Rollup merge of #134259 - compiler-errors:infer-ret-ty, r=dtolnay
Clean up `infer_return_ty_for_fn_sig` The code for lowering fn signatures from HIR currently is structured to prefer the recovery path (where users write `-> _`) over the good path. This PR pulls the recovery code out into a separate fn. Review w/o whitespace
This commit is contained in:
Matthias Krüger
GitHub
commit
1fa1f3001f
1 changed files with 95 additions and 86 deletions
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@ -1340,7 +1340,7 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<'_, ty::PolyFn
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..
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})
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| Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), .. }) => {
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infer_return_ty_for_fn_sig(sig, generics, def_id, &icx)
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lower_fn_sig_recovering_infer_ret_ty(&icx, sig, generics, def_id)
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}
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ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), generics, .. }) => {
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@ -1357,7 +1357,7 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<'_, ty::PolyFn
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None,
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)
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} else {
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infer_return_ty_for_fn_sig(sig, generics, def_id, &icx)
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lower_fn_sig_recovering_infer_ret_ty(&icx, sig, generics, def_id)
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}
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}
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@ -1407,99 +1407,108 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<'_, ty::PolyFn
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ty::EarlyBinder::bind(output)
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}
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fn infer_return_ty_for_fn_sig<'tcx>(
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sig: &hir::FnSig<'tcx>,
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generics: &hir::Generics<'_>,
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def_id: LocalDefId,
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fn lower_fn_sig_recovering_infer_ret_ty<'tcx>(
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icx: &ItemCtxt<'tcx>,
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sig: &'tcx hir::FnSig<'tcx>,
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generics: &'tcx hir::Generics<'tcx>,
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def_id: LocalDefId,
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) -> ty::PolyFnSig<'tcx> {
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if let Some(infer_ret_ty) = sig.decl.output.get_infer_ret_ty() {
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return recover_infer_ret_ty(icx, infer_ret_ty, generics, def_id);
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}
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icx.lowerer().lower_fn_ty(
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icx.tcx().local_def_id_to_hir_id(def_id),
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sig.header.safety,
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sig.header.abi,
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sig.decl,
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Some(generics),
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None,
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)
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}
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fn recover_infer_ret_ty<'tcx>(
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icx: &ItemCtxt<'tcx>,
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infer_ret_ty: &'tcx hir::Ty<'tcx>,
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generics: &'tcx hir::Generics<'tcx>,
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def_id: LocalDefId,
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) -> ty::PolyFnSig<'tcx> {
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let tcx = icx.tcx;
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let hir_id = tcx.local_def_id_to_hir_id(def_id);
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match sig.decl.output.get_infer_ret_ty() {
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Some(ty) => {
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let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
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// Typeck doesn't expect erased regions to be returned from `type_of`.
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// This is a heuristic approach. If the scope has region parameters,
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// we should change fn_sig's lifetime from `ReErased` to `ReError`,
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// otherwise to `ReStatic`.
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let has_region_params = generics.params.iter().any(|param| match param.kind {
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GenericParamKind::Lifetime { .. } => true,
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_ => false,
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});
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let fn_sig = fold_regions(tcx, fn_sig, |r, _| match *r {
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ty::ReErased => {
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if has_region_params {
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ty::Region::new_error_with_message(
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tcx,
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DUMMY_SP,
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"erased region is not allowed here in return type",
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)
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} else {
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tcx.lifetimes.re_static
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}
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}
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_ => r,
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});
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let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
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let mut visitor = HirPlaceholderCollector::default();
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visitor.visit_ty(ty);
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let mut diag = bad_placeholder(icx.lowerer(), visitor.0, "return type");
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let ret_ty = fn_sig.output();
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// Don't leak types into signatures unless they're nameable!
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// For example, if a function returns itself, we don't want that
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// recursive function definition to leak out into the fn sig.
