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Fix rustdoc ICE when a const is actually a type #119739

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Fix rustdoc ICE when a const is actually a type #119739

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d2c6faa
Fix rustdoc ICE when a const is actually a type
GuillaumeGomez Jan 8, 2024
f2236d8
Add regression test for #119529
GuillaumeGomez Jan 8, 2024
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79 changes: 58 additions & 21 deletions src/librustdoc/clean/utils.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,7 @@ use rustc_hir::def::{DefKind, Res};
use rustc_hir::def_id::{DefId, LocalDefId, LOCAL_CRATE};
use rustc_metadata::rendered_const;
use rustc_middle::mir;
use rustc_middle::ty::{self, GenericArgKind, GenericArgsRef, TyCtxt};
use rustc_middle::ty::{self, GenericArgKind, GenericArgsRef, GenericParamDef, TyCtxt};
use rustc_middle::ty::{TypeVisitable, TypeVisitableExt};
use rustc_span::symbol::{kw, sym, Symbol};
use std::fmt::Write as _;
Expand Down Expand Up @@ -75,30 +75,23 @@ pub(crate) fn krate(cx: &mut DocContext<'_>) -> Crate {
Crate { module, external_traits: cx.external_traits.clone() }
}

pub(crate) fn ty_args_to_args<'tcx>(
fn ty_arg_to_arg<'tcx>(
cx: &mut DocContext<'tcx>,
ty_args: ty::Binder<'tcx, &'tcx [ty::GenericArg<'tcx>]>,
has_self: bool,
owner: DefId,
) -> Vec<GenericArg> {
if ty_args.skip_binder().is_empty() {
// Fast path which avoids executing the query `generics_of`.
return Vec::new();
}

let params = &cx.tcx.generics_of(owner).params;
let mut elision_has_failed_once_before = false;

let offset = if has_self { 1 } else { 0 };
let mut args = Vec::with_capacity(ty_args.skip_binder().len().saturating_sub(offset));

let ty_arg_to_arg = |(index, arg): (usize, &ty::GenericArg<'tcx>)| match arg.unpack() {
params: &[GenericParamDef],
index: usize,
arg: &ty::GenericArg<'tcx>,
elision_has_failed_once_before: &mut bool,
) -> Option<GenericArg> {
match arg.unpack() {
GenericArgKind::Lifetime(lt) => {
Some(GenericArg::Lifetime(clean_middle_region(lt).unwrap_or(Lifetime::elided())))
}
GenericArgKind::Type(_) if has_self && index == 0 => None,
GenericArgKind::Type(ty) => {
if !elision_has_failed_once_before
if !*elision_has_failed_once_before
&& let Some(default) = params[index].default_value(cx.tcx)
{
let default =
Expand All @@ -108,7 +101,7 @@ pub(crate) fn ty_args_to_args<'tcx>(
return None;
}

elision_has_failed_once_before = true;
*elision_has_failed_once_before = true;
}

Some(GenericArg::Type(clean_middle_ty(
Expand All @@ -129,24 +122,68 @@ pub(crate) fn ty_args_to_args<'tcx>(
return None;
}

if !elision_has_failed_once_before
if !*elision_has_failed_once_before
&& let Some(default) = params[index].default_value(cx.tcx)
{
match default.skip_binder().unpack() {
GenericArgKind::Const(_) => {}
GenericArgKind::Type(_) | GenericArgKind::Lifetime(_) => {
Comment on lines +128 to +130
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@fmease fmease Jan 8, 2024 •
edited
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This is treating symptoms not the root cause, we shouldn't have a mismatch between generics and ty_args in the first place. The root cause is an off-by-one error introduced by me since I forgot to handle trait object types correctly whose generics args don't contain a Self type.

I'm gonna submit an alternative fix shortly.

Your PR also doesn't fix (without double-checking):

pub trait Trait<const K: u32 = 0, T = ()> {}
pub type Alias<const K: u32> = dyn Trait<K>;
pub use dependency::*;
// ICE: expected a type, but found another kind

You'd need to update the outer GenericArgKind::Type branch, too.

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I'll gladly take a look at your fix then. :)

Closing this PR then!

return ty_arg_to_arg(
cx,
ty_args,
has_self,
owner,
params,
index,
&default.skip_binder(),
elision_has_failed_once_before,
);
}
}
let default =
ty_args.map_bound(|args| default.instantiate(cx.tcx, args).expect_const());

if can_elide_generic_arg(ty_args.rebind(ct), default) {
return None;
}

elision_has_failed_once_before = true;
*elision_has_failed_once_before = true;
}

Some(GenericArg::Const(Box::new(clean_middle_const(ty_args.rebind(ct), cx))))
}
};
}
}

args.extend(ty_args.skip_binder().iter().enumerate().rev().filter_map(ty_arg_to_arg));
pub(crate) fn ty_args_to_args<'tcx>(
cx: &mut DocContext<'tcx>,
ty_args: ty::Binder<'tcx, &'tcx [ty::GenericArg<'tcx>]>,
has_self: bool,
owner: DefId,
) -> Vec<GenericArg> {
if ty_args.skip_binder().is_empty() {
// Fast path which avoids executing the query `generics_of`.
return Vec::new();
}

let params = &cx.tcx.generics_of(owner).params;
let mut elision_has_failed_once_before = false;

let offset = if has_self { 1 } else { 0 };
let mut args = Vec::with_capacity(ty_args.skip_binder().len().saturating_sub(offset));

args.extend(ty_args.skip_binder().iter().enumerate().rev().filter_map(|(index, arg)| {
ty_arg_to_arg(
cx,
ty_args,
has_self,
owner,
params,
index,
arg,
&mut elision_has_failed_once_before,
)
}));
args.reverse();
args
}
Expand Down
9 changes: 9 additions & 0 deletions tests/rustdoc/issue-119529-middle-const-ty.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
// This is a regression test for <https://github.com/rust-lang/rust/issues/119529>.

#![crate_name = "foo"]

use std::cmp::PartialEq;

// @has 'foo/type.Dyn.html'
// @has - '//*[@class="rust item-decl"]' 'pub type Dyn<Rhs> = dyn PartialEq<Rhs>;'
pub type Dyn<Rhs> = dyn PartialEq<Rhs>;