drop-tracking: ICE when using default struct update syntax #98476
Comments
jyn514
added
I-ICE
Strangely, this has to be a type with an allocator - using |
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UI test (also slightly reduced - turns out the relevant part here is having a custom Drop): // build-pass
// edition:2018
// compile-flags: -Zdrop-tracking=y
fn main() {
let _ = foo();
}
async fn from_config(x: Config) {
async {}.await;
drop(x);
}
async fn foo() {
from_config(Config {
nickname: NonCopy,
..Default::default()
})
.await;
}
#[derive(Default)]
struct NonCopy;
impl Drop for NonCopy {
fn drop(&mut self) {}
}
#[derive(Default)]
struct Config {
nickname: NonCopy,
} |
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This has to do with the fact that the temporary which serves as the base expr of the struct, namely This ICEs similarly if we have something like |
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@compiler-errors I'm not sure I follow - why do we have a live |
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Well, we have a partially live We need to keep the |
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Thanks! That makes sense to me. Here's a reproduction with just generators (no futures) and using multiple fields instead of ..Default::default(): // build-pass
// edition:2018
// compile-flags: -Zdrop-tracking=y
#![feature(generators)]
fn main() {
let _ = foo();
}
fn foo() {
|| {
yield drop(Config {
nickname: NonCopy,
b: NonCopy2,
}.nickname);
};
}
#[derive(Default)]
struct NonCopy;
impl Drop for NonCopy {
fn drop(&mut self) {}
}
#[derive(Default)]
struct NonCopy2;
impl Drop for NonCopy2 {
fn drop(&mut self) {}
}
#[derive(Default)]
struct Config {
nickname: NonCopy,
b: NonCopy2,
} |
|
@rustbot label +AsyncAwait-Triaged |
rustbot
added
the
AsyncAwait-Triaged
…impl is used across an await Previously, drop-tracking would incorrectly assume the struct would be dropped immediately, which was not true: when the field had a type with a manual `Drop` impl, the drop becomes observable and has to be dropped after the await instead. For reasons I don't understand, this also fixes another error crater popped up related to type parameters. rust-lang#98476
…-errors Fix drop-tracking ICE when a struct containing a field with a significant drop is used across an await Previously, drop-tracking would incorrectly assume the struct would be dropped immediately, which was not true. Fixes rust-lang#98476. Also fixes rust-lang#98477, I think because the parent HIR node for type variables is the whole function instead of the expression where the variable is used. r? `@eholk`
cc #97331, @eholk. Minimized from https://crater-reports.s3.amazonaws.com/pr-97334/try%23615edd3ad1cf6871c977dc900317cb6c2070fd6b/gh/AsuMagic.markov-irc/log.txt in the crater run for #97334.
Code
Meta
rustc --version: 615edd3ad1cf6871c977dc900317cb6c2070fd6bError output
Backtrace
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