// Validate AST before lowering it to HIR. // // This pass is supposed to catch things that fit into AST data structures, // but not permitted by the language. It runs after expansion when AST is frozen, // so it can check for erroneous constructions produced by syntax extensions. // This pass is supposed to perform only simple checks not requiring name resolution // or type checking or some other kind of complex analysis. use itertools::{Either, Itertools}; use rustc_ast::ptr::P; use rustc_ast::visit::{self, AssocCtxt, BoundKind, FnCtxt, FnKind, Visitor}; use rustc_ast::walk_list; use rustc_ast::*; use rustc_ast_pretty::pprust::{self, State}; use rustc_data_structures::fx::FxHashMap; use rustc_macros::Subdiagnostic; use rustc_parse::validate_attr; use rustc_session::lint::builtin::{ DEPRECATED_WHERE_CLAUSE_LOCATION, MISSING_ABI, PATTERNS_IN_FNS_WITHOUT_BODY, }; use rustc_session::lint::{BuiltinLintDiagnostics, LintBuffer}; use rustc_session::Session; use rustc_span::source_map::Spanned; use rustc_span::symbol::{kw, sym, Ident}; use rustc_span::Span; use rustc_target::spec::abi; use std::mem; use std::ops::{Deref, DerefMut}; use thin_vec::thin_vec; use crate::errors; use crate::fluent_generated as fluent; /// Is `self` allowed semantically as the first parameter in an `FnDecl`? enum SelfSemantic { Yes, No, } /// What is the context that prevents using `~const`? enum DisallowTildeConstContext<'a> { TraitObject, Fn(FnKind<'a>), } struct AstValidator<'a> { session: &'a Session, /// The span of the `extern` in an `extern { ... }` block, if any. extern_mod: Option<&'a Item>, /// Are we inside a trait impl? in_trait_impl: bool, in_const_trait_impl: bool, has_proc_macro_decls: bool, /// Used to ban nested `impl Trait`, e.g., `impl Into`. /// Nested `impl Trait` _is_ allowed in associated type position, /// e.g., `impl Iterator`. outer_impl_trait: Option, disallow_tilde_const: Option>, /// Used to ban `impl Trait` in path projections like `::Item` /// or `Foo::Bar` is_impl_trait_banned: bool, /// See [ForbiddenLetReason] forbidden_let_reason: Option, lint_buffer: &'a mut LintBuffer, } impl<'a> AstValidator<'a> { fn with_in_trait_impl( &mut self, is_in: bool, constness: Option, f: impl FnOnce(&mut Self), ) { let old = mem::replace(&mut self.in_trait_impl, is_in); let old_const = mem::replace(&mut self.in_const_trait_impl, matches!(constness, Some(Const::Yes(_)))); f(self); self.in_trait_impl = old; self.in_const_trait_impl = old_const; } fn with_banned_impl_trait(&mut self, f: impl FnOnce(&mut Self)) { let old = mem::replace(&mut self.is_impl_trait_banned, true); f(self); self.is_impl_trait_banned = old; } fn with_tilde_const( &mut self, disallowed: Option>, f: impl FnOnce(&mut Self), ) { let old = mem::replace(&mut self.disallow_tilde_const, disallowed); f(self); self.disallow_tilde_const = old; } fn with_tilde_const_allowed(&mut self, f: impl FnOnce(&mut Self)) { self.with_tilde_const(None, f) } fn with_banned_tilde_const( &mut self, ctx: DisallowTildeConstContext<'a>, f: impl FnOnce(&mut Self), ) { self.with_tilde_const(Some(ctx), f) } fn with_let_management( &mut self, forbidden_let_reason: Option, f: impl FnOnce(&mut Self, Option), ) { let old = mem::replace(&mut self.forbidden_let_reason, forbidden_let_reason); f(self, old); self.forbidden_let_reason = old; } /// Emits an error banning the `let` expression provided in the given location. fn ban_let_expr(&self, expr: &'a Expr, forbidden_let_reason: ForbiddenLetReason) { let sess = &self.session; if sess.opts.unstable_features.is_nightly_build() { sess.emit_err(errors::ForbiddenLet { span: expr.span, reason: forbidden_let_reason }); } else { sess.emit_err(errors::ForbiddenLetStable { span: expr.span }); } } fn check_gat_where( &mut self, id: NodeId, before_predicates: &[WherePredicate], where_clauses: (ast::TyAliasWhereClause, ast::TyAliasWhereClause), ) { if !before_predicates.is_empty() { let mut state = State::new(); if !where_clauses.1.0 { state.space(); state.word_space("where"); } else { state.word_space(","); } let mut first = true; for p in before_predicates.iter() { if !first { state.word_space(","); } first = false; state.print_where_predicate(p); } let suggestion = state.s.eof(); self.lint_buffer.buffer_lint_with_diagnostic( DEPRECATED_WHERE_CLAUSE_LOCATION, id, where_clauses.0.1, fluent::ast_passes_deprecated_where_clause_location, BuiltinLintDiagnostics::DeprecatedWhereclauseLocation( where_clauses.1.1.shrink_to_hi(), suggestion, ), ); } } fn with_impl_trait(&mut self, outer: Option, f: impl FnOnce(&mut Self)) { let old = mem::replace(&mut self.outer_impl_trait, outer); f(self); self.outer_impl_trait = old; } // Mirrors `visit::walk_ty`, but tracks relevant state. fn walk_ty(&mut self, t: &'a Ty) { match &t.kind { TyKind::ImplTrait(..) => { self.with_impl_trait(Some(t.span), |this| visit::walk_ty(this, t)) } TyKind::TraitObject(..) => self .with_banned_tilde_const(DisallowTildeConstContext::TraitObject, |this| { visit::walk_ty(this, t) }), TyKind::Path(qself, path) => { // We allow these: // - `Option` // - `option::Option` // - `option::Option::Foo` // // But not these: // - `::Foo` // - `option::Option::Foo`. // // To implement this, we disallow `impl Trait` from `qself` // (for cases like `::Foo>`) // but we allow `impl Trait` in `GenericArgs` // iff there are no more PathSegments. if let Some(qself) = qself { // `impl Trait` in `qself` is always illegal self.with_banned_impl_trait(|this| this.visit_ty(&qself.ty)); } // Note that there should be a call to visit_path here, // so if any logic is added to process `Path`s a call to it should be // added both in visit_path and here. This code mirrors visit::walk_path. for (i, segment) in path.segments.iter().enumerate() { // Allow `impl Trait` iff we're on the final path segment if i == path.segments.len() - 1 { self.visit_path_segment(segment); } else { self.with_banned_impl_trait(|this| this.visit_path_segment(segment)); } } } _ => visit::walk_ty(self, t), } } fn err_handler(&self) -> &rustc_errors::Handler { &self.session.diagnostic() } fn check_lifetime(&self, ident: Ident) { let valid_names = [kw::UnderscoreLifetime, kw::StaticLifetime, kw::Empty]; if !valid_names.contains(&ident.name) && ident.without_first_quote().is_reserved() { self.session.emit_err(errors::KeywordLifetime { span: ident.span }); } } fn check_label(&self, ident: Ident) { if ident.without_first_quote().is_reserved() { self.session.emit_err(errors::InvalidLabel { span: ident.span, name: ident.name }); } } fn invalid_visibility(&self, vis: &Visibility, note: Option) { if let VisibilityKind::Inherited = vis.kind { return; } self.session.emit_err(errors::InvalidVisibility { span: vis.span, implied: vis.kind.is_pub().then_some(vis.span), note, }); } fn check_decl_no_pat(decl: &FnDecl, mut report_err: impl FnMut(Span, Option, bool)) { for Param { pat, .. } in &decl.inputs { match pat.kind { PatKind::Ident(BindingAnnotation::NONE, _, None) | PatKind::Wild => {} PatKind::Ident(BindingAnnotation::MUT, ident, None) => { report_err(pat.span, Some(ident), true) } _ => report_err(pat.span, None, false), } } } fn check_trait_fn_not_const(&self, constness: Const) { if let Const::Yes(span) = constness { self.session.emit_err(errors::TraitFnConst { span }); } } fn check_fn_decl(&self, fn_decl: &FnDecl, self_semantic: SelfSemantic) { self.check_decl_num_args(fn_decl); self.check_decl_cvaradic_pos(fn_decl); self.check_decl_attrs(fn_decl); self.check_decl_self_param(fn_decl, self_semantic); } /// Emits fatal error if function declaration has more than `u16::MAX` arguments /// Error is fatal to prevent errors during typechecking fn check_decl_num_args(&self, fn_decl: &FnDecl) { let max_num_args: usize = u16::MAX.into(); if fn_decl.inputs.len() > max_num_args { let Param { span, .. } = fn_decl.inputs[0]; self.session.emit_fatal(errors::FnParamTooMany { span, max_num_args }); } } fn check_decl_cvaradic_pos(&self, fn_decl: &FnDecl) { match &*fn_decl.inputs { [Param { ty, span, .. }] => { if let TyKind::CVarArgs = ty.kind { self.session.emit_err(errors::FnParamCVarArgsOnly { span: *span }); } } [ps @ .., _] => { for Param { ty, span, .. } in ps { if let TyKind::CVarArgs = ty.kind { self.session.emit_err(errors::FnParamCVarArgsNotLast { span: *span }); } } } _ => {} } } fn check_decl_attrs(&self, fn_decl: &FnDecl) { fn_decl .inputs .iter() .flat_map(|i| i.attrs.as_ref()) .filter(|attr| { let arr = [ sym::allow, sym::cfg, sym::cfg_attr, sym::deny, sym::expect, sym::forbid, sym::warn, ]; !arr.contains(&attr.name_or_empty()) && rustc_attr::is_builtin_attr(attr) }) .for_each(|attr| { if attr.is_doc_comment() { self.session.emit_err(errors::FnParamDocComment { span: attr.span }); } else { self.session.emit_err(errors::FnParamForbiddenAttr { span: attr.span }); } }); } fn check_decl_self_param(&self, fn_decl: &FnDecl, self_semantic: SelfSemantic) { if let (SelfSemantic::No, [param, ..]) = (self_semantic, &*fn_decl.inputs) { if param.is_self() { self.session.emit_err(errors::FnParamForbiddenSelf { span: param.span }); } } } fn check_defaultness(&self, span: Span, defaultness: Defaultness) { if let Defaultness::Default(def_span) = defaultness { let span = self.session.source_map().guess_head_span(span); self.session.emit_err(errors::ForbiddenDefault { span, def_span }); } } /// If `sp` ends with a semicolon, returns it as a `Span` /// Otherwise, returns `sp.shrink_to_hi()` fn ending_semi_or_hi(&self, sp: Span) -> Span { let source_map = self.session.source_map(); let end = source_map.end_point(sp); if source_map.span_to_snippet(end).map(|s| s == ";").unwrap_or(false) { end } else { sp.shrink_to_hi() } } fn check_type_no_bounds(&self, bounds: &[GenericBound], ctx: &str) { let span = match bounds { [] => return, [b0] => b0.span(), [b0, .., bl] => b0.span().to(bl.span()), }; self.err_handler().emit_err(errors::BoundInContext { span, ctx }); } fn check_foreign_ty_genericless(&self, generics: &Generics, where_span: Span) { let cannot_have = |span, descr, remove_descr| { self.err_handler().emit_err(errors::ExternTypesCannotHave { span, descr, remove_descr, block_span: self.current_extern_span(), }); }; if !generics.params.is_empty() { cannot_have(generics.span, "generic parameters", "generic parameters"); } if !generics.where_clause.predicates.is_empty() { cannot_have(where_span, "`where` clauses", "`where` clause"); } } fn check_foreign_kind_bodyless(&self, ident: Ident, kind: &str, body: Option) { let Some(body) = body else { return; }; self.err_handler().emit_err(errors::BodyInExtern { span: ident.span, body, block: self.current_extern_span(), kind, }); } /// An `fn` in `extern { ... }` cannot have a body `{ ... }`. fn check_foreign_fn_bodyless(&self, ident: Ident, body: Option<&Block>) { let Some(body) = body else { return; }; self.err_handler().emit_err(errors::FnBodyInExtern { span: ident.span, body: body.span, block: self.current_extern_span(), }); } fn current_extern_span(&self) -> Span { self.session.source_map().guess_head_span(self.extern_mod.unwrap().span) } /// An `fn` in `extern { ... }` cannot have qualifiers, e.g. `async fn`. fn check_foreign_fn_headerless(&self, ident: Ident, span: Span, header: FnHeader) { if header.has_qualifiers() { self.err_handler().emit_err(errors::FnQualifierInExtern { span: ident.span, block: self.current_extern_span(), sugg_span: span.until(ident.span.shrink_to_lo()), }); } } /// An item in `extern { ... }` cannot use non-ascii identifier. fn check_foreign_item_ascii_only(&self, ident: Ident) { if !ident.as_str().is_ascii() { self.err_handler().emit_err(errors::ExternItemAscii { span: ident.span, block: self.current_extern_span(), }); } } /// Reject C-variadic type unless the function is foreign, /// or free and `unsafe extern "C"` semantically. fn check_c_variadic_type(&self, fk: FnKind<'a>) { match (fk.ctxt(), fk.header()) { (Some(FnCtxt::Foreign), _) => return, (Some(FnCtxt::Free), Some(header)) => match header.ext { Extern::Explicit(StrLit { symbol_unescaped: sym::C, .. }, _) | Extern::Implicit(_) if matches!(header.unsafety, Unsafe::Yes(_)) => { return; } _ => {} }, _ => {} }; for Param { ty, span, .. } in &fk.decl().inputs { if let TyKind::CVarArgs = ty.kind { self.err_handler().emit_err(errors::BadCVariadic { span: *span }); } } } fn check_item_named(&self, ident: Ident, kind: &str) { if ident.name != kw::Underscore { return; } self.err_handler().emit_err(errors::ItemUnderscore { span: ident.span, kind }); } fn check_nomangle_item_asciionly(&self, ident: Ident, item_span: Span) { if ident.name.as_str().is_ascii() { return; } let span = self.session.source_map().guess_head_span(item_span); self.session.emit_err(errors::NoMangleAscii { span }); } fn check_mod_file_item_asciionly(&self, ident: Ident) { if ident.name.as_str().is_ascii() { return; } self.session.emit_err(errors::ModuleNonAscii { span: ident.span, name: ident.name }); } fn deny_generic_params(&self, generics: &Generics, ident: Span) { if !generics.params.is_empty() { self.session.emit_err(errors::AutoTraitGeneric { span: generics.span, ident }); } } fn emit_e0568(&self, span: Span, ident: Span) { self.session.emit_err(errors::AutoTraitBounds { span, ident }); } fn deny_super_traits(&self, bounds: &GenericBounds, ident_span: Span) { if let [.., last] = &bounds[..] { let span = ident_span.shrink_to_hi().to(last.span()); self.emit_e0568(span, ident_span); } } fn deny_where_clause(&self, where_clause: &WhereClause, ident_span: Span) { if !where_clause.predicates.is_empty() { self.emit_e0568(where_clause.span, ident_span); } } fn deny_items(&self, trait_items: &[P], ident: Span) { if !trait_items.is_empty() { let spans: Vec<_> = trait_items.iter().map(|i| i.ident.span).collect(); let total = trait_items.first().unwrap().span.to(trait_items.last().unwrap().span); self.session.emit_err(errors::AutoTraitItems { spans, total, ident }); } } fn correct_generic_order_suggestion(&self, data: &AngleBracketedArgs) -> String { // Lifetimes always come first. let lt_sugg = data.args.iter().filter_map(|arg| match arg { AngleBracketedArg::Arg(lt @ GenericArg::Lifetime(_)) => { Some(pprust::to_string(|s| s.print_generic_arg(lt))) } _ => None, }); let args_sugg = data.args.iter().filter_map(|a| match a { AngleBracketedArg::Arg(GenericArg::Lifetime(_)) | AngleBracketedArg::Constraint(_) => { None } AngleBracketedArg::Arg(arg) => Some(pprust::to_string(|s| s.print_generic_arg(arg))), }); // Constraints always come last. let constraint_sugg = data.args.iter().filter_map(|a| match a { AngleBracketedArg::Arg(_) => None, AngleBracketedArg::Constraint(c) => { Some(pprust::to_string(|s| s.print_assoc_constraint(c))) } }); format!( "<{}>", lt_sugg.chain(args_sugg).chain(constraint_sugg).collect::>().join(", ") ) } /// Enforce generic args coming before constraints in `<...>` of a path segment. fn check_generic_args_before_constraints(&self, data: &AngleBracketedArgs) { // Early exit in case it's partitioned as it should be. if data.args.iter().is_partitioned(|arg| matches!