diff options
Diffstat (limited to 'compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs')
| -rw-r--r-- | compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs | 234 |
1 files changed, 234 insertions, 0 deletions
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs new file mode 100644 index 000000000..9a2ab3e32 --- /dev/null +++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs @@ -0,0 +1,234 @@ +//! Error Reporting for Anonymous Region Lifetime Errors +//! where both the regions are anonymous. + +use crate::infer::error_reporting::nice_region_error::find_anon_type::find_anon_type; +use crate::infer::error_reporting::nice_region_error::util::AnonymousParamInfo; +use crate::infer::error_reporting::nice_region_error::NiceRegionError; +use crate::infer::lexical_region_resolve::RegionResolutionError; +use crate::infer::SubregionOrigin; +use crate::infer::TyCtxt; + +use rustc_errors::{struct_span_err, Applicability, Diagnostic, ErrorGuaranteed}; +use rustc_hir as hir; +use rustc_hir::{GenericParamKind, Ty}; +use rustc_middle::ty::Region; +use rustc_span::symbol::kw; + +impl<'a, 'tcx> NiceRegionError<'a, 'tcx> { + /// Print the error message for lifetime errors when both the concerned regions are anonymous. + /// + /// Consider a case where we have + /// + /// ```compile_fail,E0623 + /// fn foo(x: &mut Vec<&u8>, y: &u8) { + /// x.push(y); + /// } + /// ``` + /// + /// The example gives + /// + /// ```text + /// fn foo(x: &mut Vec<&u8>, y: &u8) { + /// --- --- these references are declared with different lifetimes... + /// x.push(y); + /// ^ ...but data from `y` flows into `x` here + /// ``` + /// + /// It has been extended for the case of structs too. + /// + /// Consider the example + /// + /// ```no_run + /// struct Ref<'a> { x: &'a u32 } + /// ``` + /// + /// ```text + /// fn foo(mut x: Vec<Ref>, y: Ref) { + /// --- --- these structs are declared with different lifetimes... + /// x.push(y); + /// ^ ...but data from `y` flows into `x` here + /// } + /// ``` + /// + /// It will later be extended to trait objects. + pub(super) fn try_report_anon_anon_conflict(&self) -> Option<ErrorGuaranteed> { + let (span, sub, sup) = self.regions()?; + + if let Some(RegionResolutionError::ConcreteFailure( + SubregionOrigin::ReferenceOutlivesReferent(..), + .., + )) = self.error + { + // This error doesn't make much sense in this case. + return None; + } + + // Determine whether the sub and sup consist of both anonymous (elided) regions. + let anon_reg_sup = self.tcx().is_suitable_region(sup)?; + + let anon_reg_sub = self.tcx().is_suitable_region(sub)?; + let scope_def_id_sup = anon_reg_sup.def_id; + let bregion_sup = anon_reg_sup.boundregion; + let scope_def_id_sub = anon_reg_sub.def_id; + let bregion_sub = anon_reg_sub.boundregion; + + let ty_sup = find_anon_type(self.tcx(), sup, &bregion_sup)?; + + let ty_sub = find_anon_type(self.tcx(), sub, &bregion_sub)?; + + debug!( + "try_report_anon_anon_conflict: found_param1={:?} sup={:?} br1={:?}", + ty_sub, sup, bregion_sup + ); + debug!( + "try_report_anon_anon_conflict: found_param2={:?} sub={:?} br2={:?}", + ty_sup, sub, bregion_sub + ); + + let (ty_sup, ty_fndecl_sup) = ty_sup; + let (ty_sub, ty_fndecl_sub) = ty_sub; + + let AnonymousParamInfo { param: anon_param_sup, .. } = + self.find_param_with_region(sup, sup)?; + let AnonymousParamInfo { param: anon_param_sub, .. } = + self.find_param_with_region(sub, sub)?; + + let sup_is_ret_type = + self.is_return_type_anon(scope_def_id_sup, bregion_sup, ty_fndecl_sup); + let sub_is_ret_type = + self.is_return_type_anon(scope_def_id_sub, bregion_sub, ty_fndecl_sub); + + let span_label_var1 = match anon_param_sup.pat.simple_ident() { + Some(simple_ident) => format!(" from `{}`", simple_ident), + None => String::new(), + }; + + let span_label_var2 = match anon_param_sub.pat.simple_ident() { + Some(simple_ident) => format!