1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157

//! This module contains code to equate the input/output types appearing
//! in the MIR with the expected input/output types from the function
//! signature. This requires a bit of processing, as the expected types
//! are supplied to us before normalization and may contain opaque
//! `impl Trait` instances. In contrast, the input/output types found in
//! the MIR (specifically, in the special local variables for the
//! `RETURN_PLACE` the MIR arguments) are always fully normalized (and
//! contain revealed `impl Trait` values).

use rustc_infer::infer::BoundRegionConversionTime;
use rustc_middle::mir::*;
use rustc_middle::ty::{self, Ty};
use rustc_span::Span;

use crate::universal_regions::UniversalRegions;

use super::{Locations, TypeChecker};

impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
    /// Check explicit closure signature annotation,
    /// e.g., `|x: FxIndexMap<_, &'static u32>| ...`.
    #[instrument(skip(self, body), level = "debug")]
    pub(super) fn check_signature_annotation(&mut self, body: &Body<'tcx>) {
        let mir_def_id = body.source.def_id().expect_local();
        if !self.tcx().is_closure(mir_def_id.to_def_id()) {
            return;
        }
        let user_provided_poly_sig = self.tcx().closure_user_provided_sig(mir_def_id);

        // Instantiate the canonicalized variables from user-provided signature
        // (e.g., the `_` in the code above) with fresh variables.
        // Then replace the bound items in the fn sig with fresh variables,
        // so that they represent the view from "inside" the closure.
        let user_provided_sig = self
            .instantiate_canonical_with_fresh_inference_vars(body.span, &user_provided_poly_sig);
        let user_provided_sig = self.infcx.instantiate_binder_with_fresh_vars(
            body.span,
            BoundRegionConversionTime::FnCall,
            user_provided_sig,
        );

        for (&user_ty, arg_decl) in user_provided_sig.inputs().iter().zip(
            // In MIR, closure args begin with an implicit `self`. Skip it!
            body.args_iter().skip(1).map(|local| &body.local_decls[local]),
        ) {
            self.ascribe_user_type_skip_wf(
                arg_decl.ty,
                ty::UserType::Ty(user_ty),
                arg_decl.source_info.span,
            );
        }

        // If the user explicitly annotated the output type, enforce it.
        let output_decl = &body.local_decls[RETURN_PLACE];
        self.ascribe_user_type_skip_wf(
            output_decl.ty,
            ty::UserType::Ty(user_provided_sig.output()),
            output_decl.source_info.span,
        );
    }

    #[instrument(skip(self, body, universal_regions), level = "debug")]
    pub(super) fn equate_inputs_and_outputs(
        &mut self,
        body: &Body<'tcx>,
        universal_regions: &UniversalRegions<'tcx>,
        normalized_inputs_and_output: &[Ty<'tcx>],
    ) {
        let (&normalized_output_ty, normalized_input_tys) =
            normalized_inputs_and_output.split_last().unwrap();

        debug!(?normalized_output_ty);
        debug!(?normalized_input_tys);

        // Equate expected input tys with those in the MIR.
        for (argument_index, &normalized_input_ty) in normalized_input_tys.iter().enumerate() {
            if argument_index + 1 >= body.local_decls.len() {
                self.tcx()
                    .sess
                    .span_delayed_bug(body.span, "found more normalized_input_ty than local_decls");
                break;
            }

            // In MIR, argument N is stored in local N+1.
            let local = Local::from_usize(argument_index + 1);

            let mir_input_ty = body.local_decls[local].ty;

            let mir_input_span = body.local_decls[local].source_info.span;
            self.equate_normalized_input_or_output(
                normalized_input_ty,
                mir_input_ty,
                mir_input_span,
            );
        }

        debug!(
            "equate_inputs_and_outputs: body.yield_ty {:?}, universal_regions.yield_ty {:?}",
            body.yield_ty(),
            universal_regions.yield_ty
        );

        // We will not have a universal_regions.yield_ty if we yield (by accident)
        // outside of a coroutine and return an `impl Trait`, so emit a span_delayed_bug
        // because we don't want to panic in an assert here if we've already got errors.
        if body.yield_ty().is_some() != universal_regions.yield_ty.is_some() {
            self.tcx().sess.span_delayed_bug(
                body.span,
                format!(
                    "Expected body to have yield_ty ({:?}) iff we have a UR yield_ty ({:?})",
                    body.yield_ty(),
                    universal_regions.yield_ty,
                ),
            );
        }

        if let (Some(mir_yield_ty), Some(ur_yield_ty)) =
            (body.yield_ty(), universal_regions.yield_ty)
        {
            let yield_span = body.local_decls[RETURN_PLACE].source_info.span;
            self.equate_normalized_input_or_output(ur_yield_ty, mir_yield_ty, yield_span);
        }

        // Return types are a bit more complex. They may contain opaque `impl Trait` types.
        let mir_output_ty = body.local_decls[RETURN_PLACE].ty;
        let output_span = body.local_decls[RETURN_PLACE].source_info.span;
        self.equate_normalized_input_or_output(normalized_output_ty, mir_output_ty, output_span);
    }

    #[instrument(skip(self), level = "debug")]
    fn equate_normalized_input_or_output(&mut self, a: Ty<'tcx>, b: Ty<'tcx>, span: Span) {
        if let Err(_) =
            self.eq_types(a, b, Locations::All(span), ConstraintCategory::BoringNoLocation)
        {
            // FIXME(jackh726): This is a hack. It's somewhat like
            // `rustc_traits::normalize_after_erasing_regions`. Ideally, we'd
            // like to normalize *before* inserting into `local_decls`, but
            // doing so ends up causing some other trouble.
            let b = self.normalize(b, Locations::All(span));

            // Note: if we have to introduce new placeholders during normalization above, then we won't have
            // added those universes to the universe info, which we would want in `relate_tys`.
            if let Err(terr) =
                self.eq_types(a, b, Locations::All(span), ConstraintCategory::BoringNoLocation)
            {
                span_mirbug!(
                    self,
                    Location::START,
                    "equate_normalized_input_or_output: `{:?}=={:?}` failed with `{:?}`",
                    a,
                    b,
                    terr
                );
            }
        }
    }
}