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

use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
use crate::traits::{self, ObligationCtxt};

use rustc_hir::def_id::DefId;
use rustc_hir::lang_items::LangItem;
use rustc_middle::arena::ArenaAllocatable;
use rustc_middle::infer::canonical::{Canonical, CanonicalizedQueryResponse, QueryResponse};
use rustc_middle::traits::query::Fallible;
use rustc_middle::ty::{self, Ty, TypeFoldable, TypeVisitable};
use rustc_middle::ty::{GenericArg, ToPredicate};
use rustc_span::{Span, DUMMY_SP};

use std::fmt::Debug;

pub use rustc_infer::infer::*;

pub trait InferCtxtExt<'tcx> {
    fn type_is_copy_modulo_regions(
        &self,
        param_env: ty::ParamEnv<'tcx>,
        ty: Ty<'tcx>,
        span: Span,
    ) -> bool;

    fn type_is_sized_modulo_regions(
        &self,
        param_env: ty::ParamEnv<'tcx>,
        ty: Ty<'tcx>,
        span: Span,
    ) -> bool;

    /// Check whether a `ty` implements given trait(trait_def_id).
    /// The inputs are:
    ///
    /// - the def-id of the trait
    /// - the type parameters of the trait, including the self-type
    /// - the parameter environment
    ///
    /// Invokes `evaluate_obligation`, so in the event that evaluating
    /// `Ty: Trait` causes overflow, EvaluatedToRecur (or EvaluatedToUnknown)
    /// will be returned.
    fn type_implements_trait(
        &self,
        trait_def_id: DefId,
        params: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
        param_env: ty::ParamEnv<'tcx>,
    ) -> traits::EvaluationResult;
}
impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
    fn type_is_copy_modulo_regions(
        &self,
        param_env: ty::ParamEnv<'tcx>,
        ty: Ty<'tcx>,
        span: Span,
    ) -> bool {
        let ty = self.resolve_vars_if_possible(ty);

        if !(param_env, ty).needs_infer() {
            return ty.is_copy_modulo_regions(self.tcx, param_env);
        }

        let copy_def_id = self.tcx.require_lang_item(LangItem::Copy, None);

        // This can get called from typeck (by euv), and `moves_by_default`
        // rightly refuses to work with inference variables, but
        // moves_by_default has a cache, which we want to use in other
        // cases.
        traits::type_known_to_meet_bound_modulo_regions(self, param_env, ty, copy_def_id, span)
    }

    fn type_is_sized_modulo_regions(
        &self,
        param_env: ty::ParamEnv<'tcx>,
        ty: Ty<'tcx>,
        span: Span,
    ) -> bool {
        let lang_item = self.tcx.require_lang_item(LangItem::Sized, None);
        traits::type_known_to_meet_bound_modulo_regions(self, param_env, ty, lang_item, span)
    }

    #[instrument(level = "debug", skip(self, params), ret)]
    fn type_implements_trait(
        &self,
        trait_def_id: DefId,
        params: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
        param_env: ty::ParamEnv<'tcx>,
    ) -> traits::EvaluationResult {
        let trait_ref = self.tcx.mk_trait_ref(trait_def_id, params);

        let obligation = traits::Obligation {
            cause: traits::ObligationCause::dummy(),
            param_env,
            recursion_depth: 0,
            predicate: ty::Binder::dummy(trait_ref).without_const().to_predicate(self.tcx),
        };
        self.evaluate_obligation(&obligation).unwrap_or(traits::EvaluationResult::EvaluatedToErr)
    }
}

pub trait InferCtxtBuilderExt<'tcx> {
    fn enter_canonical_trait_query<K, R>(
        &mut self,
        canonical_key: &Canonical<'tcx, K>,
        operation: impl FnOnce(&ObligationCtxt<'_, 'tcx>, K) -> Fallible<R>,
    ) -> Fallible<CanonicalizedQueryResponse<'tcx, R>>
    where
        K: TypeFoldable<'tcx>,
        R: Debug + TypeFoldable<'tcx>,
        Canonical<'tcx, QueryResponse<'tcx, R>>: ArenaAllocatable<'tcx>;
}

impl<'tcx> InferCtxtBuilderExt<'tcx> for InferCtxtBuilder<'tcx> {
    /// The "main method" for a canonicalized trait query. Given the
    /// canonical key `canonical_key`, this method will create a new
    /// inference context, instantiate the key, and run your operation
    /// `op`. The operation should yield up a result (of type `R`) as
    /// well as a set of trait obligations that must be fully
    /// satisfied. These obligations will be processed and the
    /// canonical result created.
    ///
    /// Returns `NoSolution` in the event of any error.
    ///
    /// (It might be mildly nicer to implement this on `TyCtxt`, and
    /// not `InferCtxtBuilder`, but that is a bit tricky right now.
    /// In part because we would need a `for<'tcx>` sort of
    /// bound for the closure and in part because it is convenient to
    /// have `'tcx` be free on this function so that we can talk about
    /// `K: TypeFoldable<'tcx>`.)
    fn enter_canonical_trait_query<K, R>(
        &mut self,
        canonical_key: &Canonical<'tcx, K>,
        operation: impl FnOnce(&ObligationCtxt<'_, 'tcx>, K) -> Fallible<R>,
    ) -> Fallible<CanonicalizedQueryResponse<'tcx, R>>
    where
        K: TypeFoldable<'tcx>,
        R: Debug + TypeFoldable<'tcx>,
        Canonical<'tcx, QueryResponse<'tcx, R>>: ArenaAllocatable<'tcx>,
    {
        let (infcx, key, canonical_inference_vars) =
            self.build_with_canonical(DUMMY_SP, canonical_key);
        let ocx = ObligationCtxt::new(&infcx);
        let value = operation(&ocx, key)?;
        ocx.make_canonicalized_query_response(canonical_inference_vars, value)
    }
}