ICE: 'index out of bounds: the len is 0 but the index is 0', compiler/rustc_middle/src/ty/mod.rs:893:14

[chengniansun]

Sorry if this is a duplicate. I tried to search but failed to fine a duplicate one.

Code

fn sof<usize>() -> usize {}
fn test<T>() {
    let _: [u8; sof::<T>()];
}

Meta

rustc --version --verbose:

rustc 1.50.0-nightly (fa4163942 2020-12-14)
binary: rustc
commit-hash: fa416394275d2468d104b8f72ac31b1ddf7ee52e
commit-date: 2020-12-14
host: x86_64-unknown-linux-gnu
release: 1.50.0-nightly

Error output

warning: type parameter `usize` should have an upper camel case name
 --> perses_node_priority_with_dfs_delta_reduced_mutant.rs:1:8
  |
1 | fn sof<usize>() -> usize {}
  |        ^^^^^ help: convert the identifier to upper camel case (notice the capitalization): `Usize`
  |
  = note: `#[warn(non_camel_case_types)]` on by default

error[E0601]: `main` function not found in crate `perses_node_priority_with_dfs_delta_reduced_mutant`
 --> perses_node_priority_with_dfs_delta_reduced_mutant.rs:1:1
  |
1 | / fn sof<usize>() -> usize {}
2 | | fn test<T>() {
3 | |     let _: [u8; sof::<T>()];
4 | | }
  | |_^ consider adding a `main` function to `perses_node_priority_with_dfs_delta_reduced_mutant.rs`

error[E0308]: mismatched types
 --> perses_node_priority_with_dfs_delta_reduced_mutant.rs:1:20
  |
1 | fn sof<usize>() -> usize {}
  |    --- -----       ^^^^^ expected type parameter `usize`, found `()`
  |    |   |
  |    |   this type parameter
  |    implicitly returns `()` as its body has no tail or `return` expression
  |
  = note: expected type parameter `usize`
                  found unit type `()`

error[E0277]: the size for values of type `T` cannot be known at compilation time
 --> perses_node_priority_with_dfs_delta_reduced_mutant.rs:3:23
  |
1 | fn sof<usize>() -> usize {}
  |        ----- required by this bound in `sof`
2 | fn test<T>() {
  |         - this type parameter needs to be `Sized`
3 |     let _: [u8; sof::<T>()];
  |                       ^ doesn't have a size known at compile-time
  |
help: consider relaxing the implicit `Sized` restriction
  |
1 | fn sof<usize: ?Sized>() -> usize {}
  |             ^^^^^^^^

thread 'rustc' panicked at 'index out of bounds: the len is 0 but the index is 0', compiler/rustc_middle/src/ty/mod.rs:893:14
note: run with `RUST_BACKTRACE=1` environment variable to display a 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 1.50.0-nightly (fa4163942 2020-12-14) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [typeck] type-checking `test::{constant#0}`
#1 [eval_to_allocation_raw] const-evaluating + checking `test::{constant#0}`
end of query stack
error: aborting due to 3 previous errors; 1 warning emitted

Some errors have detailed explanations: E0277, E0308, E0601.
For more information about an error, try `rustc --explain E0277`.

Backtrace

warning: type parameter `usize` should have an upper camel case name
 --> perses_node_priority_with_dfs_delta_reduced_mutant.rs:1:8
  |
1 | fn sof<usize>() -> usize {}
  |        ^^^^^ help: convert the identifier to upper camel case (notice the capitalization): `Usize`
  |
  = note: `#[warn(non_camel_case_types)]` on by default

error[E0601]: `main` function not found in crate `perses_node_priority_with_dfs_delta_reduced_mutant`
 --> perses_node_priority_with_dfs_delta_reduced_mutant.rs:1:1
  |
1 | / fn sof<usize>() -> usize {}
2 | | fn test<T>() {
3 | |     let _: [u8; sof::<T>()];
4 | | }
  | |_^ consider adding a `main` function to `perses_node_priority_with_dfs_delta_reduced_mutant.rs`

