diff options
Diffstat (limited to 'compiler/rustc_resolve/src/late')
| -rw-r--r-- | compiler/rustc_resolve/src/late/diagnostics.rs | 2369 | ||||
| -rw-r--r-- | compiler/rustc_resolve/src/late/lifetimes.rs | 2144 |
2 files changed, 4513 insertions, 0 deletions
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs new file mode 100644 index 000000000..2b1f2b88e --- /dev/null +++ b/compiler/rustc_resolve/src/late/diagnostics.rs @@ -0,0 +1,2369 @@ +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, + 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_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 tracing::debug; + +type Res = def::Res<ast::NodeId>; + +/// A field or associated item from self type suggested in case of resolution failure. +enum AssocSuggestion { + Field, + MethodWithSelf, + AssocFn, + AssocType, + AssocConst, +} + +impl AssocSuggestion { + fn action(&self) -> &'static str { + match self { + AssocSuggestion::Field => "use the available field", + AssocSuggestion::MethodWithSelf => "call the method with the fully-qualified path", + AssocSuggestion::AssocFn => "call 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].to_vec(), + 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<Ident>, + /// 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), +} + +impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> { + fn def_span(&self, def_id: DefId) -> Option<Span> { + match def_id.krate { + LOCAL_CRATE => self.r.opt_span(def_id), + _ => Some(self.r.cstore().get_span_untracked(def_id, self.r.session)), + } + } + + /// 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<Res>, + ) -> (DiagnosticBuilder<'a, ErrorGuaranteed>, Vec<ImportSuggestion>) { + let ident_span = path.last().map_or(span, |ident| ident.ident.span); + let ns = source.namespace(); + let is_expected = &|res| source.is_expected(res); + let is_enum_variant = &|res| matches!(res, Res::Def(DefKind::Variant, _)); + + debug!(?res, ?source); + + // Make the base error. + struct BaseError<'a> { + msg: String, + fallback_label: String, + span: Span, + could_be_expr: bool, + suggestion: Option<(Span, &'a str, String)>, + } + let mut expected = source.descr_expected(); + let path_str = Segment::names_to_string(path); + let item_str = path.last().unwrap().ident; + let base_error = if let Some(res) = res { + BaseError { + msg: format!("expected {}, found {} `{}`", expected, res.descr(), path_str), + fallback_label: format!("not a {expected}"), + span, + 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 let Some(items) = self.diagnostic_metadata.current_impl_items + && let Some((fn_kind, _)) = self.diagnostic_metadata.current_function + && self.current_trait_ref.is_none() + && let Some(FnCtxt::Assoc(_)) = fn_kind.ctxt() + && let Some(item) = items.iter().find(|i| { + if let AssocItemKind::Fn(fn_) = &i.kind + && !fn_.sig.decl.has_self() + && i.ident.name == item_str.name + { + debug!(?item_str.name); + debug!(?fn_.sig.decl.inputs); + return true + } + false + }) + { + Some(( + item_span, + "consider using the associated function", + format!("Self::{}", item.ident) + )) + } 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) + }; + BaseError { + msg: format!("cannot find {expected} `{item_str}` in {mod_prefix}{mod_str}"), + fallback_label: if path_str == "async" && expected.starts_with("struct") { + "`async` blocks are only allowed in Rust 2018 or later".to_string() + } else { + format!("not found in {mod_str}") + }, + span: item_span, + could_be_expr: false, + suggestion, + } + }; + + 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(sugg) = base_error.suggestion { + err.span_suggestion_verbose(sugg.0, sugg.1, sugg.2, Applicability::MaybeIncorrect); + } + + 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, + ); + } + match (source, self.diagnostic_metadata.in_if_condition) { + ( + PathSource::Expr(_), + Some(Expr { span: expr_span, kind: ExprKind::Assign(lhs, _, _), .. }), + ) => { + // 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, + ); + } + } + _ => {} + } + + let is_assoc_fn = self.self_type_is_available(); + // Emit help message for fake-self from other languages (e.g., `this` in Javascript). + if ["this", "my"].contains(&item_str.as_str()) && is_assoc_fn { + 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, + ); + } + } + } + + self.detect_assoct_type_constraint_meant_as_path(base_error.span, &mut err); + + // Emit special messages for unresolved `Self` and `self`. + if is_self_type(path, ns) { + err.code(rustc_errors::error_code!(E0411)); + err.span_label( + span, + "`Self` is only available in impls, traits, and type definitions".to_string(), + ); + 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() + ), + ); + } + return (err, Vec::new()); + } + if is_self_value(path, ns) { + 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", + }); + 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() + ), + ); + } + return (err, Vec::new()); + } + + // Try to lookup name in more relaxed fashion for better error reporting. + let ident = path.last().unwrap().ident; + 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::<Vec<_>>(); + 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.delay_as_bug(); + return (err, 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, ns, is_expected); + if path.len() == 1 && self.self_type_is_available() { + if let Some(candidate) = self.lookup_assoc_candidate(ident, ns, is_expected) { + 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 if self_is_available => { + err.span_suggestion( + span, + "you might have meant to call the method", + 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(&mut err, typo_sugg, ident_span); + return (err, 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 (err, candidates); + } + } + + // Try context-dependent help if relaxed lookup didn't work. + if let Some(res) = res { + if self.smart_resolve_context_dependent_help( + &mut 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(&mut err, typo_sugg, ident_span); + return (err, candidates); + } + } + + let is_macro = + base_error.span.from_expansion() && base_error.span.desugaring_kind().is_none(); + if !self.type_ascription_suggestion(&mut err, base_error.span) { + 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<Span> = bounds + .iter() + .map(|bound| bound.span()) + .filter(|&sp| sp != base_error.span) + .collect(); + + let start_span = bounds.iter().map(|bound| bound.span()).next().unwrap(); + // `end_span` is the end of the poly trait ref (Foo + 'baz + Bar><) + let end_span = bounds.iter().map(|bound| bound.span()).last().unwrap(); + // `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, &mut err); + + if !self.r.add_typo_suggestion(&mut 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); + self.r.add_typo_suggestion(&mut err, suggestion, ident_span); + } + if fallback { + // Fallback label. + err.span_label(base_error.span, base_error.fallback_label); + } + } + 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 { + 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, + ); + } + } + } + + (err, candidates) + } + + fn detect_assoct_type_constraint_meant_as_path(&self, base_span: Span, err: &mut Diagnostic) { + 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_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_swapping_misplaced_self_ty_and_trait( + &mut self, + err: &mut Diagnostic, + source: PathSource<'_>, + res: Option<Res>, + 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 get_single_associated_item( + &mut self, + path: &[Segment], + source: &PathSource<'_>, + filter_fn: &impl Fn(Res) -> bool, + ) -> Option<TypoSuggestion> { + 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_res( + target.0.ident.name, + target.1, + )); + } + } + } + None + } + + /// Given `where <T as Bar>::Baz: String`, suggest `where T: Bar<Baz = String>`. + 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(ast::QSelf { ty, position, .. }), + 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.base_res(), + hir::def::Res::Def(hir::def::DefKind::AssocTy, _) + ) && partial_res.unresolved_segments() == 0) + { + return false; + } + (ty, 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.base_res(), + hir::def::Res::Def(hir::def::DefKind::TyParam, _) + ) && partial_res.unresolved_segments() == 0) + { + 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::<Vec<_>>() + .join("::"), + path.segments[*position..] + .iter() + .map(|segment| path_segment_to_string(segment)) + .collect::<Vec<_>>() + .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<Span>)> { + 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<Span>) { + // 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 mut sp = span; + loop { + sp = sm.next_point(sp); + match sm.span_to_snippet(sp) { + Ok(ref snippet) => { + if snippet.chars().any(|c| !c.is_whitespace()) { + break; + } + } + _ => break, + } + } + 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 mut i = 0; + let mut closing_brace = None; + loop { + sp = sm.next_point(sp); + match sm.span_to_snippet(sp) { + Ok(ref snippet) => { + if snippet == "}" { + closing_brace = Some(span.to(sp)); + break; + } + } + _ => break, + } + i += 1; + // The bigger the span, the more likely we're incorrect -- + // bound it to 100 chars long. + if i > 100 { + break; + } + } + (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| match expr.kind { + ExprKind::Field(_, ident) => { + err.span_suggestion( + expr.span, + "use the path separator to refer to an item", + format!("{}::{}", path_str, ident), + Applicability::MaybeIncorrect, + ); + true + } + ExprKind::MethodCall(ref segment, ..) => { + let span = expr.span.with_hi(segment.ident.span.hi()); + err.span_suggestion( + span, + "use the path separator to refer to an item", + format!("{}::{}", path_str, segment.ident), + Applicability::MaybeIncorrect, + ); + true + } + _ => 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) => {} + 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::<Vec<String>>() + .