Broken MIR with const_generics and async/await

[JSH32]

Explanation

This error will surface if the test arg has been accessed at least once(i did this with println!) and if there is an async function that is awaited in the body. If I remove the await for test_async_fn it will run as normal. This error happened while I was using actix-web so I reproduced the simplest version of my code.

Code

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

use actix_web::{App, Error, FromRequest, HttpServer, Responder, get};

#[derive(PartialEq, Eq)]
#[derive(Debug)]
enum TestEnum {
    ONE,
    TWO
}

struct TestExtractor<const T: TestEnum>(TestEnum);

impl<const T: TestEnum> FromRequest for TestExtractor<T> {
    type Error = Error;
    type Future = std::pin::Pin<Box<dyn futures::Future<Output = Result<TestExtractor<T>, Error>>>>;
    type Config = ();

    fn from_request(_: &actix_web::HttpRequest, _: &mut actix_web::dev::Payload) -> Self::Future {
        Box::pin(async move {
            Ok(TestExtractor(T))
        })
    }    
}

#[get("/test")]
async fn test(test: TestExtractor<{TestEnum::TWO}>) -> impl Responder {
    println!("{:?}", &test.0);
    test_async_fn().await;
    "Hello world"
}

async fn test_async_fn() -> u8 {
    return 0;
}

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    HttpServer::new(move || {
        App::new()
            .service(test)
    })
    .bind(("0.0.0.0", 8080))?
    .run()
    .await
}

Meta

rustc --version --verbose:

rustc 1.53.0-nightly (42816d61e 2021-04-24)
binary: rustc
commit-hash: 42816d61ead7e46d462df997958ccfd514f8c21c
commit-date: 2021-04-24
host: x86_64-pc-windows-msvc
release: 1.53.0-nightly
LLVM version: 12.0.0

Error output

error: internal compiler error: compiler\rustc_mir\src\transform\generator.rs:751:13: Broken MIR: generator contains type TestExtractor<TestEnum::TWO> in MIR, but typeck only knows about {ResumeTy, TestExtractor<{TestEnum::TWO}>, impl futures::Future, ()} and [TestExtractor<{TestEnum::TWO}>]
  --> src\main.rs:28:71
   |
28 |   async fn test(test: TestExtractor<{TestEnum::TWO}>) -> impl Responder {
   |  _______________________________________________________________________^
29 | |     println!("{:?}", &test.0);
30 | |     test_async_fn().await;
31 | |     "Hello world"
32 | | }
   | |_^

