use crate::diagnostics::{ImportSuggestion, LabelSuggestion, TypoSuggestion}; use crate::late::{AliasPossibility, LateResolutionVisitor, RibKind}; use crate::late::{LifetimeBinderKind, LifetimeRes, LifetimeRibKind, LifetimeUseSet}; use crate::path_names_to_string; use crate::{Module, ModuleKind, ModuleOrUniformRoot}; use crate::{PathResult, PathSource, Segment}; use rustc_ast::visit::{FnCtxt, FnKind, LifetimeCtxt}; use rustc_ast::{ self as ast, AssocItemKind, Expr, ExprKind, GenericParam, GenericParamKind, Item, ItemKind, MethodCall, NodeId, Path, Ty, TyKind, DUMMY_NODE_ID, }; use rustc_ast_pretty::pprust::path_segment_to_string; use rustc_data_structures::fx::FxHashSet; use rustc_errors::{ pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan, }; use rustc_hir as hir; use rustc_hir::def::Namespace::{self, *}; use rustc_hir::def::{self, CtorKind, CtorOf, DefKind}; use rustc_hir::def_id::{DefId, CRATE_DEF_ID, LOCAL_CRATE}; use rustc_hir::PrimTy; use rustc_middle::ty::DefIdTree; use rustc_session::lint; use rustc_session::parse::feature_err; use rustc_session::Session; use rustc_span::edition::Edition; use rustc_span::hygiene::MacroKind; use rustc_span::lev_distance::find_best_match_for_name; use rustc_span::symbol::{kw, sym, Ident, Symbol}; use rustc_span::{BytePos, Span}; use std::iter; use std::ops::Deref; use thin_vec::ThinVec; type Res = def::Res; /// A field or associated item from self type suggested in case of resolution failure. enum AssocSuggestion { Field, MethodWithSelf { called: bool }, AssocFn { called: bool }, AssocType, AssocConst, } impl AssocSuggestion { fn action(&self) -> &'static str { match self { AssocSuggestion::Field => "use the available field", AssocSuggestion::MethodWithSelf { called: true } => { "call the method with the fully-qualified path" } AssocSuggestion::MethodWithSelf { called: false } => { "refer to the method with the fully-qualified path" } AssocSuggestion::AssocFn { called: true } => "call the associated function", AssocSuggestion::AssocFn { called: false } => "refer to the associated function", AssocSuggestion::AssocConst => "use the associated `const`", AssocSuggestion::AssocType => "use the associated type", } } } fn is_self_type(path: &[Segment], namespace: Namespace) -> bool { namespace == TypeNS && path.len() == 1 && path[0].ident.name == kw::SelfUpper } fn is_self_value(path: &[Segment], namespace: Namespace) -> bool { namespace == ValueNS && path.len() == 1 && path[0].ident.name == kw::SelfLower } /// Gets the stringified path for an enum from an `ImportSuggestion` for an enum variant. fn import_candidate_to_enum_paths(suggestion: &ImportSuggestion) -> (String, String) { let variant_path = &suggestion.path; let variant_path_string = path_names_to_string(variant_path); let path_len = suggestion.path.segments.len(); let enum_path = ast::Path { span: suggestion.path.span, segments: suggestion.path.segments[0..path_len - 1].iter().cloned().collect(), tokens: None, }; let enum_path_string = path_names_to_string(&enum_path); (variant_path_string, enum_path_string) } /// Description of an elided lifetime. #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug)] pub(super) struct MissingLifetime { /// Used to overwrite the resolution with the suggestion, to avoid cascasing errors. pub id: NodeId, /// Where to suggest adding the lifetime. pub span: Span, /// How the lifetime was introduced, to have the correct space and comma. pub kind: MissingLifetimeKind, /// Number of elided lifetimes, used for elision in path. pub count: usize, } #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug)] pub(super) enum MissingLifetimeKind { /// An explicit `'_`. Underscore, /// An elided lifetime `&' ty`. Ampersand, /// An elided lifetime in brackets with written brackets. Comma, /// An elided lifetime with elided brackets. Brackets, } /// Description of the lifetimes appearing in a function parameter. /// This is used to provide a literal explanation to the elision failure. #[derive(Clone, Debug)] pub(super) struct ElisionFnParameter { /// The index of the argument in the original definition. pub index: usize, /// The name of the argument if it's a simple ident. pub ident: Option, /// The number of lifetimes in the parameter. pub lifetime_count: usize, /// The span of the parameter. pub span: Span, } /// Description of lifetimes that appear as candidates for elision. /// This is used to suggest introducing an explicit lifetime. #[derive(Debug)] pub(super) enum LifetimeElisionCandidate { /// This is not a real lifetime. Ignore, /// There is a named lifetime, we won't suggest anything. Named, Missing(MissingLifetime), } /// Only used for diagnostics. #[derive(Debug)] struct BaseError { msg: String, fallback_label: String, span: Span, span_label: Option<(Span, &'static str)>, could_be_expr: bool, suggestion: Option<(Span, &'static str, String)>, } #[derive(Debug)] enum TypoCandidate { Typo(TypoSuggestion), Shadowed(Res, Option), None, } impl TypoCandidate { fn to_opt_suggestion(self) -> Option { match self { TypoCandidate::Typo(sugg) => Some(sugg), TypoCandidate::Shadowed(_, _) | TypoCandidate::None => None, } } } impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> { fn def_span(&self, def_id: DefId) -> Option { match def_id.krate { LOCAL_CRATE => self.r.opt_span(def_id), _ => Some(self.r.cstore().get_span_untracked(def_id, self.r.session)), } } fn make_base_error( &mut self, path: &[Segment], span: Span, source: PathSource<'_>, res: Option, ) -> BaseError { // Make the base error. let mut expected = source.descr_expected(); let path_str = Segment::names_to_string(path); let item_str = path.last().unwrap().ident; if let Some(res) = res { BaseError { msg: format!("expected {}, found {} `{}`", expected, res.descr(), path_str), fallback_label: format!("not a {expected}"), span, span_label: match res { Res::Def(kind, def_id) if kind == DefKind::TyParam => { self.def_span(def_id).map(|span| (span, "found this type parameter")) } _ => None, }, could_be_expr: match res { Res::Def(DefKind::Fn, _) => { // Verify whether this is a fn call or an Fn used as a type. self.r .session .source_map() .span_to_snippet(span) .map(|snippet| snippet.ends_with(')')) .unwrap_or(false) } Res::Def( DefKind::Ctor(..) | DefKind::AssocFn | DefKind::Const | DefKind::AssocConst, _, ) | Res::SelfCtor(_) | Res::PrimTy(_) | Res::Local(_) => true, _ => false, }, suggestion: None, } } else { let item_span = path.last().unwrap().ident.span; let (mod_prefix, mod_str, suggestion) = if path.len() == 1 { debug!(?self.diagnostic_metadata.current_impl_items); debug!(?self.diagnostic_metadata.current_function); let suggestion = if self.current_trait_ref.is_none() && let Some((fn_kind, _)) = self.diagnostic_metadata.current_function && let Some(FnCtxt::Assoc(_)) = fn_kind.ctxt() && let Some(items) = self.diagnostic_metadata.current_impl_items && let Some(item) = items.iter().find(|i| { if let AssocItemKind::Fn(_) = &i.kind && i.ident.name == item_str.name { debug!(?item_str.name); return true } false }) && let AssocItemKind::Fn(fn_) = &item.kind { debug!(?fn_); let self_sugg = if fn_.sig.decl.has_self() { "self." } else { "Self::" }; Some(( item_span.shrink_to_lo(), "consider using the associated function", self_sugg.to_string() )) } else { None }; (String::new(), "this scope".to_string(), suggestion) } else if path.len() == 2 && path[0].ident.name == kw::PathRoot { if self.r.session.edition() > Edition::Edition2015 { // In edition 2018 onwards, the `::foo` syntax may only pull from the extern prelude // which overrides all other expectations of item type expected = "crate"; (String::new(), "the list of imported crates".to_string(), None) } else { (String::new(), "the crate root".to_string(), None) } } else if path.len() == 2 && path[0].ident.name == kw::Crate { (String::new(), "the crate root".to_string(), None) } else { let mod_path = &path[..path.len() - 1]; let mod_prefix = match self.resolve_path(mod_path, Some(TypeNS), None) { PathResult::Module(ModuleOrUniformRoot::Module(module)) => module.res(), _ => None, } .map_or_else(String::new, |res| format!("{} ", res.descr())); (mod_prefix, format!("`{}`", Segment::names_to_string(mod_path)), None) }; let (fallback_label, suggestion) = if path_str == "async" && expected.starts_with("struct") { ("`async` blocks are only allowed in Rust 2018 or later".to_string(), suggestion) } else { // check if we are in situation of typo like `True` instead of `true`. let override_suggestion = if ["true", "false"].contains(&item_str.to_string().to_lowercase().as_str()) { let item_typo = item_str.to_string().to_lowercase(); Some((item_span, "you may want to use a bool value instead", item_typo)) // FIXME(vincenzopalazzo): make the check smarter, // and maybe expand with levenshtein distance checks } else if item_str.as_str() == "printf" { Some(( item_span, "you may have meant to use the `print` macro", "print!".to_owned(), )) } else { suggestion }; (format!