error[E0308]: mismatched types
 --> perses_node_priority_with_dfs_delta_reduced_mutant.rs:1:20
  |
1 | fn sof<usize>() -> usize {}
  |    --- -----       ^^^^^ expected type parameter `usize`, found `()`
  |    |   |
  |    |   this type parameter
  |    implicitly returns `()` as its body has no tail or `return` expression
  |
  = note: expected type parameter `usize`
                  found unit type `()`

error[E0277]: the size for values of type `T` cannot be known at compilation time
 --> perses_node_priority_with_dfs_delta_reduced_mutant.rs:3:23
  |
1 | fn sof<usize>() -> usize {}
  |        ----- required by this bound in `sof`
2 | fn test<T>() {
  |         - this type parameter needs to be `Sized`
3 |     let _: [u8; sof::<T>()];
  |                       ^ doesn't have a size known at compile-time
  |
help: consider relaxing the implicit `Sized` restriction
  |
1 | fn sof<usize: ?Sized>() -> usize {}
  |             ^^^^^^^^

thread 'rustc' panicked at 'index out of bounds: the len is 0 but the index is 0', compiler/rustc_middle/src/ty/mod.rs:893:14
stack backtrace:
   0: rust_begin_unwind
             at /rustc/fa416394275d2468d104b8f72ac31b1ddf7ee52e/library/std/src/panicking.rs:493:5
   1: core::panicking::panic_fmt
             at /rustc/fa416394275d2468d104b8f72ac31b1ddf7ee52e/library/core/src/panicking.rs:92:14
   2: core::panicking::panic_bounds_check
             at /rustc/fa416394275d2468d104b8f72ac31b1ddf7ee52e/library/core/src/panicking.rs:69:5
   3: rustc_middle::ty::Generics::param_at
   4: rustc_middle::ty::error::<impl rustc_middle::ty::context::TyCtxt>::note_and_explain_type_err
   5: rustc_infer::infer::error_reporting::<impl rustc_infer::infer::InferCtxt>::note_type_err
   6: rustc_infer::infer::error_reporting::<impl rustc_infer::infer::InferCtxt>::report_and_explain_type_error
   7: rustc_infer::infer::InferCtxt::report_mismatched_types
   8: rustc_typeck::check::demand::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::demand_coerce_diag
   9: rustc_typeck::check::expr::<impl rustc_typeck::check::fn_ctxt::FnCtxt>::check_expr_coercable_to_type
  10: rustc_infer::infer::InferCtxtBuilder::enter
  11: rustc_typeck::check::typeck
  12: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
  13: rustc_data_structures::stack::ensure_sufficient_stack
  14: rustc_query_system::query::plumbing::get_query_impl
  15: rustc_middle::ty::context::TyCtxt::typeck_opt_const_arg
  16: rustc_mir::const_eval::eval_queries::eval_to_allocation_raw_provider
  17: 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
  18: rustc_middle::ty::query::plumbing::<impl rustc_query_system::query::QueryContext for rustc_middle::ty::context::TyCtxt>::start_query::{{closure}}::{{closure}}::{{closure}}
  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_middle::ty::query::plumbing::<impl rustc_query_system::query::QueryContext for rustc_middle::ty::context::TyCtxt>::start_query::{{closure}}::{{closure}}::{{closure}}
  23: rustc_query_system::query::plumbing::get_query_impl
  24: rustc_mir::const_eval::eval_queries::eval_to_const_value_raw_provider
  25: 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
  26: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
  27: rustc_data_structures::stack::ensure_sufficient_stack
  28: rustc_query_system::query::plumbing::get_query_impl
  29: rustc_middle::mir::interpret::queries::<impl rustc_middle::ty::context::TyCtxt>::const_eval_global_id
  30: rustc_middle::mir::interpret::queries::<impl rustc_middle::ty::context::TyCtxt>::const_eval_resolve
  31: <rustc_trait_selection::traits::project::AssocTypeNormalizer as rustc_middle::ty::fold::TypeFolder>::fold_const
  32: rustc_middle::ty::structural_impls::<impl rustc_middle::ty::fold::TypeFoldable for &rustc_middle::ty::TyS>::super_fold_with
  33: <rustc_trait_selection::traits::project::AssocTypeNormalizer as rustc_middle::ty::fold::TypeFolder>::fold_ty
  34: rustc_data_structures::stack::ensure_sufficient_stack
  35: rustc_trait_selection::traits::project::normalize
  36: <rustc_infer::infer::InferCtxt as rustc_trait_selection::infer::InferCtxtExt>::partially_normalize_associated_types_in
  37: rustc_typeck::check::inherited::Inherited::normalize_associated_types_in
  38: <rustc_typeck::check::fn_ctxt::FnCtxt as rustc_typeck::astconv::AstConv>::normalize_ty
  39: <dyn rustc_typeck::astconv::AstConv>::ast_ty_to_ty_inner
  40: <rustc_typeck::check::gather_locals::GatherLocalsVisitor as rustc_hir::intravisit::Visitor>::visit_local
  41: rustc_hir::intravisit::walk_expr
  42: rustc_typeck::check::check::check_fn
  43: rustc_infer::infer::InferCtxtBuilder::enter
  44: rustc_typeck::check::typeck
  45: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::typeck>::compute
  46: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
  47: rustc_data_structures::stack::ensure_sufficient_stack
  48: rustc_query_system::query::plumbing::get_query_impl
  49: rustc_query_system::query::plumbing::ensure_query_impl
  50: rustc_typeck::check::typeck_item_bodies
  51: 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
  52: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
  53: rustc_data_structures::stack::ensure_sufficient_stack
  54: rustc_query_system::query::plumbing::get_query_impl
  55: rustc_typeck::check_crate
  56: rustc_interface::passes::analysis
  57: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::analysis>::compute
  58: rustc_query_system::dep_graph::graph::DepGraph<K>::with_eval_always_task
  59: rustc_data_structures::stack::ensure_sufficient_stack
  60: rustc_query_system::query::plumbing::get_query_impl
  61: rustc_interface::passes::QueryContext::enter
  62: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  63: rustc_span::with_source_map
  64: rustc_interface::interface::create_compiler_and_run
  65: 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 1.50.0-nightly (fa4163942 2020-12-14) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [typeck] type-checking `test::{constant#0}`
#1 [eval_to_allocation_raw] const-evaluating + checking `test::{constant#0}`
#2 [eval_to_const_value_raw] simplifying constant for the type system `test::{constant#0}`
#3 [eval_to_const_value_raw] simplifying constant for the type system `test::{constant#0}`
#4 [typeck] type-checking `test`
#5 [typeck_item_bodies] type-checking all item bodies
#6 [analysis] running analysis passes on this crate
end of query stack
error: aborting due to 3 previous errors; 1 warning emitted

