3 use rustc_infer::infer::InferCtxt;
4 use rustc_infer::traits::{
5 query::NoSolution, FulfillmentError, FulfillmentErrorCode, MismatchedProjectionTypes,
6 PredicateObligation, SelectionError, TraitEngine,
9 use rustc_middle::ty::error::{ExpectedFound, TypeError};
11 use super::{Certainty, InferCtxtEvalExt};
13 /// A trait engine using the new trait solver.
15 /// This is mostly identical to how `evaluate_all` works inside of the
16 /// solver, except that the requirements are slightly different.
18 /// Unlike `evaluate_all` it is possible to add new obligations later on
19 /// and we also have to track diagnostics information by using `Obligation`
20 /// instead of `Goal`.
22 /// It is also likely that we want to use slightly different datastructures
23 /// here as this will have to deal with far more root goals than `evaluate_all`.
24 pub struct FulfillmentCtxt<'tcx> {
25 obligations: Vec<PredicateObligation<'tcx>>,
28 impl<'tcx> FulfillmentCtxt<'tcx> {
29 pub fn new() -> FulfillmentCtxt<'tcx> {
30 FulfillmentCtxt { obligations: Vec::new() }
34 impl<'tcx> TraitEngine<'tcx> for FulfillmentCtxt<'tcx> {
35 fn register_predicate_obligation(
37 _infcx: &InferCtxt<'tcx>,
38 obligation: PredicateObligation<'tcx>,
40 self.obligations.push(obligation);
43 fn select_all_or_error(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>> {
44 let errors = self.select_where_possible(infcx);
45 if !errors.is_empty() {
51 .map(|obligation| FulfillmentError {
52 obligation: obligation.clone(),
53 code: FulfillmentErrorCode::CodeAmbiguity,
54 root_obligation: obligation,
59 fn select_where_possible(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>> {
60 let mut errors = Vec::new();
62 if !infcx.tcx.recursion_limit().value_within_limit(i) {
63 unimplemented!("overflowed on pending obligations: {:?}", self.obligations);
66 let mut has_changed = false;
67 for obligation in mem::take(&mut self.obligations) {
68 let goal = obligation.clone().into();
69 let (changed, certainty) = match infcx.evaluate_root_goal(goal) {
72 errors.push(FulfillmentError {
73 obligation: obligation.clone(),
74 code: match goal.predicate.kind().skip_binder() {
75 ty::PredicateKind::Clause(ty::Clause::Projection(_)) => {
76 FulfillmentErrorCode::CodeProjectionError(
77 // FIXME: This could be a `Sorts` if the term is a type
78 MismatchedProjectionTypes { err: TypeError::Mismatch },
81 ty::PredicateKind::Subtype(pred) => {
82 let (a, b) = infcx.replace_bound_vars_with_placeholders(
83 goal.predicate.kind().rebind((pred.a, pred.b)),
85 let expected_found = ExpectedFound::new(true, a, b);
86 FulfillmentErrorCode::CodeSubtypeError(
88 TypeError::Sorts(expected_found),
91 ty::PredicateKind::Coerce(pred) => {
92 let (a, b) = infcx.replace_bound_vars_with_placeholders(
93 goal.predicate.kind().rebind((pred.a, pred.b)),
95 let expected_found = ExpectedFound::new(false, a, b);
96 FulfillmentErrorCode::CodeSubtypeError(
98 TypeError::Sorts(expected_found),
101 ty::PredicateKind::ConstEquate(a, b) => {
102 let (a, b) = infcx.replace_bound_vars_with_placeholders(
103 goal.predicate.kind().rebind((a, b)),
105 let expected_found = ExpectedFound::new(true, a, b);
106 FulfillmentErrorCode::CodeConstEquateError(
108 TypeError::ConstMismatch(expected_found),
111 ty::PredicateKind::Clause(_)
112 | ty::PredicateKind::WellFormed(_)
113 | ty::PredicateKind::ObjectSafe(_)
114 | ty::PredicateKind::ClosureKind(_, _, _)
115 | ty::PredicateKind::ConstEvaluatable(_)
116 | ty::PredicateKind::TypeWellFormedFromEnv(_)
117 | ty::PredicateKind::Ambiguous => {
118 FulfillmentErrorCode::CodeSelectionError(
119 SelectionError::Unimplemented,
123 root_obligation: obligation,
129 has_changed |= changed;
132 Certainty::Maybe(_) => self.obligations.push(obligation),
144 fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>> {
145 self.obligations.clone()