fake cycle detected when computing supertraits

[liamnaddell]

Code

extern "C" {
    fn printf(s: *const i8, ...);
}

#[lang = "sized"]
pub trait Sized {}

struct Foo {
    my_int: u32,
}

trait Parent<T> {
    fn parent(&self) -> T;
}

trait Child: Parent<u32> {
    fn child(&self);
}

impl Parent<u32> for Foo {
    fn parent(&self) -> u32 {
        unsafe {
            let parent = "parent%i\n\0";
            let msg = parent as *const str;
            printf(msg as *const i8,self.my_int);
            return self.my_int;
        }
    }
}

impl Child for Foo {
    fn child(&self) {
        let _ = self;
        unsafe {
            let child = "child\n\0";
            let msg = child as *const str;
            printf(msg as *const i8);
        }
    }
}

pub fn main() {
    let a = Foo{ my_int: 0xf00dfeed};
    let b: &dyn Child = &a;

    b.parent();
    b.child();
}

Meta

• What version of Rust GCC were you using, git sha if possible. be1e78ba333435e2106227905bc63dfeb8718ff3

Error output

liam@gentoo ~/super2 $ gccrs trait16.rs
trait16.rs:18:1: error: cycle detected when computing the super predicates of ‘Child’ [E0391]
   18 | trait Child: Parent<u32> {
      | ^~~~~
crab1: internal compiler error: in resolve_impl_block_substitutions, at rust/typecheck/rust-hir-type-check-item.cc:673

Backtrace

``` crab1: internal compiler error: in resolve_impl_block_substitutions, at rust/typecheck/rust-hir-type-check-item.cc:673 0x1327d4f Rust::Resolver::TypeCheckItem::resolve_impl_block_substitutions(Rust::HIR::ImplBlock&, bool&) ../../gccrs/gcc/rust/typecheck/rust-hir-type-check-item.cc:673 0x1324eaf Rust::Resolver::TypeCheckItem::ResolveImplBlockSelf(Rust::HIR::ImplBlock&) ../../gccrs/gcc/rust/typecheck/rust-hir-type-check-item.cc:73 0x138de63 Rust::Resolver::query_type(unsigned int, Rust::TyTy::BaseType**) ../../gccrs/gcc/rust/typecheck/rust-type-util.cc:91 0x130f7c7 operator() ../../gccrs/gcc/rust/typecheck/rust-tyty-bounds.cc:75 0x1312f6f __invoke_impl&, unsigned int, Rust::HIR::ImplBlock*> /usr/lib/gcc/aarch64-unknown-linux-gnu/13/include/g++-v13/bits/invoke.h:61 0x1312df7 __invoke_r&, unsigned int, Rust::HIR::ImplBlock*> /usr/lib/gcc/aarch64-unknown-linux-gnu/13/include/g++-v13/bits/invoke.h:114 0x1312cbf _M_invoke /usr/lib/gcc/aarch64-unknown-linux-gnu/13/include/g++-v13/bits/std_function.h:290 0x11ce63b Rust::Analysis::Mappings::iterate_impl_blocks(std::function) ../../gccrs/gcc/rust/util/rust-hir-map.cc:826 0x130f957 Rust::Resolver::TypeBoundsProbe::scan() ../../gccrs/gcc/rust/typecheck/rust-tyty-bounds.cc:67 0x130f54b Rust::Resolver::TypeBoundsProbe::Probe(Rust::TyTy::BaseType const*) ../../gccrs/gcc/rust/typecheck/rust-tyty-bounds.cc:35 0x12c0c07 Rust::TyTy::BaseType::satisfies_bound(Rust::TyTy::TypeBoundPredicate const&, bool) const ../../gccrs/gcc/rust/typecheck/rust-tyty.cc:296 0x12c121b Rust::TyTy::BaseType::bounds_compatible(Rust::TyTy::BaseType const&, unsigned int, bool) const ../../gccrs/gcc/rust/typecheck/rust-tyty.cc:388 0x12e31d7 Rust::TyTy::SubstitutionParamMapping::fill_param_ty(Rust::TyTy::SubstitutionArgumentMappings&, unsigned int) ../../gccrs/gcc/rust/typecheck/rust-tyty-subst.cc:139 0x1311747 Rust::TyTy::TypeBoundPredicate::apply_generic_arguments(Rust::HIR::GenericArgs*, bool) ../../gccrs/gcc/rust/typecheck/rust-tyty-bounds.cc:502 0x131044b Rust::Resolver::TypeCheckBase::get_predicate_from_bound(Rust::HIR::TypePath&, Rust::HIR::Type*, Rust::BoundPolarity) ../../gccrs/gcc/rust/typecheck/rust-tyty-bounds.cc:295 0x1327d8b Rust::Resolver::TypeCheckItem::resolve_impl_block_substitutions(Rust::HIR::ImplBlock&, bool&) ../../gccrs/gcc/rust/typecheck/rust-hir-type-check-item.cc:678 0x1324eaf Rust::Resolver::TypeCheckItem::ResolveImplBlockSelf(Rust::HIR::ImplBlock&) ../../gccrs/gcc/rust/typecheck/rust-hir-type-check-item.cc:73 0x138de63 Rust::Resolver::query_type(unsigned int, Rust::TyTy::BaseType**) ../../gccrs/gcc/rust/typecheck/rust-type-util.cc:91 0x130f7c7 operator() ../../gccrs/gcc/rust/typecheck/rust-tyty-bounds.cc:75 0x1312f6f __invoke_impl&, unsigned int, Rust::HIR::ImplBlock*> /usr/lib/gcc/aarch64-unknown-linux-gnu/13/include/g++-v13/bits/invoke.h:61 Please submit a full bug report, with preprocessed source (by using -freport-bug). Please include the complete backtrace with any bug report. See for instructions. ```

Expected output

I expected this code to compile, since rustc happily compiles this code.

[liamnaddell]

This was found during testing for #914 Likely does not block the issue, however, it means we have less tests for supertraits.