1 use crate::infer::{InferCtxt, InferOk};
2 use crate::traits::query::Fallible;
5 use crate::infer::canonical::query_response;
6 use crate::infer::canonical::QueryRegionConstraints;
7 use crate::traits::{ObligationCause, TraitEngine, TraitEngineExt};
8 use rustc_span::source_map::DUMMY_SP;
11 pub struct CustomTypeOp<F, G> {
16 impl<F, G> CustomTypeOp<F, G> {
17 pub fn new<'tcx, R>(closure: F, description: G) -> Self
19 F: FnOnce(&InferCtxt<'_, 'tcx>) -> Fallible<InferOk<'tcx, R>>,
22 CustomTypeOp { closure, description }
26 impl<'tcx, F, R, G> super::TypeOp<'tcx> for CustomTypeOp<F, G>
28 F: for<'a, 'cx> FnOnce(&'a InferCtxt<'cx, 'tcx>) -> Fallible<InferOk<'tcx, R>>,
33 /// Processes the operation and all resulting obligations,
34 /// returning the final result along with any region constraints
35 /// (they will be given over to the NLL region solver).
38 infcx: &InferCtxt<'_, 'tcx>,
39 ) -> Fallible<(Self::Output, Option<Rc<QueryRegionConstraints<'tcx>>>)> {
40 if cfg!(debug_assertions) {
41 info!("fully_perform({:?})", self);
44 scrape_region_constraints(infcx, || Ok((self.closure)(infcx)?))
48 impl<F, G> fmt::Debug for CustomTypeOp<F, G>
52 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
53 write!(f, "{}", (self.description)())
57 /// Executes `op` and then scrapes out all the "old style" region
58 /// constraints that result, creating query-region-constraints.
59 fn scrape_region_constraints<'tcx, R>(
60 infcx: &InferCtxt<'_, 'tcx>,
61 op: impl FnOnce() -> Fallible<InferOk<'tcx, R>>,
62 ) -> Fallible<(R, Option<Rc<QueryRegionConstraints<'tcx>>>)> {
63 let mut fulfill_cx = TraitEngine::new(infcx.tcx);
64 let dummy_body_id = ObligationCause::dummy().body_id;
66 // During NLL, we expect that nobody will register region
67 // obligations **except** as part of a custom type op (and, at the
68 // end of each custom type op, we scrape out the region
69 // obligations that resulted). So this vector should be empty on
71 let pre_obligations = infcx.take_registered_region_obligations();
73 pre_obligations.is_empty(),
74 "scrape_region_constraints: incoming region obligations = {:#?}",
78 let InferOk { value, obligations } = infcx.commit_if_ok(|_| op())?;
79 debug_assert!(obligations.iter().all(|o| o.cause.body_id == dummy_body_id));
80 fulfill_cx.register_predicate_obligations(infcx, obligations);
81 if let Err(e) = fulfill_cx.select_all_or_error(infcx) {
82 infcx.tcx.sess.diagnostic().delay_span_bug(
84 &format!("errors selecting obligation during MIR typeck: {:?}", e),
88 let region_obligations = infcx.take_registered_region_obligations();
90 let region_constraint_data = infcx.take_and_reset_region_constraints();
92 let region_constraints = query_response::make_query_region_constraints(
96 .map(|(_, r_o)| (r_o.sup_type, r_o.sub_region))
97 .map(|(ty, r)| (infcx.resolve_vars_if_possible(&ty), r)),
98 ®ion_constraint_data,
101 if region_constraints.is_empty() {
104 Ok((value, Some(Rc::new(region_constraints))))