("not found in {mod_str}"), override_suggestion) }; BaseError { msg: format!("cannot find {expected} `{item_str}` in {mod_prefix}{mod_str}"), fallback_label, span: item_span, span_label: None, could_be_expr: false, suggestion, } } } /// Handles error reporting for `smart_resolve_path_fragment` function. /// Creates base error and amends it with one short label and possibly some longer helps/notes. pub(crate) fn smart_resolve_report_errors( &mut self, path: &[Segment], span: Span, source: PathSource<'_>, res: Option, ) -> (DiagnosticBuilder<'a, ErrorGuaranteed>, Vec) { debug!(?res, ?source); let base_error = self.make_base_error(path, span, source, res); let code = source.error_code(res.is_some()); let mut err = self.r.session.struct_span_err_with_code(base_error.span, &base_error.msg, code); self.suggest_swapping_misplaced_self_ty_and_trait(&mut err, source, res, base_error.span); if let Some((span, label)) = base_error.span_label { err.span_label(span, label); } if let Some(ref sugg) = base_error.suggestion { err.span_suggestion_verbose(sugg.0, sugg.1, &sugg.2, Applicability::MaybeIncorrect); } self.suggest_bare_struct_literal(&mut err); if self.suggest_pattern_match_with_let(&mut err, source, span) { // Fallback label. err.span_label(base_error.span, &base_error.fallback_label); return (err, Vec::new()); } self.suggest_self_or_self_ref(&mut err, path, span); self.detect_assoct_type_constraint_meant_as_path(&mut err, &base_error); if self.suggest_self_ty(&mut err, source, path, span) || self.suggest_self_value(&mut err, source, path, span) { return (err, Vec::new()); } let (found, candidates) = self.try_lookup_name_relaxed(&mut err, source, path, span, res, &base_error); if found { return (err, candidates); } if !self.type_ascription_suggestion(&mut err, base_error.span) { let mut fallback = self.suggest_trait_and_bounds(&mut err, source, res, span, &base_error); // if we have suggested using pattern matching, then don't add needless suggestions // for typos. fallback |= self.suggest_typo(&mut err, source, path, span, &base_error); if fallback { // Fallback label. err.span_label(base_error.span, &base_error.fallback_label); } } self.err_code_special_cases(&mut err, source, path, span); (err, candidates) } fn detect_assoct_type_constraint_meant_as_path( &self, err: &mut Diagnostic, base_error: &BaseError, ) { let Some(ty) = self.diagnostic_metadata.current_type_path else { return; }; let TyKind::Path(_, path) = &ty.kind else { return; }; for segment in &path.segments { let Some(params) = &segment.args else { continue; }; let ast::GenericArgs::AngleBracketed(ref params) = params.deref() else { continue; }; for param in ¶ms.args { let ast::AngleBracketedArg::Constraint(constraint) = param else { continue; }; let ast::AssocConstraintKind::Bound { bounds } = &constraint.kind else { continue; }; for bound in bounds { let ast::GenericBound::Trait(trait_ref, ast::TraitBoundModifier::None) = bound else { continue; }; if base_error.span == trait_ref.span { err.span_suggestion_verbose( constraint.ident.span.between(trait_ref.span), "you might have meant to write a path instead of an associated type bound", "::", Applicability::MachineApplicable, ); } } } } } fn suggest_self_or_self_ref(&mut self, err: &mut Diagnostic, path: &[Segment], span: Span) { if !self.self_type_is_available() { return; } let Some(path_last_segment) = path.last() else { return }; let item_str = path_last_segment.ident; // Emit help message for fake-self from other languages (e.g., `this` in Javascript). if ["this", "my"].contains(&item_str.as_str()) { err.span_suggestion_short( span, "you might have meant to use `self` here instead", "self", Applicability::MaybeIncorrect, ); if !self.self_value_is_available(path[0].ident.span) { if let Some((FnKind::Fn(_, _, sig, ..), fn_span)) = &self.diagnostic_metadata.current_function { let (span, sugg) = if let Some(param) = sig.decl.inputs.get(0) { (param.span.shrink_to_lo(), "&self, ") } else { ( self.r .session .source_map() .span_through_char(*fn_span, '(') .shrink_to_hi(), "&self", ) }; err.span_suggestion_verbose( span, "if you meant to use `self`, you are also missing a `self` receiver \ argument", sugg, Applicability::MaybeIncorrect, ); } } } } fn try_lookup_name_relaxed( &mut self, err: &mut Diagnostic, source: PathSource<'_>, path: &[Segment], span: Span, res: Option, base_error: &BaseError, ) -> (bool, Vec) { // Try to lookup name in more relaxed fashion for better error reporting. let ident = path.last().unwrap().ident; let is_expected = &|res| source.is_expected(res); let ns = source.namespace(); let is_enum_variant = &|res| matches!(res, Res::Def(DefKind::Variant, _)); let path_str = Segment::names_to_string(path); let ident_span = path.last().map_or(span, |ident| ident.ident.span); let mut candidates = self .r .lookup_import_candidates(ident, ns, &self.parent_scope, is_expected) .into_iter() .filter(|ImportSuggestion { did, .. }| { match (did, res.and_then(|res| res.opt_def_id())) { (Some(suggestion_did), Some(actual_did)) => *suggestion_did != actual_did, _ => true, } }) .collect::>(); let crate_def_id = CRATE_DEF_ID.to_def_id(); // Try to filter out intrinsics candidates, as long as we have // some other candidates to suggest. let intrinsic_candidates: Vec<_> = candidates .drain_filter(|sugg| { let path = path_names_to_string(&sugg.path); path.starts_with("core::intrinsics::") || path.starts_with("std::intrinsics::") }) .collect(); if candidates.is_empty() { // Put them back if we have no more candidates to suggest... candidates.extend(intrinsic_candidates); } if candidates.is_empty() && is_expected(Res::Def(DefKind::Enum, crate_def_id)) { let mut enum_candidates: Vec<_> = self .r .lookup_import_candidates(ident, ns, &self.parent_scope, is_enum_variant) .into_iter() .map(|suggestion| import_candidate_to_enum_paths(&suggestion)) .filter(|(_, enum_ty_path)| !enum_ty_path.starts_with("std::prelude::")) .collect(); if !enum_candidates.is_empty() { if let (PathSource::Type, Some(span)) = (source, self.diagnostic_metadata.current_type_ascription.last()) { if self .r .session .parse_sess .type_ascription_path_suggestions .borrow() .contains(span) { // Already reported this issue on the lhs of the type ascription. err.downgrade_to_delayed_bug(); return (true, candidates); } } enum_candidates.sort(); // Contextualize for E0412 "cannot find type", but don't belabor the point // (that it's a variant) for E0573 "expected type, found variant". let preamble = if res.is_none() { let others = match enum_candidates.len() { 1 => String::new(), 2 => " and 1 other".to_owned(), n => format!(" and {} others", n), }; format!("there is an enum variant `{}`{}; ", enum_candidates[0].0, others) } else { String::new() }; let msg = format!("{}try using the variant's enum", preamble); err.span_suggestions( span, &msg, enum_candidates.into_iter().map(|(_variant_path, enum_ty_path)| enum_ty_path), Applicability::MachineApplicable, ); } } // Try Levenshtein algorithm. let typo_sugg = self.lookup_typo_candidate(path, source.namespace(), is_expected).to_opt_suggestion(); if path.len() == 1 && self.self_type_is_available() { if let Some(candidate) = self.lookup_assoc_candidate(ident, ns, is_expected, source.is_call()) { let self_is_available = self.self_value_is_available(path[0].ident.span); match candidate { AssocSuggestion::Field => { if self_is_available { err.span_suggestion( span, "you might have meant to use the available field", format!("self.{path_str}"), Applicability::MachineApplicable, ); } else { err.span_label(span, "a field by this name exists in `Self`"); } } AssocSuggestion::MethodWithSelf { called } if self_is_available => { let msg = if called { "you might have meant to call the method" } else { "you might have meant to refer to the method" }; err.span_suggestion( span, msg, format!("self.{path_str}"), Applicability::MachineApplicable, ); } AssocSuggestion::MethodWithSelf { .. } | AssocSuggestion::AssocFn { .. } | AssocSuggestion::AssocConst | AssocSuggestion::AssocType => { err.span_suggestion( span, &format!("you might have meant to {}", candidate.action()), format!("Self::{path_str}"), Applicability::MachineApplicable, ); } } self.r.add_typo_suggestion(err, typo_sugg, ident_span); return (true, candidates); } // If the first argument in call is `self` suggest calling a method. if let Some((call_span, args_span)) = self.call_has_self_arg(source) { let mut args_snippet = String::new(); if let Some(args_span) = args_span { if let Ok(snippet) = self.r.session.source_map().span_to_snippet(args_span) { args_snippet = snippet; } } err.span_suggestion( call_span, &format!("try calling `{ident}` as a method"), format!("self.