Rollup merge of #96385 - marmeladema:nll-fix-trait-lifetime-bound-suggestions, r=jackh726
Recover most `impl Trait` and `dyn Trait` lifetime bound suggestions under NLL This is done by replacing the duplicated (and very partial) implementation from borrowck with one inspsired from `NiceRegionError::try_report_static_impl_trait` and by re-using `suggest_new_region_bound`. Fixes #96277 r? ```@jackh726```
This commit is contained in:
Dylan DPC
GitHub
commit
dc1f98c655
@ -1,17 +1,17 @@
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//! Error reporting machinery for lifetime errors.
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use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
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use rustc_errors::{Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
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use rustc_infer::infer::{
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error_reporting::nice_region_error::NiceRegionError,
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error_reporting::unexpected_hidden_region_diagnostic, NllRegionVariableOrigin,
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RelateParamBound,
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error_reporting::nice_region_error::{self, find_param_with_region, NiceRegionError},
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error_reporting::unexpected_hidden_region_diagnostic,
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NllRegionVariableOrigin, RelateParamBound,
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};
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use rustc_middle::hir::place::PlaceBase;
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use rustc_middle::mir::{ConstraintCategory, ReturnConstraint};
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use rustc_middle::ty::subst::{InternalSubsts, Subst};
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use rustc_middle::ty::subst::InternalSubsts;
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use rustc_middle::ty::{self, RegionVid, Ty};
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use rustc_span::symbol::{kw, sym};
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use rustc_span::{BytePos, Span};
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use rustc_span::symbol::sym;
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use rustc_span::Span;
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use crate::borrowck_errors;
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@ -651,82 +651,47 @@ fn add_static_impl_trait_suggestion(
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fr_name: RegionName,
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outlived_fr: RegionVid,
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) {
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if let (Some(f), Some(ty::ReStatic)) =
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(self.to_error_region(fr), self.to_error_region(outlived_fr).as_deref())
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if let (Some(f), Some(outlived_f)) =
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(self.to_error_region(fr), self.to_error_region(outlived_fr))
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{
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if let Some(&ty::Opaque(did, substs)) = self
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if *outlived_f != ty::ReStatic {
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return;
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}
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let fn_returns = self
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.infcx
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.tcx
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.is_suitable_region(f)
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.map(|r| r.def_id)
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.and_then(|id| self.infcx.tcx.return_type_impl_trait(id))
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.map(|(ty, _)| ty.kind())
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{
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// Check whether or not the impl trait return type is intended to capture
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// data with the static lifetime.
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//
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// eg. check for `impl Trait + 'static` instead of `impl Trait`.
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let has_static_predicate = {
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let bounds = self.infcx.tcx.explicit_item_bounds(did);
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.map(|r| self.infcx.tcx.return_type_impl_or_dyn_traits(r.def_id))
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.unwrap_or_default();
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let mut found = false;
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for (bound, _) in bounds {
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if let ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(_, r)) =
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bound.kind().skip_binder()
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{
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let r = r.subst(self.infcx.tcx, substs);
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if r.is_static() {
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found = true;
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break;
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} else {
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// If there's already a lifetime bound, don't
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// suggest anything.
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if fn_returns.is_empty() {
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return;
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}
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}
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}
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found
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let param = if let Some(param) = find_param_with_region(self.infcx.tcx, f, outlived_f) {
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param
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} else {
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return;
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};
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debug!(
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"add_static_impl_trait_suggestion: has_static_predicate={:?}",
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has_static_predicate
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);
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let static_str = kw::StaticLifetime;
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// If there is a static predicate, then the only sensible suggestion is to replace
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// fr with `'static`.
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if has_static_predicate {
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diag.help(&format!("consider replacing `{fr_name}` with `{static_str}`"));
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} else {
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// Otherwise, we should suggest adding a constraint on the return type.
