diff options
Diffstat (limited to 'compiler/rustc_ast_passes/src/ast_validation.rs')
| -rw-r--r-- | compiler/rustc_ast_passes/src/ast_validation.rs | 1448 |
1 files changed, 1448 insertions, 0 deletions
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs new file mode 100644 index 00000000000..a01dd8c939c --- /dev/null +++ b/compiler/rustc_ast_passes/src/ast_validation.rs @@ -0,0 +1,1448 @@ +// 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, FnCtxt, FnKind, Visitor}; +use rustc_ast::walk_list; +use rustc_ast::*; +use rustc_ast_pretty::pprust; +use rustc_data_structures::fx::FxHashMap; +use rustc_errors::{error_code, pluralize, struct_span_err, Applicability}; +use rustc_parse::validate_attr; +use rustc_session::lint::builtin::PATTERNS_IN_FNS_WITHOUT_BODY; +use rustc_session::lint::LintBuffer; +use rustc_session::Session; +use rustc_span::symbol::{kw, sym, Ident}; +use rustc_span::Span; +use std::mem; +use std::ops::DerefMut; + +const MORE_EXTERN: &str = + "for more information, visit https://doc.rust-lang.org/std/keyword.extern.html"; + +/// Is `self` allowed semantically as the first parameter in an `FnDecl`? +enum SelfSemantic { + Yes, + No, +} + +/// A syntactic context that disallows certain kinds of bounds (e.g., `?Trait` or `?const Trait`). +#[derive(Clone, Copy)] +enum BoundContext { + ImplTrait, + TraitBounds, + TraitObject, +} + +impl BoundContext { + fn description(&self) -> &'static str { + match self { + Self::ImplTrait => "`impl Trait`", + Self::TraitBounds => "supertraits", + Self::TraitObject => "trait objects", + } + } +} + +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, + + has_proc_macro_decls: bool, + + /// Used to ban nested `impl Trait`, e.g., `impl Into<impl Debug>`. + /// Nested `impl Trait` _is_ allowed in associated type position, + /// e.g., `impl Iterator<Item = impl Debug>`. + outer_impl_trait: Option<Span>, + + /// Keeps track of the `BoundContext` as we recurse. + /// + /// This is used to forbid `?const Trait` bounds in, e.g., + /// `impl Iterator<Item = Box<dyn ?const Trait>`. + bound_context: Option<BoundContext>, + + /// Used to ban `impl Trait` in path projections like `<impl Iterator>::Item` + /// or `Foo::Bar<impl Trait>` + is_impl_trait_banned: bool, + + /// Used to ban associated type bounds (i.e., `Type<AssocType: Bounds>`) in + /// certain positions. + is_assoc_ty_bound_banned: bool, + + lint_buffer: &'a mut LintBuffer, +} + +impl<'a> AstValidator<'a> { + fn with_in_trait_impl(&mut self, is_in: bool, f: impl FnOnce(&mut Self)) { + let old = mem::replace(&mut self.in_trait_impl, is_in); + f(self); + self.in_trait_impl = old; + } + + 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_banned_assoc_ty_bound(&mut self, f: impl FnOnce(&mut Self)) { + let old = mem::replace(&mut self.is_assoc_ty_bound_banned, true); + f(self); + self.is_assoc_ty_bound_banned = old; + } + + fn with_impl_trait(&mut self, outer: Option<Span>, f: impl FnOnce(&mut Self)) { + let old = mem::replace(&mut self.outer_impl_trait, outer); + if outer.is_some() { + self.with_bound_context(BoundContext::ImplTrait, |this| f(this)); + } else { + f(self) + } + self.outer_impl_trait = old; + } + + fn with_bound_context(&mut self, ctx: BoundContext, f: impl FnOnce(&mut Self)) { + let old = self.bound_context.replace(ctx); + f(self); + self.bound_context = old; + } + + fn visit_assoc_ty_constraint_from_generic_args(&mut self, constraint: &'a AssocTyConstraint) { + match constraint.kind { + AssocTyConstraintKind::Equality { .. } => {} + AssocTyConstraintKind::Bound { .. } => { + if self.is_assoc_ty_bound_banned { + self.err_handler().span_err( + constraint.span, + "associated type bounds are not allowed within structs, enums, or unions", + ); + } + } + } + self.visit_assoc_ty_constraint(constraint); + } + + // 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_bound_context(BoundContext::TraitObject, |this| visit::walk_ty(this, t)); + } + TyKind::Path(ref qself, ref path) => { + // We allow these: + // - `Option<impl Trait>` + // - `option::Option<impl Trait>` + // - `option::Option<T>::Foo<impl Trait> + // + // But not these: + // - `<impl Trait>::Foo` + // - `option::Option<impl Trait>::Foo`. + // + // To implement this, we disallow `impl Trait` from `qself` + // (for cases like `<impl Trait>::Foo>`) + // but we allow `impl Trait` in `GenericArgs` + // iff there are no more PathSegments. + if let Some(ref 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(path.span, segment); + } else { + self.with_banned_impl_trait(|this| { + this.visit_path_segment(path.span, 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::Invalid]; + if !valid_names.contains(&ident.name) && ident.without_first_quote().is_reserved() { + self.err_handler().span_err(ident.span, "lifetimes cannot use keyword names"); + } + } + + fn check_label(&self, ident: Ident) { + if ident.without_first_quote().is_reserved() { + self.err_handler() + .span_err(ident.span, &format!