{path_str}({args_snippet})"), Applicability::MachineApplicable, ); return (true, candidates); } } // Try context-dependent help if relaxed lookup didn't work. if let Some(res) = res { if self.smart_resolve_context_dependent_help( err, span, source, res, &path_str, &base_error.fallback_label, ) { // We do this to avoid losing a secondary span when we override the main error span. self.r.add_typo_suggestion(err, typo_sugg, ident_span); return (true, candidates); } } // Try to find in last block rib if let Some(rib) = &self.last_block_rib && let RibKind::NormalRibKind = rib.kind { for (ident, &res) in &rib.bindings { if let Res::Local(_) = res && path.len() == 1 && ident.span.eq_ctxt(path[0].ident.span) && ident.name == path[0].ident.name { err.span_help( ident.span, &format!("the binding `{}` is available in a different scope in the same function", path_str), ); return (true, candidates); } } } return (false, candidates); } fn suggest_trait_and_bounds( &mut self, err: &mut Diagnostic, source: PathSource<'_>, res: Option, span: Span, base_error: &BaseError, ) -> bool { let is_macro = base_error.span.from_expansion() && base_error.span.desugaring_kind().is_none(); let mut fallback = false; if let ( PathSource::Trait(AliasPossibility::Maybe), Some(Res::Def(DefKind::Struct | DefKind::Enum | DefKind::Union, _)), false, ) = (source, res, is_macro) { if let Some(bounds @ [_, .., _]) = self.diagnostic_metadata.current_trait_object { fallback = true; let spans: Vec = bounds .iter() .map(|bound| bound.span()) .filter(|&sp| sp != base_error.span) .collect(); let start_span = bounds[0].span(); // `end_span` is the end of the poly trait ref (Foo + 'baz + Bar><) let end_span = bounds.last().unwrap().span(); // `last_bound_span` is the last bound of the poly trait ref (Foo + >'baz< + Bar) let last_bound_span = spans.last().cloned().unwrap(); let mut multi_span: MultiSpan = spans.clone().into(); for sp in spans { let msg = if sp == last_bound_span { format!( "...because of {these} bound{s}", these = pluralize!("this", bounds.len() - 1), s = pluralize!(bounds.len() - 1), ) } else { String::new() }; multi_span.push_span_label(sp, msg); } multi_span.push_span_label(base_error.span, "expected this type to be a trait..."); err.span_help( multi_span, "`+` is used to constrain a \"trait object\" type with lifetimes or \ auto-traits; structs and enums can't be bound in that way", ); if bounds.iter().all(|bound| match bound { ast::GenericBound::Outlives(_) => true, ast::GenericBound::Trait(tr, _) => tr.span == base_error.span, }) { let mut sugg = vec![]; if base_error.span != start_span { sugg.push((start_span.until(base_error.span), String::new())); } if base_error.span != end_span { sugg.push((base_error.span.shrink_to_hi().to(end_span), String::new())); } err.multipart_suggestion( "if you meant to use a type and not a trait here, remove the bounds", sugg, Applicability::MaybeIncorrect, ); } } } fallback |= self.restrict_assoc_type_in_where_clause(span, err); fallback } fn suggest_typo( &mut self, err: &mut Diagnostic, source: PathSource<'_>, path: &[Segment], span: Span, base_error: &BaseError, ) -> bool { let is_expected = &|res| source.is_expected(res); let ident_span = path.last().map_or(span, |ident| ident.ident.span); let typo_sugg = self.lookup_typo_candidate(path, source.namespace(), is_expected); let is_in_same_file = &|sp1, sp2| { let source_map = self.r.session.source_map(); let file1 = source_map.span_to_filename(sp1); let file2 = source_map.span_to_filename(sp2); file1 == file2 }; // print 'you might have meant' if the candidate is (1) is a shadowed name with // accessible definition and (2) either defined in the same crate as the typo // (could be in a different file) or introduced in the same file as the typo // (could belong to a different crate) if let TypoCandidate::Shadowed(res, Some(sugg_span)) = typo_sugg && res .opt_def_id() .map_or(false, |id| id.is_local() || is_in_same_file(span, sugg_span)) { err.span_label( sugg_span, format!("you might have meant to refer to this {}", res.descr()), ); return true; } let mut fallback = false; let typo_sugg = typo_sugg.to_opt_suggestion(); if !self.r.add_typo_suggestion(err, typo_sugg, ident_span) { fallback = true; match self.diagnostic_metadata.current_let_binding { Some((pat_sp, Some(ty_sp), None)) if ty_sp.contains(base_error.span) && base_error.could_be_expr => { err.span_suggestion_short( pat_sp.between(ty_sp), "use `=` if you meant to assign", " = ", Applicability::MaybeIncorrect, ); } _ => {} } // If the trait has a single item (which wasn't matched by Levenshtein), suggest it let suggestion = self.get_single_associated_item(&path, &source, is_expected); if !self.r.add_typo_suggestion(err, suggestion, ident_span) { fallback = !self.let_binding_suggestion(err, ident_span); } } fallback } fn err_code_special_cases( &mut self, err: &mut Diagnostic, source: PathSource<'_>, path: &[Segment], span: Span, ) { if let Some(err_code) = &err.code { if err_code == &rustc_errors::error_code!(E0425) { for label_rib in &self.label_ribs { for (label_ident, node_id) in &label_rib.bindings { let ident = path.last().unwrap().ident; if format!("'{}", ident) == label_ident.to_string() { err.span_label(label_ident.span, "a label with a similar name exists"); if let PathSource::Expr(Some(Expr { kind: ExprKind::Break(None, Some(_)), .. })) = source { err.span_suggestion( span, "use the similarly named label", label_ident.name, Applicability::MaybeIncorrect, ); // Do not lint against unused label when we suggest them. self.diagnostic_metadata.unused_labels.remove(node_id); } } } } } else if err_code == &rustc_errors::error_code!(E0412) { if let Some(correct) = Self::likely_rust_type(path) { err.span_suggestion( span, "perhaps you intended to use this type", correct, Applicability::MaybeIncorrect, ); } } } } /// Emit special messages for unresolved `Self` and `self`. fn suggest_self_ty( &mut self, err: &mut Diagnostic, source: PathSource<'_>, path: &[Segment], span: Span, ) -> bool { if !is_self_type(path, source.namespace()) { return false; } err.code(rustc_errors::error_code!(E0411)); err.span_label(span, "`Self` is only available in impls, traits, and type definitions"); if let Some(item_kind) = self.diagnostic_metadata.current_item { if !item_kind.ident.span.is_dummy() { err.span_label( item_kind.ident.span, format!( "`Self` not allowed in {} {}", item_kind.kind.article(), item_kind.kind.descr() ), ); } } true } fn suggest_self_value( &mut self, err: &mut Diagnostic, source: PathSource<'_>, path: &[Segment], span: Span, ) -> bool { if !is_self_value(path, source.namespace()) { return false; } debug!("smart_resolve_path_fragment: E0424, source={:?}", source); err.code(rustc_errors::error_code!(E0424)); err.span_label( span, match source { PathSource::Pat => { "`self` value is a keyword and may not be bound to variables or shadowed" } _ => "`self` value is a keyword only available in methods with a `self` parameter", }, ); let is_assoc_fn = self.self_type_is_available(); if let Some((fn_kind, span)) = &self.diagnostic_metadata.current_function { // The current function has a `self' parameter, but we were unable to resolve // a reference to `self`. This can only happen if the `self` identifier we // are resolving came from a different hygiene context. if fn_kind.decl().inputs.get(0).map_or(false, |p| p.is_self()) { err.span_label(*span, "this function has a `self` parameter, but a macro invocation can only access identifiers it receives from parameters"); } else { let doesnt = if is_assoc_fn { let (span, sugg) = fn_kind .decl() .inputs .get(0) .map(|p| (p.span.shrink_to_lo(), "&self, ")) .unwrap_or_else(|| { // Try to look for the "(" after the function name, if possible. // This avoids placing the suggestion into the visibility specifier. let span = fn_kind .ident() .map_or(*span, |ident| span.with_lo(ident.span.hi())); ( self.r .session .source_map() .span_through_char(span, '(') .shrink_to_hi(), "&self", ) }); err.span_suggestion_verbose( span, "add a `self` receiver parameter to make the associated `fn` a method", sugg, Applicability::MaybeIncorrect, ); "doesn't" } else { "can't" }; if let Some(ident) = fn_kind.ident() { err.span_label( ident.span, &format!("this function {} have a `self` parameter", doesnt), ); } } } else if let Some(item_kind) = self.diagnostic_metadata.current_item { err.span_label( item_kind.ident.span, format!