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let span = self.infcx.tcx.def_span(did);
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if let Ok(snippet) = self.infcx.tcx.sess.source_map().span_to_snippet(span) {
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let suggestable_fr_name = if fr_name.was_named() {
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fr_name.to_string()
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} else {
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"'_".to_string()
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let lifetime = if f.has_name() { fr_name.to_string() } else { "'_".to_string() };
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let arg = match param.param.pat.simple_ident() {
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Some(simple_ident) => format!("argument `{}`", simple_ident),
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None => "the argument".to_string(),
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};
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let span = if snippet.ends_with(';') {
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// `type X = impl Trait;`
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span.with_hi(span.hi() - BytePos(1))
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} else {
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span
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};
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let suggestion = format!(" + {suggestable_fr_name}");
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let span = span.shrink_to_hi();
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diag.span_suggestion(
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span,
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&format!(
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"to allow this `impl Trait` to capture borrowed data with lifetime \
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`{fr_name}`, add `{suggestable_fr_name}` as a bound",
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),
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suggestion,
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Applicability::MachineApplicable,
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let captures = format!("captures data from {}", arg);
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return nice_region_error::suggest_new_region_bound(
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self.infcx.tcx,
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diag,
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fn_returns,
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lifetime,
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Some(arg),
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captures,
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Some((param.param_ty_span, param.param_ty.to_string())),
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);
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}
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}
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}
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}
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}
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}
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@ -15,6 +15,7 @@
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mod util;
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pub use static_impl_trait::suggest_new_region_bound;
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pub use util::find_param_with_region;
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impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
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pub fn try_report_nice_region_error(&self, error: &RegionResolutionError<'tcx>) -> bool {
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@ -2,6 +2,7 @@
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//! anonymous regions.
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use crate::infer::error_reporting::nice_region_error::NiceRegionError;
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use crate::infer::TyCtxt;
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use rustc_hir as hir;
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use rustc_hir::def_id::LocalDefId;
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use rustc_middle::ty::{self, Binder, DefIdTree, Region, Ty, TypeFoldable};
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@ -9,7 +10,7 @@
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/// Information about the anonymous region we are searching for.
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#[derive(Debug)]
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pub(super) struct AnonymousParamInfo<'tcx> {
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pub struct AnonymousParamInfo<'tcx> {
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/// The parameter corresponding to the anonymous region.
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pub param: &'tcx hir::Param<'tcx>,
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/// The type corresponding to the anonymous region parameter.
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@ -22,40 +23,38 @@ pub(super) struct AnonymousParamInfo<'tcx> {
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pub is_first: bool,
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}
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impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
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// This method walks the Type of the function body parameters using
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// `fold_regions()` function and returns the
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// &hir::Param of the function parameter corresponding to the anonymous
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// region and the Ty corresponding to the named region.
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// Currently only the case where the function declaration consists of
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// one named region and one anonymous region is handled.
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// Consider the example `fn foo<'a>(x: &'a i32, y: &i32) -> &'a i32`
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// Here, we would return the hir::Param for y, we return the type &'a
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// i32, which is the type of y but with the anonymous region replaced
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// with 'a, the corresponding bound region and is_first which is true if
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// the hir::Param is the first parameter in the function declaration.
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pub(super) fn find_param_with_region(
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&self,
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// This method walks the Type of the function body parameters using
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// `fold_regions()` function and returns the
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// &hir::Param of the function parameter corresponding to the anonymous
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// region and the Ty corresponding to the named region.
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// Currently only the case where the function declaration consists of
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// one named region and one anonymous region is handled.
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// Consider the example `fn foo<'a>(x: &'a i32, y: &i32) -> &'a i32`
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// Here, we would return the hir::Param for y, we return the type &'a
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// i32, which is the type of y but with the anonymous region replaced
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// with 'a, the corresponding bound region and is_first which is true if
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// the hir::Param is the first parameter in the function declaration.
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pub fn find_param_with_region<'tcx>(
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tcx: TyCtxt<'tcx>,
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anon_region: Region<'tcx>,
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replace_region: Region<'tcx>,
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) -> Option<AnonymousParamInfo<'_>> {
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) -> Option<AnonymousParamInfo<'tcx>> {
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let (id, bound_region) = match *anon_region {
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ty::ReFree(ref free_region) => (free_region.scope, free_region.bound_region),
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ty::ReEarlyBound(ebr) => (
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self.tcx().parent(ebr.def_id).unwrap(),
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ty::BoundRegionKind::BrNamed(ebr.def_id, ebr.name),
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),
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ty::ReEarlyBound(ebr) => {
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(tcx.parent(ebr.def_id).unwrap(), ty::BoundRegionKind::BrNamed(ebr.def_id, ebr.name))
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}
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_ => return None, // not a free region
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};
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let hir = &self.tcx().hir();
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let hir = &tcx.hir();
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let hir_id = hir.local_def_id_to_hir_id(id.as_local()?);
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let body_id = hir.maybe_body_owned_by(hir_id)?;
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let body = hir.body(body_id);
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let owner_id = hir.body_owner(body_id);
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let fn_decl = hir.fn_decl_by_hir_id(owner_id).unwrap();
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let poly_fn_sig = self.tcx().fn_sig(id);
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let fn_sig = self.tcx().liberate_late_bound_regions(id, poly_fn_sig);
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let poly_fn_sig = tcx.fn_sig(id);
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let fn_sig = tcx.liberate_late_bound_regions(id, poly_fn_sig);
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body.params
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.iter()
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.take(if fn_sig.c_variadic {
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@ -69,7 +68,7 @@ pub(super) fn find_param_with_region(
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// May return None; sometimes the tables are not yet populated.