("invalid label name `{}`", ident.name)); + } + } + + fn invalid_visibility(&self, vis: &Visibility, note: Option<&str>) { + if let VisibilityKind::Inherited = vis.node { + return; + } + + let mut err = + struct_span_err!(self.session, vis.span, E0449, "unnecessary visibility qualifier"); + if vis.node.is_pub() { + err.span_label(vis.span, "`pub` not permitted here because it's implied"); + } + if let Some(note) = note { + err.note(note); + } + err.emit(); + } + + fn check_decl_no_pat(decl: &FnDecl, mut report_err: impl FnMut(Span, bool)) { + for Param { pat, .. } in &decl.inputs { + match pat.kind { + PatKind::Ident(BindingMode::ByValue(Mutability::Not), _, None) | PatKind::Wild => {} + PatKind::Ident(BindingMode::ByValue(Mutability::Mut), _, None) => { + report_err(pat.span, true) + } + _ => report_err(pat.span, false), + } + } + } + + fn check_trait_fn_not_async(&self, fn_span: Span, asyncness: Async) { + if let Async::Yes { span, .. } = asyncness { + struct_span_err!( + self.session, + fn_span, + E0706, + "functions in traits cannot be declared `async`" + ) + .span_label(span, "`async` because of this") + .note("`async` trait functions are not currently supported") + .note("consider using the `async-trait` crate: https://crates.io/crates/async-trait") + .emit(); + } + } + + fn check_trait_fn_not_const(&self, constness: Const) { + if let Const::Yes(span) = constness { + struct_span_err!( + self.session, + span, + E0379, + "functions in traits cannot be declared const" + ) + .span_label(span, "functions in traits cannot be const") + .emit(); + } + } + + // FIXME(ecstaticmorse): Instead, use `bound_context` to check this in `visit_param_bound`. + fn no_questions_in_bounds(&self, bounds: &GenericBounds, where_: &str, is_trait: bool) { + for bound in bounds { + if let GenericBound::Trait(ref poly, TraitBoundModifier::Maybe) = *bound { + let mut err = self.err_handler().struct_span_err( + poly.span, + &format!("`?Trait` is not permitted in {}", where_), + ); + if is_trait { + let path_str = pprust::path_to_string(&poly.trait_ref.path); + err.note(&format!("traits are `?{}` by default", path_str)); + } + err.emit(); + } + } + } + + /// Matches `'-' lit | lit (cf. parser::Parser::parse_literal_maybe_minus)`, + /// or paths for ranges. + // + // FIXME: do we want to allow `expr -> pattern` conversion to create path expressions? + // That means making this work: + // + // ```rust,ignore (FIXME) + // struct S; + // macro_rules! m { + // ($a:expr) => { + // let $a = S; + // } + // } + // m!(S); + // ``` + fn check_expr_within_pat(&self, expr: &Expr, allow_paths: bool) { + match expr.kind { + ExprKind::Lit(..) | ExprKind::Err => {} + ExprKind::Path(..) if allow_paths => {} + ExprKind::Unary(UnOp::Neg, ref inner) if matches!(inner.kind, ExprKind::Lit(_)) => {} + _ => self.err_handler().span_err( + expr.span, + "arbitrary expressions aren't allowed \ + in patterns", + ), + } + } + + fn check_late_bound_lifetime_defs(&self, params: &[GenericParam]) { + // Check only lifetime parameters are present and that the lifetime + // parameters that are present have no bounds. + let non_lt_param_spans: Vec<_> = params + .iter() + .filter_map(|param| match param.kind { + GenericParamKind::Lifetime { .. } => { + if !param.bounds.is_empty() { + let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect(); + self.err_handler() + .span_err(spans, "lifetime bounds cannot be used in this context"); + } + None + } + _ => Some(param.ident.span), + }) + .collect(); + if !non_lt_param_spans.is_empty() { + self.err_handler().span_err( + non_lt_param_spans, + "only lifetime parameters can be used in this context", + ); + } + } + + fn check_fn_decl(&self, fn_decl: &FnDecl, self_semantic: SelfSemantic) { + self.check_decl_cvaradic_pos(fn_decl); + self.check_decl_attrs(fn_decl); + self.check_decl_self_param(fn_decl, self_semantic); + } + + fn check_decl_cvaradic_pos(&self, fn_decl: &FnDecl) { + match &*fn_decl.inputs { + [Param { ty, span, .. }] => { + if let TyKind::CVarArgs = ty.kind { + self.err_handler().span_err( + *span, + "C-variadic function must be declared with at least one named argument", + ); + } + } + [ps @ .., _] => { + for Param { ty, span, .. } in ps { + if let TyKind::CVarArgs = ty.kind { + self.err_handler().span_err( + *span, + "`...