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(DefKind::Mod, _), PathSource::Expr(Some(parent))) => { + if !path_sep(err, &parent) { + 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::<Vec<_>>()) + } + _ => None, + }; + + if let Some(spans) = + field_spans.filter(|spans| spans.len() > 0 && fields.len() == spans.len()) + { + let non_visible_spans: Vec<Span> = 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 { + 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 | DefKind::Ctor(_, CtorKind::Fictive), + 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), def_id), _) if ns == ValueNS => { + 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::SelfTy { .. }, _) 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<Symbol> { + 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::TyAlias(..), Res::Def(DefKind::AssocTy, _)) => true, + _ => false, + }) + .map(|(key, _)| key.ident.name) + .collect::<Vec<_>>(); + + find_best_match_for_name(&targets, ident, None) + } + + fn lookup_assoc_candidate<FilterFn>( + &mut self, + ident: Ident, + ns: Namespace, + filter_fn: FilterFn, + ) -> Option<AssocSuggestion> + where + FilterFn: Fn(Res) -> bool, + { + fn extract_node_id(t: &Ty) -> Option<NodeId> { + match t.kind { + TyKind::Path(None, _) => Some(t.id), + TyKind::Rptr(_, 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) { + match resolution.base_res() { + Res::Def(DefKind::Struct | DefKind::Union, did) + if resolution.unresolved_segments() == 0 => + { + 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 + } + ast::AssocItemKind::Fn(..) => AssocSuggestion::AssocFn, + ast::AssocItemKind::TyAlias(..) => 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); + } else { + match res { + Res::Def(DefKind::AssocFn, _) => return Some(AssocSuggestion::AssocFn), + 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, + ) -> Option<TypoSuggestion> { + let mut names = Vec::new(); + if path.len() == 1 { + // Search in lexical scope. + // Walk backwards up the ribs in scope and collect candidates. + for rib in self.ribs[ns].iter().rev() { + // Locals and type parameters + for (ident, &res) in &rib.bindings { + if filter_fn(res) { + names.push(TypoSuggestion::typo_from_res(ident.name, res)); + } + } + // Items in scope + if let RibKind::ModuleRibKind(module) = rib.kind { + // Items from this module + self.r.add_module_candidates(module, &mut names, &filter_fn); + + 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_res( + ident.name, crate_mod, + )) + } else { + None + } + }, + ) + })); + + if let Some(prelude) = self.r.prelude { + self.r.add_module_candidates(prelude, &mut names, &filter_fn); + } + } + 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_res(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); + } + } + + 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::<Vec<Symbol>>(), + name, + None, + ) { + Some(found) if found != name => { + names.into_iter().find(|suggestion| suggestion.candidate == found) + } + _ => 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<Symbol> { + 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 { + let mut sp = after_colon_sp; + for _ in 0..100 { + // Try to find an assignment + sp = sm.next_point(sp); + let snippet = sm.span_to_snippet(sp.to(sm.next_point(sp))); + match snippet { + Ok(ref x) if x.as_str() == "=" => { + err.span_suggestion( + base_span, + "maybe you meant to write an assignment here", + format!("let {}", base_snippet), + Applicability::MaybeIncorrect, + ); + show_label = false; + break; + } + Ok(ref x) if x.as_str() == "\n" => break, + Err(_) => break, + Ok(_) => {} + } + } + } + } + if show_label { + err.span_label( + base_span, + "expecting a type here because of type ascription", + ); + } + return show_label; + } + } + } + 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, Vec::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<Vec<(Path, DefId, CtorKind)>> { + 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::<Vec<_>>(); + + 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.into_iter(), + 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 = |def_id: DefId, kind: CtorKind| { + 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 | CtorKind::Fictive if has_no_fields => false, + _ => true, + } + }; + + let mut 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), + CtorKind::Fictive => format!("({} {{}})", variant), + }) + .collect::<Vec<_>>(); + + if !suggestable_variants.is_empty() { + 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.drain(..), + 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)), + CtorKind::Fictive => Some(format!("({} {{ /* fields */ }})", variant)), + _ => None, + }) + .collect::<Vec<_>>(); + + if !suggestable_variants_with_placeholders.is_empty() { + let msg = match ( + suggestable_variants.is_empty(), + 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.into_iter(), + 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.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<T>()` + } + ( + Some(Item { + kind: + kind @ ItemKind::Fn(..) + | kind @ ItemKind::Enum(..) + | kind @ ItemKind::Struct(..) + | kind @ ItemKind::Union(..), + .. + }), + true, _ + ) + // Without the 2nd `true`, we'd suggest `impl <T>` 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<T: A>(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<LabelSuggestion> { + // 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::<Vec<Symbol>>(); + + 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 + generics_span + } else if param_index == 0 { + // if removing within `<>` brackets, we also want to + // delete a leading or trailing comma as appropriate + param.span().to(params[param_index + 1].span().shrink_to_lo()) + } else { + // if removing within `<>` brackets, we also want to + // delete a leading or trailing comma as appropriate + params[param_index - 1].span().shrink_to_hi().to(param.span()) + } + }; + 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::Rptr); + + 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<Ident>, + ) { + 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 DiagnosticBuilder<'_, ErrorGuaranteed>, + name: Option<&str>, + suggest: impl Fn(&mut DiagnosticBuilder<'_, ErrorGuaranteed>, 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 = format!("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 \ + <https://github.com/rust-lang/rust/issues/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<MissingLifetime>, + function_param_lifetimes: Option<(Vec<MissingLifetime>, Vec<ElisionFnParameter>)>, + ) -> 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() + } + + pub(crate) fn add_missing_lifetime_specifiers_label( + &mut self, + err: &mut DiagnosticBuilder<'_, ErrorGuaranteed>, + lifetime_refs: Vec<MissingLifetime>, + function_param_lifetimes: Option<(Vec<MissingLifetime>, Vec<ElisionFnParameter>)>, + ) { + 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.clone()) + .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<T>` 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(); +} diff --git a/compiler/rustc_resolve/src/late/lifetimes.rs b/compiler/rustc_resolve/src/late/lifetimes.rs new file mode 100644 index 000000000..94460e33d --- /dev/null +++ b/compiler/rustc_resolve/src/late/lifetimes.rs @@ -0,0 +1,2144 @@ +//! Resolution of early vs late bound lifetimes. +//! +//! Name resolution for lifetimes is performed on the AST and embedded into HIR. From this +//! information, typechecking needs to transform the lifetime parameters into bound lifetimes. +//! Lifetimes can be early-bound or late-bound. Construction of typechecking terms needs to visit +//! the types in HIR to identify late-bound lifetimes and assign their Debruijn indices. This file +//! is also responsible for assigning their semantics to implicit lifetimes in trait objects. + +use rustc_ast::walk_list; +use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet}; +use rustc_errors::struct_span_err; +use rustc_hir as hir; +use rustc_hir::def::{DefKind, Res}; +use rustc_hir::def_id::{DefIdMap, LocalDefId}; +use rustc_hir::intravisit::{self, Visitor}; +use rustc_hir::{GenericArg, GenericParam, GenericParamKind, HirIdMap, LifetimeName, Node}; +use rustc_middle::bug; +use rustc_middle::hir::map::Map; +use rustc_middle::hir::nested_filter; +use rustc_middle::middle::resolve_lifetime::*; +use rustc_middle::ty::{self, GenericParamDefKind, TyCtxt}; +use rustc_span::def_id::DefId; +use rustc_span::symbol::{sym, Ident}; +use rustc_span::Span; +use std::borrow::Cow; +use std::fmt; +use std::mem::take; + +trait RegionExt { + fn early(hir_map: Map<'_>, index: &mut u32, param: &GenericParam<'_>) -> (LocalDefId, Region); + + fn late(index: u32, hir_map: Map<'_>, param: &GenericParam<'_>) -> (LocalDefId, Region); + + fn id(&self) -> Option<DefId>; + + fn shifted(self, amount: u32) -> Region; + + fn shifted_out_to_binder(self, binder: ty::DebruijnIndex) -> Region; + + fn subst<'a, L>(self, params: L, map: &NamedRegionMap) -> Option<Region> + where + L: Iterator<Item = &'a hir::Lifetime>; +} + +impl RegionExt for Region { + fn early(hir_map: Map<'_>, index: &mut u32, param: &GenericParam<'_>) -> (LocalDefId, Region) { + let i = *index; + *index += 1; + let def_id = hir_map.local_def_id(param.hir_id); + debug!("Region::early: index={} def_id={:?}", i, def_id); + (def_id, Region::EarlyBound(i, def_id.to_def_id())) + } + + fn late(idx: u32, hir_map: Map<'_>, param: &GenericParam<'_>) -> (LocalDefId, Region) { + let depth = ty::INNERMOST; + let def_id = hir_map.local_def_id(param.hir_id); + debug!( + "Region::late: idx={:?}, param={:?} depth={:?} def_id={:?