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Diffstat (limited to '')
-rw-r--r-- | compiler/rustc_typeck/src/astconv/errors.rs | 410 |
1 files changed, 410 insertions, 0 deletions
diff --git a/compiler/rustc_typeck/src/astconv/errors.rs b/compiler/rustc_typeck/src/astconv/errors.rs new file mode 100644 index 000000000..ff39bf361 --- /dev/null +++ b/compiler/rustc_typeck/src/astconv/errors.rs @@ -0,0 +1,410 @@ +use crate::astconv::AstConv; +use crate::errors::{ManualImplementation, MissingTypeParams}; +use rustc_data_structures::fx::FxHashMap; +use rustc_errors::{pluralize, struct_span_err, Applicability, ErrorGuaranteed}; +use rustc_hir as hir; +use rustc_hir::def_id::DefId; +use rustc_middle::ty; +use rustc_session::parse::feature_err; +use rustc_span::lev_distance::find_best_match_for_name; +use rustc_span::symbol::{sym, Ident}; +use rustc_span::{Span, Symbol, DUMMY_SP}; + +use std::collections::BTreeSet; + +impl<'o, 'tcx> dyn AstConv<'tcx> + 'o { + /// On missing type parameters, emit an E0393 error and provide a structured suggestion using + /// the type parameter's name as a placeholder. + pub(crate) fn complain_about_missing_type_params( + &self, + missing_type_params: Vec<Symbol>, + def_id: DefId, + span: Span, + empty_generic_args: bool, + ) { + if missing_type_params.is_empty() { + return; + } + + self.tcx().sess.emit_err(MissingTypeParams { + span, + def_span: self.tcx().def_span(def_id), + missing_type_params, + empty_generic_args, + }); + } + + /// When the code is using the `Fn` traits directly, instead of the `Fn(A) -> B` syntax, emit + /// an error and attempt to build a reasonable structured suggestion. + pub(crate) fn complain_about_internal_fn_trait( + &self, + span: Span, + trait_def_id: DefId, + trait_segment: &'_ hir::PathSegment<'_>, + is_impl: bool, + ) { + if self.tcx().features().unboxed_closures { + return; + } + + let trait_def = self.tcx().trait_def(trait_def_id); + if !trait_def.paren_sugar { + if trait_segment.args().parenthesized { + // For now, require that parenthetical notation be used only with `Fn()` etc. + let mut err = feature_err( + &self.tcx().sess.parse_sess, + sym::unboxed_closures, + span, + "parenthetical notation is only stable when used with `Fn`-family traits", + ); + err.emit(); + } + + return; + } + + let sess = self.tcx().sess; + + if !trait_segment.args().parenthesized { + // For now, require that parenthetical notation be used only with `Fn()` etc. + let mut err = feature_err( + &sess.parse_sess, + sym::unboxed_closures, + span, + "the precise format of `Fn`-family traits' type parameters is subject to change", + ); + // Do not suggest the other syntax if we are in trait impl: + // the desugaring would contain an associated type constraint. + if !is_impl { + let args = trait_segment + .args + .as_ref() + .and_then(|args| args.args.get(0)) + .and_then(|arg| match arg { + hir::GenericArg::Type(ty) => match ty.kind { + hir::TyKind::Tup(t) => t + .iter() + .map(|e| sess.source_map().span_to_snippet(e.span)) + .collect::<Result<Vec<_>, _>>() + .map(|a| a.join(", ")), + _ => sess.source_map().span_to_snippet(ty.span), + } + .map(|s| format!("({})", s)) + .ok(), + _ => None, + }) + .unwrap_or_else(|| "()".to_string()); + let ret = trait_segment + .args() + .bindings + .iter() + .find_map(|b| match (b.ident.name == sym::Output, &b.kind) { + (true, hir::TypeBindingKind::Equality { term }) => { + let span = match term { + hir::Term::Ty(ty) => ty.span, + hir::Term::Const(c) => self.tcx().hir().span(c.hir_id), + }; + sess.source_map().span_to_snippet(span).ok() + } + _ => None, + }) + .unwrap_or_else(|| "()".to_string()); + err.span_suggestion( + span, + "use parenthetical notation instead", + format!("{}{} -> {}", trait_segment.ident, args, ret), + Applicability::MaybeIncorrect, + ); + } + err.emit(); + } + + if is_impl { + let trait_name = self.tcx().def_path_str(trait_def_id); + self.tcx().sess.emit_err(ManualImplementation { span, trait_name }); + } + } + + pub(crate) fn complain_about_assoc_type_not_found<I>( + &self, + all_candidates: impl Fn() -> I, + ty_param_name: &str, + assoc_name: Ident, + span: Span, + ) -> ErrorGuaranteed + where + I: Iterator<Item = ty::PolyTraitRef<'tcx>>, + { + // The fallback span is needed because `assoc_name` might be an `Fn()`'s `Output` without a + // valid span, so we point at the whole path segment instead. + let span = if assoc_name.span != DUMMY_SP { assoc_name.span } else { span }; + let mut err = struct_span_err!