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let ty = fn_sig.inputs()[index];
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let mut found_anon_region = false;
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let new_param_ty = self.tcx().fold_regions(ty, &mut false, |r, _| {
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let new_param_ty = tcx.fold_regions(ty, &mut false, |r, _| {
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if r == anon_region {
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found_anon_region = true;
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replace_region
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@ -92,6 +91,15 @@ pub(super) fn find_param_with_region(
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None
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}
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})
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}
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impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
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pub(super) fn find_param_with_region(
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&self,
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anon_region: Region<'tcx>,
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replace_region: Region<'tcx>,
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) -> Option<AnonymousParamInfo<'_>> {
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find_param_with_region(self.tcx(), anon_region, replace_region)
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}
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// Here, we check for the case where the anonymous region
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@ -24,10 +24,14 @@ LL | fn make_bad_impl<'b>(x: &'b ()) -> impl for<'a> Hrtb<'a, Assoc = impl Send
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LL | x
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| ^ returning this value requires that `'b` must outlive `'static`
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|
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help: to allow this `impl Trait` to capture borrowed data with lifetime `'b`, add `'b` as a bound
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help: to declare that the `impl Trait` captures data from argument `x`, you can add an explicit `'b` lifetime bound
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|
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LL | fn make_bad_impl<'b>(x: &'b ()) -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> + 'b {
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| ++++
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help: to declare that the `impl Trait` captures data from argument `x`, you can add an explicit `'b` lifetime bound
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|
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LL | fn make_bad_impl<'b>(x: &'b ()) -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a + 'b> {
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| ++++
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error: implementation of `Hrtb` is not general enough
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--> $DIR/issue-88236-2.rs:20:5
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@ -32,7 +32,14 @@ LL | fn elided2(x: &i32) -> impl Copy + 'static { x }
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| |
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| let's call the lifetime of this reference `'1`
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|
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= help: consider replacing `'1` with `'static`
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help: consider changing the `impl Trait`'s explicit `'static` bound to the lifetime of argument `x`
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|
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LL | fn elided2(x: &i32) -> impl Copy + '_ { x }
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| ~~
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help: alternatively, add an explicit `'static` bound to this reference
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|
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LL | fn elided2(x: &'static i32) -> impl Copy + 'static { x }
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| ~~~~~~~~~~~~
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error: lifetime may not live long enough
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--> $DIR/must_outlive_least_region_or_bound.rs:11:55
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@ -40,7 +47,14 @@ error: lifetime may not live long enough
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LL | fn explicit2<'a>(x: &'a i32) -> impl Copy + 'static { x }
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| -- lifetime `'a` defined here ^ returning this value requires that `'a` must outlive `'static`
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|
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= help: consider replacing `'a` with `'static`
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help: consider changing the `impl Trait`'s explicit `'static` bound to the lifetime of argument `x`
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|
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LL | fn explicit2<'a>(x: &'a i32) -> impl Copy + 'a { x }
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| ~~
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help: alternatively, add an explicit `'static` bound to this reference
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|
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LL | fn explicit2<'a>(x: &'static i32) -> impl Copy + 'static { x }
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| ~~~~~~~~~~~~
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error[E0621]: explicit lifetime required in the type of `x`
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--> $DIR/must_outlive_least_region_or_bound.rs:13:41
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@ -57,6 +71,15 @@ LL | fn elided5(x: &i32) -> (Box<dyn Debug>, impl Debug) { (Box::new(x), x) }
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| - ^^^^^^^^^^^^^^^^ returning this value requires that `'1` must outlive `'static`
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| |
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| let's call the lifetime of this reference `'1`
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|
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help: to declare that the trait object captures data from argument `x`, you can add an explicit `'_` lifetime bound
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|
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LL | fn elided5(x: &i32) -> (Box<dyn Debug + '_>, impl Debug) { (Box::new(x), x) }
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| ++++
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help: to declare that the `impl Trait` captures data from argument `x`, you can add an explicit `'_` lifetime bound
