> The downside is that you may get a weird bug and only after a while see that you accidentally overwrote a function parameter and the Rust compiler didn't even warn you about it.
It will absolutely warn about this:
fn foo(i: u32) -> u32 {
let i = 42;
i
}
fn main() {
dbg!(foo(42));
}
results in
warning: unused variable: `i`
--> src/main.rs:1:8
|
1 | fn foo(i: u32) -> u32 {
| ^ help: if this is intentional, prefix it with an underscore: `_i`
|
= note: `#[warn(unused_variables)]` on by default
I don't know what the difference was, but 1-2 years ago it definitely did not warn me. Perhaps it doesn't show a warning when you assign a different datatype?
There's only one case where shadowing has bitten me in the past: long methods with loops dealing usize almost exclusively, where shadowing external bindings inside the loop might make sense, but any mistake would be silent. This was in the context of terminal layout code. The solution there has been extensive testing, but what I should have done is split the megafunction into multiple smaller ones.
It will absolutely warn about this:
results in