ICE: `unexpected const arg parent in type_of()`

[matthiaskrgr]

auto-reduced (treereduce-rust):

#![feature(generic_const_exprs)]
#![feature(object_safe_for_dispatch)]
trait X {
    type Y<const N: i16>;
}

const _: () = {
    fn f2<'a>(arg: Box<dyn X<Y<1> = &'a ()>>) {}
};

fn main() {}

original:

#![feature(generic_const_exprs)]
#![allow(bar_to, bar_from)]

trait X {
    type Y<const N: i16>;
}

const _: () = {
    fn f2<'a>(arg: Box<dyn X<Y<1> = &'a ()>>) {}
    //~^ ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
    //~| ERROR associated type takes 0 generic arguments but 1 generic argument
    //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
    //~| ERROR associated type takes 0 generic arguments but 1 generic argument
    //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
    //~| ERROR associated type takes 0 generic arguments but 1 generic argument
    //~| ERROR `X` cannot be made into an object
};

fn main() {}

Version information

rustc 1.82.0-nightly (004e155c4 2024-07-25)
binary: rustc
commit-hash: 004e155c46a2083d4f73212cc47a6f7fb98fcbd1
commit-date: 2024-07-25
host: x86_64-unknown-linux-gnu
release: 1.82.0-nightly
LLVM version: 18.1.7

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc -Zcrate-attr=feature(object_safe_for_dispatch)

Program output

warning: the feature `generic_const_exprs` is incomplete and may not be safe to use and/or cause compiler crashes
 --> /tmp/icemaker_global_tempdir.IthovrlrGpyV/rustc_testrunner_tmpdir_reporting.lRekHjsPjvYq/mvce.rs:1:12
  |
1 | #![feature(generic_const_exprs)]
  |            ^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #76560 <https://github.com/rust-lang/rust/issues/76560> for more information
  = note: `#[warn(incomplete_features)]` on by default

warning: unused variable: `arg`
 --> /tmp/icemaker_global_tempdir.IthovrlrGpyV/rustc_testrunner_tmpdir_reporting.lRekHjsPjvYq/mvce.rs:8:15
  |
8 |     fn f2<'a>(arg: Box<dyn X<Y<1> = &'a ()>>) {}
  |               ^^^ help: if this is intentional, prefix it with an underscore: `_arg`
  |
  = note: `#[warn(unused_variables)]` on by default

warning: trait `X` is never used
 --> /tmp/icemaker_global_tempdir.IthovrlrGpyV/rustc_testrunner_tmpdir_reporting.lRekHjsPjvYq/mvce.rs:3:7
  |
3 | trait X {
  |       ^
  |
  = note: `#[warn(dead_code)]` on by default

