Simplify suggestion when returning bare dyn trait
This commit is contained in:
Michael Goulet
parent
e9e1bbc7a8
commit
795fdf7d61
@ -885,7 +885,7 @@ fn report_selection_error(
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return;
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}
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if self.suggest_impl_trait(&mut err, span, &obligation, trait_predicate) {
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if self.suggest_impl_trait(&mut err, &obligation, trait_predicate) {
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err.emit();
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return;
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}
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@ -30,9 +30,9 @@
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use rustc_middle::ty::error::TypeError::{self, Sorts};
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use rustc_middle::ty::{
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self, suggest_arbitrary_trait_bound, suggest_constraining_type_param, AdtKind,
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GeneratorDiagnosticData, GeneratorInteriorTypeCause, Infer, InferTy, InternalSubsts,
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IsSuggestable, ToPredicate, Ty, TyCtxt, TypeAndMut, TypeFoldable, TypeFolder,
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TypeSuperFoldable, TypeVisitableExt, TypeckResults,
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GeneratorDiagnosticData, GeneratorInteriorTypeCause, InferTy, InternalSubsts, IsSuggestable,
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ToPredicate, Ty, TyCtxt, TypeAndMut, TypeFoldable, TypeFolder, TypeSuperFoldable,
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TypeVisitableExt, TypeckResults,
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};
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use rustc_span::def_id::LocalDefId;
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use rustc_span::symbol::{sym, Ident, Symbol};
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@ -261,7 +261,6 @@ fn suggest_semicolon_removal(
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fn suggest_impl_trait(
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&self,
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err: &mut Diagnostic,
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span: Span,
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obligation: &PredicateObligation<'tcx>,
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trait_pred: ty::PolyTraitPredicate<'tcx>,
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) -> bool;
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@ -1792,215 +1791,66 @@ fn return_type_span(&self, obligation: &PredicateObligation<'tcx>) -> Option<Spa
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fn suggest_impl_trait(
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&self,
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err: &mut Diagnostic,
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span: Span,
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obligation: &PredicateObligation<'tcx>,
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trait_pred: ty::PolyTraitPredicate<'tcx>,
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) -> bool {
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match obligation.cause.code().peel_derives() {
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// Only suggest `impl Trait` if the return type is unsized because it is `dyn Trait`.
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ObligationCauseCode::SizedReturnType => {}
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_ => return false,
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}
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let hir = self.tcx.hir();
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let fn_hir_id = hir.local_def_id_to_hir_id(obligation.cause.body_id);
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let node = hir.find_by_def_id(obligation.cause.body_id);
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let Some(hir::Node::Item(hir::Item {
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kind: hir::ItemKind::Fn(sig, _, body_id),
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..
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})) = node
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else {
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let ObligationCauseCode::SizedReturnType = obligation.cause.code() else {
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return false;
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};
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let body = hir.body(*body_id);
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let trait_pred = self.resolve_vars_if_possible(trait_pred);
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let ty = trait_pred.skip_binder().self_ty();
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let is_object_safe = match ty.kind() {
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ty::Dynamic(predicates, _, ty::Dyn) => {
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// If the `dyn Trait` is not object safe, do not suggest `Box<dyn Trait>`.
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predicates
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.principal_def_id()
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.map_or(true, |def_id| self.tcx.check_is_object_safe(def_id))
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}
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// We only want to suggest `impl Trait` to `dyn Trait`s.
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// For example, `fn foo() -> str` needs to be filtered out.
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_ => return false,
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};
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let hir::FnRetTy::Return(ret_ty) = sig.decl.output else {
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let ty::Dynamic(_, _, ty::Dyn) = trait_pred.self_ty().skip_binder().kind() else {
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return false;
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};
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// Use `TypeVisitor` instead of the output type directly to find the span of `ty` for
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// cases like `fn foo() -> (dyn Trait, i32) {}`.
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// Recursively look for `TraitObject` types and if there's only one, use that span to
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// suggest `impl Trait`.
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// Visit to make sure there's a single `return` type to suggest `impl Trait`,
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// otherwise suggest using `Box<dyn Trait>` or an enum.
