| //! Give useful errors and suggestions to users when an item can't be |
| //! found or is otherwise invalid. |
| |
| use crate::check::FnCtxt; |
| use crate::middle::lang_items::FnOnceTraitLangItem; |
| use crate::namespace::Namespace; |
| use rustc::hir::map as hir_map; |
| use rustc::hir::map::Map; |
| use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; |
| use rustc::traits::Obligation; |
| use rustc::ty::print::with_crate_prefix; |
| use rustc::ty::{self, ToPolyTraitRef, ToPredicate, Ty, TyCtxt, TypeFoldable, WithConstness}; |
| use rustc_data_structures::fx::FxHashSet; |
| use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder}; |
| use rustc_hir as hir; |
| use rustc_hir::def::{DefKind, Res}; |
| use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX, LOCAL_CRATE}; |
| use rustc_hir::intravisit; |
| use rustc_hir::{ExprKind, Node, QPath}; |
| use rustc_span::{source_map, FileName, Span}; |
| use syntax::ast; |
| use syntax::util::lev_distance; |
| |
| use std::cmp::Ordering; |
| |
| use super::probe::Mode; |
| use super::{CandidateSource, MethodError, NoMatchData}; |
| |
| impl<'a, 'tcx> FnCtxt<'a, 'tcx> { |
| fn is_fn_ty(&self, ty: Ty<'tcx>, span: Span) -> bool { |
| let tcx = self.tcx; |
| match ty.kind { |
| // Not all of these (e.g., unsafe fns) implement `FnOnce`, |
| // so we look for these beforehand. |
| ty::Closure(..) | ty::FnDef(..) | ty::FnPtr(_) => true, |
| // If it's not a simple function, look for things which implement `FnOnce`. |
| _ => { |
| let fn_once = match tcx.lang_items().require(FnOnceTraitLangItem) { |
| Ok(fn_once) => fn_once, |
| Err(..) => return false, |
| }; |
| |
| self.autoderef(span, ty).any(|(ty, _)| { |
| self.probe(|_| { |
| let fn_once_substs = tcx.mk_substs_trait( |
| ty, |
| &[self |
| .next_ty_var(TypeVariableOrigin { |
| kind: TypeVariableOriginKind::MiscVariable, |
| span, |
| }) |
| .into()], |
| ); |
| let trait_ref = ty::TraitRef::new(fn_once, fn_once_substs); |
| let poly_trait_ref = trait_ref.to_poly_trait_ref(); |
| let obligation = Obligation::misc( |
| span, |
| self.body_id, |
| self.param_env, |
| poly_trait_ref.without_const().to_predicate(), |
| ); |
| self.predicate_may_hold(&obligation) |
| }) |
| }) |
| } |
| } |
| } |
| |
| pub fn report_method_error<'b>( |
| &self, |
| span: Span, |
| rcvr_ty: Ty<'tcx>, |
| item_name: ast::Ident, |
| source: SelfSource<'b>, |
| error: MethodError<'tcx>, |
| args: Option<&'tcx [hir::Expr<'tcx>]>, |
| ) -> Option<DiagnosticBuilder<'_>> { |
| let orig_span = span; |
| let mut span = span; |
| // Avoid suggestions when we don't know what's going on. |
| if rcvr_ty.references_error() { |
| return None; |
| } |
| |
| let report_candidates = |span: Span, |
| err: &mut DiagnosticBuilder<'_>, |
| mut sources: Vec<CandidateSource>, |
| sugg_span: Span| { |
| sources.sort(); |
| sources.dedup(); |
| // Dynamic limit to avoid hiding just one candidate, which is silly. |
| let limit = if sources.len() == 5 { 5 } else { 4 }; |
| |
| for (idx, source) in sources.iter().take(limit).enumerate() { |
| match *source { |
| CandidateSource::ImplSource(impl_did) => { |
| // Provide the best span we can. Use the item, if local to crate, else |
| // the impl, if local to crate (item may be defaulted), else nothing. |
| let item = match self |
| .associated_item(impl_did, item_name, Namespace::Value) |
| .or_else(|| { |
| let impl_trait_ref = self.tcx.impl_trait_ref(impl_did)?; |
| self.associated_item( |
| impl_trait_ref.def_id, |
| item_name, |
| Namespace::Value, |
| ) |
| }) { |
| Some(item) => item, |
| None => continue, |
| }; |
| let note_span = self |
| .tcx |
| .hir() |
| .span_if_local(item.def_id) |
| .or_else(|| self.tcx.hir().span_if_local(impl_did)); |
| |
| let impl_ty = self.impl_self_ty(span, impl_did).ty; |
| |
| let insertion = match self.tcx.impl_trait_ref(impl_did) { |
| None => String::new(), |
| Some(trait_ref) => format!( |
| " of the trait `{}`", |
| self.tcx.def_path_str(trait_ref.def_id) |
| ), |
| }; |
| |
| let (note_str, idx) = if sources.len() > 1 { |
| ( |
| format!( |
| "candidate #{} is defined in an impl{} for the type `{}`", |
| idx + 1, |
| insertion, |
| impl_ty, |
| ), |
| Some(idx + 1), |
| ) |
| } else { |
| ( |
| format!( |
| "the candidate is defined in an impl{} for the type `{}`", |
