Complex generic constants cause 'not user writable' panic when invoked by rustdoc

[zeyonaut]

Code

#![feature(const_generics, const_evaluatable_checked)]
#![allow(incomplete_features)]
struct A<T, const N: core::num::NonZeroUsize>([T; N.get()]) where [T; N.get()]: Sized;

Meta

rustc --version --verbose:

rustc 1.49.0-nightly (98edd1fbf 2020-10-06)
binary: rustc
commit-hash: 98edd1fbf8a68977a2a7c1312eb1ebff80515a92
commit-date: 2020-10-06
host: x86_64-pc-windows-msvc
release: 1.49.0-nightly
LLVM version: 11.0

Error output

cargo doc

thread 'rustc' panicked at 'not user writable', src\librustdoc\clean\mod.rs:512:63
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

error: internal compiler error: unexpected panic

error: Unrecognized option: 'crate-version'

error: could not document `bugtest`

Backtrace

stack backtrace:
   0:     0x7ff948f79859 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hc20a26e0f7659afd
   1:     0x7ff948fa6f8b - core::fmt::write::h435be716304d26a1
   2:     0x7ff948f6b1d8 - <std::io::IoSlice as core::fmt::Debug>::fmt::h997d94c78f1ba97b
   3:     0x7ff948f7ec44 - std::panicking::take_hook::hbf7e33d26fc3ca30
   4:     0x7ff948f7e828 - std::panicking::take_hook::hbf7e33d26fc3ca30
   5:     0x7ff903296257 - rustc_driver::report_ice::hf0a13013cc3176ab
   6:     0x7ff948f7f6a0 - std::panicking::rust_panic_with_hook::h19068ccbe4b337a1
   7:     0x7ff6e4f92ca4 - <unknown>
   8:     0x7ff6e4f921bf - <unknown>
   9:     0x7ff6e4df193d - <unknown>
  10:     0x7ff6e5060f92 - <unknown>
  11:     0x7ff6e5090644 - <unknown>
  12:     0x7ff6e50629ac - <unknown>
  13:     0x7ff6e4ebc376 - <unknown>
  14:     0x7ff6e4ed8b14 - <unknown>
  15:     0x7ff6e4f3ae47 - <unknown>
  16:     0x7ff6e4e9d692 - <unknown>
  17:     0x7ff6e509632d - <unknown>
  18:     0x7ff6e50cd1b8 - <unknown>
  19:     0x7ff6e4ddeb6c - <unknown>
  20:     0x7ff6e508f0a7 - <unknown>
  21:     0x7ff6e4dce6c0 - <unknown>
  22:     0x7ff6e4dde7bf - <unknown>
  23:     0x7ff6e4dd8c1f - <unknown>
  24:     0x7ff6e4d95ea8 - <unknown>
  25:     0x7ff6e4ee10c9 - <unknown>
  26:     0x7ff6e4e975f5 - <unknown>
  27:     0x7ff6e4ee2fe4 - <unknown>
  28:     0x7ff6e4de6488 - <unknown>
  29:     0x7ff6e4ed575c - <unknown>
  30:     0x7ff6e4f9284b - <unknown>
  31:     0x7ff6e50b7413 - <unknown>
  32:     0x7ff948f8f577 - std::sys::windows::thread::Thread::new::h04914a10b014a9d7
  33:     0x7ff99b6c7bd4 - BaseThreadInitThunk
  34:     0x7ff99d2ace51 - RtlUserThreadStart

Related: #77645

[jyn514]

@lcnr do you know what's going on here? The rustdoc code is

rust/src/librustdoc/clean/mod.rs

Lines 506 to 512 in 0dda415

	ty::PredicateAtom::Subtype(..)
	| ty::PredicateAtom::WellFormed(..)
	| ty::PredicateAtom::ObjectSafe(..)
	| ty::PredicateAtom::ClosureKind(..)
	| ty::PredicateAtom::ConstEvaluatable(..)
	| ty::PredicateAtom::ConstEquate(..)
	| ty::PredicateAtom::TypeWellFormedFromEnv(..) => panic!("not user writable"),

[lcnr]

Yeah, that one's somewhat expected. const_evaluatable_checked adds ConstEvaluatable predicates to predicates_of, so we now have to deal with them in rustdoc, can fix this myself next week