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let mut visitor = ReturnsVisitor::default();
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visitor.visit_body(&body);
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let typeck_results = self.typeck_results.as_ref().unwrap();
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let Some(liberated_sig) = typeck_results.liberated_fn_sigs().get(fn_hir_id).copied() else { return false; };
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let ret_types = visitor
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.returns
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.iter()
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.filter_map(|expr| Some((expr.span, typeck_results.node_type_opt(expr.hir_id)?)))
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.map(|(expr_span, ty)| (expr_span, self.resolve_vars_if_possible(ty)));
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let (last_ty, all_returns_have_same_type, only_never_return) = ret_types.clone().fold(
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(None, true, true),
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|(last_ty, mut same, only_never_return): (std::option::Option<Ty<'_>>, bool, bool),
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(_, ty)| {
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let ty = self.resolve_vars_if_possible(ty);
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same &=
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!matches!(ty.kind(), ty::Error(_))
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&& last_ty.map_or(true, |last_ty| {
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// FIXME: ideally we would use `can_coerce` here instead, but `typeck` comes
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// *after* in the dependency graph.
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match (ty.kind(), last_ty.kind()) {
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(Infer(InferTy::IntVar(_)), Infer(InferTy::IntVar(_)))
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| (Infer(InferTy::FloatVar(_)), Infer(InferTy::FloatVar(_)))
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| (Infer(InferTy::FreshIntTy(_)), Infer(InferTy::FreshIntTy(_)))
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| (
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Infer(InferTy::FreshFloatTy(_)),
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Infer(InferTy::FreshFloatTy(_)),
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) => true,
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_ => ty == last_ty,
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}
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});
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(Some(ty), same, only_never_return && matches!(ty.kind(), ty::Never))
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},
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);
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let mut spans_and_needs_box = vec![];
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match liberated_sig.output().kind() {
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ty::Dynamic(predicates, _, ty::Dyn) => {
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let cause = ObligationCause::misc(ret_ty.span, obligation.cause.body_id);
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let param_env = ty::ParamEnv::empty();
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if !only_never_return {
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for (expr_span, return_ty) in ret_types {
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let self_ty_satisfies_dyn_predicates = |self_ty| {
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predicates.iter().all(|predicate| {
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let pred = predicate.with_self_ty(self.tcx, self_ty);
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let obl = Obligation::new(self.tcx, cause.clone(), param_env, pred);
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self.predicate_may_hold(&obl)
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})
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};
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if let ty::Adt(def, substs) = return_ty.kind()
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&& def.is_box()
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&& self_ty_satisfies_dyn_predicates(substs.type_at(0))
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{
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spans_and_needs_box.push((expr_span, false));
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} else if self_ty_satisfies_dyn_predicates(return_ty) {
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spans_and_needs_box.push((expr_span, true));
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} else {
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return false;
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}
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}
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}
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}
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_ => return false,
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};
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let sm = self.tcx.sess.source_map();
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if !ret_ty.span.overlaps(span) {
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return false;
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}
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let snippet = if let hir::TyKind::TraitObject(..) = ret_ty.kind {
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if let Ok(snippet) = sm.span_to_snippet(ret_ty.span) {
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snippet
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} else {
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return false;
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}
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} else {
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// Substitute the type, so we can print a fixup given `type Alias = dyn Trait`
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let name = liberated_sig.output().to_string();
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let name =
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name.strip_prefix('(').and_then(|name| name.strip_suffix(')')).unwrap_or(&name);
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if !name.starts_with("dyn ") {
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return false;
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}
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name.to_owned()
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};
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err.code(error_code!(E0746));
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err.set_primary_message("return type cannot have an unboxed trait object");
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err.children.clear();
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let impl_trait_msg = "for information on `impl Trait`, see \
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<https://doc.rust-lang.org/book/ch10-02-traits.html\
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#returning-types-that-implement-traits>";
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let trait_obj_msg = "for information on trait objects, see \
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<https://doc.rust-lang.org/book/ch17-02-trait-objects.html\
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#using-trait-objects-that-allow-for-values-of-different-types>";
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let has_dyn = snippet.split_whitespace().next().map_or(false, |s| s == "dyn");
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let trait_obj = if has_dyn { &snippet[4..] } else { &snippet };
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if only_never_return {
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// No return paths, probably using `panic!()` or similar.