Some errors have detailed explanations: E0277, E0308, E0601.
For more information about an error, try `rustc --explain E0277`.

[matthiaskrgr]

The ice happens since 1.41
@rustbot modify labels: +regression-from-stable-to-stable

[LeSeulArtichaut]

I'd be interested in taking a look into this

[LeSeulArtichaut]

FWIW, this has nothing to do with the usize type parameter name, nor the missing return value. Consider the following code:

fn sof<T>() -> T { todo!() }
fn test<T>() {
    let _: [u8; sof::<T>()];
}

Which gives the following error

error[E0277]: the size for values of type `T` cannot be known at compilation time
 --> src/lib.rs:3:23
  |
1 | fn sof<T>() -> T { todo!() }
  |        - required by this bound in `sof`
2 | fn test<T>() {
  |         - this type parameter needs to be `Sized`
3 |     let _: [u8; sof::<T>()];
  |                       ^ doesn't have a size known at compile-time
  |
help: consider relaxing the implicit `Sized` restriction
  |
1 | fn sof<T: ?Sized>() -> T { todo!() }
  |         ^^^^^^^^

thread 'rustc' panicked at 'index out of bounds: the len is 0 but the index is 0', compiler/rustc_middle/src/ty/mod.rs:908:14
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[LeSeulArtichaut]

Assigning P-medium as discussed as part of the Prioritization WG procedure.