` must be the last argument of a C-variadic function", + ); + } + } + } + _ => {} + } + } + + 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::forbid, sym::warn]; + !arr.contains(&attr.name_or_empty()) && rustc_attr::is_builtin_attr(attr) + }) + .for_each(|attr| { + if attr.is_doc_comment() { + self.err_handler() + .struct_span_err( + attr.span, + "documentation comments cannot be applied to function parameters", + ) + .span_label(attr.span, "doc comments are not allowed here") + .emit(); + } else { + self.err_handler().span_err( + attr.span, + "allow, cfg, cfg_attr, deny, \ + forbid, and warn are the only allowed built-in attributes in function parameters", + ) + } + }); + } + + 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.err_handler() + .struct_span_err( + param.span, + "`self` parameter is only allowed in associated functions", + ) + .span_label(param.span, "not semantically valid as function parameter") + .note("associated functions are those in `impl` or `trait` definitions") + .emit(); + } + } + } + + 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.err_handler() + .struct_span_err(span, "`default` is only allowed on items in `impl` definitions") + .span_label(def_span, "`default` because of this") + .emit(); + } + } + + fn error_item_without_body(&self, sp: Span, ctx: &str, msg: &str, sugg: &str) { + self.err_handler() + .struct_span_err(sp, msg) + .span_suggestion( + self.session.source_map().end_point(sp), + &format!("provide a definition for the {}", ctx), + sugg.to_string(), + Applicability::HasPlaceholders, + ) + .emit(); + } + + fn check_impl_item_provided<T>(&self, sp: Span, body: &Option<T>, ctx: &str, sugg: &str) { + if body.is_none() { + let msg = format!("associated {} in `impl` without body", ctx); + self.error_item_without_body(sp, ctx, &msg, sugg); + } + } + + 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() + .struct_span_err(span, &format!("bounds on `type`s in {} have no effect", ctx)) + .emit(); + } + + fn check_foreign_ty_genericless(&self, generics: &Generics) { + let cannot_have = |span, descr, remove_descr| { + self.err_handler() + .struct_span_err( + span, + &format!("`type`s inside `extern` blocks cannot have {}", descr), + ) + .span_suggestion( + span, + &format!("remove the {}", remove_descr), + String::new(), + Applicability::MaybeIncorrect, + ) + .span_label(self.current_extern_span(), "`extern` block begins here") + .note(MORE_EXTERN) + .emit(); + }; + + if !generics.params.is_empty() { + cannot_have(generics.span, "generic parameters", "generic parameters"); + } + + if !generics.where_clause.predicates.is_empty() { + cannot_have(generics.where_clause.span, "`where` clauses", "`where` clause"); + } + } + + fn check_foreign_kind_bodyless(&self, ident: Ident, kind: &str, body: Option<Span>) { + let body = match body { + None => return, + Some(body) => body, + }; + self.err_handler() + .struct_span_err(ident.span, &format!("incorrect `{}` inside `extern` block", kind)) + .span_label(ident.span, "cannot have a body") + .span_label(body, "the invalid body") + .span_label( + self.current_extern_span(), + format!