warning: 3 warnings emitted

note: no errors encountered even though delayed bugs were created

note: those delayed bugs will now be shown as internal compiler errors

error: internal compiler error: unexpected const arg parent in type_of(): AssocItemConstraint(AssocItemConstraint { hir_id: HirId(DefId(0:7 ~ mvce[807a]::_::f2).13), ident: Y#0, gen_args: GenericArgs { args: [Const(ConstArg { hir_id: HirId(DefId(0:7 ~ mvce[807a]::_::f2).9), kind: Anon(AnonConst { hir_id: HirId(DefId(0:7 ~ mvce[807a]::_::f2).7), def_id: DefId(0:9 ~ mvce[807a]::_::f2::{constant#0}), body: BodyId { hir_id: HirId(DefId(0:7 ~ mvce[807a]::_::f2).8) }, span: /tmp/icemaker_global_tempdir.IthovrlrGpyV/rustc_testrunner_tmpdir_reporting.lRekHjsPjvYq/mvce.rs:8:32: 8:33 (#0) }), is_desugared_from_effects: false })], constraints: [], parenthesized: No, span_ext: /tmp/icemaker_global_tempdir.IthovrlrGpyV/rustc_testrunner_tmpdir_reporting.lRekHjsPjvYq/mvce.rs:8:31: 8:34 (#0) }, kind: Equality { term: Ty(Ty { hir_id: HirId(DefId(0:7 ~ mvce[807a]::_::f2).12), kind: Ref(Lifetime { hir_id: HirId(DefId(0:7 ~ mvce[807a]::_::f2).10), ident: 'a#0, res: Param(DefId(0:8 ~ mvce[807a]::_::f2::'a)) }, MutTy { ty: Ty { hir_id: HirId(DefId(0:7 ~ mvce[807a]::_::f2).11), kind: Tup([]), span: /tmp/icemaker_global_tempdir.IthovrlrGpyV/rustc_testrunner_tmpdir_reporting.lRekHjsPjvYq/mvce.rs:8:41: 8:43 (#0) }, mutbl: Not }), span: /tmp/icemaker_global_tempdir.IthovrlrGpyV/rustc_testrunner_tmpdir_reporting.lRekHjsPjvYq/mvce.rs:8:37: 8:43 (#0) }) }, span: /tmp/icemaker_global_tempdir.IthovrlrGpyV/rustc_testrunner_tmpdir_reporting.lRekHjsPjvYq/mvce.rs:8:30: 8:43 (#0) })
 --> /tmp/icemaker_global_tempdir.IthovrlrGpyV/rustc_testrunner_tmpdir_reporting.lRekHjsPjvYq/mvce.rs:8:32
  |
8 |     fn f2<'a>(arg: Box<dyn X<Y<1> = &'a ()>>) {}
  |                                ^
  |
note: delayed at compiler/rustc_hir_analysis/src/collect/type_of.rs:276:20 - disabled backtrace
 --> /tmp/icemaker_global_tempdir.IthovrlrGpyV/rustc_testrunner_tmpdir_reporting.lRekHjsPjvYq/mvce.rs:8:32
  |
8 |     fn f2<'a>(arg: Box<dyn X<Y<1> = &'a ()>>) {}
  |                                ^

error: internal compiler error: Const::from_anon_const: couldn't lit_to_const TypeError
 --> /tmp/icemaker_global_tempdir.IthovrlrGpyV/rustc_testrunner_tmpdir_reporting.lRekHjsPjvYq/mvce.rs:8:32
  |
8 |     fn f2<'a>(arg: Box<dyn X<Y<1> = &'a ()>>) {}
  |                                ^
  |
note: delayed at compiler/rustc_middle/src/ty/consts.rs:309:31 - disabled backtrace
 --> /tmp/icemaker_global_tempdir.IthovrlrGpyV/rustc_testrunner_tmpdir_reporting.lRekHjsPjvYq/mvce.rs:8:32
  |
8 |     fn f2<'a>(arg: Box<dyn X<Y<1> = &'a ()>>) {}
  |                                ^

error: internal compiler error: Trying to feed an already recorded value for query type_of key=DefId(0:9 ~ mvce[807a]::_::f2::{constant#0}):
                                old value: EarlyBinder { value: {type error} }
                                new value: EarlyBinder { value: i16 }
  |
  = note: delayed at compiler/rustc_middle/src/query/mod.rs:2294:1 - disabled backtrace

error: internal compiler error: mir_const_qualif: MIR had errors
 --> /tmp/icemaker_global_tempdir.IthovrlrGpyV/rustc_testrunner_tmpdir_reporting.lRekHjsPjvYq/mvce.rs:8:32
  |
8 |     fn f2<'a>(arg: Box<dyn X<Y<1> = &'a ()>>) {}
  |                                ^
  |
note: delayed at compiler/rustc_mir_transform/src/lib.rs:271:19 - disabled backtrace
 --> /tmp/icemaker_global_tempdir.IthovrlrGpyV/rustc_testrunner_tmpdir_reporting.lRekHjsPjvYq/mvce.rs:8:32
  |
8 |     fn f2<'a>(arg: Box<dyn X<Y<1> = &'a ()>>) {}
  |                                ^

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: please make sure that you have updated to the latest nightly

note: rustc 1.82.0-nightly (004e155c4 2024-07-25) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z crate-attr=feature(object_safe_for_dispatch) -Z dump-mir-dir=dir

query stack during panic:
end of query stack

@rustbot label +F-generic_const_exprs +F-object_safe_for_dispatch

[matthiaskrgr]

#126620