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Rollup merge of #111695 - fmease:dont-lump-together-alias-tys, r=comp…
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…iler-errors

Exclude inherent projections from some alias type `match`es

Updating (hopefully) all remaining `match`es which I overlooked to update when adding `AliasKind::Inherent` in #109410.

Fixes #111399.
Sadly the regression test is a clippy test instead of a rustc one as I don't know of another way to test that a trait bound like `Ty::InhProj: Trait` doesn't cause a crash without reaching a cycle error first (this is getting old ^^').

`@rustbot` label F-inherent_associated_types
r? `@compiler-errors`
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Dylan-DPC authored May 18, 2023
2 parents ea6ac45 + 434f088 commit d2823a1
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Showing 6 changed files with 29 additions and 5 deletions.
4 changes: 3 additions & 1 deletion compiler/rustc_trait_selection/src/solve/assembly/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -506,10 +506,12 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
| ty::Param(_)
| ty::Placeholder(..)
| ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
| ty::Alias(ty::Inherent, _)
| ty::Error(_) => return,
ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_))
| ty::Bound(..) => bug!("unexpected self type for `{goal:?}`"),
ty::Alias(_, alias_ty) => alias_ty,
// Excluding IATs here as they don't have meaningful item bounds.
ty::Alias(ty::Projection | ty::Opaque, alias_ty) => alias_ty,
};

for assumption in self.tcx().item_bounds(alias_ty.def_id).subst(self.tcx(), alias_ty.substs)
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5 changes: 4 additions & 1 deletion compiler/rustc_trait_selection/src/traits/project.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1543,7 +1543,10 @@ fn assemble_candidates_from_trait_def<'cx, 'tcx>(
// Check whether the self-type is itself a projection.
// If so, extract what we know from the trait and try to come up with a good answer.
let bounds = match *obligation.predicate.self_ty().kind() {
ty::Alias(_, ref data) => tcx.item_bounds(data.def_id).subst(tcx, data.substs),
// Excluding IATs here as they don't have meaningful item bounds.
ty::Alias(ty::Projection | ty::Opaque, ref data) => {
tcx.item_bounds(data.def_id).subst(tcx, data.substs)
}
ty::Infer(ty::TyVar(_)) => {
// If the self-type is an inference variable, then it MAY wind up
// being a projected type, so induce an ambiguity.
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Original file line number Diff line number Diff line change
Expand Up @@ -143,7 +143,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// Before we go into the whole placeholder thing, just
// quickly check if the self-type is a projection at all.
match obligation.predicate.skip_binder().trait_ref.self_ty().kind() {
ty::Alias(..) => {}
// Excluding IATs here as they don't have meaningful item bounds.
ty::Alias(ty::Projection | ty::Opaque, _) => {}
ty::Infer(ty::TyVar(_)) => {
span_bug!(
obligation.cause.span,
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Original file line number Diff line number Diff line change
Expand Up @@ -156,7 +156,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
let placeholder_self_ty = placeholder_trait_predicate.self_ty();
let placeholder_trait_predicate = ty::Binder::dummy(placeholder_trait_predicate);
let (def_id, substs) = match *placeholder_self_ty.kind() {
ty::Alias(_, ty::AliasTy { def_id, substs, .. }) => (def_id, substs),
// Excluding IATs here as they don't have meaningful item bounds.
ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
(def_id, substs)
}
_ => bug!("projection candidate for unexpected type: {:?}", placeholder_self_ty),
};

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4 changes: 3 additions & 1 deletion compiler/rustc_trait_selection/src/traits/select/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1645,7 +1645,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {

let tcx = self.infcx.tcx;
let (def_id, substs) = match *placeholder_trait_predicate.trait_ref.self_ty().kind() {
ty::Alias(_, ty::AliasTy { def_id, substs, .. }) => (def_id, substs),
ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
(def_id, substs)
}
_ => {
span_bug!(
obligation.cause.span,
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13 changes: 13 additions & 0 deletions src/tools/clippy/tests/ui/issue-111399.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,13 @@
#![feature(inherent_associated_types)]
#![allow(incomplete_features)]

// Check that rustc doesn't crash on the trait bound `Self::Ty: std::marker::Freeze`.

pub struct Struct;

impl Struct {
pub type Ty = usize;
pub const CT: Self::Ty = 42;
}

fn main() {}

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