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
);
46 typeck_results
.user_provided_sigs
.get(&mir_def_id
).map(|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
,
66 debug
!(?normalized_input_tys
, ?body
.local_decls
);
68 // Equate expected input tys with those in the MIR.
69 for (argument_index
, &normalized_input_ty
) in normalized_input_tys
.iter().enumerate() {
70 if argument_index
+ 1 >= body
.local_decls
.len() {
73 .delay_span_bug(body
.span
, "found more normalized_input_ty than local_decls");
77 // In MIR, argument N is stored in local N+1.
78 let local
= Local
::new(argument_index
+ 1);
80 let mir_input_ty
= body
.local_decls
[local
].ty
;
82 let mir_input_span
= body
.local_decls
[local
].source_info
.span
;
83 self.equate_normalized_input_or_output(
90 if let Some(user_provided_sig
) = user_provided_sig
{
91 for (argument_index
, &user_provided_input_ty
) in
92 user_provided_sig
.inputs().iter().enumerate()
94 // In MIR, closures begin an implicit `self`, so
95 // argument N is stored in local N+2.
96 let local
= Local
::new(argument_index
+ 2);
97 let mir_input_ty
= body
.local_decls
[local
].ty
;
98 let mir_input_span
= body
.local_decls
[local
].source_info
.span
;
100 // If the user explicitly annotated the input types, enforce those.
101 let user_provided_input_ty
=
102 self.normalize(user_provided_input_ty
, Locations
::All(mir_input_span
));
104 self.equate_normalized_input_or_output(
105 user_provided_input_ty
,
113 "equate_inputs_and_outputs: body.yield_ty {:?}, universal_regions.yield_ty {:?}",
115 universal_regions
.yield_ty
118 // We will not have a universal_regions.yield_ty if we yield (by accident)
119 // outside of a generator and return an `impl Trait`, so emit a delay_span_bug
120 // because we don't want to panic in an assert here if we've already got errors.
121 if body
.yield_ty().is_some() != universal_regions
.yield_ty
.is_some() {
122 self.tcx().sess
.delay_span_bug(
125 "Expected body to have yield_ty ({:?}) iff we have a UR yield_ty ({:?})",
127 universal_regions
.yield_ty
,
132 if let (Some(mir_yield_ty
), Some(ur_yield_ty
)) =
133 (body
.yield_ty(), universal_regions
.yield_ty
)
135 let yield_span
= body
.local_decls
[RETURN_PLACE
].source_info
.span
;
136 self.equate_normalized_input_or_output(ur_yield_ty
, mir_yield_ty
, yield_span
);
139 // Return types are a bit more complex. They may contain opaque `impl Trait` types.
140 let mir_output_ty
= body
.local_decls
[RETURN_PLACE
].ty
;
141 let output_span
= body
.local_decls
[RETURN_PLACE
].source_info
.span
;
142 if let Err(terr
) = self.eq_types(
143 normalized_output_ty
,
145 Locations
::All(output_span
),
146 ConstraintCategory
::BoringNoLocation
,
151 "equate_inputs_and_outputs: `{:?}=={:?}` failed with `{:?}`",
152 normalized_output_ty
,
158 // If the user explicitly annotated the output types, enforce those.
159 // Note that this only happens for closures.
160 if let Some(user_provided_sig
) = user_provided_sig
{
161 let user_provided_output_ty
= user_provided_sig
.output();
162 let user_provided_output_ty
=
163 self.normalize(user_provided_output_ty
, Locations
::All(output_span
));
164 if let Err(err
) = self.eq_types(
165 user_provided_output_ty
,
167 Locations
::All(output_span
),
168 ConstraintCategory
::BoringNoLocation
,
173 "equate_inputs_and_outputs: `{:?}=={:?}` failed with `{:?}`",
175 user_provided_output_ty
,
182 #[instrument(skip(self), level = "debug")]
183 fn equate_normalized_input_or_output(&mut self, a
: Ty
<'tcx
>, b
: Ty
<'tcx
>, span
: Span
) {
185 self.eq_types(a
, b
, Locations
::All(span
), ConstraintCategory
::BoringNoLocation
)
187 // FIXME(jackh726): This is a hack. It's somewhat like
188 // `rustc_traits::normalize_after_erasing_regions`. Ideally, we'd
189 // like to normalize *before* inserting into `local_decls`, but
190 // doing so ends up causing some other trouble.
191 let b
= self.normalize(b
, Locations
::All(span
));
193 // Note: if we have to introduce new placeholders during normalization above, then we won't have
194 // added those universes to the universe info, which we would want in `relate_tys`.
196 self.eq_types(a
, b
, Locations
::All(span
), ConstraintCategory
::BoringNoLocation
)
201 "equate_normalized_input_or_output: `{:?}=={:?}` failed with `{:?}`",