( "`self` not allowed in {} {}", item_kind.kind.article(), item_kind.kind.descr() ), ); } true } fn suggest_swapping_misplaced_self_ty_and_trait( &mut self, err: &mut Diagnostic, source: PathSource<'_>, res: Option, span: Span, ) { if let Some((trait_ref, self_ty)) = self.diagnostic_metadata.currently_processing_impl_trait.clone() && let TyKind::Path(_, self_ty_path) = &self_ty.kind && let PathResult::Module(ModuleOrUniformRoot::Module(module)) = self.resolve_path(&Segment::from_path(self_ty_path), Some(TypeNS), None) && let ModuleKind::Def(DefKind::Trait, ..) = module.kind && trait_ref.path.span == span && let PathSource::Trait(_) = source && let Some(Res::Def(DefKind::Struct | DefKind::Enum | DefKind::Union, _)) = res && let Ok(self_ty_str) = self.r.session.source_map().span_to_snippet(self_ty.span) && let Ok(trait_ref_str) = self.r.session.source_map().span_to_snippet(trait_ref.path.span) { err.multipart_suggestion( "`impl` items mention the trait being implemented first and the type it is being implemented for second", vec![(trait_ref.path.span, self_ty_str), (self_ty.span, trait_ref_str)], Applicability::MaybeIncorrect, ); } } fn suggest_bare_struct_literal(&mut self, err: &mut Diagnostic) { if let Some(span) = self.diagnostic_metadata.current_block_could_be_bare_struct_literal { err.multipart_suggestion( "you might have meant to write a `struct` literal", vec![ (span.shrink_to_lo(), "{ SomeStruct ".to_string()), (span.shrink_to_hi(), "}".to_string()), ], Applicability::HasPlaceholders, ); } } fn suggest_pattern_match_with_let( &mut self, err: &mut Diagnostic, source: PathSource<'_>, span: Span, ) -> bool { if let PathSource::Expr(_) = source && let Some(Expr { span: expr_span, kind: ExprKind::Assign(lhs, _, _), .. }) = self.diagnostic_metadata.in_if_condition { // Icky heuristic so we don't suggest: // `if (i + 2) = 2` => `if let (i + 2) = 2` (approximately pattern) // `if 2 = i` => `if let 2 = i` (lhs needs to contain error span) if lhs.is_approximately_pattern() && lhs.span.contains(span) { err.span_suggestion_verbose( expr_span.shrink_to_lo(), "you might have meant to use pattern matching", "let ", Applicability::MaybeIncorrect, ); return true; } } false } fn get_single_associated_item( &mut self, path: &[Segment], source: &PathSource<'_>, filter_fn: &impl Fn(Res) -> bool, ) -> Option { if let crate::PathSource::TraitItem(_) = source { let mod_path = &path[..path.len() - 1]; if let PathResult::Module(ModuleOrUniformRoot::Module(module)) = self.resolve_path(mod_path, None, None) { let resolutions = self.r.resolutions(module).borrow(); let targets: Vec<_> = resolutions .iter() .filter_map(|(key, resolution)| { resolution.borrow().binding.map(|binding| binding.res()).and_then( |res| if filter_fn(res) { Some((key, res)) } else { None }, ) }) .collect(); if targets.len() == 1 { let target = targets[0]; return Some(TypoSuggestion::single_item_from_ident(target.0.ident, target.1)); } } } None } /// Given `where ::Baz: String`, suggest `where T: Bar`. fn restrict_assoc_type_in_where_clause(&mut self, span: Span, err: &mut Diagnostic) -> bool { // Detect that we are actually in a `where` predicate. let (bounded_ty, bounds, where_span) = if let Some(ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate { bounded_ty, bound_generic_params, bounds, span, })) = self.diagnostic_metadata.current_where_predicate { if !bound_generic_params.is_empty() { return false; } (bounded_ty, bounds, span) } else { return false; }; // Confirm that the target is an associated type. let (ty, position, path) = if let ast::TyKind::Path(Some(qself), path) = &bounded_ty.kind { // use this to verify that ident is a type param. let Some(partial_res) = self.r.partial_res_map.get(&bounded_ty.id) else { return false; }; if !matches!( partial_res.full_res(), Some(hir::def::Res::Def(hir::def::DefKind::AssocTy, _)) ) { return false; } (&qself.ty, qself.position, path) } else { return false; }; let peeled_ty = ty.peel_refs(); if let ast::TyKind::Path(None, type_param_path) = &peeled_ty.kind { // Confirm that the `SelfTy` is a type parameter. let Some(partial_res) = self.r.partial_res_map.get(&peeled_ty.id) else { return false; }; if !matches!( partial_res.full_res(), Some(hir::def::Res::Def(hir::def::DefKind::TyParam, _)) ) { return false; } if let ( [ast::PathSegment { ident: constrain_ident, args: None, .. }], [ast::GenericBound::Trait(poly_trait_ref, ast::TraitBoundModifier::None)], ) = (&type_param_path.segments[..], &bounds[..]) { if let [ast::PathSegment { ident, args: None, .. }] = &poly_trait_ref.trait_ref.path.segments[..] { if ident.span == span { err.span_suggestion_verbose( *where_span, &format!("constrain the associated type to `{}`", ident), format!( "{}: {}<{} = {}>", self.r .session .source_map() .span_to_snippet(ty.span) // Account for `<&'a T as Foo>::Bar`. .unwrap_or_else(|_| constrain_ident.to_string()), path.segments[..position] .iter() .map(|segment| path_segment_to_string(segment)) .collect::>() .join("::"), path.segments[position..] .iter() .map(|segment| path_segment_to_string(segment)) .collect::>() .join("::"), ident, ), Applicability::MaybeIncorrect, ); } return true; } } } false } /// Check if the source is call expression and the first argument is `self`. If true, /// return the span of whole call and the span for all arguments expect the first one (`self`). fn call_has_self_arg(&self, source: PathSource<'_>) -> Option<(Span, Option)> { let mut has_self_arg = None; if let PathSource::Expr(Some(parent)) = source { match &parent.kind { ExprKind::Call(_, args) if !args.is_empty() => { let mut expr_kind = &args[0].kind; loop { match expr_kind { ExprKind::Path(_, arg_name) if arg_name.segments.len() == 1 => { if arg_name.segments[0].ident.name == kw::SelfLower { let call_span = parent.span; let tail_args_span = if args.len() > 1 { Some(Span::new( args[1].span.lo(), args.last().unwrap().span.hi(), call_span.ctxt(), None, )) } else { None }; has_self_arg = Some((call_span, tail_args_span)); } break; } ExprKind::AddrOf(_, _, expr) => expr_kind = &expr.kind, _ => break, } } } _ => (), } }; has_self_arg } fn followed_by_brace(&self, span: Span) -> (bool, Option) { // HACK(estebank): find a better way to figure out that this was a // parser issue where a struct literal is being used on an expression // where a brace being opened means a block is being started. Look // ahead for the next text to see if `span` is followed by a `{`. let sm = self.r.session.source_map(); let sp = sm.span_look_ahead(span, None, Some(50)); let followed_by_brace = matches!(sm.span_to_snippet(sp), Ok(ref snippet) if snippet == "{"); // In case this could be a struct literal that needs to be surrounded // by parentheses, find the appropriate span. let closing_span = sm.span_look_ahead(span, Some("}"), Some(50)); let closing_brace: Option = sm .span_to_snippet(closing_span) .map_or(None, |s| if s == "}" { Some(span.to(closing_span)) } else { None }); (followed_by_brace, closing_brace) } /// Provides context-dependent help for errors reported by the `smart_resolve_path_fragment` /// function. /// Returns `true` if able to provide context-dependent help. fn smart_resolve_context_dependent_help( &mut self, err: &mut Diagnostic, span: Span, source: PathSource<'_>, res: Res, path_str: &str, fallback_label: &str, ) -> bool { let ns = source.namespace(); let is_expected = &|res| source.is_expected(res); let path_sep = |err: &mut Diagnostic, expr: &Expr, kind: DefKind| { const MESSAGE: &str = "use the path separator to refer to an item"; let (lhs_span, rhs_span) = match &expr.kind { ExprKind::Field(base, ident) => (base.span, ident.span), ExprKind::MethodCall(box MethodCall { receiver, span, .. }) => { (receiver.span, *span) } _ => return false, }; if lhs_span.eq_ctxt(rhs_span) { err.span_suggestion( lhs_span.between(rhs_span), MESSAGE, "::", Applicability::MaybeIncorrect, ); true } else if kind == DefKind::Struct && let Some(lhs_source_span) = lhs_span.find_ancestor_inside(expr.span) && let Ok(snippet) = self.r.session.source_map().span_to_snippet(lhs_source_span) { // The LHS is a type that originates from a macro call. // We have to add angle brackets around it. err.span_suggestion_verbose( lhs_source_span.until(rhs_span), MESSAGE, format!("<{snippet}>::"), Applicability::MaybeIncorrect, ); true } else { // Either we were unable to obtain the source span / the snippet or // the LHS originates from a macro call and it is not a type and thus // there is no way to replace `.` with `::` and still somehow suggest // valid Rust code. false } }; let find_span = |source: &PathSource<'_>, err: &mut Diagnostic| { match source { PathSource::Expr(Some(Expr { span, kind: ExprKind::Call(_, _), .. })) | PathSource::TupleStruct(span, _) => { // We want the main underline to cover the suggested code as well for // cleaner output. err.set_span(*span); *span } _ => span, } }; let mut bad_struct_syntax_suggestion = |def_id: DefId| { let (followed_by_brace, closing_brace) = self.followed_by_brace(span); match source { PathSource::Expr(Some( parent @ Expr { kind: ExprKind::Field(..) | ExprKind::MethodCall(..), .. }, )) if path_sep(err, &parent, DefKind::Struct) => {} PathSource::Expr( None | Some(Expr { kind: ExprKind::Path(..) | ExprKind::Binary(..) | ExprKind::Unary(..) | ExprKind::If(..) | ExprKind::While(..) | ExprKind::ForLoop(..) | ExprKind::Match(..), .. }), ) if followed_by_brace => { if let Some(sp) = closing_brace { err.span_label(span, fallback_label); err.multipart_suggestion( "surround the struct literal with parentheses", vec![ (sp.shrink_to_lo(), "(".to_string()), (sp.shrink_to_hi(), ")".to_string()), ], Applicability::MaybeIncorrect, ); } else { err.span_label( span, // Note the parentheses surrounding the suggestion below format!