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// Suggest `-> impl Trait`, and if `Trait` is object safe, `-> Box<dyn Trait>`.
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suggest_trait_object_return_type_alternatives(
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err,
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ret_ty.span,
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trait_obj,
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is_object_safe,
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);
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} else if let (Some(last_ty), true) = (last_ty, all_returns_have_same_type) {
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// Suggest `-> impl Trait`.
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let span = obligation.cause.span;
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if let Ok(snip) = self.tcx.sess.source_map().span_to_snippet(span)
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&& snip.starts_with("dyn ")
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{
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err.span_suggestion(
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ret_ty.span,
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format!(
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"use `impl {1}` as the return type, as all return paths are of type `{}`, \
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which implements `{1}`",
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last_ty, trait_obj,
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),
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format!("impl {}", trait_obj),
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Applicability::MachineApplicable,
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span.with_hi(span.lo() + BytePos(4)),
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"return an `impl Trait` instead of a `dyn Trait`, \
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if all returned values are the same type",
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"impl ",
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Applicability::MaybeIncorrect,
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);
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err.note(impl_trait_msg);
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} else {
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if is_object_safe {
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// Suggest `-> Box<dyn Trait>` and `Box::new(returned_value)`.
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err.multipart_suggestion(
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"return a boxed trait object instead",
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vec![
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(ret_ty.span.shrink_to_lo(), "Box<".to_string()),
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(span.shrink_to_hi(), ">".to_string()),
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],
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Applicability::MaybeIncorrect,
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);
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for (span, needs_box) in spans_and_needs_box {
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if needs_box {
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err.multipart_suggestion(
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"... and box this value",
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vec![
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(span.shrink_to_lo(), "Box::new(".to_string()),
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(span.shrink_to_hi(), ")".to_string()),
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],
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Applicability::MaybeIncorrect,
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);
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}
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}
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} else {
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// This is currently not possible to trigger because E0038 takes precedence, but
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// leave it in for completeness in case anything changes in an earlier stage.
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err.note(format!(
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"if trait `{}` were object-safe, you could return a trait object",
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trait_obj,
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));
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}
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err.note(trait_obj_msg);
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err.note(format!(
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"if all the returned values were of the same type you could use `impl {}` as the \
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return type",
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trait_obj,
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));
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err.note(impl_trait_msg);