( + self.tcx().sess, + span, + E0220, + "associated type `{}` not found for `{}`", + assoc_name, + ty_param_name + ); + + let all_candidate_names: Vec<_> = all_candidates() + .flat_map(|r| self.tcx().associated_items(r.def_id()).in_definition_order()) + .filter_map( + |item| if item.kind == ty::AssocKind::Type { Some(item.name) } else { None }, + ) + .collect(); + + if let (Some(suggested_name), true) = ( + find_best_match_for_name(&all_candidate_names, assoc_name.name, None), + assoc_name.span != DUMMY_SP, + ) { + err.span_suggestion( + assoc_name.span, + "there is an associated type with a similar name", + suggested_name, + Applicability::MaybeIncorrect, + ); + return err.emit(); + } + + // If we didn't find a good item in the supertraits (or couldn't get + // the supertraits), like in ItemCtxt, then look more generally from + // all visible traits. If there's one clear winner, just suggest that. + + let visible_traits: Vec<_> = self + .tcx() + .all_traits() + .filter(|trait_def_id| { + let viz = self.tcx().visibility(*trait_def_id); + if let Some(def_id) = self.item_def_id() { + viz.is_accessible_from(def_id, self.tcx()) + } else { + viz.is_visible_locally() + } + }) + .collect(); + + let wider_candidate_names: Vec<_> = visible_traits + .iter() + .flat_map(|trait_def_id| { + self.tcx().associated_items(*trait_def_id).in_definition_order() + }) + .filter_map( + |item| if item.kind == ty::AssocKind::Type { Some(item.name) } else { None }, + ) + .collect(); + + if let (Some(suggested_name), true) = ( + find_best_match_for_name(&wider_candidate_names, assoc_name.name, None), + assoc_name.span != DUMMY_SP, + ) { + if let [best_trait] = visible_traits + .iter() + .filter(|trait_def_id| { + self.tcx() + .associated_items(*trait_def_id) + .filter_by_name_unhygienic(suggested_name) + .any(|item| item.kind == ty::AssocKind::Type) + }) + .collect::<Vec<_>>()[..] + { + err.span_label( + assoc_name.span, + format!( + "there is a similarly named associated type `{suggested_name}` in the trait `{}`", + self.tcx().def_path_str(*best_trait) + ), + ); + return err.emit(); + } + } + + err.span_label(span, format!("associated type `{}` not found", assoc_name)); + err.emit() + } + + /// When there are any missing associated types, emit an E0191 error and attempt to supply a + /// reasonable suggestion on how to write it. For the case of multiple associated types in the + /// same trait bound have the same name (as they come from different supertraits), we instead + /// emit a generic note suggesting using a `where` clause to constraint instead. + pub(crate) fn complain_about_missing_associated_types( + &self, + associated_types: FxHashMap<Span, BTreeSet<DefId>>, + potential_assoc_types: Vec<Span>, + trait_bounds: &[hir::PolyTraitRef<'_>], + ) { + if associated_types.values().all(|v| v.is_empty()) { + return; + } + let tcx = self.tcx(); + // FIXME: Marked `mut` so that we can replace the spans further below with a more + // appropriate one, but this should be handled earlier in the span assignment. + let mut associated_types: FxHashMap<Span, Vec<_>> = associated_types + .into_iter() + .map(|(span, def_ids)| { + (span, def_ids.into_iter().map(|did| tcx.associated_item(did)).collect()) + }) + .collect(); + let mut names = vec![]; + + // Account for things like `dyn Foo + 'a`, like in tests `issue-22434.rs` and + // `issue-22560.rs`. + let mut trait_bound_spans: Vec<Span> = vec![]; + for (span, items) in &associated_types { + if !items.is_empty() { + trait_bound_spans.push(*span); + } + for assoc_item in items { + let trait_def_id = assoc_item.container_id(tcx); + names.push(format!( + "`{}` (from trait `{}`)", + assoc_item.name, + tcx.def_path_str(trait_def_id), + )); + } + } + if let ([], [bound]) = (&potential_assoc_types[..], &trait_bounds) { + match bound.trait_ref.path.segments { + // FIXME: `trait_ref.path.span` can point to a full path with multiple + // segments, even though `trait_ref.path.segments` is of length `1`. Work + // around that bug here, even though it should be fixed elsewhere. + // This would otherwise cause an invalid suggestion. For an example, look at + // `src/test/ui/issues/issue-28344.rs` where instead of the following: + // + // error[E0191]: the value of the associated type `Output` + // (from trait `std::ops::BitXor`) must be specified + // --> $DIR/issue-28344.rs:4:17 + // | + // LL | let x: u8 = BitXor::bitor(0 as u8, 0 as u8); + // | ^^^^^^ help: specify the associated type: + // | `BitXor<Output = Type>` + // + // we would output: + // + // error[E0191]: the value of the associated type `Output` + // (from trait `std::ops::BitXor`) must be specified + // --> $DIR/issue-28344.rs:4:17 + // | + // LL | let x: u8 = BitXor::bitor(0 as u8, 0 as u8); + // | ^^^^^^^^^^^^^ help: specify the associated type: + // | `BitXor::bitor<Output = Type>` + [segment] if segment.args.is_none() => { + trait_bound_spans = vec![segment.ident.span]; + associated_types = associated_types + .into_iter() + .map(|(_, items)| (segment.ident.span, items)) + .collect(); + } + _ => {} + } + } + names.sort(); + trait_bound_spans.sort(); + let mut err = struct_span_err!( + tcx.sess, + trait_bound_spans, + E0191, + "the value of the associated type{} {} must be specified", + pluralize!(names.len()), + names.join(", "), + ); + let mut suggestions = vec![]; + let mut types_count = 0; + let mut where_constraints = vec![]; + let mut already_has_generics_args_suggestion = false; + for (span, assoc_items) in &associated_types { + let mut names: FxHashMap<_, usize> = FxHashMap::default(); + for item in assoc_items { + types_count += 1; + *names.entry(item.name).or_insert(0) += 1; + } + let mut dupes = false; + for item in assoc_items { + let prefix = if names[&item.name] > 1 { + let trait_def_id = item.container_id(tcx); + dupes = true; + format!("{}::", tcx.def_path_str(trait_def_id)) + } else { + String::new() + }; + if let Some(sp) = tcx.hir().span_if_local(item.def_id) { + err.span_label(sp, format!("`{}{}` defined here", prefix, item.name)); + } + } + if potential_assoc_types.len() == assoc_items.len() { + // When the amount of missing associated types equals the number of + // extra type arguments present. A suggesting to replace the generic args with + // associated types is already emitted. + already_has_generics_args_suggestion = true; + } else if let (Ok(snippet), false) = + (tcx.sess.source_map().span_to_snippet(*span), dupes) + { + let types: Vec<_> = + assoc_items.iter().map(|item| format!("{} = Type", item.name)).collect(); + let code = if snippet.ends_with('>') { + // The user wrote `Trait<'a>` or similar and we don't have a type we can + // suggest, but at least we can clue them to the correct syntax + // `Trait<'a, Item = Type>` while accounting for the `<'a>` in the + // suggestion. + format!("{}, {}>", &snippet[..snippet.len() - 1], types.join(", ")) + } else { + // The user wrote `Iterator`, so we don't have a type we can suggest, but at + // least we can clue them to the correct syntax `Iterator<Item = Type>`. + format!("{}<{}>", snippet, types.join(", ")) + }; + suggestions.push((*span, code)); + } else if dupes { + where_constraints.push(*span); + } + } + let where_msg = "consider introducing a new type parameter, adding `where` constraints \ + using the fully-qualified path to the associated types"; + if !where_constraints.is_empty() && suggestions.is_empty() { + // If there are duplicates associated type names and a single trait bound do not + // use structured suggestion, it means that there are multiple supertraits with + // the same associated type name. + err.help(where_msg); + } + if suggestions.len() != 1 || already_has_generics_args_suggestion { + // We don't need this label if there's an inline suggestion, show otherwise. + for (span, assoc_items) in &associated_types { + let mut names: FxHashMap<_, usize> = FxHashMap::default(); + for item in assoc_items { + types_count += 1; + *names.entry(item.name).or_insert(0) += 1; + } + let mut label = vec![]; + for item in assoc_items { + let postfix = if names[&item.name] > 1 { + let trait_def_id = item.container_id(tcx); + format!(" (from trait `{}`)", tcx.def_path_str(trait_def_id)) + } else { + String::new() + }; + label.push(format!("`{}`{}", item.name, postfix)); + } + if !label.is_empty() { + err.span_label( + *span, + format!( + "associated type{} {} must be specified", + pluralize!(label.len()), + label.join(", "), + ), + ); + } + } + } + if !suggestions.is_empty() { + err.multipart_suggestion( + &format!("specify the associated type{}", pluralize!(types_count)), + suggestions, + Applicability::HasPlaceholders, + ); + if !where_constraints.is_empty() { + err.span_help(where_constraints, where_msg); + } + } + err.emit(); + } +} |