}", + idx, param, depth, def_id, + ); + (def_id, Region::LateBound(depth, idx, def_id.to_def_id())) + } + + fn id(&self) -> Option<DefId> { + match *self { + Region::Static => None, + + Region::EarlyBound(_, id) | Region::LateBound(_, _, id) | Region::Free(_, id) => { + Some(id) + } + } + } + + fn shifted(self, amount: u32) -> Region { + match self { + Region::LateBound(debruijn, idx, id) => { + Region::LateBound(debruijn.shifted_in(amount), idx, id) + } + _ => self, + } + } + + fn shifted_out_to_binder(self, binder: ty::DebruijnIndex) -> Region { + match self { + Region::LateBound(debruijn, index, id) => { + Region::LateBound(debruijn.shifted_out_to_binder(binder), index, id) + } + _ => self, + } + } + + fn subst<'a, L>(self, mut params: L, map: &NamedRegionMap) -> Option<Region> + where + L: Iterator<Item = &'a hir::Lifetime>, + { + if let Region::EarlyBound(index, _) = self { + params.nth(index as usize).and_then(|lifetime| map.defs.get(&lifetime.hir_id).cloned()) + } else { + Some(self) + } + } +} + +/// Maps the id of each lifetime reference to the lifetime decl +/// that it corresponds to. +/// +/// FIXME. This struct gets converted to a `ResolveLifetimes` for +/// actual use. It has the same data, but indexed by `LocalDefId`. This +/// is silly. +#[derive(Debug, Default)] +struct NamedRegionMap { + // maps from every use of a named (not anonymous) lifetime to a + // `Region` describing how that region is bound + defs: HirIdMap<Region>, + + // Maps relevant hir items to the bound vars on them. These include: + // - function defs + // - function pointers + // - closures + // - trait refs + // - bound types (like `T` in `for<'a> T<'a>: Foo`) + late_bound_vars: HirIdMap<Vec<ty::BoundVariableKind>>, +} + +pub(crate) struct LifetimeContext<'a, 'tcx> { + pub(crate) tcx: TyCtxt<'tcx>, + map: &'a mut NamedRegionMap, + scope: ScopeRef<'a>, + + /// Indicates that we only care about the definition of a trait. This should + /// be false if the `Item` we are resolving lifetimes for is not a trait or + /// we eventually need lifetimes resolve for trait items. + trait_definition_only: bool, + + /// Cache for cross-crate per-definition object lifetime defaults. + xcrate_object_lifetime_defaults: DefIdMap<Vec<ObjectLifetimeDefault>>, +} + +#[derive(Debug)] +enum Scope<'a> { + /// Declares lifetimes, and each can be early-bound or late-bound. + /// The `DebruijnIndex` of late-bound lifetimes starts at `1` and + /// it should be shifted by the number of `Binder`s in between the + /// declaration `Binder` and the location it's referenced from. + Binder { + /// We use an IndexMap here because we want these lifetimes in order + /// for diagnostics. + lifetimes: FxIndexMap<LocalDefId, Region>, + + /// if we extend this scope with another scope, what is the next index + /// we should use for an early-bound region? + next_early_index: u32, + + /// Whether or not this binder would serve as the parent + /// binder for opaque types introduced within. For example: + /// + /// ```text + /// fn foo<'a>() -> impl for<'b> Trait<Item = impl Trait2<'a>> + /// ``` + /// + /// Here, the opaque types we create for the `impl Trait` + /// and `impl Trait2` references will both have the `foo` item + /// as their parent. When we get to `impl Trait2`, we find + /// that it is nested within the `for<>` binder -- this flag + /// allows us to skip that when looking for the parent binder + /// of the resulting opaque type. + opaque_type_parent: bool, + + scope_type: BinderScopeType, + + /// The late bound vars for a given item are stored by `HirId` to be + /// queried later. However, if we enter an elision scope, we have to + /// later append the elided bound vars to the list and need to know what + /// to append to. + hir_id: hir::HirId, + + s: ScopeRef<'a>, + + /// If this binder comes from a where clause, specify how it was created. + /// This is used to diagnose inaccessible lifetimes in APIT: + /// ```ignore (illustrative) + /// fn foo(x: impl for<'a> Trait<'a, Assoc = impl Copy + 'a>) {} + /// ``` + where_bound_origin: Option<hir::PredicateOrigin>, + }, + + /// Lifetimes introduced by a fn are scoped to the call-site for that fn, + /// if this is a fn body, otherwise the original definitions are used. + /// Unspecified lifetimes are inferred, unless an elision scope is nested, + /// e.g., `(&T, fn(&T) -> &T);` becomes `(&'_ T, for<'a> fn(&'a T) -> &'a T)`. + Body { + id: hir::BodyId, + s: ScopeRef<'a>, + }, + + /// A scope which either determines unspecified lifetimes or errors + /// on them (e.g., due to ambiguity). + Elision { + s: ScopeRef<'a>, + }, + + /// Use a specific lifetime (if `Some`) or leave it unset (to be + /// inferred in a function body or potentially error outside one), + /// for the default choice of lifetime in a trait object type. + ObjectLifetimeDefault { + lifetime: Option<Region>, + s: ScopeRef<'a>, + }, + + /// When we have nested trait refs, we concatenate late bound vars for inner + /// trait refs from outer ones. But we also need to include any HRTB + /// lifetimes encountered when identifying the trait that an associated type + /// is declared on. + Supertrait { + lifetimes: Vec<ty::BoundVariableKind>, + s: ScopeRef<'a>, + }, + + TraitRefBoundary { + s: ScopeRef<'a>, + }, + + Root, +} + +#[derive(Copy, Clone, Debug)] +enum BinderScopeType { + /// Any non-concatenating binder scopes. + Normal, + /// Within a syntactic trait ref, there may be multiple poly trait refs that + /// are nested (under the `associated_type_bounds` feature). The binders of + /// the inner poly trait refs are extended from the outer poly trait refs + /// and don't increase the late bound depth. If you had + /// `T: for<'a> Foo<Bar: for<'b> Baz<'a, 'b>>`, then the `for<'b>` scope + /// would be `Concatenating`. This also used in trait refs in where clauses + /// where we have two binders `for<> T: for<> Foo` (I've intentionally left + /// out any lifetimes because they aren't needed to show the two scopes). + /// The inner `for<>` has a scope of `Concatenating`. + Concatenating, +} + +// A helper struct for debugging scopes without printing parent scopes +struct TruncatedScopeDebug<'a>(&'a Scope<'a>); + +impl<'a> fmt::Debug for TruncatedScopeDebug<'a> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + match self.0 { + Scope::Binder { + lifetimes, + next_early_index, + opaque_type_parent, + scope_type, + hir_id, + where_bound_origin, + s: _, + } => f + .debug_struct("Binder") + .field("lifetimes", lifetimes) + .field("next_early_index", next_early_index) + .field("opaque_type_parent", opaque_type_parent) + .field("scope_type", scope_type) + .field("hir_id", hir_id) + .field("where_bound_origin", where_bound_origin) + .field("s", &"..") + .finish(), + Scope::Body { id, s: _ } => { + f.debug_struct("Body").field("id", id).field("s", &"..").finish() + } + Scope::Elision { s: _ } => f.debug_struct("Elision").field("s", &"..").finish(), + Scope::ObjectLifetimeDefault { lifetime, s: _ } => f + .debug_struct("ObjectLifetimeDefault") + .field("lifetime", lifetime) + .field("s", &"..") + .finish(), + Scope::Supertrait { lifetimes, s: _ } => f + .debug_struct("Supertrait") + .field("lifetimes", lifetimes) + .field("s", &"..") + .finish(), + Scope::TraitRefBoundary { s: _ } => f.debug_struct("TraitRefBoundary").finish(), + Scope::Root => f.debug_struct("Root").finish(), + } + } +} + +type ScopeRef<'a> = &'a Scope<'a>; + +const ROOT_SCOPE: ScopeRef<'static> = &Scope::Root; + +pub fn provide(providers: &mut ty::query::Providers) { + *providers = ty::query::Providers { + resolve_lifetimes_trait_definition, + resolve_lifetimes, + + named_region_map: |tcx, id| resolve_lifetimes_for(tcx, id).defs.get(&id), + is_late_bound_map, + object_lifetime_defaults: |tcx, id| match tcx.hir().find_by_def_id(id) { + Some(Node::Item(item)) => compute_object_lifetime_defaults(tcx, item), + _ => None, + }, + late_bound_vars_map: |tcx, id| resolve_lifetimes_for(tcx, id).late_bound_vars.get(&id), + + ..*providers + }; +} + +/// Like `resolve_lifetimes`, but does not resolve lifetimes for trait items. +/// Also does not generate any diagnostics. +/// +/// This is ultimately a subset of the `resolve_lifetimes` work. It effectively +/// resolves lifetimes only within the trait "header" -- that is, the trait +/// and supertrait list. In contrast, `resolve_lifetimes` resolves all the +/// lifetimes within the trait and its items. There is room to refactor this, +/// for example to resolve lifetimes for each trait item in separate queries, +/// but it's convenient to do the entire trait at once because the lifetimes +/// from the trait definition are in scope within the trait items as well. +/// +/// The reason for this separate call is to resolve what would otherwise +/// be a cycle. Consider this example: +/// +/// ```ignore UNSOLVED (maybe @jackh726 knows what lifetime parameter to give Sub) +/// trait Base<'a> { +/// type BaseItem; +/// } +/// trait Sub<'b>: for<'a> Base<'a> { +/// type SubItem: Sub<BaseItem = &'b u32>; +/// } +/// ``` +/// +/// When we resolve `Sub` and all its items, we also have to resolve `Sub<BaseItem = &'b u32>`. +/// To figure out the index of `'b`, we have to know about the supertraits +/// of `Sub` so that we can determine that the `for<'a>` will be in scope. +/// (This is because we -- currently at least -- flatten all the late-bound +/// lifetimes into a single binder.) This requires us to resolve the +/// *trait definition* of `Sub`; basically just enough lifetime information +/// to look at the supertraits. +#[tracing::instrument(level = "debug", skip(tcx))] +fn resolve_lifetimes_trait_definition( + tcx: TyCtxt<'_>, + local_def_id: LocalDefId, +) -> ResolveLifetimes { + convert_named_region_map(do_resolve(tcx, local_def_id, true)) +} + +/// Computes the `ResolveLifetimes` map that contains data for an entire `Item`. +/// You should not read the result of this query directly, but rather use +/// `named_region_map`, `is_late_bound_map`, etc. +#[tracing::instrument(level = "debug", skip(tcx))] +fn resolve_lifetimes(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> ResolveLifetimes { + convert_named_region_map(do_resolve(tcx, local_def_id, false)) +} + +fn do_resolve( + tcx: TyCtxt<'_>, + local_def_id: LocalDefId, + trait_definition_only: bool, +) -> NamedRegionMap { + let item = tcx.hir().expect_item(local_def_id); + let mut named_region_map = + NamedRegionMap { defs: Default::default(), late_bound_vars: Default::default() }; + let mut visitor = LifetimeContext { + tcx, + map: &mut named_region_map, + scope: ROOT_SCOPE, + trait_definition_only, + xcrate_object_lifetime_defaults: Default::default(), + }; + visitor.visit_item(item); + + named_region_map +} + +fn convert_named_region_map(named_region_map: NamedRegionMap) -> ResolveLifetimes { + let mut rl = ResolveLifetimes::default(); + + for (hir_id, v) in named_region_map.defs { + let map = rl.defs.entry(hir_id.owner).or_default(); + map.insert(hir_id.local_id, v); + } + for (hir_id, v) in named_region_map.late_bound_vars { + let map = rl.late_bound_vars.entry(hir_id.owner).or_default(); + map.insert(hir_id.local_id, v); + } + + debug!