1 //! This module contains code to equate the input/output types appearing
2 //! in the MIR with the expected input/output types from the function
3 //! signature. This requires a bit of processing, as the expected types
4 //! are supplied to us before normalization and may contain opaque
5 //! `impl Trait` instances. In contrast, the input/output types found in
6 //! the MIR (specifically, in the special local variables for the
7 //! `RETURN_PLACE` the MIR arguments) are always fully normalized (and
8 //! contain revealed `impl Trait` values).
10 use rustc_index::vec::Idx;
11 use rustc_infer::infer::LateBoundRegionConversionTime;
12 use rustc_middle::mir::*;
13 use rustc_middle::ty::Ty;
16 use crate::universal_regions::UniversalRegions;
18 use super::{Locations, TypeChecker};
20 impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
21 #[instrument(skip(self, body, universal_regions), level = "debug")]
22 pub(super) fn equate_inputs_and_outputs(
25 universal_regions: &UniversalRegions<'tcx>,
26 normalized_inputs_and_output: &[Ty<'tcx>],
28 let (&normalized_output_ty, normalized_input_tys) =
29 normalized_inputs_and_output.split_last().unwrap();
31 debug!(?normalized_output_ty);
32 debug!(?normalized_input_tys);
34 let mir_def_id = body.source.def_id().expect_local();
36 // If the user explicitly annotated the input types, extract
39 // e.g., `|x: FxHashMap<_, &'static u32>| ...`
40 let user_provided_sig;
41 if !self.tcx().is_closure(mir_def_id.to_def_id()) {
42 user_provided_sig = None;
44 let typeck_results = self.tcx().typeck(mir_def_id);
45 user_provided_sig = typeck_results.user_provided_sigs.get(&mir_def_id.to_def_id()).map(
46 |user_provided_poly_sig| {
47 // Instantiate the canonicalized variables from
48 // user-provided signature (e.g., the `_` in the code
49 // above) with fresh variables.
50 let poly_sig = self.instantiate_canonical_with_fresh_inference_vars(
52 &user_provided_poly_sig,
55 // Replace the bound items in the fn sig with fresh
56 // variables, so that they represent the view from
57 // "inside" the closure.
58 self.infcx.replace_bound_vars_with_fresh_vars(
60 LateBoundRegionConversionTime::FnCall,
67 debug!(?normalized_input_tys, ?body.local_decls);
69 // Equate expected input tys with those in the MIR.
70 for (argument_index, &normalized_input_ty) in normalized_input_tys.iter().enumerate() {
71 if argument_index + 1 >= body.local_decls.len() {
74 .delay_span_bug(body.span, "found more normalized_input_ty than local_decls");
78 // In MIR, argument N is stored in local N+1.
79 let local = Local::new(argument_index + 1);
81 let mir_input_ty = body.local_decls[local].ty;
83 let mir_input_span = body.local_decls[local].source_info.span;
84 self.equate_normalized_input_or_output(
91 if let Some(user_provided_sig) = user_provided_sig {
92 for (argument_index, &user_provided_input_ty) in
93 user_provided_sig.inputs().iter().enumerate()
95 // In MIR, closures begin an implicit `self`, so
96 // argument N is stored in local N+2.
97 let local = Local::new(argument_index + 2);
98 let mir_input_ty = body.local_decls[local].ty;
99 let mir_input_span = body.local_decls[local].source_info.span;
101 // If the user explicitly annotated the input types, enforce those.
102 let user_provided_input_ty =
103 self.normalize(user_provided_input_ty, Locations::All(mir_input_span));
105 self.equate_normalized_input_or_output(
106 user_provided_input_ty,
114 "equate_inputs_and_outputs: body.yield_ty {:?}, universal_regions.yield_ty {:?}",
116 universal_regions.yield_ty
119 // We will not have a universal_regions.yield_ty if we yield (by accident)
120 // outside of a generator and return an `impl Trait`, so emit a delay_span_bug
121 // because we don't want to panic in an assert here if we've already got errors.
122 if body.yield_ty().is_some() != universal_regions.yield_ty.is_some() {
123 self.tcx().sess.delay_span_bug(
126 "Expected body to have yield_ty ({:?}) iff we have a UR yield_ty ({:?})",
128 universal_regions.yield_ty,
133 if let (Some(mir_yield_ty), Some(ur_yield_ty)) =
134 (body.yield_ty(), universal_regions.yield_ty)
136 let yield_span = body.local_decls[RETURN_PLACE].source_info.span;
137 self.equate_normalized_input_or_output(ur_yield_ty, mir_yield_ty, yield_span);
140 // Return types are a bit more complex. They may contain opaque `impl Trait` types.
141 let mir_output_ty = body.local_decls[RETURN_PLACE].ty;
142 let output_span = body.local_decls[RETURN_PLACE].source_info.span;
143 if let Err(terr) = self.eq_types(
144 normalized_output_ty,
146 Locations::All(output_span),
147 ConstraintCategory::BoringNoLocation,
152 "equate_inputs_and_outputs: `{:?}=={:?}` failed with `{:?}`",
153 normalized_output_ty,
159 // If the user explicitly annotated the output types, enforce those.
160 // Note that this only happens for closures.
161 if let Some(user_provided_sig) = user_provided_sig {
162 let user_provided_output_ty = user_provided_sig.output();
163 let user_provided_output_ty =
164 self.normalize(user_provided_output_ty, Locations::All(output_span));
165 if let Err(err) = self.eq_types(
166 user_provided_output_ty,
168 Locations::All(output_span),
169 ConstraintCategory::BoringNoLocation,
174 "equate_inputs_and_outputs: `{:?}=={:?}` failed with `{:?}`",
176 user_provided_output_ty,
183 #[instrument(skip(self), level = "debug")]
184 fn equate_normalized_input_or_output(&mut self, a: Ty<'tcx>, b: Ty<'tcx>, span: Span) {
186 self.eq_types(a, b, Locations::All(span), ConstraintCategory::BoringNoLocation)
188 // FIXME(jackh726): This is a hack. It's somewhat like
189 // `rustc_traits::normalize_after_erasing_regions`. Ideally, we'd
190 // like to normalize *before* inserting into `local_decls`, but
191 // doing so ends up causing some other trouble.
192 let b = self.normalize(b, Locations::All(span));
194 // Note: if we have to introduce new placeholders during normalization above, then we won't have
195 // added those universes to the universe info, which we would want in `relate_tys`.
197 self.eq_types(a, b, Locations::All(span), ConstraintCategory::BoringNoLocation)
202 "equate_normalized_input_or_output: `{:?}=={:?}` failed with `{:?}`",