| use super::{ |
| EvaluationResult, Obligation, ObligationCause, ObligationCauseCode, PredicateObligation, |
| }; |
| |
| use crate::infer::InferCtxt; |
| use crate::traits::error_reporting::suggest_constraining_type_param; |
| |
| use rustc_errors::{error_code, struct_span_err, Applicability, DiagnosticBuilder, Style}; |
| use rustc_hir as hir; |
| use rustc_hir::def::DefKind; |
| use rustc_hir::def_id::DefId; |
| use rustc_hir::intravisit::Visitor; |
| use rustc_hir::Node; |
| use rustc_middle::ty::TypeckTables; |
| use rustc_middle::ty::{ |
| self, AdtKind, DefIdTree, ToPredicate, Ty, TyCtxt, TypeFoldable, WithConstness, |
| }; |
| use rustc_span::symbol::{kw, sym}; |
| use rustc_span::{MultiSpan, Span, DUMMY_SP}; |
| use std::fmt; |
| |
| use super::InferCtxtPrivExt; |
| use crate::traits::query::evaluate_obligation::InferCtxtExt as _; |
| |
| crate trait InferCtxtExt<'tcx> { |
| fn suggest_restricting_param_bound( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| trait_ref: &ty::PolyTraitRef<'_>, |
| body_id: hir::HirId, |
| ); |
| |
| fn suggest_borrow_on_unsized_slice( |
| &self, |
| code: &ObligationCauseCode<'tcx>, |
| err: &mut DiagnosticBuilder<'tcx>, |
| ); |
| |
| fn get_closure_name( |
| &self, |
| def_id: DefId, |
| err: &mut DiagnosticBuilder<'_>, |
| msg: &str, |
| ) -> Option<String>; |
| |
| fn suggest_fn_call( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| err: &mut DiagnosticBuilder<'_>, |
| trait_ref: &ty::Binder<ty::TraitRef<'tcx>>, |
| points_at_arg: bool, |
| ); |
| |
| fn suggest_add_reference_to_arg( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| err: &mut DiagnosticBuilder<'tcx>, |
| trait_ref: &ty::Binder<ty::TraitRef<'tcx>>, |
| points_at_arg: bool, |
| has_custom_message: bool, |
| ) -> bool; |
| |
| fn suggest_remove_reference( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| err: &mut DiagnosticBuilder<'tcx>, |
| trait_ref: &ty::Binder<ty::TraitRef<'tcx>>, |
| ); |
| |
| fn suggest_change_mut( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| err: &mut DiagnosticBuilder<'tcx>, |
| trait_ref: &ty::Binder<ty::TraitRef<'tcx>>, |
| points_at_arg: bool, |
| ); |
| |
| fn suggest_semicolon_removal( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| err: &mut DiagnosticBuilder<'tcx>, |
| span: Span, |
| trait_ref: &ty::Binder<ty::TraitRef<'tcx>>, |
| ); |
| |
| fn suggest_impl_trait( |
| &self, |
| err: &mut DiagnosticBuilder<'tcx>, |
| span: Span, |
| obligation: &PredicateObligation<'tcx>, |
| trait_ref: &ty::Binder<ty::TraitRef<'tcx>>, |
| ) -> bool; |
| |
| fn point_at_returns_when_relevant( |
| &self, |
| err: &mut DiagnosticBuilder<'tcx>, |
| obligation: &PredicateObligation<'tcx>, |
| ); |
| |
| fn report_closure_arg_mismatch( |
| &self, |
| span: Span, |
| found_span: Option<Span>, |
| expected_ref: ty::PolyTraitRef<'tcx>, |
| found: ty::PolyTraitRef<'tcx>, |
| ) -> DiagnosticBuilder<'tcx>; |
| |
| fn suggest_fully_qualified_path( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| def_id: DefId, |
| span: Span, |
| trait_ref: DefId, |
| ); |
| |
| fn maybe_note_obligation_cause_for_async_await( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| obligation: &PredicateObligation<'tcx>, |
| ) -> bool; |
| |
| fn note_obligation_cause_for_async_await( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| target_span: Span, |
| scope_span: &Option<Span>, |
| expr: Option<hir::HirId>, |
| snippet: String, |
| first_generator: DefId, |
| last_generator: Option<DefId>, |
| trait_ref: ty::TraitRef<'_>, |
| target_ty: Ty<'tcx>, |
| tables: &ty::TypeckTables<'_>, |
| obligation: &PredicateObligation<'tcx>, |
| next_code: Option<&ObligationCauseCode<'tcx>>, |
| ); |
| |
| fn note_obligation_cause_code<T>( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| predicate: &T, |
| cause_code: &ObligationCauseCode<'tcx>, |
| obligated_types: &mut Vec<&ty::TyS<'tcx>>, |
| ) where |
| T: fmt::Display; |
| |
| fn suggest_new_overflow_limit(&self, err: &mut DiagnosticBuilder<'_>); |
| } |
| |
| impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { |
| fn suggest_restricting_param_bound( |
| &self, |
| mut err: &mut DiagnosticBuilder<'_>, |
| trait_ref: &ty::PolyTraitRef<'_>, |
| body_id: hir::HirId, |
| ) { |
| let self_ty = trait_ref.self_ty(); |
| let (param_ty, projection) = match &self_ty.kind { |
| ty::Param(_) => (true, None), |
| ty::Projection(projection) => (false, Some(projection)), |
| _ => return, |
| }; |
| |
| let suggest_restriction = |
| |generics: &hir::Generics<'_>, msg, err: &mut DiagnosticBuilder<'_>| { |
| let span = generics.where_clause.span_for_predicates_or_empty_place(); |
| if !span.from_expansion() && span.desugaring_kind().is_none() { |
| err.span_suggestion( |
| generics.where_clause.span_for_predicates_or_empty_place().shrink_to_hi(), |
| &format!("consider further restricting {}", msg), |
| format!( |
| "{} {} ", |
| if !generics.where_clause.predicates.is_empty() { |
| "," |
| } else { |
| " where" |
| }, |
| trait_ref.without_const().to_predicate(), |
| ), |
| Applicability::MachineApplicable, |
| ); |
| } |
| }; |
| |
| // FIXME: Add check for trait bound that is already present, particularly `?Sized` so we |
| // don't suggest `T: Sized + ?Sized`. |
| let mut hir_id = body_id; |
| while let Some(node) = self.tcx.hir().find(hir_id) { |
| match node { |
| hir::Node::TraitItem(hir::TraitItem { |
| generics, |
| kind: hir::TraitItemKind::Fn(..), |
| .. |
| }) if param_ty && self_ty == self.tcx.types.self_param => { |
| // Restricting `Self` for a single method. |
| suggest_restriction(&generics, "`Self`", err); |
| return; |
| } |
| |
| hir::Node::TraitItem(hir::TraitItem { |
| generics, |
| kind: hir::TraitItemKind::Fn(..), |
| .. |
| }) |
| | hir::Node::ImplItem(hir::ImplItem { |
| generics, |
| kind: hir::ImplItemKind::Fn(..), |
| .. |
| }) |
| | hir::Node::Item( |
| hir::Item { kind: hir::ItemKind::Fn(_, generics, _), .. } |
| | hir::Item { kind: hir::ItemKind::Trait(_, _, generics, _, _), .. } |
| | hir::Item { kind: hir::ItemKind::Impl { generics, .. }, .. }, |
| ) if projection.is_some() => { |
| // Missing associated type bound. |
| suggest_restriction(&generics, "the associated type", err); |
| return; |
| } |
| |
| hir::Node::Item( |
| hir::Item { kind: hir::ItemKind::Struct(_, generics), .. } |
| | hir::Item { kind: hir::ItemKind::Enum(_, generics), .. } |
| | hir::Item { kind: hir::ItemKind::Union(_, generics), .. } |
| | hir::Item { kind: hir::ItemKind::Trait(_, _, generics, ..), .. } |
| | hir::Item { kind: hir::ItemKind::Impl { generics, .. }, .. } |
| | hir::Item { kind: hir::ItemKind::Fn(_, generics, _), .. } |
