Closed
Description
openedon Jul 18, 2019
Miri/CTFE fails to execute code where a const generic parameter is used as a value, such as what try_from for arrays does these days:
#![feature(const_generics)]
fn len<'a, T, const N: usize>(_array: &'a [T; N]) -> usize { N }
fn main() {
const N: usize = 16;
type Array = [u8; N];
let array: Array = [0; N];
len(&array);
}yields
error[E0080]: Miri evaluation error: encountered overly generic constant
--> src/main.rs:3:62
|
3 | fn len<'a, T, const N: usize>(_array: &'a [T; N]) -> usize { N }
| ^ Miri evaluation error: encountered overly generic constant
|
The "obvious" fix seems to be to call monomorphize on the const before evaluating it; i did that in RalfJung@a8754d4d33. However, that ICEs:
ICE backtrace
error: internal compiler error: src/librustc/ty/subst.rs:557: type parameter `Self/#0` (Self/0) out of range when substituting (root type=Some(<Self as float::Float>::Int)) substs=[]
thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:584:9
stack backtrace:
0: backtrace::backtrace::libunwind::trace
at /home/r/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/libunwind.rs:88
1: backtrace::backtrace::trace_unsynchronized
at /home/r/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/mod.rs:66
2: std::sys_common::backtrace::_print
at src/libstd/sys_common/backtrace.rs:47
3: std::sys_common::backtrace::print
at src/libstd/sys_common/backtrace.rs:36
4: std::panicking::default_hook::{{closure}}
at src/libstd/panicking.rs:200
5: std::panicking::default_hook
at src/libstd/panicking.rs:214
6: <alloc::boxed::Box<F> as core::ops::function::Fn<A>>::call
at /home/r/src/rust/rustc/src/liballoc/boxed.rs:780
7: rustc::util::common::panic_hook
at src/librustc/util/common.rs:40
8: std::panicking::rust_panic_with_hook
at src/libstd/panicking.rs:481
9: std::panicking::begin_panic
at /home/r/src/rust/rustc/src/libstd/panicking.rs:411
10: rustc_errors::Handler::span_bug
at /home/r/src/rust/rustc/<::std::macros::panic macros>:4
11: rustc::util::bug::opt_span_bug_fmt::{{closure}}
at src/librustc/util/bug.rs:35
12: rustc::ty::context::tls::with_opt::{{closure}}
at src/librustc/ty/context.rs:1994
13: rustc::ty::context::tls::with_context_opt
at src/librustc/ty/context.rs:1944
14: rustc::ty::context::tls::with_opt
at src/librustc/ty/context.rs:1994
15: rustc::util::bug::opt_span_bug_fmt
at src/librustc/util/bug.rs:32
16: rustc::util::bug::span_bug_fmt
at src/librustc/util/bug.rs:23
17: rustc::ty::subst::SubstFolder::ty_for_param
at src/librustc/ty/subst.rs:557
18: <rustc::ty::subst::SubstFolder as rustc::ty::fold::TypeFolder>::fold_ty
at src/librustc/ty/subst.rs:506
19: rustc::ty::structural_impls::<impl rustc::ty::fold::TypeFoldable for &rustc::ty::TyS>::fold_with
at src/librustc/ty/structural_impls.rs:1077
20: <rustc::ty::subst::Kind as rustc::ty::fold::TypeFoldable>::super_fold_with
at src/librustc/ty/subst.rs:154
21: rustc::ty::fold::TypeFoldable::fold_with
at src/librustc/ty/fold.rs:50
22: rustc::ty::subst::<impl rustc::ty::fold::TypeFoldable for &rustc::ty::List<rustc::ty::subst::Kind>>::super_fold_with::{{closure}}
at src/librustc/ty/subst.rs:386
23: core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &mut F>::call_once
at /home/r/src/rust/rustc/src/libcore/ops/function.rs:279
24: core::option::Option<T>::map
at /home/r/src/rust/rustc/src/libcore/option.rs:447
