1 use crate::infer::canonical::query_response;
2 use crate::infer::{InferCtxt, InferOk};
3 use crate::traits::engine::TraitEngineExt as _;
4 use crate::traits::query::type_op::TypeOpOutput;
5 use crate::traits::query::Fallible;
6 use crate::traits::{ObligationCause, TraitEngine};
7 use rustc_infer::traits::TraitEngineExt as _;
8 use rustc_span::source_map::DUMMY_SP;
13 pub struct CustomTypeOp<F, G> {
18 impl<F, G> CustomTypeOp<F, G> {
19 pub fn new<'tcx, R>(closure: F, description: G) -> Self
21 F: FnOnce(&InferCtxt<'_, 'tcx>) -> Fallible<InferOk<'tcx, R>>,
24 CustomTypeOp { closure, description }
28 impl<'tcx, F, R, G> super::TypeOp<'tcx> for CustomTypeOp<F, G>
30 F: for<'a, 'cx> FnOnce(&'a InferCtxt<'cx, 'tcx>) -> Fallible<InferOk<'tcx, R>>,
35 /// Processes the operation and all resulting obligations,
36 /// returning the final result along with any region constraints
37 /// (they will be given over to the NLL region solver).
38 fn fully_perform(self, infcx: &InferCtxt<'_, 'tcx>) -> Fallible<TypeOpOutput<'tcx, Self>> {
39 if cfg!(debug_assertions) {
40 info!("fully_perform({:?})", self);
43 scrape_region_constraints(infcx, || (self.closure)(infcx))
47 impl<F, G> fmt::Debug for CustomTypeOp<F, G>
51 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
52 write!(f, "{}", (self.description)())
56 /// Executes `op` and then scrapes out all the "old style" region
57 /// constraints that result, creating query-region-constraints.
58 fn scrape_region_constraints<'tcx, Op: super::TypeOp<'tcx, Output = R>, R>(
59 infcx: &InferCtxt<'_, 'tcx>,
60 op: impl FnOnce() -> Fallible<InferOk<'tcx, R>>,
61 ) -> Fallible<TypeOpOutput<'tcx, Op>> {
62 let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
63 let dummy_body_id = ObligationCause::dummy().body_id;
65 // During NLL, we expect that nobody will register region
66 // obligations **except** as part of a custom type op (and, at the
67 // end of each custom type op, we scrape out the region
68 // obligations that resulted). So this vector should be empty on
70 let pre_obligations = infcx.take_registered_region_obligations();
72 pre_obligations.is_empty(),
73 "scrape_region_constraints: incoming region obligations = {:#?}",
77 let InferOk { value, obligations } = infcx.commit_if_ok(|_| op())?;
78 debug_assert!(obligations.iter().all(|o| o.cause.body_id == dummy_body_id));
79 fulfill_cx.register_predicate_obligations(infcx, obligations);
80 let errors = fulfill_cx.select_all_or_error(infcx);
81 if !errors.is_empty() {
82 infcx.tcx.sess.diagnostic().delay_span_bug(
84 &format!("errors selecting obligation during MIR typeck: {:?}", errors),
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() {
102 Ok(TypeOpOutput { output: value, constraints: None, canonicalized_query: None })
106 constraints: Some(Rc::new(region_constraints)),
107 canonicalized_query: None,