( "you might want to surround a struct literal with parentheses: \ `({} {{ /* fields */ }})`?", path_str ), ); } } PathSource::Expr(_) | PathSource::TupleStruct(..) | PathSource::Pat => { let span = find_span(&source, err); if let Some(span) = self.def_span(def_id) { err.span_label(span, &format!("`{}` defined here", path_str)); } let (tail, descr, applicability) = match source { PathSource::Pat | PathSource::TupleStruct(..) => { ("", "pattern", Applicability::MachineApplicable) } _ => (": val", "literal", Applicability::HasPlaceholders), }; let (fields, applicability) = match self.r.field_names.get(&def_id) { Some(fields) => ( fields .iter() .map(|f| format!("{}{}", f.node, tail)) .collect::>() .join(", "), applicability, ), None => ("/* fields */".to_string(), Applicability::HasPlaceholders), }; let pad = match self.r.field_names.get(&def_id) { Some(fields) if fields.is_empty() => "", _ => " ", }; err.span_suggestion( span, &format!("use struct {} syntax instead", descr), format!("{path_str} {{{pad}{fields}{pad}}}"), applicability, ); } _ => { err.span_label(span, fallback_label); } } }; match (res, source) { ( Res::Def(DefKind::Macro(MacroKind::Bang), _), PathSource::Expr(Some(Expr { kind: ExprKind::Index(..) | ExprKind::Call(..), .. })) | PathSource::Struct, ) => { err.span_label(span, fallback_label); err.span_suggestion_verbose( span.shrink_to_hi(), "use `!` to invoke the macro", "!", Applicability::MaybeIncorrect, ); if path_str == "try" && span.rust_2015() { err.note("if you want the `try` keyword, you need Rust 2018 or later"); } } (Res::Def(DefKind::Macro(MacroKind::Bang), _), _) => { err.span_label(span, fallback_label); } (Res::Def(DefKind::TyAlias, def_id), PathSource::Trait(_)) => { err.span_label(span, "type aliases cannot be used as traits"); if self.r.session.is_nightly_build() { let msg = "you might have meant to use `#![feature(trait_alias)]` instead of a \ `type` alias"; if let Some(span) = self.def_span(def_id) { if let Ok(snip) = self.r.session.source_map().span_to_snippet(span) { // The span contains a type alias so we should be able to // replace `type` with `trait`. let snip = snip.replacen("type", "trait", 1); err.span_suggestion(span, msg, snip, Applicability::MaybeIncorrect); } else { err.span_help(span, msg); } } else { err.help(msg); } } } ( Res::Def(kind @ (DefKind::Mod | DefKind::Trait), _), PathSource::Expr(Some(parent)), ) => { if !path_sep(err, &parent, kind) { return false; } } ( Res::Def(DefKind::Enum, def_id), PathSource::TupleStruct(..) | PathSource::Expr(..), ) => { if self .diagnostic_metadata .current_type_ascription .last() .map(|sp| { self.r .session .parse_sess .type_ascription_path_suggestions .borrow() .contains(&sp) }) .unwrap_or(false) { err.downgrade_to_delayed_bug(); // We already suggested changing `:` into `::` during parsing. return false; } self.suggest_using_enum_variant(err, source, def_id, span); } (Res::Def(DefKind::Struct, def_id), source) if ns == ValueNS => { let (ctor_def, ctor_vis, fields) = if let Some(struct_ctor) = self.r.struct_constructors.get(&def_id).cloned() { if let PathSource::Expr(Some(parent)) = source { if let ExprKind::Field(..) | ExprKind::MethodCall(..) = parent.kind { bad_struct_syntax_suggestion(def_id); return true; } } struct_ctor } else { bad_struct_syntax_suggestion(def_id); return true; }; let is_accessible = self.r.is_accessible_from(ctor_vis, self.parent_scope.module); if !is_expected(ctor_def) || is_accessible { return true; } let field_spans = match source { // e.g. `if let Enum::TupleVariant(field1, field2) = _` PathSource::TupleStruct(_, pattern_spans) => { err.set_primary_message( "cannot match against a tuple struct which contains private fields", ); // Use spans of the tuple struct pattern. Some(Vec::from(pattern_spans)) } // e.g. `let _ = Enum::TupleVariant(field1, field2);` _ if source.is_call() => { err.set_primary_message( "cannot initialize a tuple struct which contains private fields", ); // Use spans of the tuple struct definition. self.r .field_names .get(&def_id) .map(|fields| fields.iter().map(|f| f.span).collect::>()) } _ => None, }; if let Some(spans) = field_spans.filter(|spans| spans.len() > 0 && fields.len() == spans.len()) { let non_visible_spans: Vec = iter::zip(&fields, &spans) .filter(|(vis, _)| { !self.r.is_accessible_from(**vis, self.parent_scope.module) }) .map(|(_, span)| *span) .collect(); if non_visible_spans.len() > 0 { if let Some(fields) = self.r.field_visibility_spans.get(&def_id) { err.multipart_suggestion_verbose( &format!( "consider making the field{} publicly accessible", pluralize!(fields.len()) ), fields.iter().map(|span| (*span, "pub ".to_string())).collect(), Applicability::MaybeIncorrect, ); } let mut m: MultiSpan = non_visible_spans.clone().into(); non_visible_spans .into_iter() .for_each(|s| m.push_span_label(s, "private field")); err.span_note(m, "constructor is not visible here due to private fields"); } return true; } err.span_label(span, "constructor is not visible here due to private fields"); } (Res::Def(DefKind::Union | DefKind::Variant, def_id), _) if ns == ValueNS => { bad_struct_syntax_suggestion(def_id); } (Res::Def(DefKind::Ctor(_, CtorKind::Const), def_id), _) if ns == ValueNS => { match source { PathSource::Expr(_) | PathSource::TupleStruct(..) | PathSource::Pat => { let span = find_span(&source, err); if let Some(span) = self.def_span(def_id) { err.span_label(span, &format!("`{}` defined here", path_str)); } err.span_suggestion( span, "use this syntax instead", path_str, Applicability::MaybeIncorrect, ); } _ => return false, } } (Res::Def(DefKind::Ctor(_, CtorKind::Fn), ctor_def_id), _) if ns == ValueNS => { let def_id = self.r.parent(ctor_def_id); if let Some(span) = self.def_span(def_id) { err.span_label(span, &format!("`{}` defined here", path_str)); } let fields = self.r.field_names.get(&def_id).map_or_else( || "/* fields */".to_string(), |fields| vec!["_"; fields.len()].join(", "), ); err.span_suggestion( span, "use the tuple variant pattern syntax instead", format!("{}({})", path_str, fields), Applicability::HasPlaceholders, ); } (Res::SelfTyParam { .. } | Res::SelfTyAlias { .. }, _) if ns == ValueNS => { err.span_label(span, fallback_label); err.note("can't use `Self` as a constructor, you must use the implemented struct"); } (Res::Def(DefKind::TyAlias | DefKind::AssocTy, _), _) if ns == ValueNS => { err.note("can't use a type alias as a constructor"); } _ => return false, } true } /// Given the target `ident` and `kind`, search for the similarly named associated item /// in `self.current_trait_ref`. pub(crate) fn find_similarly_named_assoc_item( &mut self, ident: Symbol, kind: &AssocItemKind, ) -> Option { let (module, _) = self.current_trait_ref.as_ref()?; if ident == kw::Underscore { // We do nothing for `_`. return None; } let resolutions = self.r.resolutions(module); let targets = resolutions .borrow() .iter() .filter_map(|(key, res)| res.borrow().binding.map(|binding| (key, binding.res()))) .filter(|(_, res)| match (kind, res) { (AssocItemKind::Const(..), Res::Def(DefKind::AssocConst, _)) => true, (AssocItemKind::Fn(_), Res::Def(DefKind::AssocFn, _)) => true, (AssocItemKind::Type(..), Res::Def(DefKind::AssocTy, _)) => true, _ => false, }) .map(|(key, _)| key.ident.name) .collect::>(); find_best_match_for_name(&targets, ident, None) } fn lookup_assoc_candidate( &mut self, ident: Ident, ns: Namespace, filter_fn: FilterFn, called: bool, ) -> Option where FilterFn: Fn(Res) -> bool, { fn extract_node_id(t: &Ty) -> Option { match t.kind { TyKind::Path(None, _) => Some(t.id), TyKind::Ref(_, ref mut_ty) => extract_node_id(&mut_ty.ty), // This doesn't handle the remaining `Ty` variants as they are not // that commonly the self_type, it might be interesting to provide // support for those in future. _ => None, } } // Fields are generally expected in the same contexts as locals. if filter_fn(Res::Local(ast::DUMMY_NODE_ID)) { if let Some(node_id) = self.diagnostic_metadata.current_self_type.as_ref().and_then(extract_node_id) { // Look for a field with the same name in the current self_type. if let Some(resolution) = self.r.partial_res_map.get(&node_id) { if let Some(Res::Def(DefKind::Struct | DefKind::Union, did)) = resolution.full_res() { if let Some(field_names) = self.r.field_names.get(&did) { if field_names.iter().any(|&field_name| ident.name == field_name.node) { return Some(AssocSuggestion::Field); } } } } } } if let Some(items) = self.diagnostic_metadata.current_trait_assoc_items { for assoc_item in items { if assoc_item.ident == ident { return Some(match &assoc_item.kind { ast::AssocItemKind::Const(..) => AssocSuggestion::AssocConst, ast::AssocItemKind::Fn(box ast::Fn { sig, .. }) if sig.decl.has_self() => { AssocSuggestion::MethodWithSelf { called } } ast::AssocItemKind::Fn(..) => AssocSuggestion::AssocFn { called }, ast::AssocItemKind::Type(..) => AssocSuggestion::AssocType, ast::AssocItemKind::MacCall(_) => continue, }); } } } // Look for associated items in the current