Backtrace

thread 'rustc' panicked at 'Box<Any>', /rustc/42816d61ead7e46d462df997958ccfd514f8c21c\library\std\src\panic.rs:59:5
stack backtrace:
   0:     0x7ffeb8095bce - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h65f771762210e3e5
   1:     0x7ffeb80bedac - core::fmt::write::h3d73561f801c6731
   2:     0x7ffeb8089c28 - <std::io::IoSlice as core::fmt::Debug>::fmt::h6fd08a0ca4059bc8
   3:     0x7ffeb8099c82 - std::panicking::take_hook::ha49dee799706a2d8
   4:     0x7ffeb8099774 - std::panicking::take_hook::ha49dee799706a2d8
   5:     0x7ffe9abbb2a7 - rustc_driver::report_ice::hab89c69e12b6dd11
   6:     0x7ffeb809a465 - std::panicking::rust_panic_with_hook::h9e7cc259d68b1de2
   7:     0x7ffe9de65250 - <rustc_mir::util::spanview::SpanViewable as core::fmt::Debug>::fmt::hfc04d9569cb1cb00
   8:     0x7ffe9de651c9 - <rustc_mir::util::spanview::SpanViewable as core::fmt::Debug>::fmt::hfc04d9569cb1cb00
   9:     0x7ffe9ef17d51 - <f64 as ryu::buffer::Sealed>::format_nonfinite::h0e70a5fe4e7d35d9
  10:     0x7ffe9dd60470 - <rustc_middle::mir::traversal::ReversePostorder as core::iter::traits::iterator::Iterator>::size_hint::hb5cde41105608c57
  11:     0x7ffe9dd4fd72 - <rustc_middle::mir::traversal::ReversePostorder as core::iter::traits::iterator::Iterator>::size_hint::hb5cde41105608c57
  12:     0x7ffe9dd50172 - <rustc_middle::mir::traversal::ReversePostorder as core::iter::traits::iterator::Iterator>::size_hint::hb5cde41105608c57
  13:     0x7ffe9dcc904e - <&rustc_middle::ty::sty::RegionKind as rustc_mir::borrow_check::nll::ToRegionVid>::to_region_vid::h2c9460b89eb22986
  14:     0x7ffe9dcc8010 - <&rustc_middle::ty::sty::RegionKind as rustc_mir::borrow_check::nll::ToRegionVid>::to_region_vid::h2c9460b89eb22986
  15:     0x7ffe9dcc7fb8 - <&rustc_middle::ty::sty::RegionKind as rustc_mir::borrow_check::nll::ToRegionVid>::to_region_vid::h2c9460b89eb22986
  16:     0x7ffe9dcc8f59 - <&rustc_middle::ty::sty::RegionKind as rustc_mir::borrow_check::nll::ToRegionVid>::to_region_vid::h2c9460b89eb22986
  17:     0x7ffe9ef17cb9 - <f64 as ryu::buffer::Sealed>::format_nonfinite::h0e70a5fe4e7d35d9
  18:     0x7ffe9dbe486c - <rustc_mir::transform::generator::StateTransform as rustc_mir::transform::MirPass>::run_pass::h260db0e9b77084a8
  19:     0x7ffe9dda7d71 - rustc_mir::transform::run_passes::h2ba1105ca65057bb
  20:     0x7ffe9ddae89d - rustc_mir::transform::run_passes::h2ba1105ca65057bb
  21:     0x7ffe9d9918c2 - <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::try_print_query_stack::h3c4346cc01dbde58
  22:     0x7ffe9d924b75 - rustc_query_impl::<impl rustc_query_system::query::config::QueryAccessors<rustc_query_impl::plumbing::QueryCtxt> for rustc_query_impl::queries::resolve_instance_of_const_arg>::hash_result::h18d43f9661c06064
  23:     0x7ffe9d7bc329 - <rustc_ast_lowering::item::ItemLowerer as rustc_ast::visit::Visitor>::visit_foreign_item::hbd68f25166d1e477
  24:     0x7ffe9d6da294 - <rustc_ast_lowering::item::ItemLowerer as rustc_ast::visit::Visitor>::visit_foreign_item::hbd68f25166d1e477
  25:     0x7ffe9d5f01a3 - <rustc_ast_lowering::item::ItemLowerer as rustc_ast::visit::Visitor>::visit_foreign_item::hbd68f25166d1e477
  26:     0x7ffe9d97bcb7 - <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::try_print_query_stack::h3c4346cc01dbde58
  27:     0x7ffe9e9f84b4 - rustc_middle::ty::<impl rustc_middle::ty::context::TyCtxt>::instance_mir::hc706cbca4cb43800
  28:     0x7ffe9df7c534 - <rustc_mir::monomorphize::collector::RootCollector as rustc_hir::itemlikevisit::ItemLikeVisitor>::visit_impl_item::hfb7712f4efbd0644
  29:     0x7ffe9df750bd - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  30:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  31:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  32:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  33:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  34:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  35:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  36:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  37:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  38:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  39:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  40:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  41:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  42:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  43:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  44:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  45:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  46:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  47:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  48:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  49:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  50:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  51:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  52:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  53:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  54:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  55:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  56:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  57:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  58:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  59:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  60:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  61:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  62:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  63:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  64:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  65:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  66:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  67:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  68:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  69:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  70:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  71:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  72:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  73:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  74:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  75:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  76:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  77:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  78:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  79:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  80:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  81:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  82:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  83:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  84:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  85:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  86:     0x7ffe9df749b2 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  87:     0x7ffe9dc7be6c - <rustc_mir::transform::coverage::Error as core::fmt::Debug>::fmt::he59524bc9954242b
  88:     0x7ffe9df73231 - rustc_mir::monomorphize::collector::collect_crate_mono_items::hbeb6d2045a60cd71
  89:     0x7ffe9dc87d9d - rustc_mir::monomorphize::partitioning::partition::h4e4f3b68f0632de5
  90:     0x7ffe9d7797bf - <rustc_ast_lowering::item::ItemLowerer as rustc_ast::visit::Visitor>::visit_foreign_item::hbd68f25166d1e477
  91:     0x7ffe9d993e31 - <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::try_print_query_stack::h3c4346cc01dbde58
  92:     0x7ffe9d9356c5 - rustc_query_impl::<impl rustc_query_system::query::config::QueryAccessors<rustc_query_impl::plumbing::QueryCtxt> for rustc_query_impl::queries::resolve_instance_of_const_arg>::hash_result::h18d43f9661c06064
  93:     0x7ffe9d7c377b - <rustc_ast_lowering::item::ItemLowerer as rustc_ast::visit::Visitor>::visit_foreign_item::hbd68f25166d1e477
  94:     0x7ffe9d6d315b - <rustc_ast_lowering::item::ItemLowerer as rustc_ast::visit::Visitor>::visit_foreign_item::hbd68f25166d1e477
  95:     0x7ffe9d65f94b - <rustc_ast_lowering::item::ItemLowerer as rustc_ast::visit::Visitor>::visit_foreign_item::hbd68f25166d1e477
  96:     0x7ffe9d9850e8 - <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::try_print_query_stack::h3c4346cc01dbde58
  97:     0x7ffe9ae2cfa7 - <rustc_codegen_llvm::back::lto::ThinLTOKeysMap as core::fmt::Debug>::fmt::h8425f018b01633b9
  98:     0x7ffe9ae297a9 - <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate::h3f7a7161df43cead
  99:     0x7ffe9acf27f2 - rustc_interface::passes::BoxedResolver::to_resolver_outputs::h51cffbb6bc3edf8f
 100:     0x7ffe9ad09ff6 - rustc_interface::queries::Queries::ongoing_codegen::h30f27fdc61a86ed6
 101:     0x7ffe9abc5a77 - rustc_driver::pretty::print_after_hir_lowering::h018530f73994254f
 102:     0x7ffe9abbd9dc - <rustc_driver::Compilation as core::fmt::Debug>::fmt::h4409e290eea8174b
 103:     0x7ffe9abc6d56 - rustc_driver::pretty::print_after_hir_lowering::h018530f73994254f
 104:     0x7ffe9abed0e4 - <rustc_middle::ty::SymbolName as core::fmt::Debug>::fmt::ha51d28018e278c75
 105:     0x7ffe9abef7ff - <rustc_middle::ty::SymbolName as core::fmt::Debug>::fmt::ha51d28018e278c75
 106:     0x7ffe9abf9ddd - <rustc_middle::ty::SymbolName as core::fmt::Debug>::fmt::ha51d28018e278c75
 107:     0x7ffeb80a851a - std::sys::windows::thread::Thread::new::h35832c8baf769397
 108:     0x7fff13e37c24 - BaseThreadInitThunk
 109:     0x7fff14f6d721 - RtlUserThreadStart