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err.note("you can create a new `enum` with a variant for each returned type");
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}
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let body = self.tcx.hir().body(self.tcx.hir().body_owned_by(obligation.cause.body_id));
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let mut visitor = ReturnsVisitor::default();
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visitor.visit_body(&body);
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let mut sugg =
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vec![(span.shrink_to_lo(), "Box<".to_string()), (span.shrink_to_hi(), ">".to_string())];
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sugg.extend(visitor.returns.into_iter().flat_map(|expr| {
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let span = expr.span.find_ancestor_in_same_ctxt(obligation.cause.span).unwrap_or(expr.span);
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if !span.can_be_used_for_suggestions() {
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vec![]
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} else if let hir::ExprKind::Call(path, ..) = expr.kind
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&& let hir::ExprKind::Path(hir::QPath::TypeRelative(ty, method)) = path.kind
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&& method.ident.name == sym::new
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&& let hir::TyKind::Path(hir::QPath::Resolved(.., box_path)) = ty.kind
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&& box_path.res.opt_def_id().is_some_and(|def_id| Some(def_id) == self.tcx.lang_items().owned_box())
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{
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// Don't box `Box::new`
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vec![]
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} else {
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vec![
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(span.shrink_to_lo(), "Box::new(".to_string()),
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(span.shrink_to_hi(), ")".to_string()),
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]
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}
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}));
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err.multipart_suggestion(
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"box the return type, and wrap all of the returned values in `Box::new`",
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sugg,
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Applicability::MaybeIncorrect,
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);
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true
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}
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@ -4139,37 +3989,6 @@ fn next_type_param_name(&self, name: Option<&str>) -> String {
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}
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}
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fn suggest_trait_object_return_type_alternatives(
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err: &mut Diagnostic,
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ret_ty: Span,
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trait_obj: &str,
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is_object_safe: bool,
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) {
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err.span_suggestion(
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ret_ty,
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format!(
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"use `impl {}` as the return type if all return paths have the same type but you \
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want to expose only the trait in the signature",
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trait_obj,
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),
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format!("impl {}", trait_obj),
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Applicability::MaybeIncorrect,
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);
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if is_object_safe {
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err.multipart_suggestion(
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format!(
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"use a boxed trait object if all return paths implement trait `{}`",
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trait_obj,
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),
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vec![
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(ret_ty.shrink_to_lo(), "Box<".to_string()),
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(ret_ty.shrink_to_hi(), ">".to_string()),
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],
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Applicability::MaybeIncorrect,
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);
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}