trait. if let Some((module, _)) = self.current_trait_ref { if let Ok(binding) = self.r.maybe_resolve_ident_in_module( ModuleOrUniformRoot::Module(module), ident, ns, &self.parent_scope, ) { let res = binding.res(); if filter_fn(res) { if self.r.has_self.contains(&res.def_id()) { return Some(AssocSuggestion::MethodWithSelf { called }); } else { match res { Res::Def(DefKind::AssocFn, _) => { return Some(AssocSuggestion::AssocFn { called }); } Res::Def(DefKind::AssocConst, _) => { return Some(AssocSuggestion::AssocConst); } Res::Def(DefKind::AssocTy, _) => { return Some(AssocSuggestion::AssocType); } _ => {} } } } } } None } fn lookup_typo_candidate( &mut self, path: &[Segment], ns: Namespace, filter_fn: &impl Fn(Res) -> bool, ) -> TypoCandidate { let mut names = Vec::new(); if path.len() == 1 { let mut ctxt = path.last().unwrap().ident.span.ctxt(); // Search in lexical scope. // Walk backwards up the ribs in scope and collect candidates. for rib in self.ribs[ns].iter().rev() { let rib_ctxt = if rib.kind.contains_params() { ctxt.normalize_to_macros_2_0() } else { ctxt.normalize_to_macro_rules() }; // Locals and type parameters for (ident, &res) in &rib.bindings { if filter_fn(res) && ident.span.ctxt() == rib_ctxt { names.push(TypoSuggestion::typo_from_ident(*ident, res)); } } if let RibKind::MacroDefinition(def) = rib.kind && def == self.r.macro_def(ctxt) { // If an invocation of this macro created `ident`, give up on `ident` // and switch to `ident`'s source from the macro definition. ctxt.remove_mark(); continue; } // Items in scope if let RibKind::ModuleRibKind(module) = rib.kind { // Items from this module self.r.add_module_candidates(module, &mut names, &filter_fn, Some(ctxt)); if let ModuleKind::Block = module.kind { // We can see through blocks } else { // Items from the prelude if !module.no_implicit_prelude { let extern_prelude = self.r.extern_prelude.clone(); names.extend(extern_prelude.iter().flat_map(|(ident, _)| { self.r .crate_loader() .maybe_process_path_extern(ident.name) .and_then(|crate_id| { let crate_mod = Res::Def(DefKind::Mod, crate_id.as_def_id()); if filter_fn(crate_mod) { Some(TypoSuggestion::typo_from_ident(*ident, crate_mod)) } else { None } }) })); if let Some(prelude) = self.r.prelude { self.r.add_module_candidates(prelude, &mut names, &filter_fn, None); } } break; } } } // Add primitive types to the mix if filter_fn(Res::PrimTy(PrimTy::Bool)) { names.extend(PrimTy::ALL.iter().map(|prim_ty| { TypoSuggestion::typo_from_name(prim_ty.name(), Res::PrimTy(*prim_ty)) })) } } else { // Search in module. let mod_path = &path[..path.len() - 1]; if let PathResult::Module(ModuleOrUniformRoot::Module(module)) = self.resolve_path(mod_path, Some(TypeNS), None) { self.r.add_module_candidates(module, &mut names, &filter_fn, None); } } let name = path[path.len() - 1].ident.name; // Make sure error reporting is deterministic. names.sort_by(|a, b| a.candidate.as_str().partial_cmp(b.candidate.as_str()).unwrap()); match find_best_match_for_name( &names.iter().map(|suggestion| suggestion.candidate).collect::>(), name, None, ) { Some(found) => { let Some(sugg) = names.into_iter().find(|suggestion| suggestion.candidate == found) else { return TypoCandidate::None; }; if found == name { TypoCandidate::Shadowed(sugg.res, sugg.span) } else { TypoCandidate::Typo(sugg) } } _ => TypoCandidate::None, } } // Returns the name of the Rust type approximately corresponding to // a type name in another programming language. fn likely_rust_type(path: &[Segment]) -> Option { let name = path[path.len() - 1].ident.as_str(); // Common Java types Some(match name { "byte" => sym::u8, // In Java, bytes are signed, but in practice one almost always wants unsigned bytes. "short" => sym::i16, "Bool" => sym::bool, "Boolean" => sym::bool, "boolean" => sym::bool, "int" => sym::i32, "long" => sym::i64, "float" => sym::f32, "double" => sym::f64, _ => return None, }) } /// Only used in a specific case of type ascription suggestions fn get_colon_suggestion_span(&self, start: Span) -> Span { let sm = self.r.session.source_map(); start.to(sm.next_point(start)) } fn type_ascription_suggestion(&self, err: &mut Diagnostic, base_span: Span) -> bool { let sm = self.r.session.source_map(); let base_snippet = sm.span_to_snippet(base_span); if let Some(&sp) = self.diagnostic_metadata.current_type_ascription.last() { if let Ok(snippet) = sm.span_to_snippet(sp) { let len = snippet.trim_end().len() as u32; if snippet.trim() == ":" { let colon_sp = sp.with_lo(sp.lo() + BytePos(len - 1)).with_hi(sp.lo() + BytePos(len)); let mut show_label = true; if sm.is_multiline(sp) { err.span_suggestion_short( colon_sp, "maybe you meant to write `;` here", ";", Applicability::MaybeIncorrect, ); } else { let after_colon_sp = self.get_colon_suggestion_span(colon_sp.shrink_to_hi()); if snippet.len() == 1 { // `foo:bar` err.span_suggestion( colon_sp, "maybe you meant to write a path separator here", "::", Applicability::MaybeIncorrect, ); show_label = false; if !self .r .session .parse_sess .type_ascription_path_suggestions .borrow_mut() .insert(colon_sp) { err.downgrade_to_delayed_bug(); } } if let Ok(base_snippet) = base_snippet { // Try to find an assignment let eq_span = sm.span_look_ahead(after_colon_sp, Some("="), Some(50)); if let Ok(ref snippet) = sm.span_to_snippet(eq_span) && snippet == "=" { err.span_suggestion( base_span, "maybe you meant to write an assignment here", format!("let {}", base_snippet), Applicability::MaybeIncorrect, ); show_label = false; } } } if show_label { err.span_label( base_span, "expecting a type here because of type ascription", ); } return show_label; } } } false } // try to give a suggestion for this pattern: `name = blah`, which is common in other languages // suggest `let name = blah` to introduce a new binding fn let_binding_suggestion(&mut self, err: &mut Diagnostic, ident_span: Span) -> bool { if let Some(Expr { kind: ExprKind::Assign(lhs, .. ), .. }) = self.diagnostic_metadata.in_assignment && let ast::ExprKind::Path(None, _) = lhs.kind { if !ident_span.from_expansion() { err.span_suggestion_verbose( ident_span.shrink_to_lo(), "you might have meant to introduce a new binding", "let ".to_string(), Applicability::MaybeIncorrect, ); return true; } } false } fn find_module(&mut self, def_id: DefId) -> Option<(Module<'a>, ImportSuggestion)> { let mut result = None; let mut seen_modules = FxHashSet::default(); let mut worklist = vec![(self.r.graph_root, ThinVec::new())]; while let Some((in_module, path_segments)) = worklist.pop() { // abort if the module is already found if result.is_some() { break; } in_module.for_each_child(self.r, |_, ident, _, name_binding| { // abort if the module is already found or if name_binding is private external if result.is_some() || !name_binding.vis.is_visible_locally() { return; } if let Some(module) = name_binding.module() { // form the path let mut path_segments = path_segments.clone(); path_segments.push(ast::PathSegment::from_ident(ident)); let module_def_id = module.def_id(); if module_def_id == def_id { let path = Path { span: name_binding.span, segments: path_segments, tokens: None }; result = Some(( module, ImportSuggestion { did: Some(def_id), descr: "module", path, accessible: true, note: None, }, )); } else { // add the module to the lookup if seen_modules.insert(module_def_id) { worklist.push((module, path_segments)); } } } }); } result } fn collect_enum_ctors(&mut self, def_id: DefId) -> Option> { self.find_module(def_id).map(|(enum_module, enum_import_suggestion)| { let mut variants = Vec::new(); enum_module.for_each_child(self.r, |_, ident, _, name_binding| { if let Res::Def(DefKind::Ctor(CtorOf::Variant, kind), def_id) = name_binding.res() { let mut segms = enum_import_suggestion.path.segments.clone(); segms.push(ast::PathSegment::from_ident(ident)); let path = Path { span: name_binding.span, segments: segms, tokens: None }; variants.push((path, def_id, kind)); } }); variants }) } /// Adds a suggestion for using an enum's variant when an enum is used instead. fn suggest_using_enum_variant( &mut self, err: &mut Diagnostic, source: PathSource<'_>, def_id: DefId, span: Span, ) { let Some(variants) = self.collect_enum_ctors(def_id) else { err.note("you might have meant to use one of the enum's variants"); return; }; let suggest_only_tuple_variants = matches!(source, PathSource::TupleStruct(..)) || source.is_call(); if suggest_only_tuple_variants { // Suggest only tuple variants regardless of whether they have fields and do not // suggest path with added parentheses. let suggestable_variants = variants .iter() .filter(|(.., kind)| *kind == CtorKind::Fn) .map(|(variant, ..)| path_names_to_string(variant)) .collect::>(); let non_suggestable_variant_count = variants.len() - suggestable_variants.len(); let source_msg = if source.is_call() { "to construct" } else if matches!(source, PathSource::TupleStruct(..)) { "to match against" } else { unreachable!