(arg, AngleBracketedArg::Arg(_))) { return; } // Find all generic argument coming after the first constraint... let (constraint_spans, arg_spans): (Vec, Vec) = data.args.iter().partition_map(|arg| match arg { AngleBracketedArg::Constraint(c) => Either::Left(c.span), AngleBracketedArg::Arg(a) => Either::Right(a.span()), }); let args_len = arg_spans.len(); let constraint_len = constraint_spans.len(); // ...and then error: self.err_handler().emit_err(errors::ArgsBeforeConstraint { arg_spans: arg_spans.clone(), constraints: constraint_spans[0], args: *arg_spans.iter().last().unwrap(), data: data.span, constraint_spans: errors::EmptyLabelManySpans(constraint_spans), arg_spans2: errors::EmptyLabelManySpans(arg_spans), suggestion: self.correct_generic_order_suggestion(&data), constraint_len, args_len, }); } fn visit_ty_common(&mut self, ty: &'a Ty) { match &ty.kind { TyKind::BareFn(bfty) => { self.check_fn_decl(&bfty.decl, SelfSemantic::No); Self::check_decl_no_pat(&bfty.decl, |span, _, _| { self.session.emit_err(errors::PatternFnPointer { span }); }); if let Extern::Implicit(_) = bfty.ext { let sig_span = self.session.source_map().next_point(ty.span.shrink_to_lo()); self.maybe_lint_missing_abi(sig_span, ty.id); } } TyKind::TraitObject(bounds, ..) => { let mut any_lifetime_bounds = false; for bound in bounds { if let GenericBound::Outlives(lifetime) = bound { if any_lifetime_bounds { self.session .emit_err(errors::TraitObjectBound { span: lifetime.ident.span }); break; } any_lifetime_bounds = true; } } } TyKind::ImplTrait(_, bounds) => { if self.is_impl_trait_banned { self.session.emit_err(errors::ImplTraitPath { span: ty.span }); } if let Some(outer_impl_trait_sp) = self.outer_impl_trait { self.session.emit_err(errors::NestedImplTrait { span: ty.span, outer: outer_impl_trait_sp, inner: ty.span, }); } if !bounds.iter().any(|b| matches!(b, GenericBound::Trait(..))) { self.err_handler().emit_err(errors::AtLeastOneTrait { span: ty.span }); } } _ => {} } } fn maybe_lint_missing_abi(&mut self, span: Span, id: NodeId) { // FIXME(davidtwco): This is a hack to detect macros which produce spans of the // call site which do not have a macro backtrace. See #61963. let is_macro_callsite = self .session .source_map() .span_to_snippet(span) .map(|snippet| snippet.starts_with("#[")) .unwrap_or(true); if !is_macro_callsite { self.lint_buffer.buffer_lint_with_diagnostic( MISSING_ABI, id, span, fluent::ast_passes_extern_without_abi, BuiltinLintDiagnostics::MissingAbi(span, abi::Abi::FALLBACK), ) } } } /// Checks that generic parameters are in the correct order, /// which is lifetimes, then types and then consts. (`<'a, T, const N: usize>`) fn validate_generic_param_order( handler: &rustc_errors::Handler, generics: &[GenericParam], span: Span, ) { let mut max_param: Option = None; let mut out_of_order = FxHashMap::default(); let mut param_idents = Vec::with_capacity(generics.len()); for (idx, param) in generics.iter().enumerate() { let ident = param.ident; let (kind, bounds, span) = (¶m.kind, ¶m.bounds, ident.span); let (ord_kind, ident) = match ¶m.kind { GenericParamKind::Lifetime => (ParamKindOrd::Lifetime, ident.to_string()), GenericParamKind::Type { .. } => (ParamKindOrd::TypeOrConst, ident.to_string()), GenericParamKind::Const { ty, .. } => { let ty = pprust::ty_to_string(ty); (ParamKindOrd::TypeOrConst, format!("const {}: {}", ident, ty)) } }; param_idents.push((kind, ord_kind, bounds, idx, ident)); match max_param { Some(max_param) if max_param > ord_kind => { let entry = out_of_order.entry(ord_kind).or_insert((max_param, vec![])); entry.1.push(span); } Some(_) | None => max_param = Some(ord_kind), }; } if !out_of_order.is_empty() { let mut ordered_params = "<".to_string(); param_idents.sort_by_key(|&(_, po, _, i, _)| (po, i)); let mut first = true; for (kind, _, bounds, _, ident) in param_idents { if !first { ordered_params += ", "; } ordered_params += &ident; if !bounds.is_empty() { ordered_params += ": "; ordered_params += &pprust::bounds_to_string(&bounds); } match kind { GenericParamKind::Type { default: Some(default) } => { ordered_params += " = "; ordered_params += &pprust::ty_to_string(default); } GenericParamKind::Type { default: None } => (), GenericParamKind::Lifetime => (), GenericParamKind::Const { ty: _, kw_span: _, default: Some(default) } => { ordered_params += " = "; ordered_params += &pprust::expr_to_string(&*default.value); } GenericParamKind::Const { ty: _, kw_span: _, default: None } => (), } first = false; } ordered_params += ">"; for (param_ord, (max_param, spans)) in &out_of_order { handler.emit_err(errors::OutOfOrderParams { spans: spans.clone(), sugg_span: span, param_ord, max_param, ordered_params: &ordered_params, }); } } } impl<'a> Visitor<'a> for AstValidator<'a> { fn visit_attribute(&mut self, attr: &Attribute) { validate_attr::check_attr(&self.session.parse_sess, attr); } fn visit_expr(&mut self, expr: &'a Expr) { self.with_let_management(Some(ForbiddenLetReason::GenericForbidden), |this, forbidden_let_reason| { match &expr.kind { ExprKind::Binary(Spanned { node: BinOpKind::Or, span }, lhs, rhs) => { let local_reason = Some(ForbiddenLetReason::NotSupportedOr(*span)); this.with_let_management(local_reason, |this, _| this.visit_expr(lhs)); this.with_let_management(local_reason, |this, _| this.visit_expr(rhs)); } ExprKind::If(cond, then, opt_else) => { this.visit_block(then); walk_list!(this, visit_expr, opt_else); this.with_let_management(None, |this, _| this.visit_expr(cond)); return; } ExprKind::Let(..) if let Some(elem) = forbidden_let_reason => { this.ban_let_expr(expr, elem); }, ExprKind::Match(scrutinee, arms) => { this.visit_expr(scrutinee); for arm in arms { this.visit_expr(&arm.body); this.visit_pat(&arm.pat); walk_list!