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|
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LL | fn elided5(x: &i32) -> (Box<dyn Debug>, impl Debug + '_) { (Box::new(x), x) }
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| ++++
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error: lifetime may not live long enough
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--> $DIR/must_outlive_least_region_or_bound.rs:29:69
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@ -64,7 +87,14 @@ error: lifetime may not live long enough
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LL | fn with_bound<'a>(x: &'a i32) -> impl LifetimeTrait<'a> + 'static { x }
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| -- lifetime `'a` defined here ^ returning this value requires that `'a` must outlive `'static`
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|
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= help: consider replacing `'a` with `'static`
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help: consider changing the `impl Trait`'s explicit `'static` bound to the lifetime of argument `x`
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|
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LL | fn with_bound<'a>(x: &'a i32) -> impl LifetimeTrait<'a> + 'a { x }
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| ~~
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help: alternatively, add an explicit `'static` bound to this reference
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|
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LL | fn with_bound<'a>(x: &'static i32) -> impl LifetimeTrait<'a> + 'static { x }
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| ~~~~~~~~~~~~
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error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
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--> $DIR/must_outlive_least_region_or_bound.rs:34:5
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@ -5,6 +5,11 @@ LL | fn foo<T: Any>(value: &T) -> Box<dyn Any> {
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| - let's call the lifetime of this reference `'1`
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LL | Box::new(value) as Box<dyn Any>
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| ^^^^^^^^^^^^^^^ cast requires that `'1` must outlive `'static`
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|
|
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help: to declare that the trait object captures data from argument `value`, you can add an explicit `'_` lifetime bound
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|
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LL | fn foo<T: Any>(value: &T) -> Box<dyn Any + '_> {
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| ++++
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error: aborting due to previous error
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@ -5,6 +5,11 @@ LL | fn bar<'a>(x: &'a u32) -> &'static dyn Debug {
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| -- lifetime `'a` defined here
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LL | x
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| ^ returning this value requires that `'a` must outlive `'static`
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|
|
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help: to declare that the trait object captures data from argument `x`, you can add an explicit `'a` lifetime bound
|
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|
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LL | fn bar<'a>(x: &'a u32) -> &'static dyn Debug + 'a {
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| ++++
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error: aborting due to previous error
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@ -6,6 +6,11 @@ LL | fn load(ss: &mut SomeStruct) -> Box<dyn SomeTrait> {
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...
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LL | ss.r
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| ^^^^ returning this value requires that `'1` must outlive `'static`
|
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|
|
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help: to declare that the trait object captures data from argument `ss`, you can add an explicit `'_` lifetime bound
|
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|
|
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LL | fn load(ss: &mut SomeStruct) -> Box<dyn SomeTrait + '_> {
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| ++++
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error[E0507]: cannot move out of `ss.r` which is behind a mutable reference
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--> $DIR/object-lifetime-default-from-box-error.rs:18:5
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@ -5,6 +5,15 @@ LL | fn a(v: &[u8]) -> Box<dyn Foo + 'static> {
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| - let's call the lifetime of this reference `'1`
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LL | let x: Box<dyn Foo + 'static> = Box::new(v);
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| ^^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'1` must outlive `'static`
|
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|
|
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help: consider changing the trait object's explicit `'static` bound to the lifetime of argument `v`
|
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|
|
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LL | fn a(v: &[u8]) -> Box<dyn Foo + '_> {
|
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| ~~
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help: alternatively, add an explicit `'static` bound to this reference
|
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|
|
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LL | fn a(v: &'static [u8]) -> Box<dyn Foo + 'static> {
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| ~~~~~~~~~~~~~
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error: lifetime may not live long enough
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--> $DIR/region-object-lifetime-in-coercion.rs:19:5
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@ -13,6 +22,15 @@ LL | fn b(v: &[u8]) -> Box<dyn Foo + 'static> {
|
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| - let's call the lifetime of this reference `'1`
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LL | Box::new(v)
|
||||
| ^^^^^^^^^^^ returning this value requires that `'1` must outlive `'static`
|
||||
|
|
||||
help: consider changing the trait object's explicit `'static` bound to the lifetime of argument `v`
|
||||
|
|
||||
LL | fn b(v: &[u8]) -> Box<dyn Foo + '_> {
|
||||
| ~~
|
||||
help: alternatively, add an explicit `'static` bound to this reference
|
||||
|
|
||||
LL | fn b(v: &'static [u8]) -> Box<dyn Foo + 'static> {
|
||||
| ~~~~~~~~~~~~~
|
||||
|
||||
error: lifetime may not live long enough
|
||||
--> $DIR/region-object-lifetime-in-coercion.rs:27:5
|
||||
@ -22,6 +40,11 @@ LL | fn c(v: &[u8]) -> Box<dyn Foo> {
|
||||
...