| insertion, impl_ty, |
| ), |
| None, |
| ) |
| }; |
| if let Some(note_span) = note_span { |
| // We have a span pointing to the method. Show note with snippet. |
| err.span_note( |
| self.tcx.sess.source_map().def_span(note_span), |
| ¬e_str, |
| ); |
| } else { |
| err.note(¬e_str); |
| } |
| if let Some(trait_ref) = self.tcx.impl_trait_ref(impl_did) { |
| let path = self.tcx.def_path_str(trait_ref.def_id); |
| |
| let ty = match item.kind { |
| ty::AssocKind::Const |
| | ty::AssocKind::Type |
| | ty::AssocKind::OpaqueTy => rcvr_ty, |
| ty::AssocKind::Method => self |
| .tcx |
| .fn_sig(item.def_id) |
| .inputs() |
| .skip_binder() |
| .get(0) |
| .filter(|ty| ty.is_region_ptr() && !rcvr_ty.is_region_ptr()) |
| .map(|ty| *ty) |
| .unwrap_or(rcvr_ty), |
| }; |
| print_disambiguation_help( |
| item_name, |
| args, |
| err, |
| path, |
| ty, |
| item.kind, |
| sugg_span, |
| idx, |
| self.tcx.sess.source_map(), |
| ); |
| } |
| } |
| CandidateSource::TraitSource(trait_did) => { |
| let item = |
| match self.associated_item(trait_did, item_name, Namespace::Value) { |
| Some(item) => item, |
| None => continue, |
| }; |
| let item_span = |
| self.tcx.sess.source_map().def_span(self.tcx.def_span(item.def_id)); |
| let idx = if sources.len() > 1 { |
| let msg = &format!( |
| "candidate #{} is defined in the trait `{}`", |
| idx + 1, |
| self.tcx.def_path_str(trait_did) |
| ); |
| err.span_note(item_span, msg); |
| Some(idx + 1) |
| } else { |
| let msg = &format!( |
| "the candidate is defined in the trait `{}`", |
| self.tcx.def_path_str(trait_did) |
| ); |
| err.span_note(item_span, msg); |
| None |
| }; |
| let path = self.tcx.def_path_str(trait_did); |
| print_disambiguation_help( |
| item_name, |
| args, |
| err, |
| path, |
| rcvr_ty, |
| item.kind, |
| sugg_span, |
| idx, |
| self.tcx.sess.source_map(), |
| ); |
| } |
| } |
| } |
| if sources.len() > limit { |
| err.note(&format!("and {} others", sources.len() - limit)); |
| } |
| }; |
| |
| let sugg_span = if let SelfSource::MethodCall(expr) = source { |
| // Given `foo.bar(baz)`, `expr` is `bar`, but we want to point to the whole thing. |
| self.tcx.hir().expect_expr(self.tcx.hir().get_parent_node(expr.hir_id)).span |
| } else { |
| span |
| }; |
| |
| match error { |
| MethodError::NoMatch(NoMatchData { |
| static_candidates: static_sources, |
| unsatisfied_predicates, |
| out_of_scope_traits, |
| lev_candidate, |
| mode, |
| }) => { |
| let tcx = self.tcx; |
| |
| let actual = self.resolve_vars_if_possible(&rcvr_ty); |
| let ty_str = self.ty_to_string(actual); |
| let is_method = mode == Mode::MethodCall; |
| let item_kind = if is_method { |
| "method" |
| } else if actual.is_enum() { |
| "variant or associated item" |
| } else { |
| match (item_name.as_str().chars().next(), actual.is_fresh_ty()) { |
| (Some(name), false) if name.is_lowercase() => "function or associated item", |
| (Some(_), false) => "associated item", |
| (Some(_), true) | (None, false) => "variant or associated item", |
| (None, true) => "variant", |
| } |
| }; |
| let mut err = if !actual.references_error() { |
| // Suggest clamping down the type if the method that is being attempted to |
| // be used exists at all, and the type is an ambiguous numeric type |
| // ({integer}/{float}). |
| let mut candidates = all_traits(self.tcx).into_iter().filter_map(|info| { |
| self.associated_item(info.def_id, item_name, Namespace::Value) |
| }); |
| if let (true, false, SelfSource::MethodCall(expr), Some(_)) = ( |
| actual.is_numeric(), |
| actual.has_concrete_skeleton(), |
| source, |
| candidates.next(), |
| ) { |
| let mut err = struct_span_err!( |
| tcx.sess, |
| span, |
| E0689, |
| "can't call {} `{}` on ambiguous numeric type `{}`", |
| item_kind, |
| item_name, |
| ty_str |
| ); |
| let concrete_type = if actual.is_integral() { "i32" } else { "f32" }; |
| match expr.kind { |
| ExprKind::Lit(ref lit) => { |
| // numeric literal |
| let snippet = tcx |
| .sess |
| .source_map() |
| .span_to_snippet(lit.span) |
| .unwrap_or_else(|_| "<numeric literal>".to_owned()); |
| |
| err.span_suggestion( |
| lit.span, |
| &format!( |
| "you must specify a concrete type for \ |
| this numeric value, like `{}`", |
| concrete_type |
| ), |
| format!("{}_{}", snippet, concrete_type), |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| ExprKind::Path(ref qpath) => { |