(?rl.defs); + rl +} + +/// Given `any` owner (structs, traits, trait methods, etc.), does lifetime resolution. +/// There are two important things this does. +/// First, we have to resolve lifetimes for +/// the entire *`Item`* that contains this owner, because that's the largest "scope" +/// where we can have relevant lifetimes. +/// Second, if we are asking for lifetimes in a trait *definition*, we use `resolve_lifetimes_trait_definition` +/// instead of `resolve_lifetimes`, which does not descend into the trait items and does not emit diagnostics. +/// This allows us to avoid cycles. Importantly, if we ask for lifetimes for lifetimes that have an owner +/// other than the trait itself (like the trait methods or associated types), then we just use the regular +/// `resolve_lifetimes`. +fn resolve_lifetimes_for<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx ResolveLifetimes { + let item_id = item_for(tcx, def_id); + if item_id == def_id { + let item = tcx.hir().item(hir::ItemId { def_id: item_id }); + match item.kind { + hir::ItemKind::Trait(..) => tcx.resolve_lifetimes_trait_definition(item_id), + _ => tcx.resolve_lifetimes(item_id), + } + } else { + tcx.resolve_lifetimes(item_id) + } +} + +/// Finds the `Item` that contains the given `LocalDefId` +fn item_for(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> LocalDefId { + match tcx.hir().find_by_def_id(local_def_id) { + Some(Node::Item(item)) => { + return item.def_id; + } + _ => {} + } + let item = { + let hir_id = tcx.hir().local_def_id_to_hir_id(local_def_id); + let mut parent_iter = tcx.hir().parent_iter(hir_id); + loop { + let node = parent_iter.next().map(|n| n.1); + match node { + Some(hir::Node::Item(item)) => break item.def_id, + Some(hir::Node::Crate(_)) | None => bug!("Called `item_for` on an Item."), + _ => {} + } + } + }; + item +} + +/// In traits, there is an implicit `Self` type parameter which comes before the generics. +/// We have to account for this when computing the index of the other generic parameters. +/// This function returns whether there is such an implicit parameter defined on the given item. +fn sub_items_have_self_param(node: &hir::ItemKind<'_>) -> bool { + matches!(*node, hir::ItemKind::Trait(..) | hir::ItemKind::TraitAlias(..)) +} + +fn late_region_as_bound_region<'tcx>(tcx: TyCtxt<'tcx>, region: &Region) -> ty::BoundVariableKind { + match region { + Region::LateBound(_, _, def_id) => { + let name = tcx.hir().name(tcx.hir().local_def_id_to_hir_id(def_id.expect_local())); + ty::BoundVariableKind::Region(ty::BrNamed(*def_id, name)) + } + _ => bug!("{:?} is not a late region", region), + } +} + +impl<'a, 'tcx> LifetimeContext<'a, 'tcx> { + /// Returns the binders in scope and the type of `Binder` that should be created for a poly trait ref. + fn poly_trait_ref_binder_info(&mut self) -> (Vec<ty::BoundVariableKind>, BinderScopeType) { + let mut scope = self.scope; + let mut supertrait_lifetimes = vec![]; + loop { + match scope { + Scope::Body { .. } | Scope::Root => { + break (vec![], BinderScopeType::Normal); + } + + Scope::Elision { s, .. } | Scope::ObjectLifetimeDefault { s, .. } => { + scope = s; + } + + Scope::Supertrait { s, lifetimes } => { + supertrait_lifetimes = lifetimes.clone(); + scope = s; + } + + Scope::TraitRefBoundary { .. } => { + // We should only see super trait lifetimes if there is a `Binder` above + assert!(supertrait_lifetimes.is_empty()); + break (vec![], BinderScopeType::Normal); + } + + Scope::Binder { hir_id, .. } => { + // Nested poly trait refs have the binders concatenated + let mut full_binders = + self.map.late_bound_vars.entry(*hir_id).or_default().clone(); + full_binders.extend(supertrait_lifetimes.into_iter()); + break (full_binders, BinderScopeType::Concatenating); + } + } + } + } +} +impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> { + type NestedFilter = nested_filter::All; + + fn nested_visit_map(&mut self) -> Self::Map { + self.tcx.hir() + } + + // We want to nest trait/impl items in their parent, but nothing else. + fn visit_nested_item(&mut self, _: hir::ItemId) {} + + fn visit_trait_item_ref(&mut self, ii: &'tcx hir::TraitItemRef) { + if !self.trait_definition_only { + intravisit::walk_trait_item_ref(self, ii) + } + } + + fn visit_nested_body(&mut self, body: hir::BodyId) { + let body = self.tcx.hir().body(body); + self.with(Scope::Body { id: body.id(), s: self.scope }, |this| { + this.visit_body(body); + }); + } + + fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) { + if let hir::ExprKind::Closure(hir::Closure { + binder, bound_generic_params, fn_decl, .. + }) = e.kind + { + if let &hir::ClosureBinder::For { span: for_sp, .. } = binder { + fn span_of_infer(ty: &hir::Ty<'_>) -> Option<Span> { + struct V(Option<Span>); + + impl<'v> Visitor<'v> for V { + fn visit_ty(&mut self, t: &'v hir::Ty<'v>) { + match t.kind { + _ if self.0.is_some() => (), + hir::TyKind::Infer => { + self.0 = Some(t.span); + } + _ => intravisit::walk_ty(self, t), + } + } + } + + let mut v = V(None); + v.visit_ty(ty); + v.0 + } + + let infer_in_rt_sp = match fn_decl.output { + hir::FnRetTy::DefaultReturn(sp) => Some(sp), + hir::FnRetTy::Return(ty) => span_of_infer(ty), + }; + + let infer_spans = fn_decl + .inputs + .into_iter() + .filter_map(span_of_infer) + .chain(infer_in_rt_sp) + .collect::<Vec<_>>(); + + if !infer_spans.is_empty() { + self.tcx.sess + .struct_span_err( + infer_spans, + "implicit types in closure signatures are forbidden when `for<...>` is present", + ) + .span_label(for_sp, "`for<...>` is here") + .emit(); + } + } + + let next_early_index = self.next_early_index(); + let (lifetimes, binders): (FxIndexMap<LocalDefId, Region>, Vec<_>) = + bound_generic_params + .iter() + .filter(|param| matches!(param.kind, GenericParamKind::Lifetime { .. })) + .enumerate() + .map(|(late_bound_idx, param)| { + let pair = Region::late(late_bound_idx as u32, self.tcx.hir(), param); + let r = late_region_as_bound_region(self.tcx, &pair.1); + (pair, r) + }) + .unzip(); + + self.map.late_bound_vars.insert(e.hir_id, binders); + let scope = Scope::Binder { + hir_id: e.hir_id, + lifetimes, + s: self.scope, + next_early_index, + opaque_type_parent: false, + scope_type: BinderScopeType::Normal, + where_bound_origin: None, + }; + + self.with(scope, |this| { + // a closure has no bounds, so everything + // contained within is scoped within its binder. + intravisit::walk_expr(this, e) + }); + } else { + intravisit::walk_expr(self, e) + } + } + + fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) { + match &item.kind { + hir::ItemKind::Impl(hir::Impl { of_trait, .. }) => { + if let Some(of_trait) = of_trait { + self.map.late_bound_vars.insert(of_trait.hir_ref_id, Vec::default()); + } + } + _ => {} + } + match item.kind { + hir::ItemKind::Fn(_, ref generics, _) => { + self.visit_early_late(None, item.hir_id(), generics, |this| { + intravisit::walk_item(this, item); + }); + } + + hir::ItemKind::ExternCrate(_) + | hir::ItemKind::Use(..) + | hir::ItemKind::Macro(..) + | hir::ItemKind::Mod(..) + | hir::ItemKind::ForeignMod { .. } + | hir::ItemKind::GlobalAsm(..) => { + // These sorts of items have no lifetime parameters at all. + intravisit::walk_item(self, item); + } + hir::ItemKind::Static(..) | hir::ItemKind::Const(..) => { + // No lifetime parameters, but implied 'static. + self.with(Scope::Elision { s: self.scope }, |this| { + intravisit::walk_item(this, item) + }); + } + hir::ItemKind::OpaqueTy(hir::OpaqueTy { .. }) => { + // Opaque types are visited when we visit the + // `TyKind::OpaqueDef`, so that they have the lifetimes from + // their parent opaque_ty in scope. + // + // The core idea here is that since OpaqueTys are generated with the impl Trait as + // their owner, we can keep going until we find the Item that owns that. We then + // conservatively add all resolved lifetimes. Otherwise we run into problems in + // cases like `type Foo<'a> = impl Bar<As = impl Baz + 'a>`. + for (_hir_id, node) in + self.tcx.hir().parent_iter(self.tcx.hir().local_def_id_to_hir_id(item.def_id)) + { + match node { + hir::Node::Item(parent_item) => { + let resolved_lifetimes: &ResolveLifetimes = + self.tcx.resolve_lifetimes(item_for(self.tcx, parent_item.def_id)); + // We need to add *all* deps, since opaque tys may want them from *us* + for (&owner, defs) in resolved_lifetimes.defs.iter() { + defs.iter().for_each(|(&local_id, region)| { + self.map.defs.insert(hir::HirId { owner, local_id }, *region); + }); + } + for (&owner, late_bound_vars) in + resolved_lifetimes.late_bound_vars.iter() + { + late_bound_vars.iter().for_each(|(&local_id, late_bound_vars)| { + self.map.late_bound_vars.insert( + hir::HirId { owner, local_id }, + late_bound_vars.clone(), + ); + }); + } + break; + } + hir::Node::Crate(_) => bug!("No Item about an OpaqueTy"), + _ => {} + } + } + } + hir::ItemKind::TyAlias(_, ref generics) + | hir::ItemKind::Enum(_, ref generics) + | hir::ItemKind::Struct(_, ref generics) + | hir::ItemKind::Union(_, ref generics) + | hir::ItemKind::Trait(_, _, ref generics, ..) + | hir::ItemKind::TraitAlias(ref generics, ..) + | hir::ItemKind::Impl(hir::Impl { ref generics, .. }) => { + // These kinds of items have only early-bound lifetime parameters. + let mut index = if sub_items_have_self_param(&item.kind) { + 1 // Self comes before lifetimes + } else { + 0 + }; + let mut non_lifetime_count = 0; + let lifetimes = generics + .params + .iter() + .filter_map(|param| match param.kind { + GenericParamKind::Lifetime { .. } => { + Some(Region::early(self.tcx.hir(), &mut index, param)) + } + GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => { + non_lifetime_count += 1; + None + } + }) + .collect(); + self.map.late_bound_vars.insert(item.hir_id(), vec![]); + let scope = Scope::Binder { + hir_id: item.hir_id(), + lifetimes, + next_early_index: index + non_lifetime_count, + opaque_type_parent: true, + scope_type: BinderScopeType::Normal, + s: ROOT_SCOPE, + where_bound_origin: None, + }; + self.with(scope, |this| { + let scope = Scope::TraitRefBoundary { s: this.scope }; + this.with(scope, |this| { + intravisit::walk_item(this, item); + }); + }); + } + } + } + + fn visit_foreign_item(&mut self, item: &'tcx hir::ForeignItem<'tcx>) { + match item.kind { + hir::ForeignItemKind::Fn(_, _, ref generics) => { + self.visit_early_late(None, item.hir_id(), generics, |this| { + intravisit::walk_foreign_item(this, item); + }) + } + hir::ForeignItemKind::Static(..) => { + intravisit::walk_foreign_item(self, item); + } + hir::ForeignItemKind::Type => { + intravisit::walk_foreign_item(self, item); + } + } + } + + #[tracing::instrument(level = "debug", skip(self))] + fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) { + match ty.kind { + hir::TyKind::BareFn(ref c) => { + let next_early_index = self.next_early_index(); + let (lifetimes, binders): (FxIndexMap<LocalDefId, Region>, Vec<_>) = c + .generic_params + .iter() + .filter(|param| matches!