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
158
159
160
161
162
163
164
165
166
use super::callee::DeferredCallResolution;

use rustc_data_structures::unord::{UnordMap, UnordSet};
use rustc_hir as hir;
use rustc_hir::def_id::LocalDefId;
use rustc_hir::HirIdMap;
use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt};
use rustc_middle::traits::DefiningAnchor;
use rustc_middle::ty::visit::TypeVisitableExt;
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_span::def_id::LocalDefIdMap;
use rustc_span::{self, Span};
use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
use rustc_trait_selection::traits::{self, PredicateObligation, TraitEngine, TraitEngineExt as _};

use std::cell::RefCell;
use std::ops::Deref;

/// Closures defined within the function. For example:
/// ```ignore (illustrative)
/// fn foo() {
///     bar(move|| { ... })
/// }
/// ```
/// Here, the function `foo()` and the closure passed to
/// `bar()` will each have their own `FnCtxt`, but they will
/// share the inherited fields.
pub struct Inherited<'tcx> {
    pub(super) infcx: InferCtxt<'tcx>,

    pub(super) typeck_results: RefCell<ty::TypeckResults<'tcx>>,

    pub(super) locals: RefCell<HirIdMap<Ty<'tcx>>>,

    pub(super) fulfillment_cx: RefCell<Box<dyn TraitEngine<'tcx>>>,

    /// Some additional `Sized` obligations badly affect type inference.
    /// These obligations are added in a later stage of typeck.
    /// Removing these may also cause additional complications, see #101066.
    pub(super) deferred_sized_obligations:
        RefCell<Vec<(Ty<'tcx>, Span, traits::ObligationCauseCode<'tcx>)>>,

    /// When we process a call like `c()` where `c` is a closure type,
    /// we may not have decided yet whether `c` is a `Fn`, `FnMut`, or
    /// `FnOnce` closure. In that case, we defer full resolution of the
    /// call until upvar inference can kick in and make the
    /// decision. We keep these deferred resolutions grouped by the
    /// def-id of the closure, so that once we decide, we can easily go
    /// back and process them.
    pub(super) deferred_call_resolutions: RefCell<LocalDefIdMap<Vec<DeferredCallResolution<'tcx>>>>,

    pub(super) deferred_cast_checks: RefCell<Vec<super::cast::CastCheck<'tcx>>>,

    pub(super) deferred_transmute_checks: RefCell<Vec<(Ty<'tcx>, Ty<'tcx>, hir::HirId)>>,

    pub(super) deferred_asm_checks: RefCell<Vec<(&'tcx hir::InlineAsm<'tcx>, hir::HirId)>>,

    pub(super) deferred_generator_interiors:
        RefCell<Vec<(LocalDefId, hir::BodyId, Ty<'tcx>, hir::GeneratorKind)>>,

    /// Whenever we introduce an adjustment from `!` into a type variable,
    /// we record that type variable here. This is later used to inform
    /// fallback. See the `fallback` module for details.
    pub(super) diverging_type_vars: RefCell<UnordSet<Ty<'tcx>>>,

    pub(super) infer_var_info: RefCell<UnordMap<ty::TyVid, ty::InferVarInfo>>,
}

impl<'tcx> Deref for Inherited<'tcx> {
    type Target = InferCtxt<'tcx>;
    fn deref(&self) -> &Self::Target {
        &self.infcx
    }
}

impl<'tcx> Inherited<'tcx> {
    pub fn new(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Self {
        let hir_owner = tcx.hir().local_def_id_to_hir_id(def_id).owner;

        let infcx = tcx
            .infer_ctxt()
            .ignoring_regions()
            .with_opaque_type_inference(DefiningAnchor::Bind(def_id))
            .build();
        let typeck_results = RefCell::new(ty::TypeckResults::new(hir_owner));

        Inherited {
            typeck_results,
            fulfillment_cx: RefCell::new(<dyn TraitEngine<'_>>::new(&infcx)),
            infcx,
            locals: RefCell::new(Default::default()),
            deferred_sized_obligations: RefCell::new(Vec::new()),
            deferred_call_resolutions: RefCell::new(Default::default()),
            deferred_cast_checks: RefCell::new(Vec::new()),
            deferred_transmute_checks: RefCell::new(Vec::new()),
            deferred_asm_checks: RefCell::new(Vec::new()),
            deferred_generator_interiors: RefCell::new(Vec::new()),
            diverging_type_vars: RefCell::new(Default::default()),
            infer_var_info: RefCell::new(Default::default()),
        }
    }

    #[instrument(level = "debug", skip(self))]
    pub(super) fn register_predicate(&self, obligation: traits::PredicateObligation<'tcx>) {
        if obligation.has_escaping_bound_vars() {
            span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}", obligation);
        }

        self.update_infer_var_info(&obligation);

        self.fulfillment_cx.borrow_mut().register_predicate_obligation(self, obligation);
    }

    pub(super) fn register_predicates<I>(&self, obligations: I)
    where
        I: IntoIterator<Item = traits::PredicateObligation<'tcx>>,
    {
        for obligation in obligations {
            self.register_predicate(obligation);
        }
    }

    pub(super) fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
        self.register_predicates(infer_ok.obligations);
        infer_ok.value
    }

    pub fn update_infer_var_info(&self, obligation: &PredicateObligation<'tcx>) {
        let infer_var_info = &mut self.infer_var_info.borrow_mut();

        // (*) binder skipped
        if let ty::PredicateKind::Clause(ty::ClauseKind::Trait(tpred)) = obligation.predicate.kind().skip_binder()
            && let Some(ty) = self.shallow_resolve(tpred.self_ty()).ty_vid().map(|t| self.root_var(t))
            && self.tcx.lang_items().sized_trait().is_some_and(|st| st != tpred.trait_ref.def_id)
        {
            let new_self_ty = self.tcx.types.unit;

            // Then construct a new obligation with Self = () added
            // to the ParamEnv, and see if it holds.
            let o = obligation.with(self.tcx,
                obligation
                    .predicate
                    .kind()
                    .rebind(
                        // (*) binder moved here
                        ty::PredicateKind::Clause(ty::ClauseKind::Trait(tpred.with_self_ty(self.tcx, new_self_ty)))
                    ),
            );
            // Don't report overflow errors. Otherwise equivalent to may_hold.
            if let Ok(result) = self.probe(|_| self.evaluate_obligation(&o)) && result.may_apply() {
                infer_var_info.entry(ty).or_default().self_in_trait = true;
            }
        }

        if let ty::PredicateKind::Clause(ty::ClauseKind::Projection(predicate)) =
            obligation.predicate.kind().skip_binder()
        {
            // If the projection predicate (Foo::Bar == X) has X as a non-TyVid,
            // we need to make it into one.
            if let Some(vid) = predicate.term.ty().and_then(|ty| ty.ty_vid()) {
                debug!("infer_var_info: {:?}.output = true", vid);
                infer_var_info.entry(vid).or_default().output = true;
            }
        }
    }
}