| | hir::Item { kind: hir::ItemKind::TyAlias(_, generics), .. } |
| | hir::Item { kind: hir::ItemKind::TraitAlias(generics, _), .. } |
| | hir::Item { |
| kind: hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. }), .. |
| }, |
| ) |
| | hir::Node::TraitItem(hir::TraitItem { generics, .. }) |
| | hir::Node::ImplItem(hir::ImplItem { generics, .. }) |
| if param_ty => |
| { |
| // Missing generic type parameter bound. |
| let param_name = self_ty.to_string(); |
| let constraint = trait_ref.print_only_trait_path().to_string(); |
| if suggest_constraining_type_param( |
| self.tcx, |
| generics, |
| &mut err, |
| ¶m_name, |
| &constraint, |
| Some(trait_ref.def_id()), |
| ) { |
| return; |
| } |
| } |
| |
| hir::Node::Crate(..) => return, |
| |
| _ => {} |
| } |
| |
| hir_id = self.tcx.hir().get_parent_item(hir_id); |
| } |
| } |
| |
| /// When encountering an assignment of an unsized trait, like `let x = ""[..];`, provide a |
| /// suggestion to borrow the initializer in order to use have a slice instead. |
| fn suggest_borrow_on_unsized_slice( |
| &self, |
| code: &ObligationCauseCode<'tcx>, |
| err: &mut DiagnosticBuilder<'tcx>, |
| ) { |
| if let &ObligationCauseCode::VariableType(hir_id) = code { |
| let parent_node = self.tcx.hir().get_parent_node(hir_id); |
| if let Some(Node::Local(ref local)) = self.tcx.hir().find(parent_node) { |
| if let Some(ref expr) = local.init { |
| if let hir::ExprKind::Index(_, _) = expr.kind { |
| if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(expr.span) { |
| err.span_suggestion( |
| expr.span, |
| "consider borrowing here", |
| format!("&{}", snippet), |
| Applicability::MachineApplicable, |
| ); |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| /// Given a closure's `DefId`, return the given name of the closure. |
| /// |
| /// This doesn't account for reassignments, but it's only used for suggestions. |
| fn get_closure_name( |
| &self, |
| def_id: DefId, |
| err: &mut DiagnosticBuilder<'_>, |
| msg: &str, |
| ) -> Option<String> { |
| let get_name = |
| |err: &mut DiagnosticBuilder<'_>, kind: &hir::PatKind<'_>| -> Option<String> { |
| // Get the local name of this closure. This can be inaccurate because |
| // of the possibility of reassignment, but this should be good enough. |
| match &kind { |
| hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, _, name, None) => { |
| Some(format!("{}", name)) |
| } |
| _ => { |
| err.note(&msg); |
| None |
| } |
| } |
| }; |
| |
| let hir = self.tcx.hir(); |
| let hir_id = hir.as_local_hir_id(def_id)?; |
| let parent_node = hir.get_parent_node(hir_id); |
| match hir.find(parent_node) { |
| Some(hir::Node::Stmt(hir::Stmt { kind: hir::StmtKind::Local(local), .. })) => { |
| get_name(err, &local.pat.kind) |
| } |
| // Different to previous arm because one is `&hir::Local` and the other |
| // is `P<hir::Local>`. |
| Some(hir::Node::Local(local)) => get_name(err, &local.pat.kind), |
| _ => None, |
| } |
| } |
| |
| /// We tried to apply the bound to an `fn` or closure. Check whether calling it would |
| /// evaluate to a type that *would* satisfy the trait binding. If it would, suggest calling |
| /// it: `bar(foo)` → `bar(foo())`. This case is *very* likely to be hit if `foo` is `async`. |
| fn suggest_fn_call( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| err: &mut DiagnosticBuilder<'_>, |
| trait_ref: &ty::Binder<ty::TraitRef<'tcx>>, |
| points_at_arg: bool, |
| ) { |
| let self_ty = trait_ref.self_ty(); |
| let (def_id, output_ty, callable) = match self_ty.kind { |
| ty::Closure(def_id, substs) => (def_id, substs.as_closure().sig().output(), "closure"), |
| ty::FnDef(def_id, _) => (def_id, self_ty.fn_sig(self.tcx).output(), "function"), |
| _ => return, |
| }; |
| let msg = format!("use parentheses to call the {}", callable); |
| |
| let obligation = self.mk_obligation_for_def_id( |
| trait_ref.def_id(), |
| output_ty.skip_binder(), |
| obligation.cause.clone(), |
| obligation.param_env, |
| ); |
| |
| match self.evaluate_obligation(&obligation) { |
| Ok(EvaluationResult::EvaluatedToOk) |
| | Ok(EvaluationResult::EvaluatedToOkModuloRegions) |
| | Ok(EvaluationResult::EvaluatedToAmbig) => {} |
| _ => return, |
| } |
| let hir = self.tcx.hir(); |
| // Get the name of the callable and the arguments to be used in the suggestion. |
| let (snippet, sugg) = match hir.get_if_local(def_id) { |
| Some(hir::Node::Expr(hir::Expr { |
| kind: hir::ExprKind::Closure(_, decl, _, span, ..), |
| .. |
| })) => { |
| err.span_label(*span, "consider calling this closure"); |
| let name = match self.get_closure_name(def_id, err, &msg) { |
| Some(name) => name, |
| None => return, |
| }; |
| let args = decl.inputs.iter().map(|_| "_").collect::<Vec<_>>().join(", "); |
| let sugg = format!("({})", args); |
| (format!("{}{}", name, sugg), sugg) |
| } |
| Some(hir::Node::Item(hir::Item { |
| ident, |
| kind: hir::ItemKind::Fn(.., body_id), |
| .. |
| })) => { |
| err.span_label(ident.span, "consider calling this function"); |
| let body = hir.body(*body_id); |
| let args = body |
| .params |
| .iter() |
| .map(|arg| match &arg.pat.kind { |
| hir::PatKind::Binding(_, _, ident, None) |
| // FIXME: provide a better suggestion when encountering `SelfLower`, it |
| // should suggest a method call. |
| if ident.name != kw::SelfLower => ident.to_string(), |
| _ => "_".to_string(), |
| }) |
| .collect::<Vec<_>>() |
| .join(", "); |
| let sugg = format!("({})", args); |
| (format!("{}{}", ident, sugg), sugg) |
| } |
| _ => return, |
| }; |
| if points_at_arg { |
| // When the obligation error has been ensured to have been caused by |
| // an argument, the `obligation.cause.span` points at the expression |
| // of the argument, so we can provide a suggestion. This is signaled |
| // by `points_at_arg`. Otherwise, we give a more general note. |
| err.span_suggestion_verbose( |
| obligation.cause.span.shrink_to_hi(), |
| &msg, |
| sugg, |
| Applicability::HasPlaceholders, |
| ); |
| } else { |
| err.help(&format!("{}: `{}`", msg, snippet)); |
| } |
| } |
| |
| fn suggest_add_reference_to_arg( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| err: &mut DiagnosticBuilder<'tcx>, |
| trait_ref: &ty::Binder<ty::TraitRef<'tcx>>, |
| points_at_arg: bool, |
| has_custom_message: bool, |
| ) -> bool { |
| if !points_at_arg { |
| return false; |
| } |
| |
| let span = obligation.cause.span; |
| let param_env = obligation.param_env; |
| let trait_ref = trait_ref.skip_binder(); |
| |
| if let ObligationCauseCode::ImplDerivedObligation(obligation) = &obligation.cause.code { |