25: <core::iter::adapters::Map<I,F> as core::iter::traits::iterator::Iterator>::next
at /home/r/src/rust/rustc/src/libcore/iter/adapters/mod.rs:570
26: <smallvec::SmallVec<A> as core::iter::traits::collect::Extend<<A as smallvec::Array>::Item>>::extend
at /home/r/.cargo/registry/src/github.com-1ecc6299db9ec823/smallvec-0.6.10/lib.rs:1357
27: <smallvec::SmallVec<A> as core::iter::traits::collect::FromIterator<<A as smallvec::Array>::Item>>::from_iter
at /home/r/.cargo/registry/src/github.com-1ecc6299db9ec823/smallvec-0.6.10/lib.rs:1342
28: core::iter::traits::iterator::Iterator::collect
at /home/r/src/rust/rustc/src/libcore/iter/traits/iterator.rs:1464
29: rustc::ty::subst::<impl rustc::ty::fold::TypeFoldable for &rustc::ty::List<rustc::ty::subst::Kind>>::super_fold_with
at src/librustc/ty/subst.rs:386
30: rustc::ty::fold::TypeFoldable::fold_with
at src/librustc/ty/fold.rs:50
31: rustc::ty::structural_impls::<impl rustc::ty::fold::TypeFoldable for rustc::ty::sty::ProjectionTy>::super_fold_with
at src/librustc/macros.rs:340
32: rustc::ty::fold::TypeFoldable::fold_with
at src/librustc/ty/fold.rs:50
33: rustc::ty::structural_impls::<impl rustc::ty::fold::TypeFoldable for &rustc::ty::TyS>::super_fold_with
at src/librustc/ty/structural_impls.rs:1048
34: <rustc::ty::subst::SubstFolder as rustc::ty::fold::TypeFolder>::fold_ty
at src/librustc/ty/subst.rs:509
35: rustc::ty::structural_impls::<impl rustc::ty::fold::TypeFoldable for &rustc::ty::TyS>::fold_with
at src/librustc/ty/structural_impls.rs:1077
36: rustc::ty::structural_impls::<impl rustc::ty::fold::TypeFoldable for &rustc::ty::sty::Const>::super_fold_with
at src/librustc/ty/structural_impls.rs:1346
37: <rustc::ty::subst::SubstFolder as rustc::ty::fold::TypeFolder>::fold_const
at src/librustc/ty/subst.rs:530
38: rustc::ty::structural_impls::<impl rustc::ty::fold::TypeFoldable for &rustc::ty::sty::Const>::fold_with
at /home/r/src/rust/rustc/src/librustc/ty/structural_impls.rs:1355
39: <T as rustc::ty::subst::Subst>::subst_spanned
at /home/r/src/rust/rustc/src/librustc/ty/subst.rs:427
40: rustc::ty::subst::Subst::subst
at /home/r/src/rust/rustc/src/librustc/ty/subst.rs:413
41: rustc_mir::interpret::eval_context::InterpCx<M>::monomorphize_with_substs
at src/librustc_mir/interpret/eval_context.rs:373
42: rustc_mir::interpret::eval_context::InterpCx<M>::monomorphize
at src/librustc_mir/interpret/eval_context.rs:357
43: rustc_mir::interpret::operand::<impl rustc_mir::interpret::eval_context::InterpCx<M>>::eval_const_to_op
at src/librustc_mir/interpret/operand.rs:532
44: rustc_mir::transform::const_prop::ConstPropagator::eval_constant
at src/librustc_mir/transform/const_prop.rs:369
45: rustc_mir::transform::const_prop::ConstPropagator::eval_operand
at src/librustc_mir/transform/const_prop.rs:437
46: rustc_mir::transform::const_prop::ConstPropagator::const_prop
at src/librustc_mir/transform/const_prop.rs:452
47: <rustc_mir::transform::const_prop::ConstPropagator as rustc::mir::visit::MutVisitor>::visit_statement
at src/librustc_mir/transform/const_prop.rs:783
48: rustc::mir::visit::MutVisitor::super_basic_block_data
at /home/r/src/rust/rustc/src/librustc/mir/visit.rs:314
49: rustc::mir::visit::MutVisitor::visit_basic_block_data
at /home/r/src/rust/rustc/src/librustc/mir/visit.rs:81
50: rustc::mir::visit::MutVisitor::super_body
at /home/r/src/rust/rustc/src/librustc/mir/visit.rs:272