() }; if !suggestable_variants.is_empty() { let msg = if non_suggestable_variant_count == 0 && suggestable_variants.len() == 1 { format!("try {} the enum's variant", source_msg) } else { format!("try {} one of the enum's variants", source_msg) }; err.span_suggestions( span, &msg, suggestable_variants, Applicability::MaybeIncorrect, ); } // If the enum has no tuple variants.. if non_suggestable_variant_count == variants.len() { err.help(&format!("the enum has no tuple variants {}", source_msg)); } // If there are also non-tuple variants.. if non_suggestable_variant_count == 1 { err.help(&format!( "you might have meant {} the enum's non-tuple variant", source_msg )); } else if non_suggestable_variant_count >= 1 { err.help(&format!( "you might have meant {} one of the enum's non-tuple variants", source_msg )); } } else { let needs_placeholder = |ctor_def_id: DefId, kind: CtorKind| { let def_id = self.r.parent(ctor_def_id); let has_no_fields = self.r.field_names.get(&def_id).map_or(false, |f| f.is_empty()); match kind { CtorKind::Const => false, CtorKind::Fn if has_no_fields => false, _ => true, } }; let suggestable_variants = variants .iter() .filter(|(_, def_id, kind)| !needs_placeholder(*def_id, *kind)) .map(|(variant, _, kind)| (path_names_to_string(variant), kind)) .map(|(variant, kind)| match kind { CtorKind::Const => variant, CtorKind::Fn => format!("({}())", variant), }) .collect::>(); let no_suggestable_variant = suggestable_variants.is_empty(); if !no_suggestable_variant { let msg = if suggestable_variants.len() == 1 { "you might have meant to use the following enum variant" } else { "you might have meant to use one of the following enum variants" }; err.span_suggestions( span, msg, suggestable_variants, Applicability::MaybeIncorrect, ); } let suggestable_variants_with_placeholders = variants .iter() .filter(|(_, def_id, kind)| needs_placeholder(*def_id, *kind)) .map(|(variant, _, kind)| (path_names_to_string(variant), kind)) .filter_map(|(variant, kind)| match kind { CtorKind::Fn => Some(format!("({}(/* fields */))", variant)), _ => None, }) .collect::>(); if !suggestable_variants_with_placeholders.is_empty() { let msg = match (no_suggestable_variant, suggestable_variants_with_placeholders.len()) { (true, 1) => "the following enum variant is available", (true, _) => "the following enum variants are available", (false, 1) => "alternatively, the following enum variant is available", (false, _) => { "alternatively, the following enum variants are also available" } }; err.span_suggestions( span, msg, suggestable_variants_with_placeholders, Applicability::HasPlaceholders, ); } }; if def_id.is_local() { if let Some(span) = self.def_span(def_id) { err.span_note(span, "the enum is defined here"); } } } pub(crate) fn report_missing_type_error( &self, path: &[Segment], ) -> Option<(Span, &'static str, String, Applicability)> { let (ident, span) = match path { [segment] if !segment.has_generic_args && segment.ident.name != kw::SelfUpper && segment.ident.name != kw::Dyn => { (segment.ident.to_string(), segment.ident.span) } _ => return None, }; let mut iter = ident.chars().map(|c| c.is_uppercase()); let single_uppercase_char = matches!(iter.next(), Some(true)) && matches!(iter.next(), None); if !self.diagnostic_metadata.currently_processing_generics && !single_uppercase_char { return None; } match (self.diagnostic_metadata.current_item, single_uppercase_char, self.diagnostic_metadata.currently_processing_generics) { (Some(Item { kind: ItemKind::Fn(..), ident, .. }), _, _) if ident.name == sym::main => { // Ignore `fn main()` as we don't want to suggest `fn main()` } ( Some(Item { kind: kind @ ItemKind::Fn(..) | kind @ ItemKind::Enum(..) | kind @ ItemKind::Struct(..) | kind @ ItemKind::Union(..), .. }), true, _ ) // Without the 2nd `true`, we'd suggest `impl ` for `impl T` when a type `T` isn't found | (Some(Item { kind: kind @ ItemKind::Impl(..), .. }), true, true) | (Some(Item { kind, .. }), false, _) => { // Likely missing type parameter. if let Some(generics) = kind.generics() { if span.overlaps(generics.span) { // Avoid the following: // error[E0405]: cannot find trait `A` in this scope // --> $DIR/typo-suggestion-named-underscore.rs:CC:LL // | // L | fn foo(x: T) {} // Shouldn't suggest underscore // | ^- help: you might be missing a type parameter: `, A` // | | // | not found in this scope return None; } let msg = "you might be missing a type parameter"; let (span, sugg) = if let [.., param] = &generics.params[..] { let span = if let [.., bound] = ¶m.bounds[..] { bound.span() } else if let GenericParam { kind: GenericParamKind::Const { ty, kw_span: _, default }, .. } = param { default.as_ref().map(|def| def.value.span).unwrap_or(ty.span) } else { param.ident.span }; (span, format!(", {}", ident)) } else { (generics.span, format!("<{}>", ident)) }; // Do not suggest if this is coming from macro expansion. if span.can_be_used_for_suggestions() { return Some(( span.shrink_to_hi(), msg, sugg, Applicability::MaybeIncorrect, )); } } } _ => {} } None } /// Given the target `label`, search the `rib_index`th label rib for similarly named labels, /// optionally returning the closest match and whether it is reachable. pub(crate) fn suggestion_for_label_in_rib( &self, rib_index: usize, label: Ident, ) -> Option { // Are ribs from this `rib_index` within scope? let within_scope = self.is_label_valid_from_rib(rib_index); let rib = &self.label_ribs[rib_index]; let names = rib .bindings .iter() .filter(|(id, _)| id.span.eq_ctxt(label.span)) .map(|(id, _)| id.name) .collect::>(); find_best_match_for_name(&names, label.name, None).map(|symbol| { // Upon finding a similar name, get the ident that it was from - the span // contained within helps make a useful diagnostic. In addition, determine // whether this candidate is within scope. let (ident, _) = rib.bindings.iter().find(|(ident, _)| ident.name == symbol).unwrap(); (*ident, within_scope) }) } pub(crate) fn maybe_report_lifetime_uses( &mut self, generics_span: Span, params: &[ast::GenericParam], ) { for (param_index, param) in params.iter().enumerate() { let GenericParamKind::Lifetime = param.kind else { continue }; let def_id = self.r.local_def_id(param.id); let use_set = self.lifetime_uses.remove(&def_id); debug!( "Use set for {:?}({:?} at {:?}) is {:?}", def_id, param.ident, param.ident.span, use_set ); let deletion_span = || { if params.len() == 1 { // if sole lifetime, remove the entire `<>` brackets Some(generics_span) } else if param_index == 0 { // if removing within `<>` brackets, we also want to // delete a leading or trailing comma as appropriate match ( param.span().find_ancestor_inside(generics_span), params[param_index + 1].span().find_ancestor_inside(generics_span), ) { (Some(param_span), Some(next_param_span)) => { Some(param_span.to(next_param_span.shrink_to_lo())) } _ => None, } } else { // if removing within `<>` brackets, we also want to // delete a leading or trailing comma as appropriate match ( param.span().find_ancestor_inside(generics_span), params[param_index - 1].span().find_ancestor_inside(generics_span), ) { (Some(param_span), Some(prev_param_span)) => { Some(prev_param_span.shrink_to_hi().to(param_span)) } _ => None, } } }; match use_set { Some(LifetimeUseSet::Many) => {} Some(LifetimeUseSet::One { use_span, use_ctxt }) => { debug!(?param.ident, ?param.ident.span, ?use_span); let elidable = matches!(use_ctxt, LifetimeCtxt::Ref); let deletion_span = deletion_span(); self.r.lint_buffer.buffer_lint_with_diagnostic( lint::builtin::SINGLE_USE_LIFETIMES, param.id, param.ident.span, &format!("lifetime parameter `{}` only used once", param.ident), lint::BuiltinLintDiagnostics::SingleUseLifetime { param_span: param.ident.span, use_span: Some((use_span, elidable)), deletion_span, }, ); } None => { debug!(?param.ident, ?param.ident.span); let deletion_span = deletion_span(); self.r.lint_buffer.buffer_lint_with_diagnostic( lint::builtin::UNUSED_LIFETIMES, param.id, param.ident.span, &format!("lifetime parameter `{}` never used", param.ident), lint::BuiltinLintDiagnostics::SingleUseLifetime { param_span: param.ident.span, use_span: None, deletion_span, }, ); } } } } pub(crate) fn emit_undeclared_lifetime_error( &self, lifetime_ref: &ast::Lifetime, outer_lifetime_ref: Option, ) { debug_assert_ne!(lifetime_ref.ident.name, kw::UnderscoreLifetime); let mut err = if let Some(outer) = outer_lifetime_ref { let mut err = struct_span_err!( self.r.session, lifetime_ref.ident.span, E0401, "can't use generic parameters from outer item", ); err.span_label(lifetime_ref.ident.span, "use of generic parameter from outer item"); err.span_label(outer.span, "lifetime parameter from outer item"); err } else { let mut err = struct_span_err!