( + "`extern` blocks define existing foreign {0}s and {0}s \ + inside of them cannot have a body", + kind + ), + ) + .note(MORE_EXTERN) + .emit(); + } + + /// An `fn` in `extern { ... }` cannot have a body `{ ... }`. + fn check_foreign_fn_bodyless(&self, ident: Ident, body: Option<&Block>) { + let body = match body { + None => return, + Some(body) => body, + }; + self.err_handler() + .struct_span_err(ident.span, "incorrect function inside `extern` block") + .span_label(ident.span, "cannot have a body") + .span_suggestion( + body.span, + "remove the invalid body", + ";".to_string(), + Applicability::MaybeIncorrect, + ) + .help( + "you might have meant to write a function accessible through FFI, \ + which can be done by writing `extern fn` outside of the `extern` block", + ) + .span_label( + self.current_extern_span(), + "`extern` blocks define existing foreign functions and functions \ + inside of them cannot have a body", + ) + .note(MORE_EXTERN) + .emit(); + } + + fn current_extern_span(&self) -> Span { + self.session.source_map().guess_head_span(self.extern_mod.unwrap().span) + } + + /// An `fn` in `extern { ... }` cannot have qualfiers, e.g. `async fn`. + fn check_foreign_fn_headerless(&self, ident: Ident, span: Span, header: FnHeader) { + if header.has_qualifiers() { + self.err_handler() + .struct_span_err(ident.span, "functions in `extern` blocks cannot have qualifiers") + .span_label(self.current_extern_span(), "in this `extern` block") + .span_suggestion( + span.until(ident.span.shrink_to_lo()), + "remove the qualifiers", + "fn ".to_string(), + Applicability::MaybeIncorrect, + ) + .emit(); + } + } + + /// Reject C-varadic type unless the function is foreign, + /// or free and `unsafe extern "C"` semantically. + fn check_c_varadic_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() + .struct_span_err( + *span, + "only foreign or `unsafe extern \"C\" functions may be C-variadic", + ) + .emit(); + } + } + } + + fn check_item_named(&self, ident: Ident, kind: &str) { + if ident.name != kw::Underscore { + return; + } + self.err_handler() + .struct_span_err(ident.span, &format!("`{}` items in this context need a name", kind)) + .span_label(ident.span, format!("`_` is not a valid name for this `{}` item", kind)) + .emit(); + } + + fn check_nomangle_item_asciionly(&self, ident: Ident, item_span: Span) { + if ident.name.as_str().is_ascii() { + return; + } + let head_span = self.session.source_map().guess_head_span(item_span); + struct_span_err!( + self.session, + head_span, + E0754, + "`#[no_mangle]` requires ASCII identifier" + ) + .emit(); + } + + fn check_mod_file_item_asciionly(&self, ident: Ident) { + if ident.name.as_str().is_ascii() { + return; + } + struct_span_err!( + self.session, + ident.span, + E0754, + "trying to load file for module `{}` with non ascii identifer name", + ident.name + ) + .help("consider using `#[path]` attribute to specify filesystem path") + .emit(); + } + + fn deny_generic_params(&self, generics: &Generics, ident_span: Span) { + if !generics.params.is_empty() { + struct_span_err!( + self.session, + generics.span, + E0567, + "auto traits cannot have generic parameters" + ) + .span_label(ident_span, "auto trait cannot have generic parameters") + .span_suggestion( + generics.span, + "remove the parameters", + String::new(), + Applicability::MachineApplicable, + ) + .emit(); + } + } + + fn deny_super_traits(&self, bounds: &GenericBounds, ident_span: Span) { + if let [first @ last] | [first, .., last] = &bounds[..] { + let span = first.span().to(last.span()); + struct_span_err!(self.session, span, E0568, "auto traits cannot have super traits") + .span_label(ident_span, "auto trait cannot have super traits") + .span_suggestion( + span, + "remove the super traits", + String::new(), + Applicability::MachineApplicable, + ) + .emit(); + } + } + + fn deny_items(&self, trait_items: &[P<AssocItem>], ident_span: Span) { + if !trait_items.is_empty() { + let spans: Vec<_> = trait_items.iter().map(|i| i.ident.span).collect(); + struct_span_err!( + self.session, + spans, + E0380, + "auto traits cannot have methods or associated items" + ) + .span_label(ident_span, "auto trait cannot have items") + .emit(); + } + } + + 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::<Vec<String>>().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<Span>, Vec<Span>) = + 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() + .struct_span_err( + arg_spans.clone(), + "generic arguments must come before the first constraint", + ) + .span_label(constraint_spans[0], &format!("constraint{}", pluralize!(constraint_len))) + .span_label( + *arg_spans.iter().last().unwrap(), + &format!("generic argument{}", pluralize!(args_len)), + ) + .span_labels(constraint_spans, "") + .span_labels(arg_spans, "") + .span_suggestion_verbose( + data.span, + &format!( + "move the constraint{} after the generic argument{}", + pluralize!