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}
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/// Collect the spans that we see the generic param `param_did`
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struct ReplaceImplTraitVisitor<'a> {
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ty_spans: &'a mut Vec<Span>,
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@ -1,18 +0,0 @@
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// run-rustfix
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#![allow(dead_code)]
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struct Struct;
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trait Trait {}
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impl Trait for Struct {}
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impl Trait for u32 {}
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fn foo() -> impl Trait { Struct }
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//~^ ERROR E0746
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fn bar() -> impl Trait { //~ ERROR E0746
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if true {
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return 0;
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}
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42
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}
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fn main() {}
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@ -1,5 +1,5 @@
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// run-rustfix
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#![allow(dead_code)]
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struct Struct;
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trait Trait {}
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impl Trait for Struct {}
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@ -4,11 +4,14 @@ error[E0746]: return type cannot have an unboxed trait object
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LL | fn foo() -> dyn Trait { Struct }
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| ^^^^^^^^^ doesn't have a size known at compile-time
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|
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= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
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help: use `impl Trait` as the return type, as all return paths are of type `Struct`, which implements `Trait`
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help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
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|
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LL | fn foo() -> impl Trait { Struct }
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| ~~~~~~~~~~
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| ~~~~
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help: box the return type, and wrap all of the returned values in `Box::new`
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|
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LL | fn foo() -> Box<dyn Trait> { Box::new(Struct) }
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| ++++ + +++++++++ +
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error[E0746]: return type cannot have an unboxed trait object
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--> $DIR/E0746.rs:11:13
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@ -16,11 +19,18 @@ error[E0746]: return type cannot have an unboxed trait object
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LL | fn bar() -> dyn Trait {
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| ^^^^^^^^^ doesn't have a size known at compile-time
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|
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= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
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help: use `impl Trait` as the return type, as all return paths are of type `{integer}`, which implements `Trait`
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help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
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|
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LL | fn bar() -> impl Trait {
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| ~~~~~~~~~~
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| ~~~~
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help: box the return type, and wrap all of the returned values in `Box::new`
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|
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LL ~ fn bar() -> Box<dyn Trait> {
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LL | if true {
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LL ~ return Box::new(0);
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LL | }
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LL ~ Box::new(42)
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|
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error: aborting due to 2 previous errors
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@ -46,11 +46,10 @@ error[E0746]: return type cannot have an unboxed trait object