(this, visit_attribute, &arm.attrs); if let Some(guard) = &arm.guard && let ExprKind::Let(_, guard_expr, _) = &guard.kind { this.with_let_management(None, |this, _| { this.visit_expr(guard_expr) }); return; } } } ExprKind::Paren(local_expr) => { fn has_let_expr(expr: &Expr) -> bool { match &expr.kind { ExprKind::Binary(_, lhs, rhs) => has_let_expr(lhs) || has_let_expr(rhs), ExprKind::Let(..) => true, _ => false, } } let local_reason = if has_let_expr(local_expr) { Some(ForbiddenLetReason::NotSupportedParentheses(local_expr.span)) } else { forbidden_let_reason }; this.with_let_management(local_reason, |this, _| this.visit_expr(local_expr)); } ExprKind::Binary(Spanned { node: BinOpKind::And, .. }, ..) => { this.with_let_management(forbidden_let_reason, |this, _| visit::walk_expr(this, expr)); return; } ExprKind::While(cond, then, opt_label) => { walk_list!(this, visit_label, opt_label); this.visit_block(then); this.with_let_management(None, |this, _| this.visit_expr(cond)); return; } _ => visit::walk_expr(this, expr), } }); } fn visit_ty(&mut self, ty: &'a Ty) { self.visit_ty_common(ty); self.walk_ty(ty) } fn visit_label(&mut self, label: &'a Label) { self.check_label(label.ident); visit::walk_label(self, label); } fn visit_lifetime(&mut self, lifetime: &'a Lifetime, _: visit::LifetimeCtxt) { self.check_lifetime(lifetime.ident); visit::walk_lifetime(self, lifetime); } fn visit_field_def(&mut self, field: &'a FieldDef) { visit::walk_field_def(self, field) } fn visit_item(&mut self, item: &'a Item) { if item.attrs.iter().any(|attr| self.session.is_proc_macro_attr(attr)) { self.has_proc_macro_decls = true; } if self.session.contains_name(&item.attrs, sym::no_mangle) { self.check_nomangle_item_asciionly(item.ident, item.span); } match &item.kind { ItemKind::Impl(box Impl { unsafety, polarity, defaultness: _, constness, generics, of_trait: Some(t), self_ty, items, }) => { self.with_in_trait_impl(true, Some(*constness), |this| { this.invalid_visibility(&item.vis, None); if let TyKind::Err = self_ty.kind { this.err_handler().emit_err(errors::ObsoleteAuto { span: item.span }); } if let (&Unsafe::Yes(span), &ImplPolarity::Negative(sp)) = (unsafety, polarity) { this.session.emit_err(errors::UnsafeNegativeImpl { span: sp.to(t.path.span), negative: sp, r#unsafe: span, }); } this.visit_vis(&item.vis); this.visit_ident(item.ident); if let Const::Yes(_) = constness { this.with_tilde_const_allowed(|this| this.visit_generics(generics)); } else { this.visit_generics(generics); } this.visit_trait_ref(t); this.visit_ty(self_ty); walk_list!(this, visit_assoc_item, items, AssocCtxt::Impl); }); walk_list!(self, visit_attribute, &item.attrs); return; // Avoid visiting again. } ItemKind::Impl(box Impl { unsafety, polarity, defaultness, constness, generics: _, of_trait: None, self_ty, items: _, }) => { let error = |annotation_span, annotation, only_trait: bool| errors::InherentImplCannot { span: self_ty.span, annotation_span, annotation, self_ty: self_ty.span, only_trait: only_trait.then_some(()), }; self.invalid_visibility( &item.vis, Some(errors::InvalidVisibilityNote::IndividualImplItems), ); if let &Unsafe::Yes(span) = unsafety { self.err_handler().emit_err(errors::InherentImplCannotUnsafe { span: self_ty.span, annotation_span: span, annotation: "unsafe", self_ty: self_ty.span, }); } if let &ImplPolarity::Negative(span) = polarity { self.err_handler().emit_err(error(span, "negative", false)); } if let &Defaultness::Default(def_span) = defaultness { self.err_handler().emit_err(error(def_span, "`default`", true)); } if let &Const::Yes(span) = constness { self.err_handler().emit_err(error(span, "`const`", true)); } } ItemKind::Fn(box Fn { defaultness, sig, generics, body }) => { self.check_defaultness(item.span, *defaultness); if body.is_none() { self.session.emit_err(errors::FnWithoutBody { span: item.span, replace_span: self.ending_semi_or_hi(item.span), extern_block_suggestion: match sig.header.ext { Extern::None => None, Extern::Implicit(start_span) => { Some(errors::ExternBlockSuggestion::Implicit { start_span, end_span: item.span.shrink_to_hi(), }) } Extern::Explicit(abi, start_span) => { Some(errors::ExternBlockSuggestion::Explicit { start_span, end_span: item.span.shrink_to_hi(), abi: abi.symbol_unescaped, }) } }, }); } self.visit_vis(&item.vis); self.visit_ident(item.ident); let kind = FnKind::Fn(FnCtxt::Free, item.ident, sig, &item.vis, generics, body.as_deref()); self.visit_fn(kind, item.span, item.id); walk_list!