(" into `{}`", simple_ident), + None => String::new(), + }; + + debug!( + "try_report_anon_anon_conflict: sub_is_ret_type={:?} sup_is_ret_type={:?}", + sub_is_ret_type, sup_is_ret_type + ); + + let mut err = struct_span_err!(self.tcx().sess, span, E0623, "lifetime mismatch"); + + match (sup_is_ret_type, sub_is_ret_type) { + (ret_capture @ Some(ret_span), _) | (_, ret_capture @ Some(ret_span)) => { + let param_span = + if sup_is_ret_type == ret_capture { ty_sub.span } else { ty_sup.span }; + + err.span_label( + param_span, + "this parameter and the return type are declared with different lifetimes...", + ); + err.span_label(ret_span, ""); + err.span_label(span, format!("...but data{} is returned here", span_label_var1)); + } + + (None, None) => { + if ty_sup.hir_id == ty_sub.hir_id { + err.span_label(ty_sup.span, "this type is declared with multiple lifetimes..."); + err.span_label(ty_sub.span, ""); + err.span_label(span, "...but data with one lifetime flows into the other here"); + } else { + err.span_label( + ty_sup.span, + "these two types are declared with different lifetimes...", + ); + err.span_label(ty_sub.span, ""); + err.span_label( + span, + format!("...but data{} flows{} here", span_label_var1, span_label_var2), + ); + } + } + } + + if suggest_adding_lifetime_params(self.tcx(), sub, ty_sup, ty_sub, &mut err) { + err.note("each elided lifetime in input position becomes a distinct lifetime"); + } + + let reported = err.emit(); + Some(reported) + } +} + +pub fn suggest_adding_lifetime_params<'tcx>( + tcx: TyCtxt<'tcx>, + sub: Region<'tcx>, + ty_sup: &Ty<'_>, + ty_sub: &Ty<'_>, + err: &mut Diagnostic, +) -> bool { + let ( + hir::Ty { kind: hir::TyKind::Rptr(lifetime_sub, _), .. }, + hir::Ty { kind: hir::TyKind::Rptr(lifetime_sup, _), .. }, + ) = (ty_sub, ty_sup) else { + return false; + }; + + if !lifetime_sub.name.is_anonymous() || !lifetime_sup.name.is_anonymous() { + return false; + }; + + let Some(anon_reg) = tcx.is_suitable_region(sub) else { + return false; + }; + + let hir_id = tcx.hir().local_def_id_to_hir_id(anon_reg.def_id); + + let node = tcx.hir().get(hir_id); + let is_impl = matches!(&node, hir::Node::ImplItem(_)); + let generics = match node { + hir::Node::Item(&hir::Item { kind: hir::ItemKind::Fn(_, ref generics, ..), .. }) + | hir::Node::TraitItem(&hir::TraitItem { ref generics, .. }) + | hir::Node::ImplItem(&hir::ImplItem { ref generics, .. }) => generics, + _ => return false, + }; + + let suggestion_param_name = generics + .params + .iter() + .filter(|p| matches!(p.kind, GenericParamKind::Lifetime { .. })) + .map(|p| p.name.ident().name) + .find(|i| *i != kw::UnderscoreLifetime); + let introduce_new = suggestion_param_name.is_none(); + let suggestion_param_name = + suggestion_param_name.map(|n| n.to_string()).unwrap_or_else(|| "'a".to_owned()); + + debug!(?lifetime_sup.span); + debug!(?lifetime_sub.span); + let make_suggestion = |span: rustc_span::Span| { + if span.is_empty() { + (span, format!("{}, ", suggestion_param_name)) + } else if let Ok("&") = tcx.sess.source_map().span_to_snippet(span).as_deref() { + (span.shrink_to_hi(), format!("{} ", suggestion_param_name)) + } else { + (span, suggestion_param_name.clone()) + } + }; + let mut suggestions = + vec![make_suggestion(lifetime_sub.span), make_suggestion(lifetime_sup.span)]; + + if introduce_new { + let new_param_suggestion = + if let Some(first) = generics.params.iter().find(|p| !p.name.ident().span.is_empty()) { + (first.span.shrink_to_lo(), format!("{}, ", suggestion_param_name)) + } else { + (generics.span, format!("<{}>", suggestion_param_name)) + }; + + suggestions.push(new_param_suggestion); + } + + let mut sugg = String::from("consider introducing a named lifetime parameter"); + if is_impl { + sugg.push_str(" and update trait if needed"); + } + err.multipart_suggestion(sugg, suggestions, Applicability::MaybeIncorrect); + + true +} |