| // local binding |
| if let &QPath::Resolved(_, ref path) = &qpath { |
| if let hir::def::Res::Local(hir_id) = path.res { |
| let span = tcx.hir().span(hir_id); |
| let snippet = tcx.sess.source_map().span_to_snippet(span); |
| let filename = tcx.sess.source_map().span_to_filename(span); |
| |
| let parent_node = self |
| .tcx |
| .hir() |
| .get(self.tcx.hir().get_parent_node(hir_id)); |
| let msg = format!( |
| "you must specify a type for this binding, like `{}`", |
| concrete_type, |
| ); |
| |
| match (filename, parent_node, snippet) { |
| ( |
| FileName::Real(_), |
| Node::Local(hir::Local { |
| source: hir::LocalSource::Normal, |
| ty, |
| .. |
| }), |
| Ok(ref snippet), |
| ) => { |
| err.span_suggestion( |
| // account for `let x: _ = 42;` |
| // ^^^^ |
| span.to(ty |
| .as_ref() |
| .map(|ty| ty.span) |
| .unwrap_or(span)), |
| &msg, |
| format!("{}: {}", snippet, concrete_type), |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| _ => { |
| err.span_label(span, msg); |
| } |
| } |
| } |
| } |
| } |
| _ => {} |
| } |
| err.emit(); |
| return None; |
| } else { |
| span = item_name.span; |
| let mut err = struct_span_err!( |
| tcx.sess, |
| span, |
| E0599, |
| "no {} named `{}` found for {} `{}` in the current scope", |
| item_kind, |
| item_name, |
| actual.prefix_string(), |
| ty_str, |
| ); |
| if let Some(span) = |
| tcx.sess.confused_type_with_std_module.borrow().get(&span) |
| { |
| if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(*span) { |
| err.span_suggestion( |
| *span, |
| "you are looking for the module in `std`, \ |
| not the primitive type", |
| format!("std::{}", snippet), |
| Applicability::MachineApplicable, |
| ); |
| } |
| } |
| if let ty::RawPtr(_) = &actual.kind { |
| err.note( |
| "try using `<*const T>::as_ref()` to get a reference to the \ |
| type behind the pointer: https://doc.rust-lang.org/std/\ |
| primitive.pointer.html#method.as_ref", |
| ); |
| err.note( |
| "using `<*const T>::as_ref()` on a pointer \ |
| which is unaligned or points to invalid \ |
| or uninitialized memory is undefined behavior", |
| ); |
| } |
| err |
| } |
| } else { |
| tcx.sess.diagnostic().struct_dummy() |
| }; |
| |
| if let Some(def) = actual.ty_adt_def() { |
| if let Some(full_sp) = tcx.hir().span_if_local(def.did) { |
| let def_sp = tcx.sess.source_map().def_span(full_sp); |
| err.span_label( |
| def_sp, |
| format!( |
| "{} `{}` not found {}", |
| item_kind, |
| item_name, |
| if def.is_enum() && !is_method { "here" } else { "for this" } |
| ), |
| ); |
| } |
| } |
| |
| // If the method name is the name of a field with a function or closure type, |
| // give a helping note that it has to be called as `(x.f)(...)`. |
| if let SelfSource::MethodCall(expr) = source { |
| let field_receiver = |
| self.autoderef(span, rcvr_ty).find_map(|(ty, _)| match ty.kind { |
| ty::Adt(def, substs) if !def.is_enum() => { |
| let variant = &def.non_enum_variant(); |
| self.tcx.find_field_index(item_name, variant).map(|index| { |
| let field = &variant.fields[index]; |
| let field_ty = field.ty(tcx, substs); |
| (field, field_ty) |
| }) |
| } |
| _ => None, |
| }); |
| |
| if let Some((field, field_ty)) = field_receiver { |
| let scope = self.tcx.hir().get_module_parent(self.body_id); |
| let is_accessible = field.vis.is_accessible_from(scope, self.tcx); |
| |
| if is_accessible { |
| if self.is_fn_ty(&field_ty, span) { |
| let expr_span = expr.span.to(item_name.span); |
| err.multipart_suggestion( |
| &format!( |
| "to call the function stored in `{}`, \ |
| surround the field access with parentheses", |
| item_name, |
| ), |
| vec![ |
| (expr_span.shrink_to_lo(), '('.to_string()), |
| (expr_span.shrink_to_hi(), ')'.to_string()), |
| ], |
| Applicability::MachineApplicable, |
| ); |
| } else { |
| let call_expr = self |
| .tcx |
| .hir() |
| .expect_expr(self.tcx.hir().get_parent_node(expr.hir_id)); |
| |
| if let Some(span) = call_expr.span.trim_start(item_name.span) { |
| err.span_suggestion( |
| span, |
| "remove the arguments", |
| String::new(), |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| } |
| } |
| |
| let field_kind = if is_accessible { "field" } else { "private field" }; |
| err.span_label(item_name.span, format!("{}, not a method", field_kind)); |