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LL | fn bap() -> Trait { Struct }
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| ^^^^^ doesn't have a size known at compile-time
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|
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= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
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help: use `impl Trait` as the return type, as all return paths are of type `Struct`, which implements `Trait`
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help: box the return type, and wrap all of the returned values in `Box::new`
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|
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LL | fn bap() -> impl Trait { Struct }
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| ~~~~~~~~~~
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LL | fn bap() -> Box<Trait> { Box::new(Struct) }
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| ++++ + +++++++++ +
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error[E0746]: return type cannot have an unboxed trait object
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--> $DIR/dyn-trait-return-should-be-impl-trait.rs:15:13
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@ -58,11 +57,14 @@ error[E0746]: return type cannot have an unboxed trait object
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LL | fn ban() -> dyn Trait { Struct }
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| ^^^^^^^^^ doesn't have a size known at compile-time
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|
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= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
|
||||
help: use `impl Trait` as the return type, as all return paths are of type `Struct`, which implements `Trait`
|
||||
help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
||||
|
|
||||
LL | fn ban() -> impl Trait { Struct }
|
||||
| ~~~~~~~~~~
|
||||
| ~~~~
|
||||
help: box the return type, and wrap all of the returned values in `Box::new`
|
||||
|
|
||||
LL | fn ban() -> Box<dyn Trait> { Box::new(Struct) }
|
||||
| ++++ + +++++++++ +
|
||||
|
||||
error[E0746]: return type cannot have an unboxed trait object
|
||||
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:17:13
|
||||
@ -70,14 +72,14 @@ error[E0746]: return type cannot have an unboxed trait object
|
||||
LL | fn bak() -> dyn Trait { unimplemented!() }
|
||||
| ^^^^^^^^^ doesn't have a size known at compile-time
|
||||
|
|
||||
help: use `impl Trait` as the return type if all return paths have the same type but you want to expose only the trait in the signature
|
||||
help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
||||
|
|
||||
LL | fn bak() -> impl Trait { unimplemented!() }
|
||||
| ~~~~~~~~~~
|
||||
help: use a boxed trait object if all return paths implement trait `Trait`
|
||||
| ~~~~
|
||||
help: box the return type, and wrap all of the returned values in `Box::new`
|
||||
|
|
||||
LL | fn bak() -> Box<dyn Trait> { unimplemented!() }
|
||||
| ++++ +
|
||||
LL | fn bak() -> Box<dyn Trait> { Box::new(unimplemented!()) }
|
||||
| ++++ + +++++++++ +
|
||||
|
||||
error[E0746]: return type cannot have an unboxed trait object
|
||||
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:19:13
|
||||
@ -85,22 +87,18 @@ error[E0746]: return type cannot have an unboxed trait object
|
||||
LL | fn bal() -> dyn Trait {
|
||||
| ^^^^^^^^^ doesn't have a size known at compile-time
|
||||
|
|
||||
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
|
||||
= note: if all the returned values were of the same type you could use `impl Trait` as the return type
|
||||
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
|
||||
= note: you can create a new `enum` with a variant for each returned type
|
||||
help: return a boxed trait object instead
|
||||
help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
||||
|
|
||||
LL | fn bal() -> Box<dyn Trait> {
|
||||
| ++++ +
|
||||
help: ... and box this value
|
||||
LL | fn bal() -> impl Trait {
|
||||
| ~~~~
|
||||
help: box the return type, and wrap all of the returned values in `Box::new`
|
||||
|
|
||||
LL | return Box::new(Struct);
|
||||
| +++++++++ +
|
||||
help: ... and box this value
|
||||
LL ~ fn bal() -> Box<dyn Trait> {
|
||||
LL | if true {
|
||||
LL ~ return Box::new(Struct);
|
||||
LL | }
|
||||
LL ~ Box::new(42)
|
||||
|
|
||||
LL | Box::new(42)
|
||||
| +++++++++ +
|
||||
|
||||
error[E0308]: `if` and `else` have incompatible types
|
||||
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:29:9
|
||||
@ -120,22 +118,18 @@ error[E0746]: return type cannot have an unboxed trait object
|
||||
LL | fn bax() -> dyn Trait {
|
||||
| ^^^^^^^^^ doesn't have a size known at compile-time
|
||||
|
|
||||
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
|
||||
= note: if all the returned values were of the same type you could use `impl Trait` as the return type
|
||||
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
|
||||
= note: you can create a new `enum` with a variant for each returned type
|
||||
help: return a boxed trait object instead
|
||||
help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
||||
|
|
||||
LL | fn bax() -> Box<dyn Trait> {
|
||||
| ++++ +
|
||||
help: ... and box this value
|
||||
