Closed
Description
Objects inside block expressions in the scrutinee of an if-let statement are not dropped before the body.
This is inconsistent both with declaring a temporary variable, e.g. x in test #2, and let-else behavior in test #3.
I tried this code:
fn main() {
struct S(i32);
impl Drop for S {
fn drop(&mut self) {
println!("Dropped S {}", self.0)
}
}
println!("--- test 1");
{
println!("Before if-let");
if let _ = { S(1).0 } {
println!("Inside body");
}
}
println!("--- test 2");
{
println!("Before if-let");
let x = { S(2).0 };
if let _ = x {
println!("Inside body");
}
}
println!("--- test 3");
{
println!("Before let-else");
let _ = ({ S(3).0 }) else { unreachable!() };
println!("After let-else");
}
}I expected to see this happen:
--- test 1
Before if-let
Dropped S 1
Inside body
--- test 2
Before if-let
Dropped S 2
Inside body
--- test 3
Before let-else
Dropped S 3
After let-else
Instead, this happened:
--- test 1
Before if-let
Inside body
Dropped S 1
--- test 2
Before if-let
Dropped S 2
Inside body
--- test 3
Before let-else
Dropped S 3
After let-else
Meta
Same behavior on both stable and nightly.
rustc --version --verbose:
rustc 1.82.0 (f6e511eec 2024-10-15)
binary: rustc
commit-hash: f6e511eec7342f59a25f7c0534f1dbea00d01b14
commit-date: 2024-10-15
host: x86_64-unknown-linux-gnu
release: 1.82.0
LLVM version: 19.1.1