| } else if lev_candidate.is_none() && static_sources.is_empty() { |
| err.span_label(span, format!("{} not found in `{}`", item_kind, ty_str)); |
| self.tcx.sess.trait_methods_not_found.borrow_mut().insert(orig_span); |
| } |
| } else { |
| err.span_label(span, format!("{} not found in `{}`", item_kind, ty_str)); |
| self.tcx.sess.trait_methods_not_found.borrow_mut().insert(orig_span); |
| } |
| |
| if self.is_fn_ty(&rcvr_ty, span) { |
| macro_rules! report_function { |
| ($span:expr, $name:expr) => { |
| err.note(&format!( |
| "`{}` is a function, perhaps you wish to call it", |
| $name |
| )); |
| }; |
| } |
| |
| if let SelfSource::MethodCall(expr) = source { |
| if let Ok(expr_string) = tcx.sess.source_map().span_to_snippet(expr.span) { |
| report_function!(expr.span, expr_string); |
| } else if let ExprKind::Path(QPath::Resolved(_, ref path)) = expr.kind { |
| if let Some(segment) = path.segments.last() { |
| report_function!(expr.span, segment.ident); |
| } |
| } |
| } |
| } |
| |
| if !static_sources.is_empty() { |
| err.note( |
| "found the following associated functions; to be used as methods, \ |
| functions must have a `self` parameter", |
| ); |
| err.span_label(span, "this is an associated function, not a method"); |
| } |
| if static_sources.len() == 1 { |
| let ty_str = if let Some(CandidateSource::ImplSource(impl_did)) = |
| static_sources.get(0) |
| { |
| // When the "method" is resolved through dereferencing, we really want the |
| // original type that has the associated function for accurate suggestions. |
| // (#61411) |
| let ty = self.impl_self_ty(span, *impl_did).ty; |
| match (&ty.peel_refs().kind, &actual.peel_refs().kind) { |
| (ty::Adt(def, _), ty::Adt(def_actual, _)) if def == def_actual => { |
| // Use `actual` as it will have more `substs` filled in. |
| self.ty_to_value_string(actual.peel_refs()) |
| } |
| _ => self.ty_to_value_string(ty.peel_refs()), |
| } |
| } else { |
| self.ty_to_value_string(actual.peel_refs()) |
| }; |
| if let SelfSource::MethodCall(expr) = source { |
| err.span_suggestion( |
| expr.span.to(span), |
| "use associated function syntax instead", |
| format!("{}::{}", ty_str, item_name), |
| Applicability::MachineApplicable, |
| ); |
| } else { |
| err.help(&format!("try with `{}::{}`", ty_str, item_name,)); |
| } |
| |
| report_candidates(span, &mut err, static_sources, sugg_span); |
| } else if static_sources.len() > 1 { |
| report_candidates(span, &mut err, static_sources, sugg_span); |
| } |
| |
| if !unsatisfied_predicates.is_empty() { |
| let mut bound_list = unsatisfied_predicates |
| .iter() |
| .map(|p| format!("`{} : {}`", p.self_ty(), p.print_only_trait_path())) |
| .collect::<Vec<_>>(); |
| bound_list.sort(); |
| bound_list.dedup(); // #35677 |
| let bound_list = bound_list.join("\n"); |
| err.note(&format!( |
| "the method `{}` exists but the following trait bounds \ |
| were not satisfied:\n{}", |
| item_name, bound_list |
| )); |
| } |
| |
| if actual.is_numeric() && actual.is_fresh() { |
| } else { |
| self.suggest_traits_to_import( |
| &mut err, |
| span, |
| rcvr_ty, |
| item_name, |
| source, |
| out_of_scope_traits, |
| ); |
| } |
| |
| if actual.is_enum() { |
| let adt_def = actual.ty_adt_def().expect("enum is not an ADT"); |
| if let Some(suggestion) = lev_distance::find_best_match_for_name( |
| adt_def.variants.iter().map(|s| &s.ident.name), |
| &item_name.as_str(), |
| None, |
| ) { |
| err.span_suggestion( |
| span, |
| "there is a variant with a similar name", |
| suggestion.to_string(), |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| } |
| |
| let mut fallback_span = true; |
| let msg = "remove this method call"; |
| if item_name.as_str() == "as_str" && actual.peel_refs().is_str() { |
| if let SelfSource::MethodCall(expr) = source { |
| let call_expr = |
| self.tcx.hir().expect_expr(self.tcx.hir().get_parent_node(expr.hir_id)); |
| if let Some(span) = call_expr.span.trim_start(expr.span) { |
| err.span_suggestion( |
| span, |
| msg, |
| String::new(), |
| Applicability::MachineApplicable, |
| ); |
| fallback_span = false; |
| } |
| } |
| if fallback_span { |
| err.span_label(span, msg); |
| } |
| } else if let Some(lev_candidate) = lev_candidate { |
| let def_kind = lev_candidate.def_kind(); |
| err.span_suggestion( |