51: rustc::mir::visit::MutVisitor::visit_body
at /home/r/src/rust/rustc/src/librustc/mir/visit.rs:75
52: <rustc_mir::transform::const_prop::ConstProp as rustc_mir::transform::MirPass>::run_pass
at src/librustc_mir/transform/const_prop.rs:99
53: rustc_mir::transform::run_passes::{{closure}}::{{closure}}
at src/librustc_mir/transform/mod.rs:172
54: rustc_mir::transform::run_passes::{{closure}}
at src/librustc_mir/transform/mod.rs:179
55: rustc_mir::transform::run_passes
at src/librustc_mir/transform/mod.rs:185
56: rustc_mir::transform::optimized_mir
at src/librustc_mir/transform/mod.rs:244
57: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::optimized_mir>::compute::{{closure}}
at /home/r/src/rust/rustc/src/librustc/ty/query/plumbing.rs:997
58: rustc::ty::query::__query_compute::optimized_mir
at /home/r/src/rust/rustc/src/librustc/ty/query/plumbing.rs:948
59: rustc::ty::query::<impl rustc::ty::query::config::QueryAccessors for rustc::ty::query::queries::optimized_mir>::compute
at /home/r/src/rust/rustc/src/librustc/ty/query/plumbing.rs:989
60: rustc::dep_graph::graph::DepGraph::with_task_impl
at /home/r/src/rust/rustc/src/librustc/dep_graph/graph.rs:334
61: rustc::dep_graph::graph::DepGraph::with_task
at /home/r/src/rust/rustc/src/librustc/dep_graph/graph.rs:202
62: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::force_query_with_job::{{closure}}::{{closure}}
at /home/r/src/rust/rustc/src/librustc/ty/query/plumbing.rs:556
63: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::start_query::{{closure}}::{{closure}}
at /home/r/src/rust/rustc/src/librustc/ty/query/plumbing.rs:275
64: rustc::ty::context::tls::enter_context::{{closure}}
at /home/r/src/rust/rustc/src/librustc/ty/context.rs:1866
65: rustc::ty::context::tls::set_tlv
at /home/r/src/rust/rustc/src/librustc/ty/context.rs:1799
66: rustc::ty::context::tls::enter_context
at /home/r/src/rust/rustc/src/librustc/ty/context.rs:1865
67: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::start_query::{{closure}}
at /home/r/src/rust/rustc/src/librustc/ty/query/plumbing.rs:274
68: rustc::ty::context::tls::with_related_context::{{closure}}
at /home/r/src/rust/rustc/src/librustc/ty/context.rs:1972
69: rustc::ty::context::tls::with_context::{{closure}}
at /home/r/src/rust/rustc/src/librustc/ty/context.rs:1955
70: rustc::ty::context::tls::with_context_opt
at /home/r/src/rust/rustc/src/librustc/ty/context.rs:1944
71: rustc::ty::context::tls::with_context
at /home/r/src/rust/rustc/src/librustc/ty/context.rs:1955
72: rustc::ty::context::tls::with_related_context
at /home/r/src/rust/rustc/src/librustc/ty/context.rs:1968
73: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::start_query
at /home/r/src/rust/rustc/src/librustc/ty/query/plumbing.rs:263
74: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::force_query_with_job::{{closure}}
at /home/r/src/rust/rustc/src/librustc/ty/query/plumbing.rs:548
75: rustc::ty::query::plumbing::with_diagnostics
at /home/r/src/rust/rustc/src/librustc/ty/query/plumbing.rs:209
76: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::force_query_with_job
at /home/r/src/rust/rustc/src/librustc/ty/query/plumbing.rs:547
77: rustc::ty::query::plumbing::<impl rustc::ty::context::TyCtxt>::get_query
at /home/r/src/rust/rustc/src/librustc/ty/query/plumbing.rs:376
78: rustc::ty::query::TyCtxtAt::optimized_mir
