Stable ICE with fieldless enums and dyn traits

[PatrickNorton]

Code

#![allow(dead_code)]

pub fn main() {
    // Instantiating Foo with a concrete type will not fail
    let _ = Foo::<dyn FooTrait>::new();
}

pub struct Foo<T: FooTrait + ?Sized> {
    base: FooBase,
    value: T,
}

impl<T: FooTrait + ?Sized> Foo<T> {
    pub fn new() -> Box<Foo<T>> {
        todo!()
    }
}

pub trait FooTrait {}

pub struct FooBase {
    cls: Bar,
}

// Bar *must* be a fieldless enum
pub enum Bar {}

Meta

rustc --version --verbose:

rustc 1.51.0 (2fd73fabe 2021-03-23)
binary: rustc
commit-hash: 2fd73fabe469357a12c2c974c140f67e7cdd76d0
commit-date: 2021-03-23
host: x86_64-apple-darwin
release: 1.51.0
LLVM version: 11.0.1

(also crashes on beta and nightly)

Error output

thread 'rustc' panicked at 'assertion failed: layout.abi.is_uninhabited()', compiler/rustc_middle/src/ty/layout.rs:228:21

Backtrace

   0: rust_begin_unwind
             at /rustc/2fd73fabe469357a12c2c974c140f67e7cdd76d0/library/std/src/panicking.rs:493:5
   1: core::panicking::panic_fmt
             at /rustc/2fd73fabe469357a12c2c974c140f67e7cdd76d0/library/core/src/panicking.rs:92:14
   2: core::panicking::panic
             at /rustc/2fd73fabe469357a12c2c974c140f67e7cdd76d0/library/core/src/panicking.rs:50:5
   3: rustc_middle::ty::layout::layout_raw
   4: 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
   5: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
   6: rustc_data_structures::stack::ensure_sufficient_stack
   7: rustc_query_system::query::plumbing::force_query_with_job
   8: rustc_query_system::query::plumbing::get_query_impl
   9: <rustc_middle::ty::layout::LayoutCx<rustc_middle::ty::context::TyCtxt> as rustc_target::abi::LayoutOf>::layout_of
  10: <rustc_codegen_llvm::context::CodegenCx as rustc_target::abi::LayoutOf>::spanned_layout_of
  11: rustc_middle::ty::layout::<impl rustc_target::abi::TyAndLayoutMethods<C> for &rustc_middle::ty::TyS>::pointee_info_at
  12: rustc_middle::ty::layout::<impl rustc_target::abi::TyAndLayoutMethods<C> for &rustc_middle::ty::TyS>::pointee_info_at
  13: <rustc_target::abi::call::FnAbi<&rustc_middle::ty::TyS> as rustc_middle::ty::layout::FnAbiExt<C>>::new_internal::{{closure}}::{{closure}}
  14: rustc_target::abi::call::ArgAbi<Ty>::new
  15: core::ops::function::impls::<impl core::ops::function::FnMut<A> for &mut F>::call_mut
  16: <core::iter::adapters::chain::Chain<A,B> as core::iter::traits::iterator::Iterator>::fold
  17: <alloc::vec::Vec<T> as alloc::vec::spec_from_iter::SpecFromIter<T,I>>::from_iter
  18: <rustc_target::abi::call::FnAbi<&rustc_middle::ty::TyS> as rustc_middle::ty::layout::FnAbiExt<C>>::new_internal
  19: rustc_codegen_llvm::mono_item::<impl rustc_codegen_ssa::traits::declare::PreDefineMethods for rustc_codegen_llvm::context::CodegenCx>::predefine_fn
  20: rustc_codegen_llvm::base::compile_codegen_unit::module_codegen
  21: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task
  22: rustc_codegen_llvm::base::compile_codegen_unit
  23: rustc_codegen_ssa::base::codegen_crate
  24: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate
  25: rustc_session::utils::<impl rustc_session::session::Session>::time
  26: rustc_interface::passes::QueryContext::enter
  27: rustc_interface::queries::Queries::ongoing_codegen
  28: rustc_interface::queries::<impl rustc_interface::interface::Compiler>::enter
  29: rustc_span::with_source_map
  30: rustc_interface::interface::create_compiler_and_run
  31: rustc_span::with_session_globals

[jyn514]

Possible duplicate of #82954.

[hameerabbasi]

Bisected:

found 4 bors merge commits in the specified range
  commit[0] 2019-10-03UTC: Auto merge of #64938 - estebank:ice-ice-baby, r=matthewjasper
  commit[1] 2019-10-03UTC: Auto merge of #65076 - tmandry:rollup-ka7nzb6, r=tmandry
  commit[2] 2019-10-04UTC: Auto merge of #65087 - Centril:rollup-skxq0zr, r=Centril
  commit[3] 2019-10-04UTC: Auto merge of #64994 - GuillaumeGomez:fix-rustdoc-display-js-disabled, r=Mark-Simulacrum
ERROR: no commits between 032a53a06ce293571e51bbe621a5c480e8a28e95 and 2e7244807a7878f6eca3eb7d97ae9b413aa49014 within last 167 days

[apiraino]

Assigning priority as discussed as part of the Prioritization Working Group procedure and removing I-prioritize.

@rustbot label -I-prioritize +P-medium

[Alexendoo]

Fixed by #90854