Today I found that the following program prints 92
fn main() {
let x: i32 = 92;
{
const x: i32 = 42;
println!("{}", x);
}
}
This happens because const is an item and the reference says “it is otherwise identical in meaning to declaring the item outside the statement block.”.
Is this behavior intentional?
Collisions are rare because there are different naming rules: snake case for vars and upper case for globals. It looks you are the first who found it. Compiler gives warning, but semantics looks really fickle 
Maybe it’s a reason for issue.
There’s a reason why the compiler warns on using the wrong naming convention.
Similarly,
let x = None;
match x {
Nonee => (),
_ => ()
}
will compile, even though Option doesn’t have a Nonee variant, because in this case Nonee will be a variable binding. However we will get unused variable and variable naming warnings which let us know this happened.