(param.kind, GenericParamKind::Lifetime { .. })) + .enumerate() + .map(|(late_bound_idx, param)| { + let pair = Region::late(late_bound_idx as u32, self.tcx.hir(), param); + let r = late_region_as_bound_region(self.tcx, &pair.1); + (pair, r) + }) + .unzip(); + self.map.late_bound_vars.insert(ty.hir_id, binders); + let scope = Scope::Binder { + hir_id: ty.hir_id, + lifetimes, + s: self.scope, + next_early_index, + opaque_type_parent: false, + scope_type: BinderScopeType::Normal, + where_bound_origin: None, + }; + self.with(scope, |this| { + // a bare fn has no bounds, so everything + // contained within is scoped within its binder. + intravisit::walk_ty(this, ty); + }); + } + hir::TyKind::TraitObject(bounds, ref lifetime, _) => { + debug!(?bounds, ?lifetime, "TraitObject"); + let scope = Scope::TraitRefBoundary { s: self.scope }; + self.with(scope, |this| { + for bound in bounds { + this.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None); + } + }); + match lifetime.name { + LifetimeName::ImplicitObjectLifetimeDefault => { + // If the user does not write *anything*, we + // use the object lifetime defaulting + // rules. So e.g., `Box<dyn Debug>` becomes + // `Box<dyn Debug + 'static>`. + self.resolve_object_lifetime_default(lifetime) + } + LifetimeName::Infer => { + // If the user writes `'_`, we use the *ordinary* elision + // rules. So the `'_` in e.g., `Box<dyn Debug + '_>` will be + // resolved the same as the `'_` in `&'_ Foo`. + // + // cc #48468 + } + LifetimeName::Param(..) | LifetimeName::Static => { + // If the user wrote an explicit name, use that. + self.visit_lifetime(lifetime); + } + LifetimeName::Error => {} + } + } + hir::TyKind::Rptr(ref lifetime_ref, ref mt) => { + self.visit_lifetime(lifetime_ref); + let scope = Scope::ObjectLifetimeDefault { + lifetime: self.map.defs.get(&lifetime_ref.hir_id).cloned(), + s: self.scope, + }; + self.with(scope, |this| this.visit_ty(&mt.ty)); + } + hir::TyKind::OpaqueDef(item_id, lifetimes) => { + // Resolve the lifetimes in the bounds to the lifetime defs in the generics. + // `fn foo<'a>() -> impl MyTrait<'a> { ... }` desugars to + // `type MyAnonTy<'b> = impl MyTrait<'b>;` + // ^ ^ this gets resolved in the scope of + // the opaque_ty generics + let opaque_ty = self.tcx.hir().item(item_id); + let (generics, bounds) = match opaque_ty.kind { + hir::ItemKind::OpaqueTy(hir::OpaqueTy { + origin: hir::OpaqueTyOrigin::TyAlias, + .. + }) => { + intravisit::walk_ty(self, ty); + + // Elided lifetimes are not allowed in non-return + // position impl Trait + let scope = Scope::TraitRefBoundary { s: self.scope }; + self.with(scope, |this| { + let scope = Scope::Elision { s: this.scope }; + this.with(scope, |this| { + intravisit::walk_item(this, opaque_ty); + }) + }); + + return; + } + hir::ItemKind::OpaqueTy(hir::OpaqueTy { + origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..), + ref generics, + bounds, + .. + }) => (generics, bounds), + ref i => bug!("`impl Trait` pointed to non-opaque type?? {:#?}", i), + }; + + // Resolve the lifetimes that are applied to the opaque type. + // These are resolved in the current scope. + // `fn foo<'a>() -> impl MyTrait<'a> { ... }` desugars to + // `fn foo<'a>() -> MyAnonTy<'a> { ... }` + // ^ ^this gets resolved in the current scope + for lifetime in lifetimes { + let hir::GenericArg::Lifetime(lifetime) = lifetime else { + continue + }; + self.visit_lifetime(lifetime); + + // Check for predicates like `impl for<'a> Trait<impl OtherTrait<'a>>` + // and ban them. Type variables instantiated inside binders aren't + // well-supported at the moment, so this doesn't work. + // In the future, this should be fixed and this error should be removed. + let def = self.map.defs.get(&lifetime.hir_id).cloned(); + let Some(Region::LateBound(_, _, def_id)) = def else { + continue + }; + let Some(def_id) = def_id.as_local() else { + continue + }; + let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id); + // Ensure that the parent of the def is an item, not HRTB + let parent_id = self.tcx.hir().get_parent_node(hir_id); + if !parent_id.is_owner() { + if !self.trait_definition_only { + struct_span_err!( + self.tcx.sess, + lifetime.span, + E0657, + "`impl Trait` can only capture lifetimes \ + bound at the fn or impl level" + ) + .emit(); + } + self.uninsert_lifetime_on_error(lifetime, def.unwrap()); + } + if let hir::Node::Item(hir::Item { + kind: hir::ItemKind::OpaqueTy { .. }, .. + }) = self.tcx.hir().get(parent_id) + { + if !self.trait_definition_only { + let mut err = self.tcx.sess.struct_span_err( + lifetime.span, + "higher kinded lifetime bounds on nested opaque types are not supported yet", + ); + err.span_note(self.tcx.def_span(def_id), "lifetime declared here"); + err.emit(); + } + self.uninsert_lifetime_on_error(lifetime, def.unwrap()); + } + } + + // We want to start our early-bound indices at the end of the parent scope, + // not including any parent `impl Trait`s. + let mut index = self.next_early_index_for_opaque_type(); + debug!(?index); + + let mut lifetimes = FxIndexMap::default(); + let mut non_lifetime_count = 0; + debug!(?generics.params); + for param in generics.params { + match param.kind { + GenericParamKind::Lifetime { .. } => { + let (def_id, reg) = Region::early(self.tcx.hir(), &mut index, ¶m); + lifetimes.insert(def_id, reg); + } + GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => { + non_lifetime_count += 1; + } + } + } + let next_early_index = index + non_lifetime_count; + self.map.late_bound_vars.insert(ty.hir_id, vec![]); + + let scope = Scope::Binder { + hir_id: ty.hir_id, + lifetimes, + next_early_index, + s: self.scope, + opaque_type_parent: false, + scope_type: BinderScopeType::Normal, + where_bound_origin: None, + }; + self.with(scope, |this| { + let scope = Scope::TraitRefBoundary { s: this.scope }; + this.with(scope, |this| { + this.visit_generics(generics); + for bound in bounds { + this.visit_param_bound(bound); + } + }) + }); + } + _ => intravisit::walk_ty(self, ty), + } + } + + fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) { + use self::hir::TraitItemKind::*; + match trait_item.kind { + Fn(_, _) => { + let tcx = self.tcx; + self.visit_early_late( + Some(tcx.hir().get_parent_item(trait_item.hir_id())), + trait_item.hir_id(), + &trait_item.generics, + |this| intravisit::walk_trait_item(this, trait_item), + ); + } + Type(bounds, ref ty) => { + let generics = &trait_item.generics; + let mut index = self.next_early_index(); + debug!("visit_ty: index = {}", index); + let mut non_lifetime_count = 0; + let lifetimes = generics + .params + .iter() + .filter_map(|param| match param.kind { + GenericParamKind::Lifetime { .. } => { + Some(Region::early(self.tcx.hir(), &mut index, param)) + } + GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => { + non_lifetime_count += 1; + None + } + }) + .collect(); + self.map.late_bound_vars.insert(trait_item.hir_id(), vec![]); + let scope = Scope::Binder { + hir_id: trait_item.hir_id(), + lifetimes, + next_early_index: index + non_lifetime_count, + s: self.scope, + opaque_type_parent: true, + scope_type: BinderScopeType::Normal, + where_bound_origin: None, + }; + self.with(scope, |this| { + let scope = Scope::TraitRefBoundary { s: this.scope }; + this.with(scope, |this| { + this.visit_generics(generics); + for bound in bounds { + this.visit_param_bound(bound); + } + if let Some(ty) = ty { + this.visit_ty(ty); + } + }) + }); + } + Const(_, _) => { + // Only methods and types support generics. + assert!(trait_item.generics.params.is_empty()); + intravisit::walk_trait_item(self, trait_item); + } + } + } + + fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) { + use self::hir::ImplItemKind::*; + match impl_item.kind { + Fn(..) => { + let tcx = self.tcx; + self.visit_early_late( + Some(tcx.hir().get_parent_item(impl_item.hir_id())), + impl_item.hir_id(), + &impl_item.generics, + |this| intravisit::walk_impl_item(this, impl_item), + ); + } + TyAlias(ref ty) => { + let generics = &impl_item.generics; + let mut index = self.next_early_index(); + let mut non_lifetime_count = 0; + debug!("visit_ty: index = {}", index); + let lifetimes: FxIndexMap<LocalDefId, Region> = generics + .params + .iter() + .filter_map(|param| match param.kind { + GenericParamKind::Lifetime { .. } => { + Some(Region::early(self.tcx.hir(), &mut index, param)) + } + GenericParamKind::Const { .. } | GenericParamKind::Type { .. } => { + non_lifetime_count += 1; + None + } + }) + .collect(); + self.map.late_bound_vars.insert(ty.hir_id, vec![]); + let scope = Scope::Binder { + hir_id: ty.hir_id, + lifetimes, + next_early_index: index + non_lifetime_count, + s: self.scope, + opaque_type_parent: true, + scope_type: BinderScopeType::Normal, + where_bound_origin: None, + }; + self.with(scope, |this| { + let scope = Scope::TraitRefBoundary { s: this.scope }; + this.with(scope, |this| { + this.visit_generics(generics); + this.visit_ty(ty); + }) + }); + } + Const(_, _) => { + // Only methods and types support generics. + assert!(impl_item.generics.params.is_empty()); + intravisit::walk_impl_item(self, impl_item); + } + } + } + + #[tracing::instrument(level = "debug", skip(self))] + fn visit_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime) { + match lifetime_ref.name { + hir::LifetimeName::Static => self.insert_lifetime(lifetime_ref, Region::Static), + hir::LifetimeName::Param(param_def_id, _) => { + self.resolve_lifetime_ref(param_def_id, lifetime_ref) + } + // If we've already reported an error, just ignore `lifetime_ref`. + hir::LifetimeName::Error => {} + // Those will be resolved by typechecking. + hir::LifetimeName::ImplicitObjectLifetimeDefault | hir::LifetimeName::Infer => {} + } + } + + fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, _: hir::HirId) { + for (i, segment) in path.segments.iter().enumerate() { + let depth = path.segments.len() - i - 1; + if let Some(ref args) = segment.args { + self.visit_segment_args(path.res, depth, args); + } + } + } + + fn visit_fn( + &mut self, + fk: intravisit::FnKind<'tcx>, + fd: &'tcx hir::FnDecl<'tcx>, + body_id: hir::BodyId, + _: Span, + _: hir::HirId, + ) { + let output = match fd.output { + hir::FnRetTy::DefaultReturn(_) => None, + hir::FnRetTy::Return(ref ty) => Some(&**ty), + }; + self.visit_fn_like_elision(&fd.inputs, output, matches!