( self.r.session, lifetime_ref.ident.span, E0261, "use of undeclared lifetime name `{}`", lifetime_ref.ident ); err.span_label(lifetime_ref.ident.span, "undeclared lifetime"); err }; self.suggest_introducing_lifetime( &mut err, Some(lifetime_ref.ident.name.as_str()), |err, _, span, message, suggestion| { err.span_suggestion(span, message, suggestion, Applicability::MaybeIncorrect); true }, ); err.emit(); } fn suggest_introducing_lifetime( &self, err: &mut Diagnostic, name: Option<&str>, suggest: impl Fn(&mut Diagnostic, bool, Span, &str, String) -> bool, ) { let mut suggest_note = true; for rib in self.lifetime_ribs.iter().rev() { let mut should_continue = true; match rib.kind { LifetimeRibKind::Generics { binder: _, span, kind } => { if !span.can_be_used_for_suggestions() && suggest_note && let Some(name) = name { suggest_note = false; // Avoid displaying the same help multiple times. err.span_label( span, &format!( "lifetime `{}` is missing in item created through this procedural macro", name, ), ); continue; } let higher_ranked = matches!( kind, LifetimeBinderKind::BareFnType | LifetimeBinderKind::PolyTrait | LifetimeBinderKind::WhereBound ); let (span, sugg) = if span.is_empty() { let sugg = format!( "{}<{}>{}", if higher_ranked { "for" } else { "" }, name.unwrap_or("'a"), if higher_ranked { " " } else { "" }, ); (span, sugg) } else { let span = self.r.session.source_map().span_through_char(span, '<').shrink_to_hi(); let sugg = format!("{}, ", name.unwrap_or("'a")); (span, sugg) }; if higher_ranked { let message = format!( "consider making the {} lifetime-generic with a new `{}` lifetime", kind.descr(), name.unwrap_or("'a"), ); should_continue = suggest(err, true, span, &message, sugg); err.note_once( "for more information on higher-ranked polymorphism, visit \ https://doc.rust-lang.org/nomicon/hrtb.html", ); } else if let Some(name) = name { let message = format!("consider introducing lifetime `{}` here", name); should_continue = suggest(err, false, span, &message, sugg); } else { let message = "consider introducing a named lifetime parameter"; should_continue = suggest(err, false, span, &message, sugg); } } LifetimeRibKind::Item => break, _ => {} } if !should_continue { break; } } } pub(crate) fn emit_non_static_lt_in_const_generic_error(&self, lifetime_ref: &ast::Lifetime) { struct_span_err!( self.r.session, lifetime_ref.ident.span, E0771, "use of non-static lifetime `{}` in const generic", lifetime_ref.ident ) .note( "for more information, see issue #74052 \ ", ) .emit(); } /// Non-static lifetimes are prohibited in anonymous constants under `min_const_generics`. /// This function will emit an error if `generic_const_exprs` is not enabled, the body identified by /// `body_id` is an anonymous constant and `lifetime_ref` is non-static. pub(crate) fn maybe_emit_forbidden_non_static_lifetime_error( &self, lifetime_ref: &ast::Lifetime, ) { let feature_active = self.r.session.features_untracked().generic_const_exprs; if !feature_active { feature_err( &self.r.session.parse_sess, sym::generic_const_exprs, lifetime_ref.ident.span, "a non-static lifetime is not allowed in a `const`", ) .emit(); } } pub(crate) fn report_missing_lifetime_specifiers( &mut self, lifetime_refs: Vec, function_param_lifetimes: Option<(Vec, Vec)>, ) -> ErrorGuaranteed { let num_lifetimes: usize = lifetime_refs.iter().map(|lt| lt.count).sum(); let spans: Vec<_> = lifetime_refs.iter().map(|lt| lt.span).collect(); let mut err = struct_span_err!( self.r.session, spans, E0106, "missing lifetime specifier{}", pluralize!(num_lifetimes) ); self.add_missing_lifetime_specifiers_label( &mut err, lifetime_refs, function_param_lifetimes, ); err.emit() } fn add_missing_lifetime_specifiers_label( &mut self, err: &mut Diagnostic, lifetime_refs: Vec, function_param_lifetimes: Option<(Vec, Vec)>, ) { for < in &lifetime_refs { err.span_label( lt.span, format!( "expected {} lifetime parameter{}", if lt.count == 1 { "named".to_string() } else { lt.count.to_string() }, pluralize!(lt.count), ), ); } let mut in_scope_lifetimes: Vec<_> = self .lifetime_ribs .iter() .rev() .take_while(|rib| !matches!(rib.kind, LifetimeRibKind::Item)) .flat_map(|rib| rib.bindings.iter()) .map(|(&ident, &res)| (ident, res)) .filter(|(ident, _)| ident.name != kw::UnderscoreLifetime) .collect(); debug!(?in_scope_lifetimes); debug!(?function_param_lifetimes); if let Some((param_lifetimes, params)) = &function_param_lifetimes { let elided_len = param_lifetimes.len(); let num_params = params.len(); let mut m = String::new(); for (i, info) in params.iter().enumerate() { let ElisionFnParameter { ident, index, lifetime_count, span } = *info; debug_assert_ne!(lifetime_count, 0); err.span_label(span, ""); if i != 0 { if i + 1 < num_params { m.push_str(", "); } else if num_params == 2 { m.push_str(" or "); } else { m.push_str(", or "); } } let help_name = if let Some(ident) = ident { format!("`{}`", ident) } else { format!("argument {}", index + 1) }; if lifetime_count == 1 { m.push_str(&help_name[..]) } else { m.push_str(&format!("one of {}'s {} lifetimes", help_name, lifetime_count)[..]) } } if num_params == 0 { err.help( "this function's return type contains a borrowed value, \ but there is no value for it to be borrowed from", ); if in_scope_lifetimes.is_empty() { in_scope_lifetimes = vec![( Ident::with_dummy_span(kw::StaticLifetime), (DUMMY_NODE_ID, LifetimeRes::Static), )]; } } else if elided_len == 0 { err.help( "this function's return type contains a borrowed value with \ an elided lifetime, but the lifetime cannot be derived from \ the arguments", ); if in_scope_lifetimes.is_empty() { in_scope_lifetimes = vec![( Ident::with_dummy_span(kw::StaticLifetime), (DUMMY_NODE_ID, LifetimeRes::Static), )]; } } else if num_params == 1 { err.help(&format!( "this function's return type contains a borrowed value, \ but the signature does not say which {} it is borrowed from", m )); } else { err.help(&format!( "this function's return type contains a borrowed value, \ but the signature does not say whether it is borrowed from {}", m )); } } let existing_name = match &in_scope_lifetimes[..] { [] => Symbol::intern("'a"), [(existing, _)] => existing.name, _ => Symbol::intern("'lifetime"), }; let mut spans_suggs: Vec<_> = Vec::new(); let build_sugg = |lt: MissingLifetime| match lt.kind { MissingLifetimeKind::Underscore => { debug_assert_eq!(lt.count, 1); (lt.span, existing_name.to_string()) } MissingLifetimeKind::Ampersand => { debug_assert_eq!(lt.count, 1); (lt.span.shrink_to_hi(), format!("{} ", existing_name)) } MissingLifetimeKind::Comma => { let sugg: String = std::iter::repeat([existing_name.as_str(), ", "]) .take(lt.count) .flatten() .collect(); (lt.span.shrink_to_hi(), sugg) } MissingLifetimeKind::Brackets => { let sugg: String = std::iter::once("<") .chain( std::iter::repeat(existing_name.as_str()).take(lt.count).intersperse(", "), ) .chain([">"]) .collect(); (lt.span.shrink_to_hi(), sugg) } }; for < in &lifetime_refs { spans_suggs.push(build_sugg(lt)); } debug!(?spans_suggs); match in_scope_lifetimes.len() { 0 => { if let Some((param_lifetimes, _)) = function_param_lifetimes { for lt in param_lifetimes { spans_suggs.push(build_sugg(lt)) } } self.suggest_introducing_lifetime( err, None, |err, higher_ranked, span, message, intro_sugg| { err.multipart_suggestion_verbose( message, std::iter::once((span, intro_sugg)) .chain(spans_suggs.iter().cloned()) .collect(), Applicability::MaybeIncorrect, ); higher_ranked }, ); } 1 => { err.multipart_suggestion_verbose( &format!("consider using the `{}` lifetime", existing_name), spans_suggs, Applicability::MaybeIncorrect, ); // Record as using the suggested resolution. let (_, (_, res)) = in_scope_lifetimes[0]; for < in &lifetime_refs { self.r.lifetimes_res_map.insert(lt.id, res); } } _ => { let lifetime_spans: Vec<_> = in_scope_lifetimes.iter().map(|(ident, _)| ident.span).collect(); err.span_note(lifetime_spans, "these named lifetimes are available to use"); if spans_suggs.len() > 0 { // This happens when we have `Foo` where we point at the space before `T`, // but this can be confusing so we give a suggestion with placeholders. err.multipart_suggestion_verbose( "consider using one of the available lifetimes here", spans_suggs, Applicability::HasPlaceholders, ); } } } } } /// Report lifetime/lifetime shadowing as an error. pub fn signal_lifetime_shadowing(sess: &Session, orig: Ident, shadower: Ident) { let mut err = struct_span_err!( sess, shadower.span, E0496, "lifetime name `{}` shadows a lifetime name that is already in scope", orig.name, ); err.span_label(orig.span, "first declared here"); err.span_label(shadower.span, format!("lifetime `{}` already in scope", orig.name)); err.emit(); } /// Shadowing involving a label is only a warning for historical reasons. //FIXME: make this a proper lint. pub fn signal_label_shadowing(sess: &Session, orig: Span, shadower: Ident) { let name = shadower.name; let shadower = shadower.span; let mut err = sess.struct_span_warn( shadower, &format!("label name `{}` shadows a label name that is already in scope", name), ); err.span_label(orig, "first declared here"); err.span_label(shadower, format!("label `{}` already in scope", name)); err.emit(); }