| // Try to apply the original trait binding obligation by borrowing. |
| let self_ty = trait_ref.self_ty(); |
| let found = self_ty.to_string(); |
| let new_self_ty = self.tcx.mk_imm_ref(self.tcx.lifetimes.re_static, self_ty); |
| let substs = self.tcx.mk_substs_trait(new_self_ty, &[]); |
| let new_trait_ref = ty::TraitRef::new(obligation.parent_trait_ref.def_id(), substs); |
| let new_obligation = Obligation::new( |
| ObligationCause::dummy(), |
| param_env, |
| new_trait_ref.without_const().to_predicate(), |
| ); |
| if self.predicate_must_hold_modulo_regions(&new_obligation) { |
| if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) { |
| // We have a very specific type of error, where just borrowing this argument |
| // might solve the problem. In cases like this, the important part is the |
| // original type obligation, not the last one that failed, which is arbitrary. |
| // Because of this, we modify the error to refer to the original obligation and |
| // return early in the caller. |
| let msg = format!( |
| "the trait bound `{}: {}` is not satisfied", |
| found, |
| obligation.parent_trait_ref.skip_binder().print_only_trait_path(), |
| ); |
| if has_custom_message { |
| err.note(&msg); |
| } else { |
| err.message = vec![(msg, Style::NoStyle)]; |
| } |
| if snippet.starts_with('&') { |
| // This is already a literal borrow and the obligation is failing |
| // somewhere else in the obligation chain. Do not suggest non-sense. |
| return false; |
| } |
| err.span_label( |
| span, |
| &format!( |
| "expected an implementor of trait `{}`", |
| obligation.parent_trait_ref.skip_binder().print_only_trait_path(), |
| ), |
| ); |
| err.span_suggestion( |
| span, |
| "consider borrowing here", |
| format!("&{}", snippet), |
| Applicability::MaybeIncorrect, |
| ); |
| return true; |
| } |
| } |
| } |
| false |
| } |
| |
| /// Whenever references are used by mistake, like `for (i, e) in &vec.iter().enumerate()`, |
| /// suggest removing these references until we reach a type that implements the trait. |
| fn suggest_remove_reference( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| err: &mut DiagnosticBuilder<'tcx>, |
| trait_ref: &ty::Binder<ty::TraitRef<'tcx>>, |
| ) { |
| let trait_ref = trait_ref.skip_binder(); |
| let span = obligation.cause.span; |
| |
| if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) { |
| let refs_number = |
| snippet.chars().filter(|c| !c.is_whitespace()).take_while(|c| *c == '&').count(); |
| if let Some('\'') = snippet.chars().filter(|c| !c.is_whitespace()).nth(refs_number) { |
| // Do not suggest removal of borrow from type arguments. |
| return; |
| } |
| |
| let mut trait_type = trait_ref.self_ty(); |
| |
| for refs_remaining in 0..refs_number { |
| if let ty::Ref(_, t_type, _) = trait_type.kind { |
| trait_type = t_type; |
| |
| let new_obligation = self.mk_obligation_for_def_id( |
| trait_ref.def_id, |
| trait_type, |
| ObligationCause::dummy(), |
| obligation.param_env, |
| ); |
| |
| if self.predicate_may_hold(&new_obligation) { |
| let sp = self |
| .tcx |
| .sess |
| .source_map() |
| .span_take_while(span, |c| c.is_whitespace() || *c == '&'); |
| |
| let remove_refs = refs_remaining + 1; |
| |
| let msg = if remove_refs == 1 { |
| "consider removing the leading `&`-reference".to_string() |
| } else { |
| format!("consider removing {} leading `&`-references", remove_refs) |
| }; |
| |
| err.span_suggestion_short( |
| sp, |
| &msg, |
| String::new(), |
| Applicability::MachineApplicable, |
| ); |
| break; |
| } |
| } else { |
| break; |
| } |
| } |
| } |
| } |
| |
| /// Check if the trait bound is implemented for a different mutability and note it in the |
| /// final error. |
| fn suggest_change_mut( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| err: &mut DiagnosticBuilder<'tcx>, |
| trait_ref: &ty::Binder<ty::TraitRef<'tcx>>, |
| points_at_arg: bool, |
| ) { |
| let span = obligation.cause.span; |
| if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) { |
| let refs_number = |
| snippet.chars().filter(|c| !c.is_whitespace()).take_while(|c| *c == '&').count(); |
| if let Some('\'') = snippet.chars().filter(|c| !c.is_whitespace()).nth(refs_number) { |
| // Do not suggest removal of borrow from type arguments. |
| return; |
| } |
| let trait_ref = self.resolve_vars_if_possible(trait_ref); |
| if trait_ref.has_infer_types_or_consts() { |
| // Do not ICE while trying to find if a reborrow would succeed on a trait with |
| // unresolved bindings. |
| return; |
| } |
| |
| if let ty::Ref(region, t_type, mutability) = trait_ref.skip_binder().self_ty().kind { |
| let trait_type = match mutability { |
| hir::Mutability::Mut => self.tcx.mk_imm_ref(region, t_type), |
| hir::Mutability::Not => self.tcx.mk_mut_ref(region, t_type), |
| }; |
| |
| let new_obligation = self.mk_obligation_for_def_id( |
| trait_ref.skip_binder().def_id, |
| trait_type, |
| ObligationCause::dummy(), |
| obligation.param_env, |
| ); |
| |
| if self.evaluate_obligation_no_overflow(&new_obligation).must_apply_modulo_regions() |
| { |
| let sp = self |
| .tcx |
| .sess |
| .source_map() |
| .span_take_while(span, |c| c.is_whitespace() || *c == '&'); |
| if points_at_arg && mutability == hir::Mutability::Not && refs_number > 0 { |
| err.span_suggestion_verbose( |
| sp, |
| "consider changing this borrow's mutability", |
| "&mut ".to_string(), |
| Applicability::MachineApplicable, |
| ); |
| } else { |
| err.note(&format!( |
| "`{}` is implemented for `{:?}`, but not for `{:?}`", |
| trait_ref.print_only_trait_path(), |
| trait_type, |
| trait_ref.skip_binder().self_ty(), |
| )); |
| } |
| } |
| } |
| } |
| } |
| |
| fn suggest_semicolon_removal( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| err: &mut DiagnosticBuilder<'tcx>, |
| span: Span, |
| trait_ref: &ty::Binder<ty::TraitRef<'tcx>>, |
| ) { |
| let hir = self.tcx.hir(); |
| let parent_node = hir.get_parent_node(obligation.cause.body_id); |
| let node = hir.find(parent_node); |
| if let Some(hir::Node::Item(hir::Item { |
| kind: hir::ItemKind::Fn(sig, _, body_id), .. |
| })) = node |
| { |
| let body = hir.body(*body_id); |
| if let hir::ExprKind::Block(blk, _) = &body.value.kind { |
| if sig.decl.output.span().overlaps(span) |
| && blk.expr.is_none() |
| && "()" == &trait_ref.self_ty().to_string() |
| { |
| // FIXME(estebank): When encountering a method with a trait |
| // bound not satisfied in the return type with a body that has |
| // no return, suggest removal of semicolon on last statement. |
| // Once that is added, close #54771. |
| if let Some(ref stmt) = blk.stmts.last() { |
| let sp = self.tcx.sess.source_map().end_point(stmt.span); |