LL | fn bax() -> impl Trait {
|
||||
| ~~~~
|
||||
help: box the return type, and wrap all of the returned values in `Box::new`
|
||||
|
|
||||
LL | Box::new(Struct)
|
||||
| +++++++++ +
|
||||
help: ... and box this value
|
||||
LL ~ fn bax() -> Box<dyn Trait> {
|
||||
LL | if true {
|
||||
LL ~ Box::new(Struct)
|
||||
LL | } else {
|
||||
LL ~ Box::new(42)
|
||||
|
|
||||
LL | Box::new(42)
|
||||
| +++++++++ +
|
||||
|
||||
error[E0308]: mismatched types
|
||||
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:34:16
|
||||
@ -279,11 +273,18 @@ error[E0746]: return type cannot have an unboxed trait object
|
||||
LL | fn bat() -> dyn Trait {
|
||||
| ^^^^^^^^^ doesn't have a size known at compile-time
|
||||
|
|
||||
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
|
||||
help: use `impl Trait` as the return type, as all return paths are of type `{integer}`, which implements `Trait`
|
||||
help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
||||
|
|
||||
LL | fn bat() -> impl Trait {
|
||||
| ~~~~~~~~~~
|
||||
| ~~~~
|
||||
help: box the return type, and wrap all of the returned values in `Box::new`
|
||||
|
|
||||
LL ~ fn bat() -> Box<dyn Trait> {
|
||||
LL | if true {
|
||||
LL ~ return Box::new(0);
|
||||
LL | }
|
||||
LL ~ Box::new(42)
|
||||
|
|
||||
|
||||
error[E0746]: return type cannot have an unboxed trait object
|
||||
--> $DIR/dyn-trait-return-should-be-impl-trait.rs:66:13
|
||||
@ -291,11 +292,18 @@ error[E0746]: return type cannot have an unboxed trait object
|
||||
LL | fn bay() -> dyn Trait {
|
||||
| ^^^^^^^^^ doesn't have a size known at compile-time
|
||||
|
|
||||
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
|
||||
help: use `impl Trait` as the return type, as all return paths are of type `{integer}`, which implements `Trait`
|
||||
help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
||||
|
|
||||
LL | fn bay() -> impl Trait {
|
||||
| ~~~~~~~~~~
|
||||
| ~~~~
|
||||
help: box the return type, and wrap all of the returned values in `Box::new`
|
||||
|
|
||||
LL ~ fn bay() -> Box<dyn Trait> {
|
||||
LL | if true {
|
||||
LL ~ Box::new(0)
|
||||
LL | } else {
|
||||
LL ~ Box::new(42)
|
||||
|
|
||||
|
||||
error: aborting due to 20 previous errors
|
||||
|
||||
|
||||
@ -171,22 +171,20 @@ error[E0746]: return type cannot have an unboxed trait object
|
||||
LL | fn hat() -> dyn std::fmt::Display {
|
||||
| ^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
|
||||
|
|
||||
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
|
||||
= note: if all the returned values were of the same type you could use `impl std::fmt::Display` as the return type
|
||||
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
|
||||
= note: you can create a new `enum` with a variant for each returned type
|
||||
help: return a boxed trait object instead
|
||||
help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
||||
|
|
||||
LL | fn hat() -> Box<dyn std::fmt::Display> {
|
||||
| ++++ +
|
||||
help: ... and box this value
|
||||
LL | fn hat() -> impl std::fmt::Display {
|
||||
| ~~~~
|
||||
help: box the return type, and wrap all of the returned values in `Box::new`
|
||||
|
|
||||
LL | return Box::new(0i32);
|
||||
| +++++++++ +
|
||||
help: ... and box this value
|
||||
LL ~ fn hat() -> Box<dyn std::fmt::Display> {
|
||||
LL | match 13 {
|
||||
LL | 0 => {
|
||||
LL ~ return Box::new(0i32);
|
||||
LL | }
|
||||
LL | _ => {
|
||||
LL ~ Box::new(1u32)
|
||||
|
|
||||
LL | Box::new(1u32)
|
||||
| +++++++++ +
|
||||
|
||||
error[E0308]: `match` arms have incompatible types
|
||||
--> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:80:14
|
||||
@ -211,26 +209,18 @@ error[E0746]: return type cannot have an unboxed trait object
|
||||
LL | fn pug() -> dyn std::fmt::Display {
|
||||
| ^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
|
||||
|
|
||||
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
|
||||
= note: if all the returned values were of the same type you could use `impl std::fmt::Display` as the return type
|
||||
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
|
||||
= note: you can create a new `enum` with a variant for each returned type
|
||||
help: return a boxed trait object instead
|
||||
help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
||||
|
|
||||
LL | fn pug() -> Box<dyn std::fmt::Display> {
|
||||
| ++++ +
|
||||
help: ... and box this value
|
||||
LL | fn pug() -> impl std::fmt::Display {
|
||||
| ~~~~
|
||||
help: box the return type, and wrap all of the returned values in `Box::new`
|
||||
|
|
||||
LL | 0 => Box::new(0i32),
|
||||
| +++++++++ +
|
||||
help: ... and box this value
|
||||
LL ~ fn pug() -> Box<dyn std::fmt::Display> {
|
||||
LL | match 13 {
|
||||
LL ~ 0 => Box::new(0i32),
|
||||
LL ~ 1 => Box::new(1u32),
|
||||
LL ~ _ => Box::new(2u32),
|
||||
|
|
||||
LL | 1 => Box::new(1u32),
|
||||
| +++++++++ +
|
||||
help: ... and box this value
|
||||
|
|
||||
LL | _ => Box::new(2u32),
|
||||
| +++++++++ +
|
||||
|
||||
error[E0308]: `if` and `else` have incompatible types
|
||||
--> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:89:9
|
||||
@ -255,22 +245,18 @@ error[E0746]: return type cannot have an unboxed trait object
|
||||
LL | fn man() -> dyn std::fmt::Display {
|
||||
| ^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
|
||||
|
|
||||
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