(fk, intravisit::FnKind::Closure)); + intravisit::walk_fn_kind(self, fk); + self.visit_nested_body(body_id) + } + + fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) { + let scope = Scope::TraitRefBoundary { s: self.scope }; + self.with(scope, |this| { + for param in generics.params { + match param.kind { + GenericParamKind::Lifetime { .. } => {} + GenericParamKind::Type { ref default, .. } => { + if let Some(ref ty) = default { + this.visit_ty(&ty); + } + } + GenericParamKind::Const { ref ty, default } => { + this.visit_ty(&ty); + if let Some(default) = default { + this.visit_body(this.tcx.hir().body(default.body)); + } + } + } + } + for predicate in generics.predicates { + match predicate { + &hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate { + ref bounded_ty, + bounds, + ref bound_generic_params, + origin, + .. + }) => { + let (lifetimes, binders): (FxIndexMap<LocalDefId, Region>, Vec<_>) = + bound_generic_params + .iter() + .filter(|param| { + matches!(param.kind, GenericParamKind::Lifetime { .. }) + }) + .enumerate() + .map(|(late_bound_idx, param)| { + let pair = + Region::late(late_bound_idx as u32, this.tcx.hir(), param); + let r = late_region_as_bound_region(this.tcx, &pair.1); + (pair, r) + }) + .unzip(); + this.map.late_bound_vars.insert(bounded_ty.hir_id, binders.clone()); + let next_early_index = this.next_early_index(); + // Even if there are no lifetimes defined here, we still wrap it in a binder + // scope. If there happens to be a nested poly trait ref (an error), that + // will be `Concatenating` anyways, so we don't have to worry about the depth + // being wrong. + let scope = Scope::Binder { + hir_id: bounded_ty.hir_id, + lifetimes, + s: this.scope, + next_early_index, + opaque_type_parent: false, + scope_type: BinderScopeType::Normal, + where_bound_origin: Some(origin), + }; + this.with(scope, |this| { + this.visit_ty(&bounded_ty); + walk_list!(this, visit_param_bound, bounds); + }) + } + &hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate { + ref lifetime, + bounds, + .. + }) => { + this.visit_lifetime(lifetime); + walk_list!(this, visit_param_bound, bounds); + + if lifetime.name != hir::LifetimeName::Static { + for bound in bounds { + let hir::GenericBound::Outlives(ref lt) = bound else { + continue; + }; + if lt.name != hir::LifetimeName::Static { + continue; + } + this.insert_lifetime(lt, Region::Static); + this.tcx + .sess + .struct_span_warn( + lifetime.span, + &format!( + "unnecessary lifetime parameter `{}`", + lifetime.name.ident(), + ), + ) + .help(&format!( + "you can use the `'static` lifetime directly, in place of `{}`", + lifetime.name.ident(), + )) + .emit(); + } + } + } + &hir::WherePredicate::EqPredicate(hir::WhereEqPredicate { + ref lhs_ty, + ref rhs_ty, + .. + }) => { + this.visit_ty(lhs_ty); + this.visit_ty(rhs_ty); + } + } + } + }) + } + + fn visit_param_bound(&mut self, bound: &'tcx hir::GenericBound<'tcx>) { + match bound { + hir::GenericBound::LangItemTrait(_, _, hir_id, _) => { + // FIXME(jackh726): This is pretty weird. `LangItemTrait` doesn't go + // through the regular poly trait ref code, so we don't get another + // chance to introduce a binder. For now, I'm keeping the existing logic + // of "if there isn't a Binder scope above us, add one", but I + // imagine there's a better way to go about this. + let (binders, scope_type) = self.poly_trait_ref_binder_info(); + + self.map.late_bound_vars.insert(*hir_id, binders); + let scope = Scope::Binder { + hir_id: *hir_id, + lifetimes: FxIndexMap::default(), + s: self.scope, + next_early_index: self.next_early_index(), + opaque_type_parent: false, + scope_type, + where_bound_origin: None, + }; + self.with(scope, |this| { + intravisit::walk_param_bound(this, bound); + }); + } + _ => intravisit::walk_param_bound(self, bound), + } + } + + fn visit_poly_trait_ref( + &mut self, + trait_ref: &'tcx hir::PolyTraitRef<'tcx>, + _modifier: hir::TraitBoundModifier, + ) { + debug!("visit_poly_trait_ref(trait_ref={:?})", trait_ref); + + let next_early_index = self.next_early_index(); + let (mut binders, scope_type) = self.poly_trait_ref_binder_info(); + + let initial_bound_vars = binders.len() as u32; + let mut lifetimes: FxIndexMap<LocalDefId, Region> = FxIndexMap::default(); + let binders_iter = trait_ref + .bound_generic_params + .iter() + .filter(|param| matches!(param.kind, GenericParamKind::Lifetime { .. })) + .enumerate() + .map(|(late_bound_idx, param)| { + let pair = + Region::late(initial_bound_vars + late_bound_idx as u32, self.tcx.hir(), param); + let r = late_region_as_bound_region(self.tcx, &pair.1); + lifetimes.insert(pair.0, pair.1); + r + }); + binders.extend(binders_iter); + + debug!(?binders); + self.map.late_bound_vars.insert(trait_ref.trait_ref.hir_ref_id, binders); + + // Always introduce a scope here, even if this is in a where clause and + // we introduced the binders around the bounded Ty. In that case, we + // just reuse the concatenation functionality also present in nested trait + // refs. + let scope = Scope::Binder { + hir_id: trait_ref.trait_ref.hir_ref_id, + lifetimes, + s: self.scope, + next_early_index, + opaque_type_parent: false, + scope_type, + where_bound_origin: None, + }; + self.with(scope, |this| { + walk_list!(this, visit_generic_param, trait_ref.bound_generic_params); + this.visit_trait_ref(&trait_ref.trait_ref); + }); + } +} + +fn compute_object_lifetime_defaults<'tcx>( + tcx: TyCtxt<'tcx>, + item: &hir::Item<'_>, +) -> Option<&'tcx [ObjectLifetimeDefault]> { + match item.kind { + hir::ItemKind::Struct(_, ref generics) + | hir::ItemKind::Union(_, ref generics) + | hir::ItemKind::Enum(_, ref generics) + | hir::ItemKind::OpaqueTy(hir::OpaqueTy { + ref generics, + origin: hir::OpaqueTyOrigin::TyAlias, + .. + }) + | hir::ItemKind::TyAlias(_, ref generics) + | hir::ItemKind::Trait(_, _, ref generics, ..) => { + let result = object_lifetime_defaults_for_item(tcx, generics); + + // Debugging aid. + let attrs = tcx.hir().attrs(item.hir_id()); + if tcx.sess.contains_name(attrs, sym::rustc_object_lifetime_default) { + let object_lifetime_default_reprs: String = result + .iter() + .map(|set| match *set { + Set1::Empty => "BaseDefault".into(), + Set1::One(Region::Static) => "'static".into(), + Set1::One(Region::EarlyBound(mut i, _)) => generics + .params + .iter() + .find_map(|param| match param.kind { + GenericParamKind::Lifetime { .. } => { + if i == 0 { + return Some(param.name.ident().to_string().into()); + } + i -= 1; + None + } + _ => None, + }) + .unwrap(), + Set1::One(_) => bug!(), + Set1::Many => "Ambiguous".into(), + }) + .collect::<Vec<Cow<'static, str>>>() + .join(","); + tcx.sess.span_err(item.span, &object_lifetime_default_reprs); + } + + Some(result) + } + _ => None, + } +} + +/// Scan the bounds and where-clauses on parameters to extract bounds +/// of the form `T:'a` so as to determine the `ObjectLifetimeDefault` +/// for each type parameter. +fn object_lifetime_defaults_for_item<'tcx>( + tcx: TyCtxt<'tcx>, + generics: &hir::Generics<'_>, +) -> &'tcx [ObjectLifetimeDefault] { + fn add_bounds(set: &mut Set1<hir::LifetimeName>, bounds: &[hir::GenericBound<'_>]) { + for bound in bounds { + if let hir::GenericBound::Outlives(ref lifetime) = *bound { + set.insert(lifetime.name.normalize_to_macros_2_0()); + } + } + } + + let process_param = |param: &hir::GenericParam<'_>| match param.kind { + GenericParamKind::Lifetime { .. } => None, + GenericParamKind::Type { .. } => { + let mut set = Set1::Empty; + + let param_def_id = tcx.hir().local_def_id(param.hir_id); + for predicate in generics.predicates { + // Look for `type: ...` where clauses. + let hir::WherePredicate::BoundPredicate(ref data) = *predicate else { continue }; + + // Ignore `for<'a> type: ...` as they can change what + // lifetimes mean (although we could "just" handle it). + if !data.bound_generic_params.is_empty() { + continue; + } + + let res = match data.bounded_ty.kind { + hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => path.res, + _ => continue, + }; + + if res == Res::Def(DefKind::TyParam, param_def_id.to_def_id()) { + add_bounds(&mut set, &data.bounds); + } + } + + Some(match set { + Set1::Empty => Set1::Empty, + Set1::One(name) => { + if name == hir::LifetimeName::Static { + Set1::One(Region::Static) + } else { + generics + .params + .iter() + .filter_map(|param| match param.kind { + GenericParamKind::Lifetime { .. } => { + let param_def_id = tcx.hir().local_def_id(param.hir_id); + Some(( + param_def_id, + hir::LifetimeName::Param(param_def_id, param.name), + )) + } + _ => None, + }) + .enumerate() + .find(|&(_, (_, lt_name))| lt_name == name) + .map_or(Set1::Many, |(i, (def_id, _))| { + Set1::One(Region::EarlyBound(i as u32, def_id.to_def_id())) + }) + } + } + Set1::Many => Set1::Many, + }) + } + GenericParamKind::Const { .. } => { + // Generic consts don't impose any constraints. + // + // We still store a dummy value here to allow generic parameters + // in an arbitrary order. + Some(Set1::Empty) + } + }; + + tcx.arena.alloc_from_iter(generics.params.iter().filter_map(process_param)) +} + +impl<'a, 'tcx> LifetimeContext<'a, 'tcx> { + fn with<F>(&mut self, wrap_scope: Scope<'_>, f: F) + where + F: for<'b> FnOnce(&mut LifetimeContext<'b, 'tcx>), + { + let LifetimeContext { tcx, map, .. } = self; + let xcrate_object_lifetime_defaults = take(&mut self.xcrate_object_lifetime_defaults); + let mut this = LifetimeContext { + tcx: *tcx, + map, + scope: &wrap_scope, + trait_definition_only: self.trait_definition_only, + xcrate_object_lifetime_defaults, + }; + let span = tracing::debug_span!