(constraint_len), + pluralize!(args_len) + ), + self.correct_generic_order_suggestion(&data), + Applicability::MachineApplicable, + ) + .emit(); + } +} + +/// 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<'a>( + sess: &Session, + handler: &rustc_errors::Handler, + generics: impl Iterator<Item = (ParamKindOrd, Option<&'a [GenericBound]>, Span, Option<String>)>, + span: Span, +) { + let mut max_param: Option<ParamKindOrd> = None; + let mut out_of_order = FxHashMap::default(); + let mut param_idents = vec![]; + + for (kind, bounds, span, ident) in generics { + if let Some(ident) = ident { + param_idents.push((kind, bounds, param_idents.len(), ident)); + } + let max_param = &mut max_param; + match max_param { + Some(max_param) if *max_param > kind => { + let entry = out_of_order.entry(kind).or_insert((*max_param, vec![])); + entry.1.push(span); + } + Some(_) | None => *max_param = Some(kind), + }; + } + + let mut ordered_params = "<".to_string(); + if !out_of_order.is_empty() { + param_idents.sort_by_key(|&(po, _, i, _)| (po, i)); + let mut first = true; + for (_, bounds, _, ident) in param_idents { + if !first { + ordered_params += ", "; + } + ordered_params += &ident; + if let Some(bounds) = bounds { + if !bounds.is_empty() { + ordered_params += ": "; + ordered_params += &pprust::bounds_to_string(&bounds); + } + } + first = false; + } + } + ordered_params += ">"; + + for (param_ord, (max_param, spans)) in &out_of_order { + let mut err = + handler.struct_span_err( + spans.clone(), + &format!( + "{} parameters must be declared prior to {} parameters", + param_ord, max_param, + ), + ); + err.span_suggestion( + span, + &format!( + "reorder the parameters: lifetimes{}", + if sess.features_untracked().const_generics { + ", then consts and types" + } else if sess.features_untracked().min_const_generics { + ", then types, then consts" + } else { + ", then types" + }, + ), + ordered_params.clone(), + Applicability::MachineApplicable, + ); + err.emit(); + } +} + +impl<'a> Visitor<'a> for AstValidator<'a> { + fn visit_attribute(&mut self, attr: &Attribute) { + validate_attr::check_meta(&self.session.parse_sess, attr); + } + + fn visit_expr(&mut self, expr: &'a Expr) { + match &expr.kind { + ExprKind::LlvmInlineAsm(..) if !self.session.target.target.options.allow_asm => { + struct_span_err!( + self.session, + expr.span, + E0472, + "llvm_asm! is unsupported on this target" + ) + .emit(); + } + _ => {} + } + + visit::walk_expr(self, expr); + } + + fn visit_ty(&mut self, ty: &'a Ty) { + match ty.kind { + TyKind::BareFn(ref bfty) => { + self.check_fn_decl(&bfty.decl, SelfSemantic::No); + Self::check_decl_no_pat(&bfty.decl, |span, _| { + struct_span_err!( + self.session, + span, + E0561, + "patterns aren't allowed in function pointer types" + ) + .emit(); + }); + self.check_late_bound_lifetime_defs(&bfty.generic_params); + } + TyKind::TraitObject(ref bounds, ..) => { + let mut any_lifetime_bounds = false; + for bound in bounds { + if let GenericBound::Outlives(ref lifetime) = *bound { + if any_lifetime_bounds { + struct_span_err!( + self.session, + lifetime.ident.span, + E0226, + "only a single explicit lifetime bound is permitted" + ) + .emit(); + break; + } + any_lifetime_bounds = true; + } + } + self.no_questions_in_bounds(bounds, "trait object types", false); + } + TyKind::ImplTrait(_, ref bounds) => { + if self.is_impl_trait_banned { + struct_span_err!( + self.session, + ty.span, + E0667, + "`impl Trait` is not allowed in path parameters" + ) + .emit(); + } + + if let Some(outer_impl_trait_sp) = self.outer_impl_trait { + struct_span_err!( + self.session, + ty.span, + E0666, + "nested `impl Trait` is not allowed" + ) + .span_label(outer_impl_trait_sp, "outer `impl Trait`") + .span_label(ty.span, "nested `impl Trait` here") + .emit(); + } + + if !bounds + .iter() + .any(|b| if let GenericBound::Trait(..) = *b { true } else { false }) + { + self.err_handler().span_err(ty.span, "at least one trait must be specified"); + } + + self.walk_ty(ty); + return; + } + _ => {} + } + + 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) { + self.check_lifetime(lifetime.ident); + visit::walk_lifetime(self, lifetime); + } + + 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 { + unsafety, + polarity, + defaultness: _, + constness: _, + generics: _, + of_trait: Some(ref t), + ref self_ty, + items: _, + } => { + self.with_in_trait_impl(true, |this| { + this.invalid_visibility(&item.vis, None); + if let TyKind::Err = self_ty.kind { + this.err_handler() + .struct_span_err( + item.span, + "`impl Trait for .. {}` is an obsolete syntax", + ) + .help("use `auto trait Trait {}` instead") + .emit(); + } + if let (Unsafe::Yes(span), ImplPolarity::Negative(sp)) = (unsafety, polarity) { + struct_span_err!