| err.span_label(sp, "consider removing this semicolon"); |
| } |
| } |
| } |
| } |
| } |
| |
| /// If all conditions are met to identify a returned `dyn Trait`, suggest using `impl Trait` if |
| /// applicable and signal that the error has been expanded appropriately and needs to be |
| /// emitted. |
| fn suggest_impl_trait( |
| &self, |
| err: &mut DiagnosticBuilder<'tcx>, |
| span: Span, |
| obligation: &PredicateObligation<'tcx>, |
| trait_ref: &ty::Binder<ty::TraitRef<'tcx>>, |
| ) -> bool { |
| match obligation.cause.code.peel_derives() { |
| // Only suggest `impl Trait` if the return type is unsized because it is `dyn Trait`. |
| ObligationCauseCode::SizedReturnType => {} |
| _ => return false, |
| } |
| |
| let hir = self.tcx.hir(); |
| let parent_node = hir.get_parent_node(obligation.cause.body_id); |
| let node = hir.find(parent_node); |
| let (sig, body_id) = if let Some(hir::Node::Item(hir::Item { |
| kind: hir::ItemKind::Fn(sig, _, body_id), |
| .. |
| })) = node |
| { |
| (sig, body_id) |
| } else { |
| return false; |
| }; |
| let body = hir.body(*body_id); |
| let trait_ref = self.resolve_vars_if_possible(trait_ref); |
| let ty = trait_ref.skip_binder().self_ty(); |
| let is_object_safe = match ty.kind { |
| ty::Dynamic(predicates, _) => { |
| // If the `dyn Trait` is not object safe, do not suggest `Box<dyn Trait>`. |
| predicates |
| .principal_def_id() |
| .map_or(true, |def_id| self.tcx.object_safety_violations(def_id).is_empty()) |
| } |
| // We only want to suggest `impl Trait` to `dyn Trait`s. |
| // For example, `fn foo() -> str` needs to be filtered out. |
| _ => return false, |
| }; |
| |
| let ret_ty = if let hir::FnRetTy::Return(ret_ty) = sig.decl.output { |
| ret_ty |
| } else { |
| return false; |
| }; |
| |
| // Use `TypeVisitor` instead of the output type directly to find the span of `ty` for |
| // cases like `fn foo() -> (dyn Trait, i32) {}`. |
| // Recursively look for `TraitObject` types and if there's only one, use that span to |
| // suggest `impl Trait`. |
| |
| // Visit to make sure there's a single `return` type to suggest `impl Trait`, |
| // otherwise suggest using `Box<dyn Trait>` or an enum. |
| let mut visitor = ReturnsVisitor::default(); |
| visitor.visit_body(&body); |
| |
| let tables = self.in_progress_tables.map(|t| t.borrow()).unwrap(); |
| |
| let mut ret_types = visitor |
| .returns |
| .iter() |
| .filter_map(|expr| tables.node_type_opt(expr.hir_id)) |
| .map(|ty| self.resolve_vars_if_possible(&ty)); |
| let (last_ty, all_returns_have_same_type) = ret_types.clone().fold( |
| (None, true), |
| |(last_ty, mut same): (std::option::Option<Ty<'_>>, bool), ty| { |
| let ty = self.resolve_vars_if_possible(&ty); |
| same &= last_ty.map_or(true, |last_ty| last_ty == ty) && ty.kind != ty::Error; |
| (Some(ty), same) |
| }, |
| ); |
| let all_returns_conform_to_trait = |
| if let Some(ty_ret_ty) = tables.node_type_opt(ret_ty.hir_id) { |
| match ty_ret_ty.kind { |
| ty::Dynamic(predicates, _) => { |
| let cause = ObligationCause::misc(ret_ty.span, ret_ty.hir_id); |
| let param_env = ty::ParamEnv::empty(); |
| ret_types.all(|returned_ty| { |
| predicates.iter().all(|predicate| { |
| let pred = predicate.with_self_ty(self.tcx, returned_ty); |
| let obl = Obligation::new(cause.clone(), param_env, pred); |
| self.predicate_may_hold(&obl) |
| }) |
| }) |
| } |
| _ => false, |
| } |
| } else { |
| true |
| }; |
| |
| let (snippet, last_ty) = |
| if let (true, hir::TyKind::TraitObject(..), Ok(snippet), true, Some(last_ty)) = ( |
| // Verify that we're dealing with a return `dyn Trait` |
| ret_ty.span.overlaps(span), |
| &ret_ty.kind, |
| self.tcx.sess.source_map().span_to_snippet(ret_ty.span), |
| // If any of the return types does not conform to the trait, then we can't |
| // suggest `impl Trait` nor trait objects, it is a type mismatch error. |
| all_returns_conform_to_trait, |
| last_ty, |
| ) { |
| (snippet, last_ty) |
| } else { |
| return false; |
| }; |
| err.code(error_code!(E0746)); |
| err.set_primary_message("return type cannot have an unboxed trait object"); |
| err.children.clear(); |
| let impl_trait_msg = "for information on `impl Trait`, see \ |
| <https://doc.rust-lang.org/book/ch10-02-traits.html\ |
| #returning-types-that-implement-traits>"; |
| let trait_obj_msg = "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>"; |
| let has_dyn = snippet.split_whitespace().next().map_or(false, |s| s == "dyn"); |
| let trait_obj = if has_dyn { &snippet[4..] } else { &snippet[..] }; |
| if all_returns_have_same_type { |
| // Suggest `-> impl Trait`. |
| err.span_suggestion( |
| ret_ty.span, |
| &format!( |
| "return `impl {1}` instead, as all return paths are of type `{}`, \ |
| which implements `{1}`", |
| last_ty, trait_obj, |
| ), |
| format!("impl {}", trait_obj), |
| Applicability::MachineApplicable, |
| ); |
| err.note(impl_trait_msg); |
| } else { |
| if is_object_safe { |
| // Suggest `-> Box<dyn Trait>` and `Box::new(returned_value)`. |
| // Get all the return values and collect their span and suggestion. |
| let mut suggestions = visitor |
| .returns |
| .iter() |
| .map(|expr| { |
| ( |
| expr.span, |
| format!( |
| "Box::new({})", |
| self.tcx.sess.source_map().span_to_snippet(expr.span).unwrap() |
| ), |
| ) |
| }) |
| .collect::<Vec<_>>(); |
| // Add the suggestion for the return type. |
| suggestions.push((ret_ty.span, format!("Box<dyn {}>", trait_obj))); |
| err.multipart_suggestion( |
| "return a boxed trait object instead", |
| suggestions, |
| Applicability::MaybeIncorrect, |
| ); |
| } else { |
| // This is currently not possible to trigger because E0038 takes precedence, but |
| // leave it in for completeness in case anything changes in an earlier stage. |
| err.note(&format!( |
| "if trait `{}` was object safe, you could return a trait object", |
| trait_obj, |
| )); |
| } |
| err.note(trait_obj_msg); |
| err.note(&format!( |
| "if all the returned values were of the same type you could use \ |
| `impl {}` as the return type", |
| trait_obj, |
| )); |
| err.note(impl_trait_msg); |
| err.note("you can create a new `enum` with a variant for each returned type"); |
| } |
| true |
| } |
| |
| fn point_at_returns_when_relevant( |
| &self, |
| err: &mut DiagnosticBuilder<'tcx>, |
| obligation: &PredicateObligation<'tcx>, |
| ) { |
| match obligation.cause.code.peel_derives() { |
| ObligationCauseCode::SizedReturnType => {} |
| _ => return, |
| } |
| |
| let hir = self.tcx.hir(); |
| let parent_node = hir.get_parent_node(obligation.cause.body_id); |
| let node = hir.find(parent_node); |
