With shadowing, you can use or mutate a variable, thinking you are using/mutating the outer instance because you’re unaware of the inner (shadowing) instance, which is the one you are really using/mutating. An IDE doesn’t help catching such an inadvertent error (unless it warns about shadowing variables, but then you’d want to rename it anyway, to get rid of the warning).

I’ve tripped over unexpected shadowing often enough that I wish more languages would forbid it. I rarely have trouble choosing appropriate variable names to avoid shadowing.

it's a footgun indeed and no IDE per se doesn't solve all the problems. But since rust was mentioned, there are other rust features that make that less of a problem: most of the rust code uses immutable variables and only rarely you do use mut variables and mut references and these can be under bigger scrutiny by reviews and linters.

I focused on IDEs in my comment because I find shadowing to be a problem even with immutable variables, because it's hard for you to tell what is the type of a variable if it keeps change throughout the function body.