| span, |
| &format!( |
| "there is {} {} with a similar name", |
| def_kind.article(), |
| def_kind.descr(lev_candidate.def_id), |
| ), |
| lev_candidate.ident.to_string(), |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| |
| return Some(err); |
| } |
| |
| MethodError::Ambiguity(sources) => { |
| let mut err = struct_span_err!( |
| self.sess(), |
| span, |
| E0034, |
| "multiple applicable items in scope" |
| ); |
| err.span_label(span, format!("multiple `{}` found", item_name)); |
| |
| report_candidates(span, &mut err, sources, sugg_span); |
| err.emit(); |
| } |
| |
| MethodError::PrivateMatch(kind, def_id, out_of_scope_traits) => { |
| let mut err = struct_span_err!( |
| self.tcx.sess, |
| span, |
| E0624, |
| "{} `{}` is private", |
| kind.descr(def_id), |
| item_name |
| ); |
| self.suggest_valid_traits(&mut err, out_of_scope_traits); |
| err.emit(); |
| } |
| |
| MethodError::IllegalSizedBound(candidates, needs_mut) => { |
| let msg = format!("the `{}` method cannot be invoked on a trait object", item_name); |
| let mut err = self.sess().struct_span_err(span, &msg); |
| if !candidates.is_empty() { |
| let help = format!( |
| "{an}other candidate{s} {were} found in the following trait{s}, perhaps \ |
| add a `use` for {one_of_them}:", |
| an = if candidates.len() == 1 { "an" } else { "" }, |
| s = pluralize!(candidates.len()), |
| were = if candidates.len() == 1 { "was" } else { "were" }, |
| one_of_them = if candidates.len() == 1 { "it" } else { "one_of_them" }, |
| ); |
| self.suggest_use_candidates(&mut err, help, candidates); |
| } |
| if let ty::Ref(region, t_type, mutability) = rcvr_ty.kind { |
| if needs_mut { |
| let trait_type = self.tcx.mk_ref( |
| region, |
| ty::TypeAndMut { ty: t_type, mutbl: mutability.invert() }, |
| ); |
| err.note(&format!("you need `{}` instead of `{}`", trait_type, rcvr_ty)); |
| } |
| } |
| err.emit(); |
| } |
| |
| MethodError::BadReturnType => bug!("no return type expectations but got BadReturnType"), |
| } |
| None |
| } |
| |
| /// Print out the type for use in value namespace. |
| fn ty_to_value_string(&self, ty: Ty<'tcx>) -> String { |
| match ty.kind { |
| ty::Adt(def, substs) => format!("{}", ty::Instance::new(def.did, substs)), |
| _ => self.ty_to_string(ty), |
| } |
| } |
| |
| fn suggest_use_candidates( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| mut msg: String, |
| candidates: Vec<DefId>, |
| ) { |
| let module_did = self.tcx.hir().get_module_parent(self.body_id); |
| let module_id = self.tcx.hir().as_local_hir_id(module_did).unwrap(); |
| let krate = self.tcx.hir().krate(); |
| let (span, found_use) = UsePlacementFinder::check(self.tcx, krate, module_id); |
| if let Some(span) = span { |
| let path_strings = candidates.iter().map(|did| { |
| // Produce an additional newline to separate the new use statement |
| // from the directly following item. |
| let additional_newline = if found_use { "" } else { "\n" }; |
| format!( |
| "use {};\n{}", |
| with_crate_prefix(|| self.tcx.def_path_str(*did)), |
| additional_newline |
| ) |
| }); |
| |
| err.span_suggestions(span, &msg, path_strings, Applicability::MaybeIncorrect); |
| } else { |
| let limit = if candidates.len() == 5 { 5 } else { 4 }; |
| for (i, trait_did) in candidates.iter().take(limit).enumerate() { |
| if candidates.len() > 1 { |
| msg.push_str(&format!( |
| "\ncandidate #{}: `use {};`", |
| i + 1, |
| with_crate_prefix(|| self.tcx.def_path_str(*trait_did)) |
| )); |
| } else { |
| msg.push_str(&format!( |
| "\n`use {};`", |
| with_crate_prefix(|| self.tcx.def_path_str(*trait_did)) |
| )); |
| } |
| } |
| if candidates.len() > limit { |
| msg.push_str(&format!("\nand {} others", candidates.len() - limit)); |
| } |
| err.note(&msg[..]); |
| } |
| } |
| |
| fn suggest_valid_traits( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| valid_out_of_scope_traits: Vec<DefId>, |
| ) -> bool { |
| if !valid_out_of_scope_traits.is_empty() { |
| let mut candidates = valid_out_of_scope_traits; |
| candidates.sort(); |
| candidates.dedup(); |
| err.help("items from traits can only be used if the trait is in scope"); |
| let msg = format!( |
| "the following {traits_are} implemented but not in scope; \ |
| perhaps add a `use` for {one_of_them}:", |
| traits_are = if candidates.len() == 1 { "trait is" } else { "traits are" }, |