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 1.53.0-nightly (42816d61e 2021-04-24) running on x86_64-pc-windows-msvc

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

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

query stack during panic:
#0 [optimized_mir] optimizing MIR for `<impl at src\main.rs:27:1: 27:16>::register::test::{closure#0}`
#1 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack

[tmandry]

Maybe related to #83972.

@rustbot label +requires-nightly +AsyncAwait-Triaged

[JSH32]

Looks like someone used the wrong variable in one of the two places

[shisoft]

I also meet this problem but was unable to reproduce it. The compiler complains about

error: internal compiler error: compiler/rustc_mir/src/transform/generator.rs:751:13: Broken MIR: generator contains type &GenericKey<32_usize> in MIR, but typeck only knows about {ResumeTy, &mut ClientCursor, std::option::Optiondovahkiin::types::Id, std::option::Option<&dovahkiin::types::Id>, ClientCursor, std::option::Option<GenericKey<KEY_SIZE>>, &std::option::Option<GenericKey<KEY_SIZE>>, impl futures::Future, (), &GenericKey<KEY_SIZE>, std::sync::Arc, &std::sync::Arc, trees::Ordering, u16, impl futures::Future} and [&mut index::ranged::client::cursor::ClientCursor]

But here &GenericKey<32_usize> is &GenericKey<KEY_SIZE>, because KEY_SIZE = 32. I tried to play with this issue on my own project by replacing all occurrence of KEY_SIZE to 32, it would complain something like

error: internal compiler error: compiler/rustc_mir/src/transform/generator.rs:751:13: Broken MIR: generator contains type btree::GenericBPlusTree<[GenericKey<32_usize>; 8], [cell_ref::NodeCellRef; 9]> in MIR, but typeck only knows about {ResumeTy, &std::sync::Arc, &dovahkiin::types::Id, std::sync::Arc<lightning::map::HashSet<GenericKey<32_usize>>>, btree::GenericBPlusTree<[GenericKey<32_usize>; _], [cell_ref::NodeCellRef; _]>, btree::GenericBPlusTree<[GenericKey<32_usize>; _], [cell_ref::NodeCellRef; _]>, btree::GenericBPlusTree<[GenericKey<32_usize>; _], [cell_ref::NodeCellRef; _]>, &btree::GenericBPlusTree<[GenericKey<32_usize>; _], [cell_ref::NodeCellRef; _]>, impl futures::Future, (), &btree::GenericBPlusTree<[GenericKey<32_usize>; _], [cell_ref::NodeCellRef; _]>, impl futures::Future, std::vec::Vecdovahkiin::types::Id, ram::cell::OwnedCell, &AsyncClient, impl futures::Future} and [&std::sync::Arcclient::AsyncClient, &dovahkiin::types::Id]

In this cause btree::GenericBPlusTree<[GenericKey<32_usize>; 8], [cell_ref::NodeCellRef; 9]> is one of the btree::GenericBPlusTree<[GenericKey<32_usize>; _], [cell_ref::NodeCellRef; _]>.

It seems like this problem is because the generator is trying to find a type with a concrete name, but there are different corresponding name in MIR.

[Skepfyr]

Minimised to:

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

async fn test(test: [(); { 0 }]) {
    let _ = &test;
    async {}.await;
}

Interestingly, removing the braces around the 0 allows it to compile fine.

Regression bisected to: 2021-03-28 9b0edb7

bisected with cargo-bisect-rustc v0.6.0

Host triple: x86_64-unknown-linux-gnu
Reproduce with:

cargo bisect-rustc --preserve --start=2021-02-06 --end=2021-04-24

Best guess is that it's an effect of: #81351

[shisoft]

In my case, I found out that it only breaks with #![feature(const_generics, const_evaluatable_checked)].

[JSH32]

Interestingly, removing the braces around the 0 allows it to compile fine.

When it is surrounded by {} it evaluates it, which as shown above is finding two separate symbols that don't match (that's what this issue is for)