(self, visit_attribute, &item.attrs); return; // Avoid visiting again. } ItemKind::ForeignMod(ForeignMod { abi, unsafety, .. }) => { let old_item = mem::replace(&mut self.extern_mod, Some(item)); self.invalid_visibility( &item.vis, Some(errors::InvalidVisibilityNote::IndividualForeignItems), ); if let &Unsafe::Yes(span) = unsafety { self.err_handler().emit_err(errors::UnsafeItem { span, kind: "extern block" }); } if abi.is_none() { self.maybe_lint_missing_abi(item.span, item.id); } visit::walk_item(self, item); self.extern_mod = old_item; return; // Avoid visiting again. } ItemKind::Enum(def, _) => { for variant in &def.variants { self.invalid_visibility(&variant.vis, None); for field in variant.data.fields() { self.invalid_visibility(&field.vis, None); } } } ItemKind::Trait(box Trait { is_auto, generics, bounds, items, .. }) => { if *is_auto == IsAuto::Yes { // Auto traits cannot have generics, super traits nor contain items. self.deny_generic_params(generics, item.ident.span); self.deny_super_traits(bounds, item.ident.span); self.deny_where_clause(&generics.where_clause, item.ident.span); self.deny_items(items, item.ident.span); } // Equivalent of `visit::walk_item` for `ItemKind::Trait` that inserts a bound // context for the supertraits. self.visit_vis(&item.vis); self.visit_ident(item.ident); self.visit_generics(generics); self.with_tilde_const_allowed(|this| { walk_list!(this, visit_param_bound, bounds, BoundKind::SuperTraits) }); walk_list!(self, visit_assoc_item, items, AssocCtxt::Trait); walk_list!(self, visit_attribute, &item.attrs); return; // Avoid visiting again } ItemKind::Mod(unsafety, mod_kind) => { if let &Unsafe::Yes(span) = unsafety { self.err_handler().emit_err(errors::UnsafeItem { span, kind: "module" }); } // Ensure that `path` attributes on modules are recorded as used (cf. issue #35584). if !matches!(mod_kind, ModKind::Loaded(_, Inline::Yes, _)) && !self.session.contains_name(&item.attrs, sym::path) { self.check_mod_file_item_asciionly(item.ident); } } ItemKind::Union(vdata, ..) => { if vdata.fields().is_empty() { self.err_handler().emit_err(errors::FieldlessUnion { span: item.span }); } } ItemKind::Const(def, .., None) => { self.check_defaultness(item.span, *def); self.session.emit_err(errors::ConstWithoutBody { span: item.span, replace_span: self.ending_semi_or_hi(item.span), }); } ItemKind::Static(.., None) => { self.session.emit_err(errors::StaticWithoutBody { span: item.span, replace_span: self.ending_semi_or_hi(item.span), }); } ItemKind::TyAlias(box TyAlias { defaultness, where_clauses, bounds, ty, .. }) => { self.check_defaultness(item.span, *defaultness); if ty.is_none() { self.session.emit_err(errors::TyAliasWithoutBody { span: item.span, replace_span: self.ending_semi_or_hi(item.span), }); } self.check_type_no_bounds(bounds, "this context"); if where_clauses.1.0 { self.err_handler() .emit_err(errors::WhereAfterTypeAlias { span: where_clauses.1.1 }); } } _ => {} } visit::walk_item(self, item); } fn visit_foreign_item(&mut self, fi: &'a ForeignItem) { match &fi.kind { ForeignItemKind::Fn(box Fn { defaultness, sig, body, .. }) => { self.check_defaultness(fi.span, *defaultness); self.check_foreign_fn_bodyless(fi.ident, body.as_deref()); self.check_foreign_fn_headerless(fi.ident, fi.span, sig.header); self.check_foreign_item_ascii_only(fi.ident); } ForeignItemKind::TyAlias(box TyAlias { defaultness, generics, where_clauses, bounds, ty, .. }) => { self.check_defaultness(fi.span, *defaultness); self.check_foreign_kind_bodyless(fi.ident, "type", ty.as_ref().map(|b| b.span)); self.check_type_no_bounds(bounds, "`extern` blocks"); self.check_foreign_ty_genericless(generics, where_clauses.0.1); self.check_foreign_item_ascii_only(fi.ident); } ForeignItemKind::Static(_, _, body) => { self.check_foreign_kind_bodyless(fi.ident, "static", body.as_ref().map(|b| b.span)); self.check_foreign_item_ascii_only(fi.ident); } ForeignItemKind::MacCall(..) => {} } visit::walk_foreign_item(self, fi) } // Mirrors `visit::walk_generic_args`, but tracks relevant state. fn visit_generic_args(&mut self, generic_args: &'a GenericArgs) { match generic_args { GenericArgs::AngleBracketed(data) => { self.check_generic_args_before_constraints(data); for arg in &data.args { match arg { AngleBracketedArg::Arg(arg) => self.visit_generic_arg(arg), // Type bindings such as `Item = impl Debug` in `Iterator` // are allowed to contain nested `impl Trait`. AngleBracketedArg::Constraint(constraint) => { self.with_impl_trait(None, |this| { this.visit_assoc_constraint(constraint); }); } } } } GenericArgs::Parenthesized(data) => { walk_list!(self, visit_ty, &data.inputs); if let FnRetTy::Ty(ty) = &data.output { // `-> Foo` syntax is essentially an associated type binding, // so it is also allowed to contain nested `impl Trait`. self.with_impl_trait(None, |this| this.visit_ty(ty)); } } } } fn visit_generics(&mut self, generics: &'a Generics) { let mut prev_param_default = None; for param in &generics.params { match param.kind { GenericParamKind::Lifetime => (), GenericParamKind::Type { default: Some(_), .. } | GenericParamKind::Const { default: Some(_), .. } => { prev_param_default = Some(param.ident.span); } GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => { if let Some(span) = prev_param_default { self.err_handler().emit_err(errors::GenericDefaultTrailing { span }); break; } } } } validate_generic_param_order(self.err_handler(), &generics.params, generics.span); for predicate in &generics.where_clause.predicates { if let WherePredicate::EqPredicate(predicate) = predicate { deny_equality_constraints(self, predicate, generics); } } walk_list!