rustdoc/clean/
blanket_impl.rs

1use rustc_hir as hir;
2use rustc_infer::infer::{DefineOpaqueTypes, InferOk, TyCtxtInferExt};
3use rustc_infer::traits;
4use rustc_middle::ty::{self, TypingMode, Upcast};
5use rustc_span::DUMMY_SP;
6use rustc_span::def_id::DefId;
7use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
8use thin_vec::ThinVec;
9use tracing::{debug, instrument, trace};
10
11use crate::clean;
12use crate::clean::{
13    clean_middle_assoc_item, clean_middle_ty, clean_trait_ref_with_constraints, clean_ty_generics,
14};
15use crate::core::DocContext;
16
17#[instrument(level = "debug", skip(cx))]
18pub(crate) fn synthesize_blanket_impls(
19    cx: &mut DocContext<'_>,
20    item_def_id: DefId,
21) -> Vec<clean::Item> {
22    let tcx = cx.tcx;
23    let ty = tcx.type_of(item_def_id);
24
25    let mut blanket_impls = Vec::new();
26    for trait_def_id in tcx.visible_traits() {
27        if !cx.cache.effective_visibilities.is_reachable(tcx, trait_def_id)
28            || cx.generated_synthetics.contains(&(ty.skip_binder(), trait_def_id))
29        {
30            continue;
31        }
32        // NOTE: doesn't use `for_each_relevant_impl` to avoid looking at anything besides blanket impls
33        let trait_impls = tcx.trait_impls_of(trait_def_id);
34        'blanket_impls: for &impl_def_id in trait_impls.blanket_impls() {
35            trace!("considering impl `{impl_def_id:?}` for trait `{trait_def_id:?}`");
36
37            let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
38            if !matches!(trait_ref.skip_binder().self_ty().kind(), ty::Param(_)) {
39                continue;
40            }
41            let infcx = tcx.infer_ctxt().build(TypingMode::non_body_analysis());
42            let args = infcx.fresh_args_for_item(DUMMY_SP, item_def_id);
43            let impl_ty = ty.instantiate(tcx, args);
44            let param_env = ty::ParamEnv::empty();
45
46            let impl_args = infcx.fresh_args_for_item(DUMMY_SP, impl_def_id);
47            let impl_trait_ref = trait_ref.instantiate(tcx, impl_args);
48
49            // Require the type the impl is implemented on to match
50            // our type, and ignore the impl if there was a mismatch.
51            let Ok(eq_result) = infcx.at(&traits::ObligationCause::dummy(), param_env).eq(
52                DefineOpaqueTypes::Yes,
53                impl_trait_ref.self_ty(),
54                impl_ty,
55            ) else {
56                continue;
57            };
58            let InferOk { value: (), obligations } = eq_result;
59            // FIXME(eddyb) ignoring `obligations` might cause false positives.
60            drop(obligations);
61
62            let predicates = tcx
63                .predicates_of(impl_def_id)
64                .instantiate(tcx, impl_args)
65                .predicates
66                .into_iter()
67                .chain(Some(impl_trait_ref.upcast(tcx)));
68            for predicate in predicates {
69                let obligation = traits::Obligation::new(
70                    tcx,
71                    traits::ObligationCause::dummy(),
72                    param_env,
73                    predicate,
74                );
75                match infcx.evaluate_obligation(&obligation) {
76                    Ok(eval_result) if eval_result.may_apply() => {}
77                    Err(traits::OverflowError::Canonical) => {}
78                    _ => continue 'blanket_impls,
79                }
80            }
81            debug!("found applicable impl for trait ref {trait_ref:?}");
82
83            cx.generated_synthetics.insert((ty.skip_binder(), trait_def_id));
84
85            blanket_impls.push(clean::Item {
86                inner: Box::new(clean::ItemInner {
87                    name: None,
88                    item_id: clean::ItemId::Blanket { impl_id: impl_def_id, for_: item_def_id },
89                    attrs: Default::default(),
90                    stability: None,
91                    kind: clean::ImplItem(Box::new(clean::Impl {
92                        safety: hir::Safety::Safe,
93                        generics: clean_ty_generics(cx, impl_def_id),
94                        // FIXME(eddyb) compute both `trait_` and `for_` from
95                        // the post-inference `trait_ref`, as it's more accurate.
96                        trait_: Some(clean_trait_ref_with_constraints(
97                            cx,
98                            ty::Binder::dummy(trait_ref.instantiate_identity()),
99                            ThinVec::new(),
100                        )),
101                        for_: clean_middle_ty(
102                            ty::Binder::dummy(ty.instantiate_identity()),
103                            cx,
104                            None,
105                            None,
106                        ),
107                        items: tcx
108                            .associated_items(impl_def_id)
109                            .in_definition_order()
110                            .filter(|item| !item.is_impl_trait_in_trait())
111                            .map(|item| clean_middle_assoc_item(item, cx))
112                            .collect(),
113                        polarity: ty::ImplPolarity::Positive,
114                        kind: clean::ImplKind::Blanket(Box::new(clean_middle_ty(
115                            ty::Binder::dummy(trait_ref.instantiate_identity().self_ty()),
116                            cx,
117                            None,
118                            None,
119                        ))),
120                    })),
121                    cfg: None,
122                    inline_stmt_id: None,
123                }),
124            });
125        }
126    }
127
128    blanket_impls
129}
rustdoc/clean/blanket_impl.rs

rustdoc/clean/
blanket_impl.rs
