[nightly] ICE when using GATs with const generics

[svenknobloch]

playground

Code

#![allow(incomplete_features)]
#![feature(generic_associated_types)]
#![feature(const_generics)]

pub trait Buffer<const T: usize> {}

pub trait Device {
    type Buffer<const T: usize>: Buffer<{ T }>;

    fn create_buffer<const T: usize>(&self) -> Option<Self::Buffer<{ T }>>;
}

fn main() {}

Meta

rustc --version --verbose:

rustc 1.47.0-nightly (6c8927b0c 2020-07-26)
binary: rustc
commit-hash: 6c8927b0cf80ceee19386026cf9d7fd4fd9d486f
commit-date: 2020-07-26
host: x86_64-apple-darwin
release: 1.47.0-nightly
LLVM version: 10.0

Error output

error: internal compiler error: src/librustc_typeck/collect/type_of.rs:82:26: unexpected const parent path Ty(Ty { hir_id: HirId { owner: DefId(0:9 ~ playground[a09e]::Device[0]::create_buffer[0]), local_id: 8 }, kind: Path(TypeRelative(Ty { hir_id: HirId { owner: DefId(0:9 ~ playground[a09e]::Device[0]::create_buffer[0]), local_id: 10 }, kind: Path(Resolved(None, Path { span: src/main.rs:10:55: 10:74 (#0), res: SelfTy(Some(DefId(0:5 ~ playground[a09e]::Device[0])), None), segments: [PathSegment { ident: Self#0, hir_id: Some(HirId { owner: DefId(0:9 ~ playground[a09e]::Device[0]::create_buffer[0]), local_id: 9 }), res: Some(SelfTy(Some(DefId(0:5 ~ playground[a09e]::Device[0])), None)), args: None, infer_args: false }] })), span: src/main.rs:10:55: 10:74 (#0) }, PathSegment { ident: Buffer#0, hir_id: Some(HirId { owner: DefId(0:9 ~ playground[a09e]::Device[0]::create_buffer[0]), local_id: 16 }), res: Some(Err), args: Some(GenericArgs { args: [Const(ConstArg { value: AnonConst { hir_id: HirId { owner: DefId(0:9 ~ playground[a09e]::Device[0]::create_buffer[0]), local_id: 11 }, body: BodyId { hir_id: HirId { owner: DefId(0:9 ~ playground[a09e]::Device[0]::create_buffer[0]), local_id: 15 } } }, span: src/main.rs:10:68: 10:73 (#0) })], bindings: [], parenthesized: false }), infer_args: false })), span: src/main.rs:10:55: 10:74 (#0) }

Backtrace

error: internal compiler error: src/librustc_typeck/collect/type_of.rs:82:26: unexpected const parent path Ty(Ty { hir_id: HirId { owner: DefId(0:37 ~ gfx[85a5]::device[0]::Device[0]::create_buffer[0]), local_id: 13 }, kind: Path(TypeRelative(Ty { hir_id: HirId { owner: DefId(0:37 ~ gfx[85a5]::device[0]::Device[0]::create_buffer[0]), local_id: 15 }, kind: Path(Resolved(None, Path { span: gfx/src/device.rs:15:66: 15:91 (#0), res: SelfTy(Some(DefId(0:30 ~ gfx[85a5]::device[0]::Device[0])), None), segments: [PathSegment { ident: Self#0, hir_id: Some(HirId { owner: DefId(0:37 ~ gfx[85a5]::device[0]::Device[0]::create_buffer[0]), local_id: 14 }), res: Some(SelfTy(Some(DefId(0:30 ~ gfx[85a5]::device[0]::Device[0])), None)), args: None, infer_args: false }] })), span: gfx/src/device.rs:15:66: 15:91 (#0) }, PathSegment { ident: Buffer#0, hir_id: Some(HirId { owner: DefId(0:37 ~ gfx[85a5]::device[0]::Device[0]::create_buffer[0]), local_id: 23 }), res: Some(Err), args: Some(GenericArgs { args: [Type(Ty { hir_id: HirId { owner: DefId(0:37 ~ gfx[85a5]::device[0]::Device[0]::create_buffer[0]), local_id: 16 }, kind: Path(Resolved(None, Path { span: gfx/src/device.rs:15:79: 15:80 (#0), res: Def(TyParam, DefId(0:38 ~ gfx[85a5]::device[0]::Device[0]::create_buffer[0]::T[0])), segments: [PathSegment { ident: T#0, hir_id: Some(HirId { owner: DefId(0:37 ~ gfx[85a5]::device[0]::Device[0]::create_buffer[0]), local_id: 17 }), res: Some(Def(TyParam, DefId(0:38 ~ gfx[85a5]::device[0]::Device[0]::create_buffer[0]::T[0]))), args: None, infer_args: false }] })), span: gfx/src/device.rs:15:79: 15:80 (#0) }), Const(ConstArg { value: AnonConst { hir_id: HirId { owner: DefId(0:37 ~ gfx[85a5]::device[0]::Device[0]::create_buffer[0]), local_id: 18 }, body: BodyId { hir_id: HirId { owner: DefId(0:37 ~ gfx[85a5]::device[0]::Device[0]::create_buffer[0]), local_id: 22 } } }, span: gfx/src/device.rs:15:82: 15:90 (#0) })], bindings: [], parenthesized: false }), infer_args: false })), span: gfx/src/device.rs:15:66: 15:91 (#0) })