at /home/r/src/rust/rustc/src/librustc/ty/query/plumbing.rs:1074
79: rustc::ty::query::<impl rustc::ty::context::TyCtxt>::optimized_mir
at /home/r/src/rust/rustc/src/librustc/ty/query/plumbing.rs:1066
80: rustc_metadata::encoder::EncodeContext::encode_optimized_mir
at src/librustc_metadata/encoder.rs:1031
81: rustc_metadata::encoder::EncodeContext::encode_info_for_item
at src/librustc_metadata/encoder.rs:0
82: core::ops::function::FnOnce::call_once
at /home/r/src/rust/rustc/src/libcore/ops/function.rs:231
83: rustc_metadata::encoder::EncodeContext::record
at src/librustc_metadata/encoder.rs:314
84: <rustc_metadata::encoder::EncodeContext as rustc::hir::intravisit::Visitor>::visit_item
at src/librustc_metadata/encoder.rs:1663
85: <rustc::hir::itemlikevisit::DeepVisitor<V> as rustc::hir::itemlikevisit::ItemLikeVisitor>::visit_item
at /home/r/src/rust/rustc/src/librustc/hir/itemlikevisit.rs:70
86: rustc::hir::Crate::visit_all_item_likes
at /home/r/src/rust/rustc/src/librustc/hir/mod.rs:782
87: rustc_metadata::encoder::EncodeContext::encode_info_for_items
at src/librustc_metadata/encoder.rs:325
88: rustc_metadata::encoder::EncodeContext::encode_crate_root
at src/librustc_metadata/encoder.rs:428
89: rustc_metadata::encoder::encode_metadata::{{closure}}
at src/librustc_metadata/encoder.rs:1893
90: rustc::dep_graph::graph::DepGraph::with_ignore::{{closure}}::{{closure}}
at /home/r/src/rust/rustc/src/librustc/dep_graph/graph.rs:159
91: rustc::ty::context::tls::enter_context::{{closure}}
at /home/r/src/rust/rustc/src/librustc/ty/context.rs:1866
92: rustc::ty::context::tls::set_tlv
at /home/r/src/rust/rustc/src/librustc/ty/context.rs:1799
93: rustc::ty::context::tls::enter_context
at /home/r/src/rust/rustc/src/librustc/ty/context.rs:1865
94: rustc::dep_graph::graph::DepGraph::with_ignore::{{closure}}
at /home/r/src/rust/rustc/src/librustc/dep_graph/graph.rs:158
95: rustc::ty::context::tls::with_context::{{closure}}
at /home/r/src/rust/rustc/src/librustc/ty/context.rs:1955
96: rustc::ty::context::tls::with_context_opt
at /home/r/src/rust/rustc/src/librustc/ty/context.rs:1944
97: rustc::ty::context::tls::with_context
at /home/r/src/rust/rustc/src/librustc/ty/context.rs:1955
98: rustc::dep_graph::graph::DepGraph::with_ignore
at /home/r/src/rust/rustc/src/librustc/dep_graph/graph.rs:152
99: rustc_metadata::encoder::encode_metadata
at src/librustc_metadata/encoder.rs:1875
100: rustc_metadata::cstore_impl::<impl rustc::middle::cstore::CrateStore for rustc_metadata::cstore::CStore>::encode_metadata
at src/librustc_metadata/cstore_impl.rs:554
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
query stack during panic:
#0 [optimized_mir] processing `float::conv::__fixsfsi`
end of query stack
error: aborting due to previous error
The backtrace shows that it is the first monomorphize in eval_const_to_op that fails. The backtrace also involves const-prop -- of course it does, there is hardly any ICE for the Miri engine that does not.
@eddyb says
What constprop should do is use identity Substs, that match the ParamEnv it should already be using (otherwise it'd get ICEs all over the place).
I am not sure what this means.^^ @oli-obk does this help to find the ICE that currently prevents supporting const-generics? It's something in const-prop again. :/
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