| one_of_them = if candidates.len() == 1 { "it" } else { "one of them" }, |
| ); |
| |
| self.suggest_use_candidates(err, msg, candidates); |
| true |
| } else { |
| false |
| } |
| } |
| |
| fn suggest_traits_to_import<'b>( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| span: Span, |
| rcvr_ty: Ty<'tcx>, |
| item_name: ast::Ident, |
| source: SelfSource<'b>, |
| valid_out_of_scope_traits: Vec<DefId>, |
| ) { |
| if self.suggest_valid_traits(err, valid_out_of_scope_traits) { |
| return; |
| } |
| |
| let type_is_local = self.type_derefs_to_local(span, rcvr_ty, source); |
| |
| // There are no traits implemented, so lets suggest some traits to |
| // implement, by finding ones that have the item name, and are |
| // legal to implement. |
| let mut candidates = all_traits(self.tcx) |
| .into_iter() |
| .filter(|info| { |
| // We approximate the coherence rules to only suggest |
| // traits that are legal to implement by requiring that |
| // either the type or trait is local. Multi-dispatch means |
| // this isn't perfect (that is, there are cases when |
| // implementing a trait would be legal but is rejected |
| // here). |
| (type_is_local || info.def_id.is_local()) |
| && self |
| .associated_item(info.def_id, item_name, Namespace::Value) |
| .filter(|item| { |
| // We only want to suggest public or local traits (#45781). |
| item.vis == ty::Visibility::Public || info.def_id.is_local() |
| }) |
| .is_some() |
| }) |
| .collect::<Vec<_>>(); |
| |
| if !candidates.is_empty() { |
| // Sort from most relevant to least relevant. |
| candidates.sort_by(|a, b| a.cmp(b).reverse()); |
| candidates.dedup(); |
| |
| let param_type = match rcvr_ty.kind { |
| ty::Param(param) => Some(param), |
| ty::Ref(_, ty, _) => match ty.kind { |
| ty::Param(param) => Some(param), |
| _ => None, |
| }, |
| _ => None, |
| }; |
| err.help(if param_type.is_some() { |
| "items from traits can only be used if the type parameter is bounded by the trait" |
| } else { |
| "items from traits can only be used if the trait is implemented and in scope" |
| }); |
| let message = |action| { |
| format!( |
| "the following {traits_define} an item `{name}`, perhaps you need to {action} \ |
| {one_of_them}:", |
| traits_define = |
| if candidates.len() == 1 { "trait defines" } else { "traits define" }, |
| action = action, |
| one_of_them = if candidates.len() == 1 { "it" } else { "one of them" }, |
| name = item_name, |
| ) |
| }; |
| // Obtain the span for `param` and use it for a structured suggestion. |
| let mut suggested = false; |
| if let (Some(ref param), Some(ref table)) = (param_type, self.in_progress_tables) { |
| let table = table.borrow(); |
| if let Some(did) = table.local_id_root { |
| let generics = self.tcx.generics_of(did); |
| let type_param = generics.type_param(param, self.tcx); |
| let hir = &self.tcx.hir(); |
| if let Some(id) = hir.as_local_hir_id(type_param.def_id) { |
| // Get the `hir::Param` to verify whether it already has any bounds. |
| // We do this to avoid suggesting code that ends up as `T: FooBar`, |
| // instead we suggest `T: Foo + Bar` in that case. |
| match hir.get(id) { |
| Node::GenericParam(ref param) => { |
| let mut impl_trait = false; |
| let has_bounds = if let hir::GenericParamKind::Type { |
| synthetic: Some(_), |
| .. |
| } = ¶m.kind |
| { |
| // We've found `fn foo(x: impl Trait)` instead of |
| // `fn foo<T>(x: T)`. We want to suggest the correct |
| // `fn foo(x: impl Trait + TraitBound)` instead of |
| // `fn foo<T: TraitBound>(x: T)`. (#63706) |
| impl_trait = true; |
| param.bounds.get(1) |
| } else { |
| param.bounds.get(0) |
| }; |
| let sp = hir.span(id); |
| let sp = if let Some(first_bound) = has_bounds { |
| // `sp` only covers `T`, change it so that it covers |
| // `T:` when appropriate |
| sp.until(first_bound.span()) |
| } else { |
| sp |
| }; |
| // FIXME: contrast `t.def_id` against `param.bounds` to not suggest |
| // traits already there. That can happen when the cause is that |
| // we're in a const scope or associated function used as a method. |
| err.span_suggestions( |
| sp, |
| &message(format!( |
| "restrict type parameter `{}` with", |
| param.name.ident(), |
| )), |
| candidates.iter().map(|t| { |
| format!( |
| "{}{} {}{}", |
| param.name.ident(), |