("scope", scope = ?TruncatedScopeDebug(&this.scope)); + { + let _enter = span.enter(); + f(&mut this); + } + self.xcrate_object_lifetime_defaults = this.xcrate_object_lifetime_defaults; + } + + /// Visits self by adding a scope and handling recursive walk over the contents with `walk`. + /// + /// Handles visiting fns and methods. These are a bit complicated because we must distinguish + /// early- vs late-bound lifetime parameters. We do this by checking which lifetimes appear + /// within type bounds; those are early bound lifetimes, and the rest are late bound. + /// + /// For example: + /// + /// fn foo<'a,'b,'c,T:Trait<'b>>(...) + /// + /// Here `'a` and `'c` are late bound but `'b` is early bound. Note that early- and late-bound + /// lifetimes may be interspersed together. + /// + /// If early bound lifetimes are present, we separate them into their own list (and likewise + /// for late bound). They will be numbered sequentially, starting from the lowest index that is + /// already in scope (for a fn item, that will be 0, but for a method it might not be). Late + /// bound lifetimes are resolved by name and associated with a binder ID (`binder_id`), so the + /// ordering is not important there. + fn visit_early_late<F>( + &mut self, + parent_id: Option<LocalDefId>, + hir_id: hir::HirId, + generics: &'tcx hir::Generics<'tcx>, + walk: F, + ) where + F: for<'b, 'c> FnOnce(&'b mut LifetimeContext<'c, 'tcx>), + { + // Find the start of nested early scopes, e.g., in methods. + let mut next_early_index = 0; + if let Some(parent_id) = parent_id { + let parent = self.tcx.hir().expect_item(parent_id); + if sub_items_have_self_param(&parent.kind) { + next_early_index += 1; // Self comes before lifetimes + } + match parent.kind { + hir::ItemKind::Trait(_, _, ref generics, ..) + | hir::ItemKind::Impl(hir::Impl { ref generics, .. }) => { + next_early_index += generics.params.len() as u32; + } + _ => {} + } + } + + let mut non_lifetime_count = 0; + let mut named_late_bound_vars = 0; + let lifetimes: FxIndexMap<LocalDefId, Region> = generics + .params + .iter() + .filter_map(|param| match param.kind { + GenericParamKind::Lifetime { .. } => { + if self.tcx.is_late_bound(param.hir_id) { + let late_bound_idx = named_late_bound_vars; + named_late_bound_vars += 1; + Some(Region::late(late_bound_idx, self.tcx.hir(), param)) + } else { + Some(Region::early(self.tcx.hir(), &mut next_early_index, param)) + } + } + GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => { + non_lifetime_count += 1; + None + } + }) + .collect(); + let next_early_index = next_early_index + non_lifetime_count; + + let binders: Vec<_> = generics + .params + .iter() + .filter(|param| { + matches!(param.kind, GenericParamKind::Lifetime { .. }) + && self.tcx.is_late_bound(param.hir_id) + }) + .enumerate() + .map(|(late_bound_idx, param)| { + let pair = Region::late(late_bound_idx as u32, self.tcx.hir(), param); + late_region_as_bound_region(self.tcx, &pair.1) + }) + .collect(); + self.map.late_bound_vars.insert(hir_id, binders); + let scope = Scope::Binder { + hir_id, + lifetimes, + next_early_index, + s: self.scope, + opaque_type_parent: true, + scope_type: BinderScopeType::Normal, + where_bound_origin: None, + }; + self.with(scope, walk); + } + + fn next_early_index_helper(&self, only_opaque_type_parent: bool) -> u32 { + let mut scope = self.scope; + loop { + match *scope { + Scope::Root => return 0, + + Scope::Binder { next_early_index, opaque_type_parent, .. } + if (!only_opaque_type_parent || opaque_type_parent) => + { + return next_early_index; + } + + Scope::Binder { s, .. } + | Scope::Body { s, .. } + | Scope::Elision { s, .. } + | Scope::ObjectLifetimeDefault { s, .. } + | Scope::Supertrait { s, .. } + | Scope::TraitRefBoundary { s, .. } => scope = s, + } + } + } + + /// Returns the next index one would use for an early-bound-region + /// if extending the current scope. + fn next_early_index(&self) -> u32 { + self.next_early_index_helper(true) + } + + /// Returns the next index one would use for an `impl Trait` that + /// is being converted into an opaque type alias `impl Trait`. This will be the + /// next early index from the enclosing item, for the most + /// part. See the `opaque_type_parent` field for more info. + fn next_early_index_for_opaque_type(&self) -> u32 { + self.next_early_index_helper(false) + } + + #[tracing::instrument(level = "debug", skip(self))] + fn resolve_lifetime_ref( + &mut self, + region_def_id: LocalDefId, + lifetime_ref: &'tcx hir::Lifetime, + ) { + // Walk up the scope chain, tracking the number of fn scopes + // that we pass through, until we find a lifetime with the + // given name or we run out of scopes. + // search. + let mut late_depth = 0; + let mut scope = self.scope; + let mut outermost_body = None; + let result = loop { + match *scope { + Scope::Body { id, s } => { + outermost_body = Some(id); + scope = s; + } + + Scope::Root => { + break None; + } + + Scope::Binder { ref lifetimes, scope_type, s, where_bound_origin, .. } => { + if let Some(&def) = lifetimes.get(®ion_def_id) { + break Some(def.shifted(late_depth)); + } + match scope_type { + BinderScopeType::Normal => late_depth += 1, + BinderScopeType::Concatenating => {} + } + // Fresh lifetimes in APIT used to be allowed in async fns and forbidden in + // regular fns. + if let Some(hir::PredicateOrigin::ImplTrait) = where_bound_origin + && let hir::LifetimeName::Param(_, hir::ParamName::Fresh) = lifetime_ref.name + && let hir::IsAsync::NotAsync = self.tcx.asyncness(lifetime_ref.hir_id.owner) + && !self.tcx.features().anonymous_lifetime_in_impl_trait + { + rustc_session::parse::feature_err( + &self.tcx.sess.parse_sess, + sym::anonymous_lifetime_in_impl_trait, + lifetime_ref.span, + "anonymous lifetimes in `impl Trait` are unstable", + ).emit(); + return; + } + scope = s; + } + + Scope::Elision { s, .. } + | Scope::ObjectLifetimeDefault { s, .. } + | Scope::Supertrait { s, .. } + | Scope::TraitRefBoundary { s, .. } => { + scope = s; + } + } + }; + + if let Some(mut def) = result { + if let Region::EarlyBound(..) = def { + // Do not free early-bound regions, only late-bound ones. + } else if let Some(body_id) = outermost_body { + let fn_id = self.tcx.hir().body_owner(body_id); + match self.tcx.hir().get(fn_id) { + Node::Item(&hir::Item { kind: hir::ItemKind::Fn(..), .. }) + | Node::TraitItem(&hir::TraitItem { + kind: hir::TraitItemKind::Fn(..), .. + }) + | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) => { + let scope = self.tcx.hir().local_def_id(fn_id); + def = Region::Free(scope.to_def_id(), def.id().unwrap()); + } + _ => {} + } + } + + self.insert_lifetime(lifetime_ref, def); + return; + } + + // We may fail to resolve higher-ranked lifetimes that are mentionned by APIT. + // AST-based resolution does not care for impl-trait desugaring, which are the + // responibility of lowering. This may create a mismatch between the resolution + // AST found (`region_def_id`) which points to HRTB, and what HIR allows. + // ``` + // fn foo(x: impl for<'a> Trait<'a, Assoc = impl Copy + 'a>) {} + // ``` + // + // In such case, walk back the binders to diagnose it properly. + let mut scope = self.scope; + loop { + match *scope { + Scope::Binder { + where_bound_origin: Some(hir::PredicateOrigin::ImplTrait), .. + } => { + let mut err = self.tcx.sess.struct_span_err( + lifetime_ref.span, + "`impl Trait` can only mention lifetimes bound at the fn or impl level", + ); + err.span_note(self.tcx.def_span(region_def_id), "lifetime declared here"); + err.emit(); + return; + } + Scope::Root => break, + Scope::Binder { s, .. } + | Scope::Body { s, .. } + | Scope::Elision { s, .. } + | Scope::ObjectLifetimeDefault { s, .. } + | Scope::Supertrait { s, .. } + | Scope::TraitRefBoundary { s, .. } => { + scope = s; + } + } + } + + self.tcx.sess.delay_span_bug( + lifetime_ref.span, + &format!("Could not resolve {:?} in scope {:#?}", lifetime_ref, self.scope,), + ); + } + + fn visit_segment_args( + &mut self, + res: Res, + depth: usize, + generic_args: &'tcx hir::GenericArgs<'tcx>, + ) { + debug!( + "visit_segment_args(res={:?}, depth={:?}, generic_args={:?})", + res, depth, generic_args, + ); + + if generic_args.parenthesized { + self.visit_fn_like_elision( + generic_args.inputs(), + Some(generic_args.bindings[0].ty()), + false, + ); + return; + } + + for arg in generic_args.args { + if let hir::GenericArg::Lifetime(lt) = arg { + self.visit_lifetime(lt); + } + } + + // Figure out if this is a type/trait segment, + // which requires object lifetime defaults. + let parent_def_id = |this: &mut Self, def_id: DefId| { + let def_key = this.tcx.def_key(def_id); + DefId { krate: def_id.krate, index: def_key.parent.expect("missing parent") } + }; + let type_def_id = match res { + Res::Def(DefKind::AssocTy, def_id) if depth == 1 => Some(parent_def_id(self, def_id)), + Res::Def(DefKind::Variant, def_id) if depth == 0 => Some(parent_def_id(self, def_id)), + Res::Def( + DefKind::Struct + | DefKind::Union + | DefKind::Enum + | DefKind::TyAlias + | DefKind::Trait, + def_id, + ) if depth == 0 => Some(def_id), + _ => None, + }; + + debug!("visit_segment_args: type_def_id={:?}", type_def_id); + + // Compute a vector of defaults, one for each type parameter, + // per the rules given in RFCs 599 and 1156. Example: + // + // ```rust + // struct Foo<'a, T: 'a, U> { } + // ``` + // + // If you have `Foo<'x, dyn Bar, dyn Baz>`, we want to default + // `dyn Bar` to `dyn Bar + 'x` (because of the `T: 'a` bound) + // and `dyn Baz` to `dyn Baz + 'static` (because there is no + // such bound). + // + // Therefore, we would compute `object_lifetime_defaults` to a + // vector like `['x, 'static]`. Note that the vector only + // includes type parameters. + let object_lifetime_defaults = type_def_id.map_or_else(Vec::new, |def_id| { + let in_body = { + let mut scope = self.scope; + loop { + match *scope { + Scope::Root => break false, + + Scope::Body { .. } => break true, + + Scope::Binder { s, .. } + | Scope::Elision { s, .. } + | Scope::ObjectLifetimeDefault { s, .. } + | Scope::Supertrait { s, .. } + | Scope::TraitRefBoundary { s, .. } => { + scope = s; + } + } + } + }; + + let map = &self.map; + let set_to_region = |set: &ObjectLifetimeDefault| match *set { + Set1::Empty => { + if in_body { + None + } else { + Some(Region::Static) + } + } + Set1::One(r) => { + let lifetimes = generic_args.args.iter().filter_map(|arg| match arg { + GenericArg::Lifetime(lt) => Some(lt), + _ => None, + }); + r.subst(lifetimes, map) + } + Set1::Many => None, + }; + if let Some(def_id) = def_id.as_local() { + let id = self.tcx.hir().local_def_id_to_hir_id(def_id); + self.tcx + .object_lifetime_defaults(id.owner) + .unwrap() + .iter() + .map(set_to_region) + .collect() + } else { + let tcx = self.tcx; + self.xcrate_object_lifetime_defaults + .entry(def_id) + .or_insert_with(|| { + tcx.generics_of(def_id) + .params + .iter() + .filter_map(|param| match param.kind { + GenericParamDefKind::Type { object_lifetime_default, .. } => { + Some(object_lifetime_default) + } + GenericParamDefKind::Const { .. } => Some(Set1::Empty), + GenericParamDefKind::Lifetime => None, + }) + .collect() + }) + .iter() + .map(set_to_region) + .collect() + } + }); + + debug!("visit_segment_args: object_lifetime_defaults={:?