bug: deriving Destruct leads to 'Internal error, cycle detected:` panic

[enitrat]

Bug Report

Cairo version:
1f83b95

Current behavior:
Compiling the code below leads to the following error:

thread 'main' panicked at 'Internal error, cycle detected:

DatabaseKeyIndex { group_index: 5, query_index: 13, key_index: 0 }
DatabaseKeyIndex { group_index: 5, query_index: 12, key_index: 1 }
DatabaseKeyIndex { group_index: 5, query_index: 11, key_index: 1 }
', /Users/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/salsa-0.16.1/src/lib.rs:490:48

Expected behavior:
The code compiles successfully

Steps to reproduce:
Compile the following code

#[derive(Destruct)]
struct MinimalStruct {}

fn execute() {
    let mut ctx = MinimalStruct {};
}

Other information:
The bug seems to be related to the Destruct derivation. Removing it and replacing it by Drop works fine. However, this is just a minimal reproducible example I've been able to build. In my real use case, I have struct containing a Dict, and thus I cannot derive Drop.

[enitrat]

It also looks like there might be a problem when we create a type T that implements destruct and put it in a box (which is what I'm trying to do originally in my codebase)
e.g

the following code will not compile because Destruct<Box> is not implemented

#[derive(Destruct)]
struct InnerStruct {// dict: Felt252Dict<u128>
}

#[derive(Destruct)]
struct OuterStruct {
    dict: Felt252Dict<u128>,
    inner: Box<InnerStruct>
}

fn execute() {
    let mut ctx = OuterStruct { dict: Default::default(), inner: BoxTrait::new(InnerStruct {}) };
}

so, I add an implementation of destruct for it following @orizi's advice in #3854

struct InnerStruct {}

impl DestructBoxInnerStruct of Destruct<Box<InnerStruct>> {
    fn destruct(self: Box<InnerStruct>) nopanic {}
}

#[derive(Destruct)]
struct OuterStruct {
    dict: Felt252Dict<u128>,
    inner: Box<InnerStruct>
}

fn execute() {
    let mut ctx = OuterStruct { dict: Default::default(), inner: BoxTrait::new(InnerStruct {}) };
}

And same error:

thread 'main' panicked at 'Internal error, cycle detected:

DatabaseKeyIndex { group_index: 5, query_index: 16, key_index: 1 }
DatabaseKeyIndex { group_index: 5, query_index: 15, key_index: 2 }
DatabaseKeyIndex { group_index: 5, query_index: 14, key_index: 2 }
', /Users/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/salsa-0.16.1/src/lib.rs:490:48
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[orizi]

do note that the destruct implementation is wrong - but the compiler panic is indeed bad:

impl DestructBoxInnerStruct of Destruct<Box<InnerStruct>> {
    fn destruct(self: Box<InnerStruct>) nopanic {
        self.unbox().destruct()
    }
}

[enitrat]

Thanks for the correction! The compiler still panics if the struct is empty. But with your right destruct implementation, it fixed my original problem 😉

use box::BoxTrait;
use traits::Destruct;

#[derive(Destruct)]
struct InnerStruct {}

impl DestructBoxInnerStruct of Destruct<Box<InnerStruct>> {
    fn destruct(self: Box<InnerStruct>) nopanic {
        self.unbox().destruct()
    }
}

#[derive(Destruct)]
struct OuterStruct {
    dict: Felt252Dict<u128>,
    inner: Box<InnerStruct>
}

fn execute() {
    let mut ctx = OuterStruct { dict: Default::default(), inner: BoxTrait::new(InnerStruct {}) };
}