|
||||
= note: if all the returned values were of the same type you could use `impl std::fmt::Display` as the return type
|
||||
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
|
||||
= note: you can create a new `enum` with a variant for each returned type
|
||||
help: return a boxed trait object instead
|
||||
help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
||||
|
|
||||
LL | fn man() -> Box<dyn std::fmt::Display> {
|
||||
| ++++ +
|
||||
help: ... and box this value
|
||||
LL | fn man() -> impl std::fmt::Display {
|
||||
| ~~~~
|
||||
help: box the return type, and wrap all of the returned values in `Box::new`
|
||||
|
|
||||
LL | Box::new(0i32)
|
||||
| +++++++++ +
|
||||
help: ... and box this value
|
||||
LL ~ fn man() -> Box<dyn std::fmt::Display> {
|
||||
LL | if false {
|
||||
LL ~ Box::new(0i32)
|
||||
LL | } else {
|
||||
LL ~ Box::new(1u32)
|
||||
|
|
||||
LL | Box::new(1u32)
|
||||
| +++++++++ +
|
||||
|
||||
error: aborting due to 14 previous errors
|
||||
|
||||
|
||||
@ -4,14 +4,18 @@ error[E0746]: return type cannot have an unboxed trait object
|
||||
LL | dyn AbstractRenderer
|
||||
| ^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
|
||||
|
|
||||
help: use `impl AbstractRenderer` as the return type if all return paths have the same type but you want to expose only the trait in the signature
|
||||
help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
||||
|
|
||||
LL | impl AbstractRenderer
|
||||
| ~~~~
|
||||
help: box the return type, and wrap all of the returned values in `Box::new`
|
||||
|
|
||||
help: use a boxed trait object if all return paths implement trait `AbstractRenderer`
|
||||
LL ~ Box<dyn AbstractRenderer>
|
||||
LL |
|
||||
LL | {
|
||||
LL | match 0 {
|
||||
LL ~ _ => Box::new(unimplemented!())
|
||||
|
|
||||
LL | Box<dyn AbstractRenderer>
|
||||
| ++++ +
|
||||
|
||||
error: aborting due to previous error
|
||||
|
||||
|
||||
@ -23,18 +23,17 @@ error[E0746]: return type cannot have an unboxed trait object
|
||||
LL | fn print_on_or_the_other<'a>(a: i32, b: &'a String) -> dyn Fn() + 'a {
|
||||
| ^^^^^^^^^^^^^ doesn't have a size known at compile-time
|
||||
|
|
||||
= note: for information on trait objects, see <https://doc.rust-lang.org/book/ch17-02-trait-objects.html#using-trait-objects-that-allow-for-values-of-different-types>
|
||||
= note: if all the returned values were of the same type you could use `impl Fn() + 'a` as the return type
|
||||
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
|
||||
= note: you can create a new `enum` with a variant for each returned type
|
||||
help: return a boxed trait object instead
|
||||
help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
||||
|
|
||||
LL | fn print_on_or_the_other<'a>(a: i32, b: &'a String) -> Box<dyn Fn() + 'a> {
|
||||
| ++++ +
|
||||
help: ... and box this value
|
||||
LL | fn print_on_or_the_other<'a>(a: i32, b: &'a String) -> impl Fn() + 'a {
|
||||
| ~~~~
|
||||
help: box the return type, and wrap all of the returned values in `Box::new`
|
||||
|
|
||||
LL ~ fn print_on_or_the_other<'a>(a: i32, b: &'a String) -> Box<dyn Fn() + 'a> {
|
||||
LL |
|
||||
LL | if a % 2 == 0 {
|
||||
LL ~ Box::new(move || println!("{a}"))
|
||||
|
|
||||
LL | Box::new(move || println!("{a}"))
|
||||
| +++++++++ +
|
||||
|
||||
error: aborting due to 2 previous errors
|
||||
|
||||
|
||||
@ -4,11 +4,10 @@ error[E0746]: return type cannot have an unboxed trait object
|
||||
LL | fn or<'a>(first: &'static Validator<'a>, second: &'static Validator<'a>) -> Validator<'a> {
|
||||
| ^^^^^^^^^^^^^ doesn't have a size known at compile-time
|
||||
|
|
||||
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
|
||||
help: use `impl Fn(&'a Something) -> Result<(), ()> + Send + Sync + 'a` as the return type, as all return paths are of type `Box<[closure@$DIR/issue-91801.rs:10:21: 10:70]>`, which implements `Fn(&'a Something) -> Result<(), ()> + Send + Sync + 'a`
|
||||
help: box the return type, and wrap all of the returned values in `Box::new`
|
||||
|
|
||||
LL | fn or<'a>(first: &'static Validator<'a>, second: &'static Validator<'a>) -> impl Fn(&'a Something) -> Result<(), ()> + Send + Sync + 'a {
|
||||
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
LL | fn or<'a>(first: &'static Validator<'a>, second: &'static Validator<'a>) -> Box<Validator<'a>> {
|
||||
| ++++ +
|
||||
|
||||
error: aborting due to previous error
|
||||
|
||||
|
||||
@ -4,11 +4,14 @@ error[E0746]: return type cannot have an unboxed trait object
|
||||
LL | fn or<'a>(first: &'static dyn Foo<'a>) -> dyn Foo<'a> {
|
||||
| ^^^^^^^^^^^ doesn't have a size known at compile-time
|
||||
|
|
||||
= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
|
||||
help: use `impl Foo<'a>` as the return type, as all return paths are of type `Box<_>`, which implements `Foo<'a>`
|
||||
help: return an `impl Trait` instead of a `dyn Trait`, if all returned values are the same type
|
||||
|
|
||||
LL | fn or<'a>(first: &'static dyn Foo<'a>) -> impl Foo<'a> {
|
||||
| ~~~~~~~~~~~~
|
||||
| ~~~~
|
||||
help: box the return type, and wrap all of the returned values in `Box::new`
|
||||
|
|
||||
LL | fn or<'a>(first: &'static dyn Foo<'a>) -> Box<dyn Foo<'a>> {
|
||||
| ++++ +
|
||||
|
||||
error: aborting due to previous error
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user