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Add AliasKind::Weak for type aliases.

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Only use it when the type alias contains an opaque type.

Also does wf-checking on such type aliases.
This commit is contained in:
Oli Scherer
2023-03-07 12:03:11 +00:00
parent 4fdd07fe88
commit f3b7dd6388
86 changed files with 474 additions and 199 deletions
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3
compiler/rustc_trait_selection/src/solve/assembly/mod.rs
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@@ -508,10 +508,11 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
| ty::Placeholder(..)
| ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
| ty::Alias(ty::Inherent, _)
| ty::Alias(ty::Weak, _)
| ty::Error(_) => return,
ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_))
| ty::Bound(..) => bug!("unexpected self type for `{goal:?}`"),
// Excluding IATs here as they don't have meaningful item bounds.
// Excluding IATs and type aliases here as they don't have meaningful item bounds.
ty::Alias(ty::Projection | ty::Opaque, alias_ty) => alias_ty,
};

2
compiler/rustc_trait_selection/src/solve/assembly/structural_traits.rs
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@@ -33,7 +33,7 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_auto_trait<'tcx>(
ty::Dynamic(..)
| ty::Param(..)
| ty::Foreign(..)
| ty::Alias(ty::Projection | ty::Inherent, ..)
| ty::Alias(ty::Projection | ty::Inherent | ty::Weak, ..)
| ty::Placeholder(..)
| ty::Bound(..)
| ty::Infer(_) => {

1
compiler/rustc_trait_selection/src/solve/mod.rs
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@@ -29,6 +29,7 @@ mod opaques;
mod project_goals;
mod search_graph;
mod trait_goals;
mod weak_types;
pub use eval_ctxt::{EvalCtxt, InferCtxtEvalExt};
pub use fulfill::FulfillmentCtxt;

1
compiler/rustc_trait_selection/src/solve/project_goals.rs
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@@ -57,6 +57,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
}
DefKind::AnonConst => self.normalize_anon_const(goal),
DefKind::OpaqueTy => self.normalize_opaque_type(goal),
DefKind::TyAlias => self.normalize_weak_type(goal),
kind => bug!("unknown DefKind {} in projection goal: {goal:#?}", kind.descr(def_id)),
}
}

2
compiler/rustc_trait_selection/src/solve/trait_goals.rs
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@@ -618,7 +618,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
ty::Dynamic(..)
| ty::Param(..)
| ty::Foreign(..)
| ty::Alias(ty::Projection | ty::Inherent, ..)
| ty::Alias(ty::Projection | ty::Weak | ty::Inherent, ..)
| ty::Placeholder(..) => Some(Err(NoSolution)),
ty::Infer(_) | ty::Bound(_, _) => bug!("unexpected type `{self_ty}`"),

19
compiler/rustc_trait_selection/src/solve/weak_types.rs Normal file
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@@ -0,0 +1,19 @@
use rustc_middle::traits::solve::{Certainty, Goal, QueryResult};
use rustc_middle::ty;
use super::EvalCtxt;
impl<'tcx> EvalCtxt<'_, 'tcx> {
pub(super) fn normalize_weak_type(
&mut self,
goal: Goal<'tcx, ty::ProjectionPredicate<'tcx>>,
) -> QueryResult<'tcx> {
let tcx = self.tcx();
let weak_ty = goal.predicate.projection_ty;
let expected = goal.predicate.term.ty().expect("no such thing as a const alias");
let actual = tcx.type_of(weak_ty.def_id).subst(tcx, weak_ty.substs);
self.eq(goal.param_env, expected, actual)?;
self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}
}