|
||||
LL | Box::new(v)
|
||||
| ^^^^^^^^^^^ returning this value requires that `'1` must outlive `'static`
|
||||
|
|
||||
help: to declare that the trait object captures data from argument `v`, you can add an explicit `'_` lifetime bound
|
||||
|
|
||||
LL | fn c(v: &[u8]) -> Box<dyn Foo + '_> {
|
||||
| ++++
|
||||
|
||||
error: lifetime may not live long enough
|
||||
--> $DIR/region-object-lifetime-in-coercion.rs:33:5
|
||||
|
||||
@ -5,6 +5,15 @@ LL | fn g<'a, T: 'static>(v: Box<dyn A<T> + 'a>) -> Box<dyn X + 'static> {
|
||||
| -- lifetime `'a` defined here
|
||||
LL | Box::new(B(&*v)) as Box<dyn X>
|
||||
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ returning this value requires that `'a` must outlive `'static`
|
||||
|
|
||||
help: consider changing the trait object's explicit `'static` bound to the lifetime of argument `v`
|
||||
|
|
||||
LL | fn g<'a, T: 'static>(v: Box<dyn A<T> + 'a>) -> Box<dyn X + 'a> {
|
||||
| ~~
|
||||
help: alternatively, add an explicit `'static` bound to this reference
|
||||
|
|
||||
LL | fn g<'a, T: 'static>(v: Box<(dyn A<T> + 'static)>) -> Box<dyn X + 'static> {
|
||||
| ~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
error[E0515]: cannot return value referencing local data `*v`
|
||||
--> $DIR/regions-close-object-into-object-2.rs:13:5
|
||||
|
||||
@ -29,6 +29,15 @@ LL | fn i<'a, T, U>(v: Box<dyn A<U>+'a>) -> Box<dyn X + 'static> {
|
||||
| -- lifetime `'a` defined here
|
||||
LL | Box::new(B(&*v)) as Box<dyn X>
|
||||
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ returning this value requires that `'a` must outlive `'static`
|
||||
|
|
||||
help: consider changing the trait object's explicit `'static` bound to the lifetime of argument `v`
|
||||
|
|
||||
LL | fn i<'a, T, U>(v: Box<dyn A<U>+'a>) -> Box<dyn X + 'a> {
|
||||
| ~~
|
||||
help: alternatively, add an explicit `'static` bound to this reference
|
||||
|
|
||||
LL | fn i<'a, T, U>(v: Box<(dyn A<U> + 'static)>) -> Box<dyn X + 'static> {
|
||||
| ~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
error[E0515]: cannot return value referencing local data `*v`
|
||||
--> $DIR/regions-close-object-into-object-4.rs:13:5
|
||||
|
||||
@ -6,6 +6,15 @@ LL | fn static_proc(x: &isize) -> Box<dyn FnMut() -> (isize) + 'static> {
|
||||
LL | // This is illegal, because the region bound on `proc` is 'static.