| if let Some(hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(_, _, body_id), .. })) = |
| node |
| { |
| let body = hir.body(*body_id); |
| // Point at all the `return`s in the function as they have failed trait bounds. |
| let mut visitor = ReturnsVisitor::default(); |
| visitor.visit_body(&body); |
| let tables = self.in_progress_tables.map(|t| t.borrow()).unwrap(); |
| for expr in &visitor.returns { |
| if let Some(returned_ty) = tables.node_type_opt(expr.hir_id) { |
| let ty = self.resolve_vars_if_possible(&returned_ty); |
| err.span_label(expr.span, &format!("this returned value is of type `{}`", ty)); |
| } |
| } |
| } |
| } |
| |
| fn report_closure_arg_mismatch( |
| &self, |
| span: Span, |
| found_span: Option<Span>, |
| expected_ref: ty::PolyTraitRef<'tcx>, |
| found: ty::PolyTraitRef<'tcx>, |
| ) -> DiagnosticBuilder<'tcx> { |
| crate fn build_fn_sig_string<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| trait_ref: &ty::TraitRef<'tcx>, |
| ) -> String { |
| let inputs = trait_ref.substs.type_at(1); |
| let sig = if let ty::Tuple(inputs) = inputs.kind { |
| tcx.mk_fn_sig( |
| inputs.iter().map(|k| k.expect_ty()), |
| tcx.mk_ty_infer(ty::TyVar(ty::TyVid { index: 0 })), |
| false, |
| hir::Unsafety::Normal, |
| ::rustc_target::spec::abi::Abi::Rust, |
| ) |
| } else { |
| tcx.mk_fn_sig( |
| ::std::iter::once(inputs), |
| tcx.mk_ty_infer(ty::TyVar(ty::TyVid { index: 0 })), |
| false, |
| hir::Unsafety::Normal, |
| ::rustc_target::spec::abi::Abi::Rust, |
| ) |
| }; |
| ty::Binder::bind(sig).to_string() |
| } |
| |
| let argument_is_closure = expected_ref.skip_binder().substs.type_at(0).is_closure(); |
| let mut err = struct_span_err!( |
| self.tcx.sess, |
| span, |
| E0631, |
| "type mismatch in {} arguments", |
| if argument_is_closure { "closure" } else { "function" } |
| ); |
| |
| let found_str = format!( |
| "expected signature of `{}`", |
| build_fn_sig_string(self.tcx, found.skip_binder()) |
| ); |
| err.span_label(span, found_str); |
| |
| let found_span = found_span.unwrap_or(span); |
| let expected_str = format!( |
| "found signature of `{}`", |
| build_fn_sig_string(self.tcx, expected_ref.skip_binder()) |
| ); |
| err.span_label(found_span, expected_str); |
| |
| err |
| } |
| |
| fn suggest_fully_qualified_path( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| def_id: DefId, |
| span: Span, |
| trait_ref: DefId, |
| ) { |
| if let Some(assoc_item) = self.tcx.opt_associated_item(def_id) { |
| if let ty::AssocKind::Const | ty::AssocKind::Type = assoc_item.kind { |
| err.note(&format!( |
| "{}s cannot be accessed directly on a `trait`, they can only be \ |
| accessed through a specific `impl`", |
| assoc_item.kind.suggestion_descr(), |
| )); |
| err.span_suggestion( |
| span, |
| "use the fully qualified path to an implementation", |
| format!("<Type as {}>::{}", self.tcx.def_path_str(trait_ref), assoc_item.ident), |
| Applicability::HasPlaceholders, |
| ); |
| } |
| } |
| } |
| |
| /// Adds an async-await specific note to the diagnostic when the future does not implement |
| /// an auto trait because of a captured type. |
| /// |
| /// ```ignore (diagnostic) |
| /// note: future does not implement `Qux` as this value is used across an await |
| /// --> $DIR/issue-64130-3-other.rs:17:5 |
| /// | |
| /// LL | let x = Foo; |
| /// | - has type `Foo` |
| /// LL | baz().await; |
| /// | ^^^^^^^^^^^ await occurs here, with `x` maybe used later |
| /// LL | } |
| /// | - `x` is later dropped here |
| /// ``` |
| /// |
| /// When the diagnostic does not implement `Send` or `Sync` specifically, then the diagnostic |
| /// is "replaced" with a different message and a more specific error. |
| /// |
| /// ```ignore (diagnostic) |
| /// error: future cannot be sent between threads safely |
| /// --> $DIR/issue-64130-2-send.rs:21:5 |
| /// | |
| /// LL | fn is_send<T: Send>(t: T) { } |
| /// | ------- ---- required by this bound in `is_send` |
| /// ... |
| /// LL | is_send(bar()); |
| /// | ^^^^^^^ future returned by `bar` is not send |
| /// | |
| /// = help: within `impl std::future::Future`, the trait `std::marker::Send` is not |
| /// implemented for `Foo` |
| /// note: future is not send as this value is used across an await |
| /// --> $DIR/issue-64130-2-send.rs:15:5 |
| /// | |
| /// LL | let x = Foo; |
| /// | - has type `Foo` |
| /// LL | baz().await; |
| /// | ^^^^^^^^^^^ await occurs here, with `x` maybe used later |
| /// LL | } |
| /// | - `x` is later dropped here |
| /// ``` |
| /// |
| /// Returns `true` if an async-await specific note was added to the diagnostic. |
| fn maybe_note_obligation_cause_for_async_await( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| obligation: &PredicateObligation<'tcx>, |
| ) -> bool { |
| debug!( |
| "maybe_note_obligation_cause_for_async_await: obligation.predicate={:?} \ |
| obligation.cause.span={:?}", |
| obligation.predicate, obligation.cause.span |
| ); |
| let source_map = self.tcx.sess.source_map(); |
| |
| // Attempt to detect an async-await error by looking at the obligation causes, looking |
| // for a generator to be present. |
| // |
| // When a future does not implement a trait because of a captured type in one of the |
| // generators somewhere in the call stack, then the result is a chain of obligations. |
| // |
| // Given a `async fn` A that calls a `async fn` B which captures a non-send type and that |
| // future is passed as an argument to a function C which requires a `Send` type, then the |
| // chain looks something like this: |
| // |
| // - `BuiltinDerivedObligation` with a generator witness (B) |
| // - `BuiltinDerivedObligation` with a generator (B) |
| // - `BuiltinDerivedObligation` with `std::future::GenFuture` (B) |
| // - `BuiltinDerivedObligation` with `impl std::future::Future` (B) |
| // - `BuiltinDerivedObligation` with `impl std::future::Future` (B) |
| // - `BuiltinDerivedObligation` with a generator witness (A) |
| // - `BuiltinDerivedObligation` with a generator (A) |
| // - `BuiltinDerivedObligation` with `std::future::GenFuture` (A) |
| // - `BuiltinDerivedObligation` with `impl std::future::Future` (A) |
| // - `BuiltinDerivedObligation` with `impl std::future::Future` (A) |
| // - `BindingObligation` with `impl_send (Send requirement) |
| // |
| // The first obligation in the chain is the most useful and has the generator that captured |
| // the type. The last generator has information about where the bound was introduced. At |
| // least one generator should be present for this diagnostic to be modified. |
| let (mut trait_ref, mut target_ty) = match obligation.predicate { |