| if impl_trait { " +" } else { ":" }, |
| self.tcx.def_path_str(t.def_id), |
| if has_bounds.is_some() { " + " } else { "" }, |
| ) |
| }), |
| Applicability::MaybeIncorrect, |
| ); |
| suggested = true; |
| } |
| Node::Item(hir::Item { |
| kind: hir::ItemKind::Trait(.., bounds, _), |
| ident, |
| .. |
| }) => { |
| let (sp, sep, article) = if bounds.is_empty() { |
| (ident.span.shrink_to_hi(), ":", "a") |
| } else { |
| (bounds.last().unwrap().span().shrink_to_hi(), " +", "another") |
| }; |
| err.span_suggestions( |
| sp, |
| &message(format!("add {} supertrait for", article)), |
| candidates.iter().map(|t| { |
| format!("{} {}", sep, self.tcx.def_path_str(t.def_id),) |
| }), |
| Applicability::MaybeIncorrect, |
| ); |
| suggested = true; |
| } |
| _ => {} |
| } |
| } |
| }; |
| } |
| |
| if !suggested { |
| let mut msg = message(if let Some(param) = param_type { |
| format!("restrict type parameter `{}` with", param) |
| } else { |
| "implement".to_string() |
| }); |
| for (i, trait_info) in candidates.iter().enumerate() { |
| msg.push_str(&format!( |
| "\ncandidate #{}: `{}`", |
| i + 1, |
| self.tcx.def_path_str(trait_info.def_id), |
| )); |
| } |
| err.note(&msg[..]); |
| } |
| } |
| } |
| |
| /// Checks whether there is a local type somewhere in the chain of |
| /// autoderefs of `rcvr_ty`. |
| fn type_derefs_to_local(&self, span: Span, rcvr_ty: Ty<'tcx>, source: SelfSource<'_>) -> bool { |
| fn is_local(ty: Ty<'_>) -> bool { |
| match ty.kind { |
| ty::Adt(def, _) => def.did.is_local(), |
| ty::Foreign(did) => did.is_local(), |
| |
| ty::Dynamic(ref tr, ..) => { |
| tr.principal().map(|d| d.def_id().is_local()).unwrap_or(false) |
| } |
| |
| ty::Param(_) => true, |
| |
| // Everything else (primitive types, etc.) is effectively |
| // non-local (there are "edge" cases, e.g., `(LocalType,)`, but |
| // the noise from these sort of types is usually just really |
| // annoying, rather than any sort of help). |
| _ => false, |
| } |
| } |
| |
| // This occurs for UFCS desugaring of `T::method`, where there is no |
| // receiver expression for the method call, and thus no autoderef. |
| if let SelfSource::QPath(_) = source { |
| return is_local(self.resolve_vars_with_obligations(rcvr_ty)); |
| } |
| |
| self.autoderef(span, rcvr_ty).any(|(ty, _)| is_local(ty)) |
| } |
| } |
| |
| #[derive(Copy, Clone)] |
| pub enum SelfSource<'a> { |
| QPath(&'a hir::Ty<'a>), |
| MethodCall(&'a hir::Expr<'a> /* rcvr */), |
| } |
| |
| #[derive(Copy, Clone)] |
| pub struct TraitInfo { |
| pub def_id: DefId, |
| } |
| |
| impl PartialEq for TraitInfo { |
| fn eq(&self, other: &TraitInfo) -> bool { |
| self.cmp(other) == Ordering::Equal |
| } |
| } |
| impl Eq for TraitInfo {} |
| impl PartialOrd for TraitInfo { |
| fn partial_cmp(&self, other: &TraitInfo) -> Option<Ordering> { |
| Some(self.cmp(other)) |
| } |
| } |
| impl Ord for TraitInfo { |
| fn cmp(&self, other: &TraitInfo) -> Ordering { |
| // Local crates are more important than remote ones (local: |
| // `cnum == 0`), and otherwise we throw in the defid for totality. |
| |
| let lhs = (other.def_id.krate, other.def_id); |
| let rhs = (self.def_id.krate, self.def_id); |
| lhs.cmp(&rhs) |
| } |
| } |
| |
| /// Retrieves all traits in this crate and any dependent crates. |
| pub fn all_traits(tcx: TyCtxt<'_>) -> Vec<TraitInfo> { |
| tcx.all_traits(LOCAL_CRATE).iter().map(|&def_id| TraitInfo { def_id }).collect() |
| } |
| |
| /// Computes all traits in this crate and any dependent crates. |
| fn compute_all_traits(tcx: TyCtxt<'_>) -> Vec<DefId> { |
| use hir::itemlikevisit; |
| |
| let mut traits = vec![]; |
| |
| // Crate-local: |
| |
| struct Visitor<'a, 'tcx> { |
| map: &'a hir_map::Map<'tcx>, |
| traits: &'a mut Vec<DefId>, |
| } |
| |
| impl<'v, 'a, 'tcx> itemlikevisit::ItemLikeVisitor<'v> for Visitor<'a, 'tcx> { |
| fn visit_item(&mut self, i: &'v hir::Item<'v>) { |
| match i.kind { |
| hir::ItemKind::Trait(..) | hir::ItemKind::TraitAlias(..) => { |
| let def_id = self.map.local_def_id(i.hir_id); |
| self.traits.push(def_id); |
| } |
| _ => (), |
| } |
| } |
| |
| fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem<'_>) {} |
| |
| fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem<'_>) {} |
| } |
| |
| tcx.hir().krate().visit_all_item_likes(&mut Visitor { map: &tcx.hir(), traits: &mut traits }); |