}", object_lifetime_defaults); + + let mut i = 0; + for arg in generic_args.args { + match arg { + GenericArg::Lifetime(_) => {} + GenericArg::Type(ty) => { + if let Some(<) = object_lifetime_defaults.get(i) { + let scope = Scope::ObjectLifetimeDefault { lifetime: lt, s: self.scope }; + self.with(scope, |this| this.visit_ty(ty)); + } else { + self.visit_ty(ty); + } + i += 1; + } + GenericArg::Const(ct) => { + self.visit_anon_const(&ct.value); + i += 1; + } + GenericArg::Infer(inf) => { + self.visit_id(inf.hir_id); + i += 1; + } + } + } + + // Hack: when resolving the type `XX` in binding like `dyn + // Foo<'b, Item = XX>`, the current object-lifetime default + // would be to examine the trait `Foo` to check whether it has + // a lifetime bound declared on `Item`. e.g., if `Foo` is + // declared like so, then the default object lifetime bound in + // `XX` should be `'b`: + // + // ```rust + // trait Foo<'a> { + // type Item: 'a; + // } + // ``` + // + // but if we just have `type Item;`, then it would be + // `'static`. However, we don't get all of this logic correct. + // + // Instead, we do something hacky: if there are no lifetime parameters + // to the trait, then we simply use a default object lifetime + // bound of `'static`, because there is no other possibility. On the other hand, + // if there ARE lifetime parameters, then we require the user to give an + // explicit bound for now. + // + // This is intended to leave room for us to implement the + // correct behavior in the future. + let has_lifetime_parameter = + generic_args.args.iter().any(|arg| matches!(arg, GenericArg::Lifetime(_))); + + // Resolve lifetimes found in the bindings, so either in the type `XX` in `Item = XX` or + // in the trait ref `YY<...>` in `Item: YY<...>`. + for binding in generic_args.bindings { + let scope = Scope::ObjectLifetimeDefault { + lifetime: if has_lifetime_parameter { None } else { Some(Region::Static) }, + s: self.scope, + }; + if let Some(type_def_id) = type_def_id { + let lifetimes = LifetimeContext::supertrait_hrtb_lifetimes( + self.tcx, + type_def_id, + binding.ident, + ); + self.with(scope, |this| { + let scope = Scope::Supertrait { + lifetimes: lifetimes.unwrap_or_default(), + s: this.scope, + }; + this.with(scope, |this| this.visit_assoc_type_binding(binding)); + }); + } else { + self.with(scope, |this| this.visit_assoc_type_binding(binding)); + } + } + } + + /// Returns all the late-bound vars that come into scope from supertrait HRTBs, based on the + /// associated type name and starting trait. + /// For example, imagine we have + /// ```ignore (illustrative) + /// trait Foo<'a, 'b> { + /// type As; + /// } + /// trait Bar<'b>: for<'a> Foo<'a, 'b> {} + /// trait Bar: for<'b> Bar<'b> {} + /// ``` + /// In this case, if we wanted to the supertrait HRTB lifetimes for `As` on + /// the starting trait `Bar`, we would return `Some(['b, 'a])`. + fn supertrait_hrtb_lifetimes( + tcx: TyCtxt<'tcx>, + def_id: DefId, + assoc_name: Ident, + ) -> Option<Vec<ty::BoundVariableKind>> { + let trait_defines_associated_type_named = |trait_def_id: DefId| { + tcx.associated_items(trait_def_id) + .find_by_name_and_kind(tcx, assoc_name, ty::AssocKind::Type, trait_def_id) + .is_some() + }; + + use smallvec::{smallvec, SmallVec}; + let mut stack: SmallVec<[(DefId, SmallVec<[ty::BoundVariableKind; 8]>); 8]> = + smallvec![(def_id, smallvec![])]; + let mut visited: FxHashSet<DefId> = FxHashSet::default(); + loop { + let Some((def_id, bound_vars)) = stack.pop() else { + break None; + }; + // See issue #83753. If someone writes an associated type on a non-trait, just treat it as + // there being no supertrait HRTBs. + match tcx.def_kind(def_id) { + DefKind::Trait | DefKind::TraitAlias | DefKind::Impl => {} + _ => break None, + } + + if trait_defines_associated_type_named(def_id) { + break Some(bound_vars.into_iter().collect()); + } + let predicates = + tcx.super_predicates_that_define_assoc_type((def_id, Some(assoc_name))); + let obligations = predicates.predicates.iter().filter_map(|&(pred, _)| { + let bound_predicate = pred.kind(); + match bound_predicate.skip_binder() { + ty::PredicateKind::Trait(data) => { + // The order here needs to match what we would get from `subst_supertrait` + let pred_bound_vars = bound_predicate.bound_vars(); + let mut all_bound_vars = bound_vars.clone(); + all_bound_vars.extend(pred_bound_vars.iter()); + let super_def_id = data.trait_ref.def_id; + Some((super_def_id, all_bound_vars)) + } + _ => None, + } + }); + + let obligations = obligations.filter(|o| visited.insert(o.0)); + stack.extend(obligations); + } + } + + #[tracing::instrument(level = "debug", skip(self))] + fn visit_fn_like_elision( + &mut self, + inputs: &'tcx [hir::Ty<'tcx>], + output: Option<&'tcx hir::Ty<'tcx>>, + in_closure: bool, + ) { + self.with(Scope::Elision { s: self.scope }, |this| { + for input in inputs { + this.visit_ty(input); + } + if !in_closure && let Some(output) = output { + this.visit_ty(output); + } + }); + if in_closure && let Some(output) = output { + self.visit_ty(output); + } + } + + fn resolve_object_lifetime_default(&mut self, lifetime_ref: &'tcx hir::Lifetime) { + debug!("resolve_object_lifetime_default(lifetime_ref={:?})", lifetime_ref); + let mut late_depth = 0; + let mut scope = self.scope; + let lifetime = loop { + match *scope { + Scope::Binder { s, scope_type, .. } => { + match scope_type { + BinderScopeType::Normal => late_depth += 1, + BinderScopeType::Concatenating => {} + } + scope = s; + } + + Scope::Root | Scope::Elision { .. } => break Region::Static, + + Scope::Body { .. } | Scope::ObjectLifetimeDefault { lifetime: None, .. } => return, + + Scope::ObjectLifetimeDefault { lifetime: Some(l), .. } => break l, + + Scope::Supertrait { s, .. } | Scope::TraitRefBoundary { s, .. } => { + scope = s; + } + } + }; + self.insert_lifetime(lifetime_ref, lifetime.shifted(late_depth)); + } + + #[tracing::instrument(level = "debug", skip(self))] + fn insert_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime, def: Region) { + debug!( + node = ?self.tcx.hir().node_to_string(lifetime_ref.hir_id), + span = ?self.tcx.sess.source_map().span_to_diagnostic_string(lifetime_ref.span) + ); + self.map.defs.insert(lifetime_ref.hir_id, def); + } + + /// Sometimes we resolve a lifetime, but later find that it is an + /// error (esp. around impl trait). In that case, we remove the + /// entry into `map.defs` so as not to confuse later code. + fn uninsert_lifetime_on_error(&mut self, lifetime_ref: &'tcx hir::Lifetime, bad_def: Region) { + let old_value = self.map.defs.remove(&lifetime_ref.hir_id); + assert_eq!(old_value, Some(bad_def)); + } +} + +/// Detects late-bound lifetimes and inserts them into +/// `late_bound`. +/// +/// A region declared on a fn is **late-bound** if: +/// - it is constrained by an argument type; +/// - it does not appear in a where-clause. +/// +/// "Constrained" basically means that it appears in any type but +/// not amongst the inputs to a projection. In other words, `<&'a +/// T as Trait<''b>>::Foo` does not constrain `'a` or `'b`. +fn is_late_bound_map(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<&FxIndexSet<LocalDefId>> { + let hir_id = tcx.hir().local_def_id_to_hir_id(def_id); + let decl = tcx.hir().fn_decl_by_hir_id(hir_id)?; + let generics = tcx.hir().get_generics(def_id)?; + + let mut late_bound = FxIndexSet::default(); + + let mut constrained_by_input = ConstrainedCollector::default(); + for arg_ty in decl.inputs { + constrained_by_input.visit_ty(arg_ty); + } + + let mut appears_in_output = AllCollector::default(); + intravisit::walk_fn_ret_ty(&mut appears_in_output, &decl.output); + + debug!(?constrained_by_input.regions); + + // Walk the lifetimes that appear in where clauses. + // + // Subtle point: because we disallow nested bindings, we can just + // ignore binders here and scrape up all names we see. + let mut appears_in_where_clause = AllCollector::default(); + appears_in_where_clause.visit_generics(generics); + debug!(?appears_in_where_clause.regions); + + // Late bound regions are those that: + // - appear in the inputs + // - do not appear in the where-clauses + // - are not implicitly captured by `impl Trait` + for param in generics.params { + match param.kind { + hir::GenericParamKind::Lifetime { .. } => { /* fall through */ } + + // Neither types nor consts are late-bound. + hir::GenericParamKind::Type { .. } | hir::GenericParamKind::Const { .. } => continue, + } + + let param_def_id = tcx.hir().local_def_id(param.hir_id); + + // appears in the where clauses? early-bound. + if appears_in_where_clause.regions.contains(¶m_def_id) { + continue; + } + + // does not appear in the inputs, but appears in the return type? early-bound. + if !constrained_by_input.regions.contains(¶m_def_id) + && appears_in_output.regions.contains(¶m_def_id) + { + continue; + } + + debug!("lifetime {:?} with id {:?} is late-bound", param.name.ident(), param.hir_id); + + let inserted = late_bound.insert(param_def_id); + assert!(inserted, "visited lifetime {:?} twice", param.hir_id); + } + + debug!(?late_bound); + return Some(tcx.arena.alloc(late_bound)); + + #[derive(Default)] + struct ConstrainedCollector { + regions: FxHashSet<LocalDefId>, + } + + impl<'v> Visitor<'v> for ConstrainedCollector { + fn visit_ty(&mut self, ty: &'v hir::Ty<'v>) { + match ty.kind { + hir::TyKind::Path( + hir::QPath::Resolved(Some(_), _) | hir::QPath::TypeRelative(..), + ) => { + // ignore lifetimes appearing in associated type + // projections, as they are not *constrained* + // (defined above) + } + + hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => { + // consider only the lifetimes on the final + // segment; I am not sure it's even currently + // valid to have them elsewhere, but even if it + // is, those would be potentially inputs to + // projections + if let Some(last_segment) = path.segments.last() { + self.visit_path_segment(path.span, last_segment); + } + } + + _ => { + intravisit::walk_ty(self, ty); + } + } + } + + fn visit_lifetime(&mut self, lifetime_ref: &'v hir::Lifetime) { + if let hir::LifetimeName::Param(def_id, _) = lifetime_ref.name { + self.regions.insert(def_id); + } + } + } + + #[derive(Default)] + struct AllCollector { + regions: FxHashSet<LocalDefId>, + } + + impl<'v> Visitor<'v> for AllCollector { + fn visit_lifetime(&mut self, lifetime_ref: &'v hir::Lifetime) { + if let hir::LifetimeName::Param(def_id, _) = lifetime_ref.name { + self.regions.insert(def_id); + } + } + } +} |