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use rustc_infer::infer::at::At;
use rustc_infer::traits::TraitEngine;
use rustc_macros::extension;
use rustc_middle::ty::{self, Ty};
use crate::traits::{NormalizeExt, Obligation};
#[extension(pub trait StructurallyNormalizeExt<'tcx>)]
impl<'tcx> At<'_, 'tcx> {
fn structurally_normalize_ty<E: 'tcx>(
&self,
ty: Ty<'tcx>,
fulfill_cx: &mut dyn TraitEngine<'tcx, E>,
) -> Result<Ty<'tcx>, Vec<E>> {
self.structurally_normalize_term(ty.into(), fulfill_cx).map(|term| term.expect_type())
}
fn structurally_normalize_const<E: 'tcx>(
&self,
ct: ty::Const<'tcx>,
fulfill_cx: &mut dyn TraitEngine<'tcx, E>,
) -> Result<ty::Const<'tcx>, Vec<E>> {
if self.infcx.tcx.features().generic_const_exprs() {
return Ok(super::evaluate_const(&self.infcx, ct, self.param_env));
}
self.structurally_normalize_term(ct.into(), fulfill_cx).map(|term| term.expect_const())
}
fn structurally_normalize_term<E: 'tcx>(
&self,
term: ty::Term<'tcx>,
fulfill_cx: &mut dyn TraitEngine<'tcx, E>,
) -> Result<ty::Term<'tcx>, Vec<E>> {
assert!(!term.is_infer(), "should have resolved vars before calling");
if self.infcx.next_trait_solver() {
if let None = term.to_alias_term() {
return Ok(term);
}
let new_infer = self.infcx.next_term_var_of_kind(term, self.cause.span);
// We simply emit an `alias-eq` goal here, since that will take care of
// normalizing the LHS of the projection until it is a rigid projection
// (or a not-yet-defined opaque in scope).
let obligation = Obligation::new(
self.infcx.tcx,
self.cause.clone(),
self.param_env,
ty::PredicateKind::AliasRelate(term, new_infer, ty::AliasRelationDirection::Equate),
);
fulfill_cx.register_predicate_obligation(self.infcx, obligation);
let errors = fulfill_cx.select_where_possible(self.infcx);
if !errors.is_empty() {
return Err(errors);
}
Ok(self.infcx.resolve_vars_if_possible(new_infer))
} else {
Ok(self.normalize(term).into_value_registering_obligations(self.infcx, fulfill_cx))
}
}
}
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