| ty::Predicate::Trait(p, _) => { |
| (Some(p.skip_binder().trait_ref), Some(p.skip_binder().self_ty())) |
| } |
| _ => (None, None), |
| }; |
| let mut generator = None; |
| let mut last_generator = None; |
| let mut next_code = Some(&obligation.cause.code); |
| while let Some(code) = next_code { |
| debug!("maybe_note_obligation_cause_for_async_await: code={:?}", code); |
| match code { |
| ObligationCauseCode::BuiltinDerivedObligation(derived_obligation) |
| | ObligationCauseCode::ImplDerivedObligation(derived_obligation) => { |
| let ty = derived_obligation.parent_trait_ref.self_ty(); |
| debug!( |
| "maybe_note_obligation_cause_for_async_await: \ |
| parent_trait_ref={:?} self_ty.kind={:?}", |
| derived_obligation.parent_trait_ref, ty.kind |
| ); |
| |
| match ty.kind { |
| ty::Generator(did, ..) => { |
| generator = generator.or(Some(did)); |
| last_generator = Some(did); |
| } |
| ty::GeneratorWitness(..) => {} |
| _ if generator.is_none() => { |
| trait_ref = Some(*derived_obligation.parent_trait_ref.skip_binder()); |
| target_ty = Some(ty); |
| } |
| _ => {} |
| } |
| |
| next_code = Some(derived_obligation.parent_code.as_ref()); |
| } |
| _ => break, |
| } |
| } |
| |
| // Only continue if a generator was found. |
| debug!( |
| "maybe_note_obligation_cause_for_async_await: generator={:?} trait_ref={:?} \ |
| target_ty={:?}", |
| generator, trait_ref, target_ty |
| ); |
| let (generator_did, trait_ref, target_ty) = match (generator, trait_ref, target_ty) { |
| (Some(generator_did), Some(trait_ref), Some(target_ty)) => { |
| (generator_did, trait_ref, target_ty) |
| } |
| _ => return false, |
| }; |
| |
| let span = self.tcx.def_span(generator_did); |
| |
| // Do not ICE on closure typeck (#66868). |
| if self.tcx.hir().as_local_hir_id(generator_did).is_none() { |
| return false; |
| } |
| |
| // Get the tables from the infcx if the generator is the function we are |
| // currently type-checking; otherwise, get them by performing a query. |
| // This is needed to avoid cycles. |
| let in_progress_tables = self.in_progress_tables.map(|t| t.borrow()); |
| let generator_did_root = self.tcx.closure_base_def_id(generator_did); |
| debug!( |
| "maybe_note_obligation_cause_for_async_await: generator_did={:?} \ |
| generator_did_root={:?} in_progress_tables.hir_owner={:?} span={:?}", |
| generator_did, |
| generator_did_root, |
| in_progress_tables.as_ref().map(|t| t.hir_owner), |
| span |
| ); |
| let query_tables; |
| let tables: &TypeckTables<'tcx> = match &in_progress_tables { |
| Some(t) if t.hir_owner.map(|owner| owner.to_def_id()) == Some(generator_did_root) => t, |
| _ => { |
| query_tables = self.tcx.typeck_tables_of(generator_did); |
| &query_tables |
| } |
| }; |
| |
| // Look for a type inside the generator interior that matches the target type to get |
| // a span. |
| let target_ty_erased = self.tcx.erase_regions(&target_ty); |
| let target_span = tables |
| .generator_interior_types |
| .iter() |
| .find(|ty::GeneratorInteriorTypeCause { ty, .. }| { |
| // Careful: the regions for types that appear in the |
| // generator interior are not generally known, so we |
| // want to erase them when comparing (and anyway, |
| // `Send` and other bounds are generally unaffected by |
| // the choice of region). When erasing regions, we |
| // also have to erase late-bound regions. This is |
| // because the types that appear in the generator |
| // interior generally contain "bound regions" to |
| // represent regions that are part of the suspended |
| // generator frame. Bound regions are preserved by |
| // `erase_regions` and so we must also call |
| // `erase_late_bound_regions`. |
| let ty_erased = self.tcx.erase_late_bound_regions(&ty::Binder::bind(*ty)); |
| let ty_erased = self.tcx.erase_regions(&ty_erased); |
| let eq = ty::TyS::same_type(ty_erased, target_ty_erased); |
| debug!( |
| "maybe_note_obligation_cause_for_async_await: ty_erased={:?} \ |
| target_ty_erased={:?} eq={:?}", |
| ty_erased, target_ty_erased, eq |
| ); |
| eq |
| }) |
| .map(|ty::GeneratorInteriorTypeCause { span, scope_span, expr, .. }| { |
| (span, source_map.span_to_snippet(*span), scope_span, expr) |
| }); |
| |
| debug!( |
| "maybe_note_obligation_cause_for_async_await: target_ty={:?} \ |
| generator_interior_types={:?} target_span={:?}", |
| target_ty, tables.generator_interior_types, target_span |
| ); |
| if let Some((target_span, Ok(snippet), scope_span, expr)) = target_span { |
| self.note_obligation_cause_for_async_await( |
| err, |
| *target_span, |
| scope_span, |
| *expr, |
| snippet, |
| generator_did, |
| last_generator, |
| trait_ref, |
| target_ty, |
| tables, |
| obligation, |
| next_code, |
| ); |
| true |
| } else { |
| false |
| } |
| } |
| |
| /// Unconditionally adds the diagnostic note described in |
| /// `maybe_note_obligation_cause_for_async_await`'s documentation comment. |
| fn note_obligation_cause_for_async_await( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| target_span: Span, |
| scope_span: &Option<Span>, |
| expr: Option<hir::HirId>, |
| snippet: String, |
| first_generator: DefId, |
| last_generator: Option<DefId>, |
| trait_ref: ty::TraitRef<'_>, |
| target_ty: Ty<'tcx>, |
| tables: &ty::TypeckTables<'_>, |
| obligation: &PredicateObligation<'tcx>, |
| next_code: Option<&ObligationCauseCode<'tcx>>, |
| ) { |
| let source_map = self.tcx.sess.source_map(); |
| |
| let is_async_fn = self |
| .tcx |
| .parent(first_generator) |
| .map(|parent_did| self.tcx.asyncness(parent_did)) |
| .map(|parent_asyncness| parent_asyncness == hir::IsAsync::Async) |
| .unwrap_or(false); |
| let is_async_move = self |
| .tcx |
| .hir() |
| .as_local_hir_id(first_generator) |
| .and_then(|hir_id| self.tcx.hir().maybe_body_owned_by(hir_id)) |
| .map(|body_id| self.tcx.hir().body(body_id)) |
| .and_then(|body| body.generator_kind()) |
| .map(|generator_kind| match generator_kind { |
| hir::GeneratorKind::Async(..) => true, |
| _ => false, |
| }) |
| .unwrap_or(false); |
| let await_or_yield = if is_async_fn || is_async_move { "await" } else { "yield" }; |
| |
| // Special case the primary error message when send or sync is the trait that was |
| // not implemented. |
| let is_send = self.tcx.is_diagnostic_item(sym::send_trait, trait_ref.def_id); |
| let is_sync = self.tcx.is_diagnostic_item(sym::sync_trait, trait_ref.def_id); |
| let hir = self.tcx.hir(); |
| let trait_explanation = if is_send || is_sync { |
| let (trait_name, trait_verb) = |
| if is_send { ("`Send`", "sent") } else { ("`Sync`", "shared") }; |
| |
| err.clear_code(); |
| err.set_primary_message(format!( |
