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use super::InferCtxt;
use super::type_variable::TypeVariableOrigin;
use traits::ObligationCause;
use ty::TyVar;
use ty::{self, Ty};
use ty::relate::{RelateResult, TypeRelation};
pub trait LatticeDir<'f, 'gcx: 'f+'tcx, 'tcx: 'f> : TypeRelation<'f, 'gcx, 'tcx> {
fn infcx(&self) -> &'f InferCtxt<'f, 'gcx, 'tcx>;
fn cause(&self) -> &ObligationCause<'tcx>;
fn relate_bound(&mut self, v: Ty<'tcx>, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, ()>;
}
pub fn super_lattice_tys<'a, 'gcx, 'tcx, L>(this: &mut L,
a: Ty<'tcx>,
b: Ty<'tcx>)
-> RelateResult<'tcx, Ty<'tcx>>
where L: LatticeDir<'a, 'gcx, 'tcx>, 'gcx: 'a+'tcx, 'tcx: 'a
{
debug!("{}.lattice_tys({:?}, {:?})",
this.tag(),
a,
b);
if a == b {
return Ok(a);
}
let infcx = this.infcx();
let a = infcx.type_variables.borrow_mut().replace_if_possible(a);
let b = infcx.type_variables.borrow_mut().replace_if_possible(b);
match (&a.sty, &b.sty) {
(&ty::TyInfer(TyVar(..)), &ty::TyInfer(TyVar(..)))
if infcx.type_var_diverges(a) && infcx.type_var_diverges(b) => {
let v = infcx.next_diverging_ty_var(
TypeVariableOrigin::LatticeVariable(this.cause().span));
this.relate_bound(v, a, b)?;
Ok(v)
}
(&ty::TyInfer(TyVar(..)), _) |
(_, &ty::TyInfer(TyVar(..))) => {
let v = infcx.next_ty_var(TypeVariableOrigin::LatticeVariable(this.cause().span));
this.relate_bound(v, a, b)?;
Ok(v)
}
_ => {
infcx.super_combine_tys(this, a, b)
}
}
}