

The value of global this depends on the code context.

• In ESM code, this is undefined.
• In CommonJS code, this is module.exports.
• In script context, this is globalThis.
• In indirect eval (0,eval)(...), this is globalThis.

this which has no local binding is currently treated as a global, so () => this is output unchanged as () => this.

This is mostly correct as long as output format is same as input format. But:

1. If CommonJS input is output as CommonJS, this in output will refer to the wrong module.exports.
2. If e.g. CommonJS input is being output as ESM, the value of this in output will be different from what it was in input.

@babel/plugin-transform-modules-commonjs which is used to transform ESM to CommonJS does substitute void 0 for this, so output is correct for ESM input. But the other cases don't work correctly.