[ICE] With wrong rustc_layout_scalar_valid_range_start

[leonardo-m]

#![feature(rustc_attrs)]
#[rustc_layout_scalar_valid_range_start(u32::MAX)]
struct Foo(u32);
fn main() {
    const N: usize = std::mem::size_of::<Foo>();
}

Gives:

thread 'rustc' panicked at 'attribute takes lit', compiler\rustc_middle\src\ty\context.rs:1082:38
stack backtrace:
   0: rust_begin_unwind
             at /rustc/152f6609246558be5e2582e67376194815e6ba0d\/library\std\src\panicking.rs:493:5
   1: core::panicking::panic_fmt
             at /rustc/152f6609246558be5e2582e67376194815e6ba0d\/library\core\src\panicking.rs:92:14
   2: core::option::expect_failed
             at /rustc/152f6609246558be5e2582e67376194815e6ba0d\/library\core\src\option.rs:1292:5
   3: rustc_middle::ty::context::TyCtxt::layout_scalar_valid_range::{{closure}}
   4: rustc_middle::ty::layout::LayoutCx<rustc_middle::ty::context::TyCtxt>::layout_raw_uncached
   5: rustc_middle::ty::layout::layout_raw
   6: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::layout_raw>::compute
   7: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
   8: rustc_data_structures::stack::ensure_sufficient_stack
   9: rustc_query_system::query::plumbing::force_query_with_job
  10: rustc_query_system::query::plumbing::get_query_impl
  11: <rustc_middle::ty::layout::LayoutCx<rustc_middle::ty::query::TyCtxtAt> as rustc_target::abi::LayoutOf>::layout_of
  12: rustc_mir::interpret::step::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::eval_rvalue_into_place
  13: rustc_mir::interpret::step::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::run
  14: rustc_mir::const_eval::eval_queries::eval_to_allocation_raw_provider
  15: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::eval_to_allocation_raw>::compute
  16: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  17: rustc_data_structures::stack::ensure_sufficient_stack
  18: rustc_query_system::query::plumbing::force_query_with_job
  19: rustc_query_system::query::plumbing::get_query_impl
  20: rustc_mir::const_eval::eval_queries::eval_to_const_value_raw_provider
  21: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::eval_to_const_value_raw>::compute
  22: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  23: rustc_data_structures::stack::ensure_sufficient_stack
  24: rustc_query_system::query::plumbing::force_query_with_job
  25: rustc_query_system::query::plumbing::get_query_impl
  26: rustc_mir::const_eval::eval_queries::eval_to_const_value_raw_provider
  27: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::eval_to_const_value_raw>::compute
  28: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  29: rustc_data_structures::stack::ensure_sufficient_stack
  30: rustc_query_system::query::plumbing::force_query_with_job
  31: rustc_query_system::query::plumbing::get_query_impl
  32: rustc_middle::mir::interpret::queries::<impl rustc_middle::ty::context::TyCtxt>::const_eval_global_id
  33: rustc_middle::mir::interpret::queries::<impl rustc_middle::ty::context::TyCtxt>::const_eval_poly
  34: <rustc_lint::BuiltinCombinedLateLintPass as rustc_lint::passes::LateLintPass>::check_item
  35: rustc_hir::intravisit::Visitor::visit_nested_item
  36: <rustc_lint::late::LateContextAndPass<T> as rustc_hir::intravisit::Visitor>::visit_stmt
  37: rustc_hir::intravisit::walk_expr
  38: <rustc_lint::late::LateContextAndPass<T> as rustc_hir::intravisit::Visitor>::visit_expr
  39: <rustc_lint::late::LateContextAndPass<T> as rustc_hir::intravisit::Visitor>::visit_nested_body
  40: <rustc_lint::late::LateContextAndPass<T> as rustc_hir::intravisit::Visitor>::visit_fn
  41: rustc_hir::intravisit::walk_item
  42: rustc_hir::intravisit::Visitor::visit_nested_item
  43: rustc_hir::intravisit::walk_crate
  44: rustc_session::utils::<impl rustc_session::session::Session>::time
  45: std::panicking::try
  46: <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
  47: rustc_session::utils::<impl rustc_session::session::Session>::time
  48: rustc_interface::passes::analysis
  49: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute
  50: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
  51: rustc_data_structures::stack::ensure_sufficient_stack
  52: rustc_query_system::query::plumbing::force_query_with_job
  53: rustc_query_system::query::plumbing::get_query_impl
  54: rustc_interface::passes::QueryContext::enter
  55: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  56: rustc_span::with_source_map
  57: scoped_tls::ScopedKey<T>::set
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

error: internal compiler error: unexpected panic

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 1.52.0-nightly (152f66092 2021-02-17) running on x86_64-pc-windows-gnu

query stack during panic:
#0 [layout_raw] computing layout of `Foo`
#1 [eval_to_allocation_raw] const-evaluating + checking `main::N`
#2 [eval_to_const_value_raw] simplifying constant for the type system `main::N`
#3 [eval_to_const_value_raw] simplifying constant for the type system `main::N`
#4 [analysis] running analysis passes on this crate
end of query stack

[eddyb]

cc @oli-obk ICE-ing instead of user error on misuse seems somewhat okay given that it's an internal attribute, IMO.

[oli-obk]

agreed. We don't protect against mis-use of rustc internal attributes beyond making sure that you can't trivially create buggy code. I don't think we should put any effort into making this nicer to use and instead create the const-generic based replacement.