ICE `in apply_argument_mappings, at rust/typecheck/r... | Rust-GCC/gccrs

Nobody has claimed this yet.

auto-reduced (treereduce-rust):

//@compile-flags: -frust-incomplete-and-experimental-compiler-do-not-use
trait A: B {
    type Assoc;
}

trait B {}

fn upcast(a: &dyn A<Assoc = i32>) -> &dyn B {
    a
}

original:

//@ check-pass
// issue: 114035
//@ revisions: current next
//@ ignore-compare-mode-next-solver (explicit revisions)
//@[next] compile-flags: -Znext-solver

trait A: B {
    type Assoc;
}

trait B {}

fn upcast(a: &dyn A<Assoc = i32>) -> &dyn B {
    a
}

// Make sure that we can drop the existential projection `A::Assoc = i32`
// when upcasting `dyn A<Assoc = i32>` to `dyn B`. Before, we used some
// issue: 114035
// different bounds in order to test that an upcast was valid, but this
// didn't allow upcasting to t that have fewer associated types
// than the source type.

fn main() {}

Version information:

5dc8c4d20d62462ebce137c6e5146235ab9e9e2e

Command:
/home/matthias/vcs/github/gccrs/gccrs-build/gcc/crab1 -frust-incomplete-and-experimental-compiler-do-not-use

Program output

crab1: internal compiler error: in apply_argument_mappings, at rust/typecheck/rust-tyty-bounds.cc:580
0x2fecaf8 internal_error(char const*, ...)
	../../gcc/diagnostic-global-context.cc:517
0xc0e04d fancy_abort(char const*, int, char const*)
	../../gcc/diagnostic.cc:1803
0x903e03 Rust::TyTy::TypeBoundPredicate::apply_argument_mappings(Rust::TyTy::SubstitutionArgumentMappings&, bool)
	../../gcc/rust/typecheck/rust-tyty-bounds.cc:580
0x105d109 Rust::TyTy::TypeBoundPredicate::apply_argument_mappings(Rust::TyTy::SubstitutionArgumentMappings&, bool)
	../../gcc/rust/typecheck/rust-tyty-bounds.cc:591
0x105d5ae Rust::TyTy::TypeBoundPredicate::apply_generic_arguments(Rust::HIR::GenericArgs*, bool, bool)
	../../gcc/rust/typecheck/rust-tyty-bounds.cc:551
0x105fb94 Rust::Resolver::TypeCheckBase::get_predicate_from_bound(Rust::HIR::TypePath&, tl::optional<std::reference_wrapper<Rust::HIR::Type> >, Rust::BoundPolarity, bool, bool)
	../../gcc/rust/typecheck/rust-tyty-bounds.cc:347
0x108c872 Rust::Resolver::TypeCheckType::visit(Rust::HIR::TraitObjectType&)
	../../gcc/rust/typecheck/rust-hir-type-check-type.cc:674
0x1082477 Rust::Resolver::TypeCheckType::Resolve(Rust::HIR::Type&)
	../../gcc/rust/typecheck/rust-hir-type-check-type.cc:71
0x1082be4 Rust::Resolver::TypeCheckType::Resolve(Rust::HIR::Type&)
	../../gcc/rust/typecheck/rust-hir-type-check-type.cc:67
0x1082be4 Rust::Resolver::TypeCheckType::visit(Rust::HIR::ReferenceType&)
	../../gcc/rust/typecheck/rust-hir-type-check-type.cc:735
0x1082477 Rust::Resolver::TypeCheckType::Resolve(Rust::HIR::Type&)
	../../gcc/rust/typecheck/rust-hir-type-check-type.cc:71
0x10838b7 Rust::Resolver::TypeCheckType::Resolve(Rust::HIR::Type&)
	../../gcc/rust/typecheck/rust-hir-type-check-type.cc:67
0x107409c Rust::Resolver::TypeCheckItem::visit(Rust::HIR::Function&)
	../../gcc/rust/typecheck/rust-hir-type-check-item.cc:598
0x106e185 Rust::Resolver::TypeCheckItem::Resolve(Rust::HIR::Item&)
	../../gcc/rust/typecheck/rust-hir-type-check-item.cc:59
0x100adcb Rust::Resolver::TypeResolution::Resolve(Rust::HIR::Crate&)
	../../gcc/rust/typecheck/rust-hir-type-check.cc:74
0xdb97f8 Rust::Session::compile_crate(char const*)
	../../gcc/rust/rust-session-manager.cc:685
Please submit a full bug report, with preprocessed source (by using -freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

Start with the reduced Rust reproducer in the issue and run it using the shown crab1 command and compiler flag. Read gcc/rust/typecheck/rust-tyty-bounds.cc around apply_argument_mappings at line 580, then verify the reproducer no longer triggers an internal compiler error and preserves the expected trait-object upcast behavior.

Written by the indexing model from the issue text.

ICE `in apply_argument_mappings, at rust/typecheck/rust-tyty-bounds.cc:580`

Description

Contributor guide

First steps

Research direction

Assessment