| "future cannot be {} between threads safely", |
| trait_verb |
| )); |
| |
| let original_span = err.span.primary_span().unwrap(); |
| let mut span = MultiSpan::from_span(original_span); |
| |
| let message = if let Some(name) = last_generator |
| .and_then(|generator_did| self.tcx.parent(generator_did)) |
| .and_then(|parent_did| hir.as_local_hir_id(parent_did)) |
| .and_then(|parent_hir_id| hir.opt_name(parent_hir_id)) |
| { |
| format!("future returned by `{}` is not {}", name, trait_name) |
| } else { |
| format!("future is not {}", trait_name) |
| }; |
| |
| span.push_span_label(original_span, message); |
| err.set_span(span); |
| |
| format!("is not {}", trait_name) |
| } else { |
| format!("does not implement `{}`", trait_ref.print_only_trait_path()) |
| }; |
| |
| // Look at the last interior type to get a span for the `.await`. |
| let await_span = tables.generator_interior_types.iter().map(|t| t.span).last().unwrap(); |
| let mut span = MultiSpan::from_span(await_span); |
| span.push_span_label( |
| await_span, |
| format!("{} occurs here, with `{}` maybe used later", await_or_yield, snippet), |
| ); |
| |
| span.push_span_label(target_span, format!("has type `{}`", target_ty)); |
| |
| // If available, use the scope span to annotate the drop location. |
| if let Some(scope_span) = scope_span { |
| span.push_span_label( |
| source_map.end_point(*scope_span), |
| format!("`{}` is later dropped here", snippet), |
| ); |
| } |
| |
| err.span_note( |
| span, |
| &format!( |
| "future {} as this value is used across an {}", |
| trait_explanation, await_or_yield, |
| ), |
| ); |
| |
| if let Some(expr_id) = expr { |
| let expr = hir.expect_expr(expr_id); |
| debug!("target_ty evaluated from {:?}", expr); |
| |
| let parent = hir.get_parent_node(expr_id); |
| if let Some(hir::Node::Expr(e)) = hir.find(parent) { |
| let parent_span = hir.span(parent); |
| let parent_did = parent.owner.to_def_id(); |
| // ```rust |
| // impl T { |
| // fn foo(&self) -> i32 {} |
| // } |
| // T.foo(); |
| // ^^^^^^^ a temporary `&T` created inside this method call due to `&self` |
| // ``` |
| // |
| let is_region_borrow = |
| tables.expr_adjustments(expr).iter().any(|adj| adj.is_region_borrow()); |
| |
| // ```rust |
| // struct Foo(*const u8); |
| // bar(Foo(std::ptr::null())).await; |
| // ^^^^^^^^^^^^^^^^^^^^^ raw-ptr `*T` created inside this struct ctor. |
| // ``` |
| debug!("parent_def_kind: {:?}", self.tcx.def_kind(parent_did)); |
| let is_raw_borrow_inside_fn_like_call = match self.tcx.def_kind(parent_did) { |
| Some(DefKind::Fn) | Some(DefKind::Ctor(..)) => target_ty.is_unsafe_ptr(), |
| _ => false, |
| }; |
| |
| if (tables.is_method_call(e) && is_region_borrow) |
| || is_raw_borrow_inside_fn_like_call |
| { |
| err.span_help( |
| parent_span, |
| "consider moving this into a `let` \ |
| binding to create a shorter lived borrow", |
| ); |
| } |
| } |
| } |
| |
| // Add a note for the item obligation that remains - normally a note pointing to the |
| // bound that introduced the obligation (e.g. `T: Send`). |
| debug!("note_obligation_cause_for_async_await: next_code={:?}", next_code); |
| self.note_obligation_cause_code( |
| err, |
| &obligation.predicate, |
| next_code.unwrap(), |
| &mut Vec::new(), |
| ); |
| } |
| |
| fn note_obligation_cause_code<T>( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| predicate: &T, |
| cause_code: &ObligationCauseCode<'tcx>, |
| obligated_types: &mut Vec<&ty::TyS<'tcx>>, |
| ) where |
| T: fmt::Display, |
| { |
| let tcx = self.tcx; |
| match *cause_code { |
| ObligationCauseCode::ExprAssignable |
| | ObligationCauseCode::MatchExpressionArm { .. } |
| | ObligationCauseCode::Pattern { .. } |
| | ObligationCauseCode::IfExpression { .. } |
| | ObligationCauseCode::IfExpressionWithNoElse |
| | ObligationCauseCode::MainFunctionType |
| | ObligationCauseCode::StartFunctionType |
| | ObligationCauseCode::IntrinsicType |
| | ObligationCauseCode::MethodReceiver |
| | ObligationCauseCode::ReturnNoExpression |
| | ObligationCauseCode::MiscObligation => {} |
| ObligationCauseCode::SliceOrArrayElem => { |
| err.note("slice and array elements must have `Sized` type"); |
| } |
| ObligationCauseCode::TupleElem => { |
| err.note("only the last element of a tuple may have a dynamically sized type"); |
| } |
| ObligationCauseCode::ProjectionWf(data) => { |
| err.note(&format!("required so that the projection `{}` is well-formed", data,)); |
| } |
| ObligationCauseCode::ReferenceOutlivesReferent(ref_ty) => { |
| err.note(&format!( |
| "required so that reference `{}` does not outlive its referent", |
| ref_ty, |
| )); |
| } |
| ObligationCauseCode::ObjectTypeBound(object_ty, region) => { |
| err.note(&format!( |
| "required so that the lifetime bound of `{}` for `{}` is satisfied", |
| region, object_ty, |
| )); |
| } |
| ObligationCauseCode::ItemObligation(item_def_id) => { |
| let item_name = tcx.def_path_str(item_def_id); |
| let msg = format!("required by `{}`", item_name); |
| |
| if let Some(sp) = tcx.hir().span_if_local(item_def_id) { |
| let sp = tcx.sess.source_map().guess_head_span(sp); |
| err.span_label(sp, &msg); |
| } else { |
| err.note(&msg); |
| } |
| } |
| ObligationCauseCode::BindingObligation(item_def_id, span) => { |
| let item_name = tcx.def_path_str(item_def_id); |
| let msg = format!("required by this bound in `{}`", item_name); |
| if let Some(ident) = tcx.opt_item_name(item_def_id) { |
| err.span_label(ident.span, ""); |
| } |
| if span != DUMMY_SP { |
| err.span_label(span, &msg); |
| } else { |
| err.note(&msg); |
| } |
| } |
| ObligationCauseCode::ObjectCastObligation(object_ty) => { |
| err.note(&format!( |
| "required for the cast to the object type `{}`", |
| self.ty_to_string(object_ty) |
| )); |
| } |
| ObligationCauseCode::Coercion { source: _, target } => { |
| err.note(&format!("required by cast to type `{}`", self.ty_to_string(target))); |
| } |
| ObligationCauseCode::RepeatVec(suggest_const_in_array_repeat_expressions) => { |
| err.note( |
| "the `Copy` trait is required because the repeated element will be copied", |
| ); |
| if suggest_const_in_array_repeat_expressions { |
| err.note( |
| "this array initializer can be evaluated at compile-time, see issue \ |
| #48147 <https://github.com/rust-lang/rust/issues/49147> \ |
| for more information", |
| ); |
| if tcx.sess.opts.unstable_features.is_nightly_build() { |
| err.help( |
| "add `#![feature(const_in_array_repeat_expressions)]` to the \ |
| crate attributes to enable", |
| ); |
| } |
| } |
| } |
| ObligationCauseCode::VariableType(_) => { |
| err.note("all local variables must have a statically known size"); |