(self, visit_generic_param, &generics.params); for predicate in &generics.where_clause.predicates { match predicate { WherePredicate::BoundPredicate(bound_pred) => { // This is slightly complicated. Our representation for poly-trait-refs contains a single // binder and thus we only allow a single level of quantification. However, // the syntax of Rust permits quantification in two places in where clauses, // e.g., `T: for <'a> Foo<'a>` and `for <'a, 'b> &'b T: Foo<'a>`. If both are // defined, then error. if !bound_pred.bound_generic_params.is_empty() { for bound in &bound_pred.bounds { match bound { GenericBound::Trait(t, _) => { if !t.bound_generic_params.is_empty() { self.err_handler() .emit_err(errors::NestedLifetimes { span: t.span }); } } GenericBound::Outlives(_) => {} } } } } _ => {} } self.visit_where_predicate(predicate); } } fn visit_generic_param(&mut self, param: &'a GenericParam) { if let GenericParamKind::Lifetime { .. } = param.kind { self.check_lifetime(param.ident); } visit::walk_generic_param(self, param); } fn visit_param_bound(&mut self, bound: &'a GenericBound, ctxt: BoundKind) { if let GenericBound::Trait(poly, modify) = bound { match (ctxt, modify) { (BoundKind::SuperTraits, TraitBoundModifier::Maybe) => { self.err_handler().emit_err(errors::OptionalTraitSupertrait { span: poly.span, path_str: pprust::path_to_string(&poly.trait_ref.path) }); } (BoundKind::TraitObject, TraitBoundModifier::Maybe) => { self.err_handler().emit_err(errors::OptionalTraitObject {span: poly.span}); } (_, TraitBoundModifier::MaybeConst) if let Some(reason) = &self.disallow_tilde_const => { let reason = match reason { DisallowTildeConstContext::TraitObject => errors::TildeConstReason::TraitObject, DisallowTildeConstContext::Fn(FnKind::Closure(..)) => errors::TildeConstReason::Closure, DisallowTildeConstContext::Fn(FnKind::Fn(_, ident, ..)) => errors::TildeConstReason::Function { ident: ident.span }, }; self.err_handler().emit_err(errors::TildeConstDisallowed { span: bound.span(), reason }); } (_, TraitBoundModifier::MaybeConstMaybe) => { self.err_handler().emit_err(errors::OptionalConstExclusive {span: bound.span()}); } _ => {} } } visit::walk_param_bound(self, bound) } fn visit_fn(&mut self, fk: FnKind<'a>, span: Span, id: NodeId) { // Only associated `fn`s can have `self` parameters. let self_semantic = match fk.ctxt() { Some(FnCtxt::Assoc(_)) => SelfSemantic::Yes, _ => SelfSemantic::No, }; self.check_fn_decl(fk.decl(), self_semantic); self.check_c_variadic_type(fk); // Functions cannot both be `const async` if let Some(&FnHeader { constness: Const::Yes(cspan), asyncness: Async::Yes { span: aspan, .. }, .. }) = fk.header() { self.err_handler().emit_err(errors::ConstAndAsync { spans: vec![cspan, aspan], cspan, aspan, span, }); } if let FnKind::Fn( _, _, FnSig { span: sig_span, header: FnHeader { ext: Extern::Implicit(_), .. }, .. }, _, _, _, ) = fk { self.maybe_lint_missing_abi(*sig_span, id); } // Functions without bodies cannot have patterns. if let FnKind::Fn(ctxt, _, sig, _, _, None) = fk { Self::check_decl_no_pat(&sig.decl, |span, ident, mut_ident| { if mut_ident && matches!(ctxt, FnCtxt::Assoc(_)) { if let Some(ident) = ident { let msg = match ctxt { FnCtxt::Foreign => fluent::ast_passes_pattern_in_foreign, _ => fluent::ast_passes_pattern_in_bodiless, }; let diag = BuiltinLintDiagnostics::PatternsInFnsWithoutBody(span, ident); self.lint_buffer.buffer_lint_with_diagnostic( PATTERNS_IN_FNS_WITHOUT_BODY, id, span, msg, diag, ) } } else { match ctxt { FnCtxt::Foreign => { self.err_handler().emit_err(errors::PatternInForeign { span }) } _ => self.err_handler().emit_err(errors::PatternInBodiless { span }), }; } }); } let tilde_const_allowed = matches!(fk.header(), Some(FnHeader { constness: ast::Const::Yes(_), .. })) || matches!(fk.ctxt(), Some(FnCtxt::Assoc(_))); let disallowed = (!tilde_const_allowed).then(|| DisallowTildeConstContext::Fn(fk)); self.with_tilde_const(disallowed, |this| visit::walk_fn(this, fk)); } fn visit_assoc_item(&mut self, item: &'a AssocItem, ctxt: AssocCtxt) { if self.session.contains_name(&item.attrs, sym::no_mangle) { self.check_nomangle_item_asciionly(item.ident, item.span); } if ctxt == AssocCtxt::Trait || !self.in_trait_impl { self.check_defaultness(item.span, item.kind.defaultness()); } if ctxt == AssocCtxt::Impl { match &item.kind { AssocItemKind::Const(_, _, body) => { if body.is_none() { self.session.emit_err(errors::AssocConstWithoutBody { span: item.span, replace_span: self.ending_semi_or_hi(item.span), }); } } AssocItemKind::Fn(box Fn { body, .. }) => { if body.is_none() { self.session.emit_err(errors::AssocFnWithoutBody { span: item.span, replace_span: self.ending_semi_or_hi(item.span), }); } } AssocItemKind::Type(box TyAlias { generics, where_clauses, where_predicates_split, bounds, ty, .. }) => { if ty.is_none() { self.session.emit_err(errors::AssocTypeWithoutBody { span: item.span, replace_span: self.ending_semi_or_hi(item.span), }); } self.check_type_no_bounds(bounds, "`impl`s"); if ty.is_some() { self.check_gat_where( item.id, generics.where_clause.predicates.split_at(*where_predicates_split).0, *where_clauses, ); } } _ => {} } } if ctxt == AssocCtxt::Trait || self.in_trait_impl { self.invalid_visibility(&item.vis, None); if let AssocItemKind::Fn(box Fn { sig, .. }) = &item.kind { self.check_trait_fn_not_const(sig.header.constness); } } if let AssocItemKind::Const(..) = item.kind { self.check_item_named(item.ident, "const"); } match &item.kind { AssocItemKind::Type(box TyAlias { generics, bounds, ty, .. }) if ctxt == AssocCtxt::Trait => { self.visit_vis(&item.vis); self.visit_ident(item.ident); walk_list!