thread 'rustc' panicked at 'Box<Any>', /rustc/6c8927b0cf80ceee19386026cf9d7fd4fd9d486f/src/libstd/macros.rs:13:23
stack backtrace:
   0: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
   1: core::fmt::write
   2: std::io::Write::write_fmt
   3: std::panicking::default_hook::{{closure}}
   4: std::panicking::default_hook
   5: rustc_driver::report_ice
   6: std::panicking::rust_panic_with_hook
   7: std::panicking::begin_panic
   8: rustc_errors::HandlerInner::span_bug
   9: rustc_errors::Handler::span_bug
  10: rustc_middle::util::bug::opt_span_bug_fmt::{{closure}}
  11: rustc_middle::ty::context::tls::with_opt::{{closure}}
  12: rustc_middle::ty::context::tls::with_opt
  13: rustc_middle::util::bug::opt_span_bug_fmt
  14: rustc_middle::util::bug::span_bug_fmt
  15: rustc_typeck::collect::type_of::opt_const_param_of
  16: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::opt_const_param_of>::compute
  17: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  18: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  19: rustc_data_structures::stack::ensure_sufficient_stack
  20: rustc_query_system::query::plumbing::get_query_impl
  21: rustc_typeck::check::typeck
  22: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::typeck>::compute
  23: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  24: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  25: rustc_data_structures::stack::ensure_sufficient_stack
  26: rustc_query_system::query::plumbing::get_query_impl
  27: rustc_query_system::query::plumbing::ensure_query_impl
  28: rustc_typeck::check::typeck_item_bodies
  29: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::typeck_item_bodies>::compute
  30: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  31: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  32: rustc_data_structures::stack::ensure_sufficient_stack
  33: rustc_query_system::query::plumbing::get_query_impl
  34: rustc_typeck::check_crate
  35: rustc_interface::passes::analysis
  36: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute
  37: rustc_middle::dep_graph::<impl rustc_query_system::dep_graph::DepKind for rustc_middle::dep_graph::dep_node::DepKind>::with_deps
  38: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  39: rustc_query_system::query::plumbing::get_query_impl
  40: rustc_middle::ty::context::tls::enter_global
  41: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  42: rustc_span::with_source_map
  43: rustc_interface::interface::create_compiler_and_run
  44: scoped_tls::ScopedKey<T>::set
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.47.0-nightly (6c8927b0c 2020-07-26) running on x86_64-apple-darwin

note: compiler flags: -C embed-bitcode=no -C debuginfo=2 -C incremental --crate-type lib

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [opt_const_param_of] computing the optional const parameter of `device::Device::create_buffer::{{constant}}#0`
#1 [typeck] type-checking `device::Device::create_buffer::{{constant}}#0`
#2 [typeck_item_bodies] type-checking all item bodies
#3 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to previous error

[matthewjasper]

This no longer needs feature(const_generics) since min_const_generics has been stabilized. cc @lcnr

[BoxyUwU]

@rustbot claim