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let mut recovered_ret_ty = None;
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if let Some(suggestable_ret_ty) = ret_ty.make_suggestable(tcx, false, None) {
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diag.span_suggestion(
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ty.span,
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"replace with the correct return type",
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suggestable_ret_ty,
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Applicability::MachineApplicable,
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);
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recovered_ret_ty = Some(suggestable_ret_ty);
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} else if let Some(sugg) = suggest_impl_trait(
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&tcx.infer_ctxt().build(TypingMode::non_body_analysis()),
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tcx.param_env(def_id),
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ret_ty,
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) {
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diag.span_suggestion(
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ty.span,
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"replace with an appropriate return type",
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sugg,
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Applicability::MachineApplicable,
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);
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} else if ret_ty.is_closure() {
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diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
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// Typeck doesn't expect erased regions to be returned from `type_of`.
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// This is a heuristic approach. If the scope has region parameters,
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// we should change fn_sig's lifetime from `ReErased` to `ReError`,
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// otherwise to `ReStatic`.
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let has_region_params = generics.params.iter().any(|param| match param.kind {
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GenericParamKind::Lifetime { .. } => true,
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_ => false,
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});
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let fn_sig = fold_regions(tcx, fn_sig, |r, _| match *r {
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ty::ReErased => {
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if has_region_params {
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ty::Region::new_error_with_message(
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tcx,
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DUMMY_SP,
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"erased region is not allowed here in return type",
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)
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} else {
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tcx.lifetimes.re_static
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}
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// Also note how `Fn` traits work just in case!
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if ret_ty.is_closure() {
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diag.note(
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"for more information on `Fn` traits and closure types, see \
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https://doc.rust-lang.org/book/ch13-01-closures.html",
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);
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}
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let guar = diag.emit();
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ty::Binder::dummy(tcx.mk_fn_sig(
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fn_sig.inputs().iter().copied(),
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recovered_ret_ty.unwrap_or_else(|| Ty::new_error(tcx, guar)),
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fn_sig.c_variadic,
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fn_sig.safety,
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fn_sig.abi,
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))
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}
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None => icx.lowerer().lower_fn_ty(
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hir_id,
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sig.header.safety,
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sig.header.abi,
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sig.decl,
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Some(generics),
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None,
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),
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_ => r,
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});
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let mut visitor = HirPlaceholderCollector::default();
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visitor.visit_ty(infer_ret_ty);
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let mut diag = bad_placeholder(icx.lowerer(), visitor.0, "return type");
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let ret_ty = fn_sig.output();
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// Don't leak types into signatures unless they're nameable!
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// For example, if a function returns itself, we don't want that
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// recursive function definition to leak out into the fn sig.
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let mut recovered_ret_ty = None;
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if let Some(suggestable_ret_ty) = ret_ty.make_suggestable(tcx, false, None) {
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diag.span_suggestion(
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infer_ret_ty.span,
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"replace with the correct return type",
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suggestable_ret_ty,
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Applicability::MachineApplicable,
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);
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recovered_ret_ty = Some(suggestable_ret_ty);
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} else if let Some(sugg) = suggest_impl_trait(
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&tcx.infer_ctxt().build(TypingMode::non_body_analysis()),
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tcx.param_env(def_id),
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ret_ty,
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) {
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diag.span_suggestion(
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infer_ret_ty.span,
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"replace with an appropriate return type",
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sugg,
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Applicability::MachineApplicable,
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);
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} else if ret_ty.is_closure() {
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diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
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}
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// Also note how `Fn` traits work just in case!
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if ret_ty.is_closure() {
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diag.note(
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"for more information on `Fn` traits and closure types, see \
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https://doc.rust-lang.org/book/ch13-01-closures.html",
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);
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}
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let guar = diag.emit();
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ty::Binder::dummy(tcx.mk_fn_sig(
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fn_sig.inputs().iter().copied(),
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recovered_ret_ty.unwrap_or_else(|| Ty::new_error(tcx, guar)),
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fn_sig.c_variadic,
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fn_sig.safety,
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fn_sig.abi,
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))
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}
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pub fn suggest_impl_trait<'tcx>(
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