1 //! Helper functions corresponding to lifetime errors due to
4 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
6 use rustc_hir::def_id::LocalDefId;
7 use rustc_middle::ty::{self, Binder, DefIdTree, Region, Ty, TypeFoldable};
10 /// Information about the anonymous region we are searching for.
12 pub(super) struct AnonymousParamInfo<'tcx> {
13 /// The parameter corresponding to the anonymous region.
14 pub param: &'tcx hir::Param<'tcx>,
15 /// The type corresponding to the anonymous region parameter.
16 pub param_ty: Ty<'tcx>,
17 /// The ty::BoundRegionKind corresponding to the anonymous region.
18 pub bound_region: ty::BoundRegionKind,
19 /// The `Span` of the parameter type.
20 pub param_ty_span: Span,
21 /// Signals that the argument is the first parameter in the declaration.
25 impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
26 // This method walks the Type of the function body parameters using
27 // `fold_regions()` function and returns the
28 // &hir::Param of the function parameter corresponding to the anonymous
29 // region and the Ty corresponding to the named region.
30 // Currently only the case where the function declaration consists of
31 // one named region and one anonymous region is handled.
32 // Consider the example `fn foo<'a>(x: &'a i32, y: &i32) -> &'a i32`
33 // Here, we would return the hir::Param for y, we return the type &'a
34 // i32, which is the type of y but with the anonymous region replaced
35 // with 'a, the corresponding bound region and is_first which is true if
36 // the hir::Param is the first parameter in the function declaration.
37 pub(super) fn find_param_with_region(
39 anon_region: Region<'tcx>,
40 replace_region: Region<'tcx>,
41 ) -> Option<AnonymousParamInfo<'_>> {
42 let (id, bound_region) = match *anon_region {
43 ty::ReFree(ref free_region) => (free_region.scope, free_region.bound_region),
44 ty::ReEarlyBound(ebr) => (
45 self.tcx().parent(ebr.def_id).unwrap(),
46 ty::BoundRegionKind::BrNamed(ebr.def_id, ebr.name),
48 _ => return None, // not a free region
51 let hir = &self.tcx().hir();
52 let hir_id = hir.local_def_id_to_hir_id(id.as_local()?);
53 let body_id = hir.maybe_body_owned_by(hir_id)?;
54 let body = hir.body(body_id);
55 let owner_id = hir.body_owner(body_id);
56 let fn_decl = hir.fn_decl_by_hir_id(owner_id).unwrap();
57 let poly_fn_sig = self.tcx().fn_sig(id);
58 let fn_sig = self.tcx().liberate_late_bound_regions(id, poly_fn_sig);
61 .take(if fn_sig.c_variadic {
64 assert_eq!(fn_sig.inputs().len(), body.params.len());
68 .find_map(|(index, param)| {
69 // May return None; sometimes the tables are not yet populated.
70 let ty = fn_sig.inputs()[index];
71 let mut found_anon_region = false;
72 let new_param_ty = self.tcx().fold_regions(ty, &mut false, |r, _| {
73 if *r == *anon_region {
74 found_anon_region = true;
80 if found_anon_region {
81 let ty_hir_id = fn_decl.inputs[index].hir_id;
82 let param_ty_span = hir.span(ty_hir_id);
83 let is_first = index == 0;
84 Some(AnonymousParamInfo {
86 param_ty: new_param_ty,
97 // Here, we check for the case where the anonymous region
98 // is in the return type as written by the user.
99 // FIXME(#42703) - Need to handle certain cases here.
100 pub(super) fn is_return_type_anon(
102 scope_def_id: LocalDefId,
103 br: ty::BoundRegionKind,
104 hir_sig: &hir::FnSig<'_>,
106 let fn_ty = self.tcx().type_of(scope_def_id);
107 if let ty::FnDef(_, _) = fn_ty.kind() {
108 let ret_ty = fn_ty.fn_sig(self.tcx()).output();
109 let span = hir_sig.decl.output.span();
110 let future_output = if hir_sig.header.is_async() {
111 ret_ty.map_bound(|ty| self.infcx.get_impl_future_output_ty(ty)).transpose()
115 return match future_output {
116 Some(output) if self.includes_region(output, br) => Some(span),
117 None if self.includes_region(ret_ty, br) => Some(span),
126 ty: Binder<'tcx, impl TypeFoldable<'tcx>>,
127 region: ty::BoundRegionKind,
129 let late_bound_regions = self.tcx().collect_referenced_late_bound_regions(&ty);
130 late_bound_regions.iter().any(|r| *r == region)
133 // Here we check for the case where anonymous region
134 // corresponds to self and if yes, we display E0312.
135 // FIXME(#42700) - Need to format self properly to
136 // enable E0621 for it.
137 pub(super) fn is_self_anon(&self, is_first: bool, scope_def_id: LocalDefId) -> bool {
141 .opt_associated_item(scope_def_id.to_def_id())
142 .map(|i| i.fn_has_self_parameter)