( + this.session, + sp.to(t.path.span), + E0198, + "negative impls cannot be unsafe" + ) + .span_label(sp, "negative because of this") + .span_label(span, "unsafe because of this") + .emit(); + } + + visit::walk_item(this, item); + }); + return; // Avoid visiting again. + } + ItemKind::Impl { + unsafety, + polarity, + defaultness, + constness, + generics: _, + of_trait: None, + ref self_ty, + items: _, + } => { + let error = |annotation_span, annotation| { + let mut err = self.err_handler().struct_span_err( + self_ty.span, + &format!("inherent impls cannot be {}", annotation), + ); + err.span_label(annotation_span, &format!("{} because of this", annotation)); + err.span_label(self_ty.span, "inherent impl for this type"); + err + }; + + self.invalid_visibility( + &item.vis, + Some("place qualifiers on individual impl items instead"), + ); + if let Unsafe::Yes(span) = unsafety { + error(span, "unsafe").code(error_code!(E0197)).emit(); + } + if let ImplPolarity::Negative(span) = polarity { + error(span, "negative").emit(); + } + if let Defaultness::Default(def_span) = defaultness { + error(def_span, "`default`") + .note("only trait implementations may be annotated with `default`") + .emit(); + } + if let Const::Yes(span) = constness { + error(span, "`const`") + .note("only trait implementations may be annotated with `const`") + .emit(); + } + } + ItemKind::Fn(def, _, _, ref body) => { + self.check_defaultness(item.span, def); + + if body.is_none() { + let msg = "free function without a body"; + self.error_item_without_body(item.span, "function", msg, " { <body> }"); + } + } + ItemKind::ForeignMod(_) => { + let old_item = mem::replace(&mut self.extern_mod, Some(item)); + self.invalid_visibility( + &item.vis, + Some("place qualifiers on individual foreign items instead"), + ); + visit::walk_item(self, item); + self.extern_mod = old_item; + return; // Avoid visiting again. + } + ItemKind::Enum(ref 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(is_auto, _, ref generics, ref bounds, ref trait_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_items(trait_items, item.ident.span); + } + self.no_questions_in_bounds(bounds, "supertraits", true); + + // 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_bound_context(BoundContext::TraitBounds, |this| { + walk_list!(this, visit_param_bound, bounds); + }); + walk_list!(self, visit_assoc_item, trait_items, AssocCtxt::Trait); + walk_list!(self, visit_attribute, &item.attrs); + return; + } + ItemKind::Mod(Mod { inline, .. }) => { + // Ensure that `path` attributes on modules are recorded as used (cf. issue #35584). + if !inline && !self.session.contains_name(&item.attrs, sym::path) { + self.check_mod_file_item_asciionly(item.ident); + } + } + ItemKind::Union(ref vdata, _) => { + if let VariantData::Tuple(..) | VariantData::Unit(..) = vdata { + self.err_handler() + .span_err(item.span, "tuple and unit unions are not permitted"); + } + if vdata.fields().is_empty() { + self.err_handler().span_err(item.span, "unions cannot have zero fields"); + } + } + ItemKind::Const(def, .., None) => { + self.check_defaultness(item.span, def); + let msg = "free constant item without body"; + self.error_item_without_body(item.span, "constant", msg, " = <expr>;"); + } + ItemKind::Static(.., None) => { + let msg = "free static item without body"; + self.error_item_without_body(item.span, "static", msg, " = <expr>;"); + } + ItemKind::TyAlias(def, _, ref bounds, ref body) => { + self.check_defaultness(item.span, def); + if body.is_none() { + let msg = "free type alias without body"; + self.error_item_without_body(item.span, "type", msg, " = <type>;"); + } + self.check_type_no_bounds(bounds, "this context"); + } + _ => {} + } + + visit::walk_item(self, item) + } + + fn visit_foreign_item(&mut self, fi: &'a ForeignItem) { + match &fi.kind { + ForeignItemKind::Fn(def, sig, _, body) => { + self.check_defaultness(fi.span, *def); + self.check_foreign_fn_bodyless(fi.ident, body.as_deref()); + self.check_foreign_fn_headerless(fi.ident, fi.span, sig.header); + } + ForeignItemKind::TyAlias(def, generics, bounds, body) => { + self.check_defaultness(fi.span, *def); + self.check_foreign_kind_bodyless(fi.ident, "type", body.as_ref().map(|b| b.span)); + self.check_type_no_bounds(bounds, "`extern` blocks"); + self.check_foreign_ty_genericless(generics); + } + ForeignItemKind::Static(_, _, body) => { + self.check_foreign_kind_bodyless(fi.ident, "static", body.as_ref().map(|b| b.span)); + } + ForeignItemKind::MacCall(..) => {} + } + + visit::walk_foreign_item(self, fi) + } + + // Mirrors `visit::walk_generic_args`, but tracks relevant state. + fn visit_generic_args(&mut self, _: Span, generic_args: &'a GenericArgs) { + match *generic_args { + GenericArgs::AngleBracketed(ref 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<Item = Debug>` + // are allowed to contain nested `impl Trait`. + AngleBracketedArg::Constraint(constraint) => { + self.with_impl_trait(None, |this| { + this.visit_assoc_ty_constraint_from_generic_args(constraint); + }); + } + } + } + } + GenericArgs::Parenthesized(ref 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_ty_default = None; + for param in &generics.params { + match param.kind { + GenericParamKind::Lifetime => (), + GenericParamKind::Type { default: Some(_), .. } => { + prev_ty_default = Some(param.ident.span); + } + GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => { + if let Some(span) = prev_ty_default { + let mut err = self.err_handler().struct_span_err( + span, + "type parameters with a default must be trailing", + ); + if matches!(param.kind, GenericParamKind::Const { .. }) { + err.note( + "using type defaults and const parameters \ + in the same parameter list is currently not permitted", + ); + } + err.emit(); + break; + } + } + } + } + + validate_generic_param_order( + self.session, + self.err_handler(), + generics.params.iter().map(|param| { + let ident = Some(param.ident.to_string()); + let (kind, ident) = match ¶m.kind { + GenericParamKind::Lifetime => (ParamKindOrd::Lifetime, ident), + GenericParamKind::Type { default: _ } => (ParamKindOrd::Type, ident), + GenericParamKind::Const { ref ty, kw_span: _ } => { + let ty = pprust::ty_to_string(ty); + let unordered = self.session.features_untracked().const_generics; + ( + ParamKindOrd::Const { unordered }, + Some(format!("const {}: {}", param.ident, ty)), + ) + } + }; + (kind, Some(&*param.bounds), param.ident.span, ident) + }), + generics.span, + ); + + for predicate in &generics.where_clause.predicates { + if let WherePredicate::EqPredicate(ref predicate) = *predicate { + deny_equality_constraints(self, predicate, generics); + } + } + + visit::walk_generics(self, generics) + } + + 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) { + match bound { + GenericBound::Trait(_, TraitBoundModifier::MaybeConst) => { + if let Some(ctx) = self.bound_context { + let msg = format!("`?const` is not permitted in {}", ctx.description()); + self.err_handler().span_err(bound.span(), &msg); + } + } + + GenericBound::Trait(_, TraitBoundModifier::MaybeConstMaybe) => { + self.err_handler() + .span_err(bound.span(), "`?const` and `?` are mutually exclusive"); + } + + _ => {} + } + + visit::walk_param_bound(self, bound) + } + + fn visit_pat(&mut self, pat: &'a Pat) { + match pat.kind { + PatKind::Lit(ref expr) => { + self.check_expr_within_pat(expr, false); + } + PatKind::Range(ref start, ref end, _) => { + if let Some(expr) = start { + self.check_expr_within_pat(expr, true); + } + if let Some(expr) = end { + self.check_expr_within_pat(expr, true); + } + } + _ => {} + } + + visit::walk_pat(self, pat) + } + + fn visit_where_predicate(&mut self, p: &'a WherePredicate) { + if let &WherePredicate::BoundPredicate(ref bound_predicate) = p { + // A type binding, eg `for<'c> Foo: Send+Clone+'c` + self.check_late_bound_lifetime_defs(&bound_predicate.bound_generic_params); + } + visit::walk_where_predicate(self, p); + } + + fn visit_poly_trait_ref(&mut self, t: &'a PolyTraitRef, m: &'a TraitBoundModifier) { + self.check_late_bound_lifetime_defs(&t.bound_generic_params); + visit::walk_poly_trait_ref(self, t, m); + } + + fn visit_variant_data(&mut self, s: &'a