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 crate::type_check::constraint_conversion::ConstraintConversion;
11 use rustc_index::vec::Idx;
12 use rustc_infer::infer::LateBoundRegionConversionTime;
13 use rustc_middle::mir::*;
14 use rustc_middle::ty::Ty;
16 use rustc_span::DUMMY_SP;
17 use rustc_trait_selection::traits::query::type_op::{self, TypeOp};
18 use rustc_trait_selection::traits::query::Fallible;
19 use type_op::TypeOpOutput;
21 use crate::universal_regions::UniversalRegions;
23 use super::{Locations, TypeChecker};
25 impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
26 #[instrument(skip(self, body, universal_regions), level = "debug")]
27 pub(super) fn equate_inputs_and_outputs(
30 universal_regions: &UniversalRegions<'tcx>,
31 normalized_inputs_and_output: &[Ty<'tcx>],
33 let (&normalized_output_ty, normalized_input_tys) =
34 normalized_inputs_and_output.split_last().unwrap();
36 debug!(?normalized_output_ty);
37 debug!(?normalized_input_tys);
39 let mir_def_id = body.source.def_id().expect_local();
41 // If the user explicitly annotated the input types, extract
44 // e.g., `|x: FxHashMap<_, &'static u32>| ...`
45 let user_provided_sig;
46 if !self.tcx().is_closure(mir_def_id.to_def_id()) {
47 user_provided_sig = None;
49 let typeck_results = self.tcx().typeck(mir_def_id);
50 user_provided_sig = typeck_results.user_provided_sigs.get(&mir_def_id.to_def_id()).map(
51 |user_provided_poly_sig| {
52 // Instantiate the canonicalized variables from
53 // user-provided signature (e.g., the `_` in the code
54 // above) with fresh variables.
55 let poly_sig = self.instantiate_canonical_with_fresh_inference_vars(
57 &user_provided_poly_sig,
60 // Replace the bound items in the fn sig with fresh
61 // variables, so that they represent the view from
62 // "inside" the closure.
63 self.infcx.replace_bound_vars_with_fresh_vars(
65 LateBoundRegionConversionTime::FnCall,
72 debug!(?normalized_input_tys, ?body.local_decls);
74 // Equate expected input tys with those in the MIR.
75 for (argument_index, &normalized_input_ty) in normalized_input_tys.iter().enumerate() {
76 if argument_index + 1 >= body.local_decls.len() {
79 .delay_span_bug(body.span, "found more normalized_input_ty than local_decls");
83 // In MIR, argument N is stored in local N+1.
84 let local = Local::new(argument_index + 1);
86 let mir_input_ty = body.local_decls[local].ty;
88 let mir_input_span = body.local_decls[local].source_info.span;
89 self.equate_normalized_input_or_output(
96 if let Some(user_provided_sig) = user_provided_sig {
97 for (argument_index, &user_provided_input_ty) in
98 user_provided_sig.inputs().iter().enumerate()
100 // In MIR, closures begin an implicit `self`, so
101 // argument N is stored in local N+2.
102 let local = Local::new(argument_index + 2);
103 let mir_input_ty = body.local_decls[local].ty;
104 let mir_input_span = body.local_decls[local].source_info.span;
106 // If the user explicitly annotated the input types, enforce those.
107 let user_provided_input_ty =
108 self.normalize(user_provided_input_ty, Locations::All(mir_input_span));
110 self.equate_normalized_input_or_output(
111 user_provided_input_ty,
119 "equate_inputs_and_outputs: body.yield_ty {:?}, universal_regions.yield_ty {:?}",
121 universal_regions.yield_ty
124 // We will not have a universal_regions.yield_ty if we yield (by accident)
125 // outside of a generator and return an `impl Trait`, so emit a delay_span_bug
126 // because we don't want to panic in an assert here if we've already got errors.
127 if body.yield_ty().is_some() != universal_regions.yield_ty.is_some() {
128 self.tcx().sess.delay_span_bug(
131 "Expected body to have yield_ty ({:?}) iff we have a UR yield_ty ({:?})",
133 universal_regions.yield_ty,
138 if let (Some(mir_yield_ty), Some(ur_yield_ty)) =
139 (body.yield_ty(), universal_regions.yield_ty)
141 let yield_span = body.local_decls[RETURN_PLACE].source_info.span;
142 self.equate_normalized_input_or_output(ur_yield_ty, mir_yield_ty, yield_span);
145 // Return types are a bit more complex. They may contain opaque `impl Trait` types.
146 let mir_output_ty = body.local_decls[RETURN_PLACE].ty;
147 let output_span = body.local_decls[RETURN_PLACE].source_info.span;
148 if let Err(terr) = self.eq_types(
149 normalized_output_ty,
151 Locations::All(output_span),
152 ConstraintCategory::BoringNoLocation,
157 "equate_inputs_and_outputs: `{:?}=={:?}` failed with `{:?}`",
158 normalized_output_ty,
164 // If the user explicitly annotated the output types, enforce those.
165 // Note that this only happens for closures.
166 if let Some(user_provided_sig) = user_provided_sig {
167 let user_provided_output_ty = user_provided_sig.output();
168 let user_provided_output_ty =
169 self.normalize(user_provided_output_ty, Locations::All(output_span));
170 if let Err(err) = self.eq_types(
171 user_provided_output_ty,
173 Locations::All(output_span),
174 ConstraintCategory::BoringNoLocation,
179 "equate_inputs_and_outputs: `{:?}=={:?}` failed with `{:?}`",
181 user_provided_output_ty,
188 #[instrument(skip(self, span), level = "debug")]
189 fn equate_normalized_input_or_output(&mut self, a: Ty<'tcx>, b: Ty<'tcx>, span: Span) {
191 self.eq_types(a, b, Locations::All(span), ConstraintCategory::BoringNoLocation)
193 // FIXME(jackh726): This is a hack. It's somewhat like
194 // `rustc_traits::normalize_after_erasing_regions`. Ideally, we'd
195 // like to normalize *before* inserting into `local_decls`, but
196 // doing so ends up causing some other trouble.
197 let b = match self.normalize_and_add_constraints(b) {
200 debug!("equate_inputs_and_outputs: NoSolution");
205 // Note: if we have to introduce new placeholders during normalization above, then we won't have
206 // added those universes to the universe info, which we would want in `relate_tys`.
208 self.eq_types(a, b, Locations::All(span), ConstraintCategory::BoringNoLocation)
213 "equate_normalized_input_or_output: `{:?}=={:?}` failed with `{:?}`",
222 pub(crate) fn normalize_and_add_constraints(&mut self, t: Ty<'tcx>) -> Fallible<Ty<'tcx>> {
223 let TypeOpOutput { output: norm_ty, constraints, .. } =
224 self.param_env.and(type_op::normalize::Normalize::new(t)).fully_perform(self.infcx)?;
226 debug!("{:?} normalized to {:?}", t, norm_ty);
228 for data in constraints {
229 ConstraintConversion::new(
231 &self.borrowck_context.universal_regions,
232 &self.region_bound_pairs,
233 self.implicit_region_bound,
235 Locations::All(DUMMY_SP),
237 ConstraintCategory::Internal,
238 &mut self.borrowck_context.constraints,
240 .convert_all(&*data);