|
||||
LL | Box::new(move || { *x })
|
||||
| ^^^^^^^^^^^^^^^^^^^^^^^^ returning this value requires that `'1` must outlive `'static`
|
||||
|
|
||||
help: consider changing the trait object's explicit `'static` bound to the lifetime of argument `x`
|
||||
|
|
||||
LL | fn static_proc(x: &isize) -> Box<dyn FnMut() -> (isize) + '_> {
|
||||
| ~~
|
||||
help: alternatively, add an explicit `'static` bound to this reference
|
||||
|
|
||||
LL | fn static_proc(x: &'static isize) -> Box<dyn FnMut() -> (isize) + 'static> {
|
||||
| ~~~~~~~~~~~~~~
|
||||
|
||||
error: aborting due to previous error
|
||||
|
||||
|
||||
@ -9,10 +9,14 @@ LL | | remaining: self.0.iter(),
|
||||
LL | | }
|
||||
| |_________^ returning this value requires that `'1` must outlive `'static`
|
||||
|
|
||||
help: to allow this `impl Trait` to capture borrowed data with lifetime `'1`, add `'_` as a bound
|
||||
help: to declare that the `impl Trait` captures data from argument `self`, you can add an explicit `'_` lifetime bound
|
||||
|
|
||||
LL | fn iter(&self) -> impl Iterator<Item = Box<dyn Foo>> + '_ {
|
||||
| ++++
|
||||
help: to declare that the trait object captures data from argument `self`, you can add an explicit `'_` lifetime bound
|
||||
|
|
||||
LL | fn iter(&self) -> impl Iterator<Item = Box<dyn Foo + '_>> {
|
||||
| ++++
|
||||
|
||||
error: lifetime may not live long enough
|
||||
--> $DIR/trait-object-nested-in-impl-trait.rs:39:9
|
||||
@ -24,6 +28,11 @@ LL | | current: None,
|
||||
LL | | remaining: self.0.iter(),
|
||||
LL | | }
|
||||
| |_________^ returning this value requires that `'1` must outlive `'static`
|
||||
|
|
||||
help: to declare that the trait object captures data from argument `self`, you can add an explicit `'_` lifetime bound
|
||||
|
|
||||
LL | fn iter(&self) -> impl Iterator<Item = Box<dyn Foo + '_>> + '_ {
|
||||
| ++++
|
||||
|
||||
error: lifetime may not live long enough
|
||||
--> $DIR/trait-object-nested-in-impl-trait.rs:50:9
|
||||
@ -35,6 +44,11 @@ LL | | current: None,
|
||||
LL | | remaining: self.0.iter(),
|
||||
LL | | }
|
||||
| |_________^ returning this value requires that `'a` must outlive `'static`
|
||||
|
|
||||
help: to declare that the trait object captures data from argument `self`, you can add an explicit `'a` lifetime bound
|
||||
|
|
||||
LL | fn iter<'a>(&'a self) -> impl Iterator<Item = Box<dyn Foo + 'a>> + 'a {
|
||||
| ++++
|
||||
|
||||
error: lifetime may not live long enough
|
||||
--> $DIR/trait-object-nested-in-impl-trait.rs:61:9
|
||||
@ -47,10 +61,14 @@ LL | | remaining: self.0.iter(),
|
||||
LL | | }
|
||||
| |_________^ returning this value requires that `'a` must outlive `'static`
|
||||
|
|
||||
help: to allow this `impl Trait` to capture borrowed data with lifetime `'a`, add `'a` as a bound
|
||||
help: to declare that the `impl Trait` captures data from argument `self`, you can add an explicit `'a` lifetime bound
|
||||
|
|
||||
LL | fn iter<'a>(&'a self) -> impl Iterator<Item = Box<dyn Foo>> + 'a {
|
||||
| ++++
|
||||
help: to declare that the trait object captures data from argument `self`, you can add an explicit `'a` lifetime bound
|
||||
|
|
||||
LL | fn iter<'a>(&'a self) -> impl Iterator<Item = Box<dyn Foo + 'a>> {
|
||||
| ++++
|
||||
|
||||
error: aborting due to 4 previous errors
|
||||
|
||||
|
||||
@ -6,6 +6,11 @@ LL | fn a<T>(items: &[T]) -> Box<dyn Iterator<Item=&T>> {
|
||||
LL | // ^^^^^^^^^^^^^^^^^^^^^ bound *here* defaults to `'static`
|
||||
LL | Box::new(items.iter())
|
||||
| ^^^^^^^^^^^^^^^^^^^^^^ returning this value requires that `'1` must outlive `'static`
|
||||
|
|
||||
help: to declare that the trait object captures data from argument `items`, you can add an explicit `'_` lifetime bound
|
||||
|
|
||||
LL | fn a<T>(items: &[T]) -> Box<dyn Iterator<Item=&T> + '_> {
|
||||
| ++++
|
||||
|
||||
error: aborting due to previous error
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user