VariantData) { + self.with_banned_assoc_ty_bound(|this| visit::walk_struct_def(this, s)) + } + + fn visit_enum_def( + &mut self, + enum_definition: &'a EnumDef, + generics: &'a Generics, + item_id: NodeId, + _: Span, + ) { + self.with_banned_assoc_ty_bound(|this| { + visit::walk_enum_def(this, enum_definition, generics, item_id) + }) + } + + 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_varadic_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() + .struct_span_err( + vec![*cspan, *aspan], + "functions cannot be both `const` and `async`", + ) + .span_label(*cspan, "`const` because of this") + .span_label(*aspan, "`async` because of this") + .span_label(span, "") // Point at the fn header. + .emit(); + } + + // Functions without bodies cannot have patterns. + if let FnKind::Fn(ctxt, _, sig, _, None) = fk { + Self::check_decl_no_pat(&sig.decl, |span, mut_ident| { + let (code, msg, label) = match ctxt { + FnCtxt::Foreign => ( + error_code!(E0130), + "patterns aren't allowed in foreign function declarations", + "pattern not allowed in foreign function", + ), + _ => ( + error_code!(E0642), + "patterns aren't allowed in functions without bodies", + "pattern not allowed in function without body", + ), + }; + if mut_ident && matches!(ctxt, FnCtxt::Assoc(_)) { + self.lint_buffer.buffer_lint(PATTERNS_IN_FNS_WITHOUT_BODY, id, span, msg); + } else { + self.err_handler() + .struct_span_err(span, msg) + .span_label(span, label) + .code(code) + .emit(); + } + }); + } + + visit::walk_fn(self, fk, span); + } + + fn visit_assoc_item(&mut self, item: &'a AssocItem, ctxt: AssocCtxt) { + 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) => { + self.check_impl_item_provided(item.span, body, "constant", " = <expr>;"); + } + AssocItemKind::Fn(_, _, _, body) => { + self.check_impl_item_provided(item.span, body, "function", " { <body> }"); + } + AssocItemKind::TyAlias(_, _, bounds, body) => { + self.check_impl_item_provided(item.span, body, "type", " = <type>;"); + self.check_type_no_bounds(bounds, "`impl`s"); + } + _ => {} + } + } + + if ctxt == AssocCtxt::Trait || self.in_trait_impl { + self.invalid_visibility(&item.vis, None); + if let AssocItemKind::Fn(_, sig, _, _) = &item.kind { + self.check_trait_fn_not_const(sig.header.constness); + self.check_trait_fn_not_async(item.span, sig.header.asyncness); + } + } + + if let AssocItemKind::Const(..) = item.kind { + self.check_item_named(item.ident, "const"); + } + + self.with_in_trait_impl(false, |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 = this.err_handler().struct_span_err( + predicate.span, + "equality constraints are not yet supported in `where` clauses", + ); + err.span_label(predicate.span, "not supported"); + + // Given `<A as Foo>::Bar = RhsTy`, suggest `A: Foo<Bar = RhsTy>`. + 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, .. }] => { + // Make a new `Path` from `foo::Bar` to `Foo<Bar = RhsTy>`. + let mut assoc_path = full_path.clone(); + // Remove `Bar` from `Foo::Bar`. + assoc_path.segments.pop(); + let len = assoc_path.segments.len() - 1; + // Build `<Bar = RhsTy>`. + let arg = AngleBracketedArg::Constraint(AssocTyConstraint { + id: rustc_ast::node_id::DUMMY_NODE_ID, + ident: *ident, + kind: AssocTyConstraintKind::Equality { + ty: predicate.rhs_ty.clone(), + }, + span: ident.span, + }); + // Add `<Bar = RhsTy>` 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: vec![arg], + } + .into(); + } + } + err.span_suggestion_verbose( + predicate.span, + &format!( + "if `{}` is an associated type you're trying to set, \ + use the associated type binding syntax", + ident + ), + format!( + "{}: {}", + param, + pprust::path_to_string(&assoc_path) + ), + Applicability::MaybeIncorrect, + ); + } + _ => {} + }; + } + } + } + _ => {} + } + } + } + err.note( + "see issue #20041 <https://github.com/rust-lang/rust/issues/20041> for more information", + ); + err.emit(); +} + +pub fn check_crate(session: &Session, krate: &Crate, lints: &mut LintBuffer) -> bool { + let mut validator = AstValidator { + session, + extern_mod: None, + in_trait_impl: false, + has_proc_macro_decls: false, + outer_impl_trait: None, + bound_context: None, + is_impl_trait_banned: false, + is_assoc_ty_bound_banned: false, + lint_buffer: lints, + }; + visit::walk_crate(&mut validator, krate); + + validator.has_proc_macro_decls +} |