| |
| // Cross-crate: |
| |
| let mut external_mods = FxHashSet::default(); |
| fn handle_external_res( |
| tcx: TyCtxt<'_>, |
| traits: &mut Vec<DefId>, |
| external_mods: &mut FxHashSet<DefId>, |
| res: Res, |
| ) { |
| match res { |
| Res::Def(DefKind::Trait, def_id) | Res::Def(DefKind::TraitAlias, def_id) => { |
| traits.push(def_id); |
| } |
| Res::Def(DefKind::Mod, def_id) => { |
| if !external_mods.insert(def_id) { |
| return; |
| } |
| for child in tcx.item_children(def_id).iter() { |
| handle_external_res(tcx, traits, external_mods, child.res) |
| } |
| } |
| _ => {} |
| } |
| } |
| for &cnum in tcx.crates().iter() { |
| let def_id = DefId { krate: cnum, index: CRATE_DEF_INDEX }; |
| handle_external_res(tcx, &mut traits, &mut external_mods, Res::Def(DefKind::Mod, def_id)); |
| } |
| |
| traits |
| } |
| |
| pub fn provide(providers: &mut ty::query::Providers<'_>) { |
| providers.all_traits = |tcx, cnum| { |
| assert_eq!(cnum, LOCAL_CRATE); |
| &tcx.arena.alloc(compute_all_traits(tcx))[..] |
| } |
| } |
| |
| struct UsePlacementFinder<'tcx> { |
| target_module: hir::HirId, |
| span: Option<Span>, |
| found_use: bool, |
| tcx: TyCtxt<'tcx>, |
| } |
| |
| impl UsePlacementFinder<'tcx> { |
| fn check( |
| tcx: TyCtxt<'tcx>, |
| krate: &'tcx hir::Crate<'tcx>, |
| target_module: hir::HirId, |
| ) -> (Option<Span>, bool) { |
| let mut finder = UsePlacementFinder { target_module, span: None, found_use: false, tcx }; |
| intravisit::walk_crate(&mut finder, krate); |
| (finder.span, finder.found_use) |
| } |
| } |
| |
| impl intravisit::Visitor<'tcx> for UsePlacementFinder<'tcx> { |
| fn visit_mod(&mut self, module: &'tcx hir::Mod<'tcx>, _: Span, hir_id: hir::HirId) { |
| if self.span.is_some() { |
| return; |
| } |
| if hir_id != self.target_module { |
| intravisit::walk_mod(self, module, hir_id); |
| return; |
| } |
| // Find a `use` statement. |
| for item_id in module.item_ids { |
| let item = self.tcx.hir().expect_item(item_id.id); |
| match item.kind { |
| hir::ItemKind::Use(..) => { |
| // Don't suggest placing a `use` before the prelude |
| // import or other generated ones. |
| if !item.span.from_expansion() { |
| self.span = Some(item.span.shrink_to_lo()); |
| self.found_use = true; |
| return; |
| } |
| } |
| // Don't place `use` before `extern crate`... |
| hir::ItemKind::ExternCrate(_) => {} |
| // ...but do place them before the first other item. |
| _ => { |
| if self.span.map_or(true, |span| item.span < span) { |
| if !item.span.from_expansion() { |
| // Don't insert between attributes and an item. |
| if item.attrs.is_empty() { |
| self.span = Some(item.span.shrink_to_lo()); |
| } else { |
| // Find the first attribute on the item. |
| for attr in item.attrs { |
| if self.span.map_or(true, |span| attr.span < span) { |
| self.span = Some(attr.span.shrink_to_lo()); |
| } |
| } |
| } |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| type Map = Map<'tcx>; |
| |
| fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> { |
| intravisit::NestedVisitorMap::None |
| } |
| } |
| |
| fn print_disambiguation_help( |
| item_name: ast::Ident, |
| args: Option<&'tcx [hir::Expr<'tcx>]>, |
| err: &mut DiagnosticBuilder<'_>, |
| trait_name: String, |
| rcvr_ty: Ty<'_>, |
| kind: ty::AssocKind, |
| span: Span, |
| candidate: Option<usize>, |
| source_map: &source_map::SourceMap, |
| ) { |
| let mut applicability = Applicability::MachineApplicable; |
| let sugg_args = if let (ty::AssocKind::Method, Some(args)) = (kind, args) { |
| format!( |
| "({}{})", |
| if rcvr_ty.is_region_ptr() { |
| if rcvr_ty.is_mutable_ptr() { "&mut " } else { "&" } |
| } else { |
| "" |
| }, |
| args.iter() |
| .map(|arg| source_map.span_to_snippet(arg.span).unwrap_or_else(|_| { |
| applicability = Applicability::HasPlaceholders; |
| "_".to_owned() |
| })) |
| .collect::<Vec<_>>() |
| .join(", "), |
| ) |
| } else { |
| String::new() |
| }; |
| let sugg = format!("{}::{}{}", trait_name, item_name, sugg_args); |
| err.span_suggestion( |
| span, |
| &format!( |
| "disambiguate the {} for {}", |
| kind.suggestion_descr(), |
| if let Some(candidate) = candidate { |
| format!("candidate #{}", candidate) |
| } else { |
| "the candidate".to_string() |
| }, |
| ), |
| sugg, |
| applicability, |
| ); |
| } |