| if !self.tcx.features().unsized_locals { |
| err.help("unsized locals are gated as an unstable feature"); |
| } |
| } |
| ObligationCauseCode::SizedArgumentType => { |
| err.note("all function arguments must have a statically known size"); |
| if !self.tcx.features().unsized_locals { |
| err.help("unsized locals are gated as an unstable feature"); |
| } |
| } |
| ObligationCauseCode::SizedReturnType => { |
| err.note("the return type of a function must have a statically known size"); |
| } |
| ObligationCauseCode::SizedYieldType => { |
| err.note("the yield type of a generator must have a statically known size"); |
| } |
| ObligationCauseCode::AssignmentLhsSized => { |
| err.note("the left-hand-side of an assignment must have a statically known size"); |
| } |
| ObligationCauseCode::TupleInitializerSized => { |
| err.note("tuples must have a statically known size to be initialized"); |
| } |
| ObligationCauseCode::StructInitializerSized => { |
| err.note("structs must have a statically known size to be initialized"); |
| } |
| ObligationCauseCode::FieldSized { adt_kind: ref item, last } => match *item { |
| AdtKind::Struct => { |
| if last { |
| err.note( |
| "the last field of a packed struct may only have a \ |
| dynamically sized type if it does not need drop to be run", |
| ); |
| } else { |
| err.note( |
| "only the last field of a struct may have a dynamically sized type", |
| ); |
| } |
| } |
| AdtKind::Union => { |
| err.note("no field of a union may have a dynamically sized type"); |
| } |
| AdtKind::Enum => { |
| err.note("no field of an enum variant may have a dynamically sized type"); |
| } |
| }, |
| ObligationCauseCode::ConstSized => { |
| err.note("constant expressions must have a statically known size"); |
| } |
| ObligationCauseCode::ConstPatternStructural => { |
| err.note("constants used for pattern-matching must derive `PartialEq` and `Eq`"); |
| } |
| ObligationCauseCode::SharedStatic => { |
| err.note("shared static variables must have a type that implements `Sync`"); |
| } |
| ObligationCauseCode::BuiltinDerivedObligation(ref data) => { |
| let parent_trait_ref = self.resolve_vars_if_possible(&data.parent_trait_ref); |
| let ty = parent_trait_ref.skip_binder().self_ty(); |
| err.note(&format!("required because it appears within the type `{}`", ty)); |
| obligated_types.push(ty); |
| |
| let parent_predicate = parent_trait_ref.without_const().to_predicate(); |
| if !self.is_recursive_obligation(obligated_types, &data.parent_code) { |
| self.note_obligation_cause_code( |
| err, |
| &parent_predicate, |
| &data.parent_code, |
| obligated_types, |
| ); |
| } |
| } |
| ObligationCauseCode::ImplDerivedObligation(ref data) => { |
| let parent_trait_ref = self.resolve_vars_if_possible(&data.parent_trait_ref); |
| err.note(&format!( |
| "required because of the requirements on the impl of `{}` for `{}`", |
| parent_trait_ref.print_only_trait_path(), |
| parent_trait_ref.skip_binder().self_ty() |
| )); |
| let parent_predicate = parent_trait_ref.without_const().to_predicate(); |
| self.note_obligation_cause_code( |
| err, |
| &parent_predicate, |
| &data.parent_code, |
| obligated_types, |
| ); |
| } |
| ObligationCauseCode::CompareImplMethodObligation { .. } => { |
| err.note(&format!( |
| "the requirement `{}` appears on the impl method \ |
| but not on the corresponding trait method", |
| predicate |
| )); |
| } |
| ObligationCauseCode::CompareImplTypeObligation { .. } => { |
| err.note(&format!( |
| "the requirement `{}` appears on the associated impl type \ |
| but not on the corresponding associated trait type", |
| predicate |
| )); |
| } |
| ObligationCauseCode::ReturnType |
| | ObligationCauseCode::ReturnValue(_) |
| | ObligationCauseCode::BlockTailExpression(_) => (), |
| ObligationCauseCode::TrivialBound => { |
| err.help("see issue #48214"); |
| if tcx.sess.opts.unstable_features.is_nightly_build() { |
| err.help("add `#![feature(trivial_bounds)]` to the crate attributes to enable"); |
| } |
| } |
| ObligationCauseCode::AssocTypeBound(ref data) => { |
| err.span_label(data.original, "associated type defined here"); |
| if let Some(sp) = data.impl_span { |
| err.span_label(sp, "in this `impl` item"); |
| } |
| for sp in &data.bounds { |
| err.span_label(*sp, "restricted in this bound"); |
| } |
| } |
| } |
| } |
| |
| fn suggest_new_overflow_limit(&self, err: &mut DiagnosticBuilder<'_>) { |
| let current_limit = self.tcx.sess.recursion_limit.get(); |
| let suggested_limit = current_limit * 2; |
| err.help(&format!( |
| "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate (`{}`)", |
| suggested_limit, self.tcx.crate_name, |
| )); |
| } |
| } |
| |
| /// Collect all the returned expressions within the input expression. |
| /// Used to point at the return spans when we want to suggest some change to them. |
| #[derive(Default)] |
| struct ReturnsVisitor<'v> { |
| returns: Vec<&'v hir::Expr<'v>>, |
| in_block_tail: bool, |
| } |
| |
| impl<'v> Visitor<'v> for ReturnsVisitor<'v> { |
| type Map = hir::intravisit::ErasedMap<'v>; |
| |
| fn nested_visit_map(&mut self) -> hir::intravisit::NestedVisitorMap<Self::Map> { |
| hir::intravisit::NestedVisitorMap::None |
| } |
| |
| fn visit_expr(&mut self, ex: &'v hir::Expr<'v>) { |
| // Visit every expression to detect `return` paths, either through the function's tail |
| // expression or `return` statements. We walk all nodes to find `return` statements, but |
| // we only care about tail expressions when `in_block_tail` is `true`, which means that |
| // they're in the return path of the function body. |
| match ex.kind { |
| hir::ExprKind::Ret(Some(ex)) => { |
| self.returns.push(ex); |
| } |
| hir::ExprKind::Block(block, _) if self.in_block_tail => { |
| self.in_block_tail = false; |
| for stmt in block.stmts { |
| hir::intravisit::walk_stmt(self, stmt); |
| } |
| self.in_block_tail = true; |
| if let Some(expr) = block.expr { |
| self.visit_expr(expr); |
| } |
| } |
| hir::ExprKind::Match(_, arms, _) if self.in_block_tail => { |
| for arm in arms { |
| self.visit_expr(arm.body); |
| } |
| } |
| // We need to walk to find `return`s in the entire body. |
| _ if !self.in_block_tail => hir::intravisit::walk_expr(self, ex), |
| _ => self.returns.push(ex), |
| } |
| } |
| |
| fn visit_body(&mut self, body: &'v hir::Body<'v>) { |
| assert!(!self.in_block_tail); |
| if body.generator_kind().is_none() { |
| if let hir::ExprKind::Block(block, None) = body.value.kind { |
| if block.expr.is_some() { |
| self.in_block_tail = true; |
| } |
| } |
| } |
| hir::intravisit::walk_body(self, body); |
| } |
| } |