(self, visit_attribute, &item.attrs); self.with_tilde_const_allowed(|this| { this.visit_generics(generics); walk_list!(this, visit_param_bound, bounds, BoundKind::Bound); }); walk_list!(self, visit_ty, ty); } AssocItemKind::Fn(box Fn { sig, generics, body, .. }) if self.in_const_trait_impl || ctxt == AssocCtxt::Trait || matches!(sig.header.constness, Const::Yes(_)) => { self.visit_vis(&item.vis); self.visit_ident(item.ident); let kind = FnKind::Fn( FnCtxt::Assoc(ctxt), item.ident, sig, &item.vis, generics, body.as_deref(), ); self.visit_fn(kind, item.span, item.id); } _ => self .with_in_trait_impl(false, None, |this| visit::walk_assoc_item(this, item, ctxt)), } } } /// When encountering an equality constraint in a `where` clause, emit an error. If the code seems /// like it's setting an associated type, provide an appropriate suggestion. fn deny_equality_constraints( this: &mut AstValidator<'_>, predicate: &WhereEqPredicate, generics: &Generics, ) { let mut err = errors::EqualityInWhere { span: predicate.span, assoc: None, assoc2: None }; // Given `::Bar = RhsTy`, suggest `A: Foo`. if let TyKind::Path(Some(qself), full_path) = &predicate.lhs_ty.kind { if let TyKind::Path(None, path) = &qself.ty.kind { match &path.segments[..] { [PathSegment { ident, args: None, .. }] => { for param in &generics.params { if param.ident == *ident { let param = ident; match &full_path.segments[qself.position..] { [PathSegment { ident, args, .. }] => { // Make a new `Path` from `foo::Bar` to `Foo`. let mut assoc_path = full_path.clone(); // Remove `Bar` from `Foo::Bar`. assoc_path.segments.pop(); let len = assoc_path.segments.len() - 1; let gen_args = args.as_deref().cloned(); // Build ``. let arg = AngleBracketedArg::Constraint(AssocConstraint { id: rustc_ast::node_id::DUMMY_NODE_ID, ident: *ident, gen_args, kind: AssocConstraintKind::Equality { term: predicate.rhs_ty.clone().into(), }, span: ident.span, }); // Add `` to `Foo`. match &mut assoc_path.segments[len].args { Some(args) => match args.deref_mut() { GenericArgs::Parenthesized(_) => continue, GenericArgs::AngleBracketed(args) => { args.args.push(arg); } }, empty_args => { *empty_args = AngleBracketedArgs { span: ident.span, args: thin_vec![arg], } .into(); } } err.assoc = Some(errors::AssociatedSuggestion { span: predicate.span, ident: *ident, param: *param, path: pprust::path_to_string(&assoc_path), }) } _ => {} }; } } } _ => {} } } } // Given `A: Foo, A::Bar = RhsTy`, suggest `A: Foo`. if let TyKind::Path(None, full_path) = &predicate.lhs_ty.kind { if let [potential_param, potential_assoc] = &full_path.segments[..] { for param in &generics.params { if param.ident == potential_param.ident { for bound in ¶m.bounds { if let ast::GenericBound::Trait(trait_ref, TraitBoundModifier::None) = bound { if let [trait_segment] = &trait_ref.trait_ref.path.segments[..] { let assoc = pprust::path_to_string(&ast::Path::from_ident( potential_assoc.ident, )); let ty = pprust::ty_to_string(&predicate.rhs_ty); let (args, span) = match &trait_segment.args { Some(args) => match args.deref() { ast::GenericArgs::AngleBracketed(args) => { let Some(arg) = args.args.last() else { continue; }; ( format!(", {} = {}", assoc, ty), arg.span().shrink_to_hi(), ) } _ => continue, }, None => ( format!("<{} = {}>", assoc, ty), trait_segment.span().shrink_to_hi(), ), }; err.assoc2 = Some(errors::AssociatedSuggestion2 { span, args, predicate: predicate.span, trait_segment: trait_segment.ident, potential_assoc: potential_assoc.ident, }); } } } } } } } this.err_handler().emit_err(err); } pub fn check_crate(session: &Session, krate: &Crate, lints: &mut LintBuffer) -> bool { let mut validator = AstValidator { session, extern_mod: None, in_trait_impl: false, in_const_trait_impl: false, has_proc_macro_decls: false, outer_impl_trait: None, disallow_tilde_const: None, is_impl_trait_banned: false, forbidden_let_reason: Some(ForbiddenLetReason::GenericForbidden), lint_buffer: lints, }; visit::walk_crate(&mut validator, krate); validator.has_proc_macro_decls } /// Used to forbid `let` expressions in certain syntactic locations. #[derive(Clone, Copy, Subdiagnostic)] pub(crate) enum ForbiddenLetReason { /// `let` is not valid and the source environment is not important GenericForbidden, /// A let chain with the `||` operator #[note(ast_passes_not_supported_or)] NotSupportedOr(#[primary_span] Span), /// A let chain with invalid parentheses /// /// For example, `let 1 = 1 && (expr && expr)` is allowed /// but `(let 1 = 1 && (let 1 = 1 && (let 1 = 1))) && let a = 1` is not #[note(ast_passes_not_supported_parentheses)] NotSupportedParentheses(#[primary_span] Span), }