| // 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 rustc::lint; |
| use rustc::session::Session; |
| use syntax::ast::*; |
| use syntax::attr; |
| use syntax::source_map::Spanned; |
| use syntax::symbol::keywords; |
| use syntax::ptr::P; |
| use syntax::visit::{self, Visitor}; |
| use syntax_pos::Span; |
| use errors; |
| use errors::Applicability; |
| |
| struct AstValidator<'a> { |
| session: &'a Session, |
| } |
| |
| impl<'a> AstValidator<'a> { |
| fn err_handler(&self) -> &errors::Handler { |
| &self.session.diagnostic() |
| } |
| |
| fn check_lifetime(&self, ident: Ident) { |
| let valid_names = [keywords::UnderscoreLifetime.name(), |
| keywords::StaticLifetime.name(), |
| keywords::Invalid.name()]; |
| 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_non_exhaustive_attribute(&self, variant: &Variant) { |
| let has_non_exhaustive = attr::contains_name(&variant.node.attrs, "non_exhaustive"); |
| if has_non_exhaustive { |
| self.err_handler().span_err(variant.span, |
| "#[non_exhaustive] is not yet supported on variants"); |
| } |
| } |
| |
| 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<ReportFn: Fn(Span, bool)>(&self, decl: &FnDecl, report_err: ReportFn) { |
| for arg in &decl.inputs { |
| match arg.pat.node { |
| PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), _, None) | |
| PatKind::Wild => {} |
| PatKind::Ident(BindingMode::ByValue(Mutability::Mutable), _, None) => |
| report_err(arg.pat.span, true), |
| _ => report_err(arg.pat.span, false), |
| } |
| } |
| } |
| |
| fn check_trait_fn_not_async(&self, span: Span, asyncness: IsAsync) { |
| if asyncness.is_async() { |
| struct_span_err!(self.session, span, E0706, |
| "trait fns cannot be declared `async`").emit() |
| } |
| } |
| |
| fn check_trait_fn_not_const(&self, constness: Spanned<Constness>) { |
| if constness.node == Constness::Const { |
| struct_span_err!(self.session, constness.span, E0379, |
| "trait fns cannot be declared const") |
| .span_label(constness.span, "trait fns cannot be const") |
| .emit(); |
| } |
| } |
| |
| 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 { |
| err.note(&format!("traits are `?{}` by default", poly.trait_ref.path)); |
| } |
| err.emit(); |
| } |
| } |
| } |
| |
| /// matches '-' lit | lit (cf. parser::Parser::parse_literal_maybe_minus), |
| /// or path 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.node { |
| ExprKind::Lit(..) => {} |
| ExprKind::Path(..) if allow_paths => {} |
| ExprKind::Unary(UnOp::Neg, ref inner) |
| if match inner.node { ExprKind::Lit(_) => true, _ => false } => {} |
| _ => 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"); |
| } |
| } |
| |
| /// With eRFC 2497, we need to check whether an expression is ambiguous and warn or error |
| /// depending on the edition, this function handles that. |
| fn while_if_let_ambiguity(&self, expr: &P<Expr>) { |
| if let Some((span, op_kind)) = self.while_if_let_expr_ambiguity(&expr) { |
| let mut err = self.err_handler().struct_span_err( |
| span, &format!("ambiguous use of `{}`", op_kind.to_string()) |
| ); |
| |
| err.note( |
| "this will be a error until the `let_chains` feature is stabilized" |
| ); |
| err.note( |
| "see rust-lang/rust#53668 for more information" |
| ); |
| |
| if let Ok(snippet) = self.session.source_map().span_to_snippet(span) { |
| err.span_suggestion_with_applicability( |
| span, "consider adding parentheses", format!("({})", snippet), |
| Applicability::MachineApplicable, |
| ); |
| } |
| |
| err.emit(); |
| } |
| } |
| |
| /// With eRFC 2497 adding if-let chains, there is a requirement that the parsing of |
| /// `&&` and `||` in a if-let statement be unambiguous. This function returns a span and |
| /// a `BinOpKind` (either `&&` or `||` depending on what was ambiguous) if it is determined |
| /// that the current expression parsed is ambiguous and will break in future. |
| fn while_if_let_expr_ambiguity(&self, expr: &P<Expr>) -> Option<(Span, BinOpKind)> { |
| debug!("while_if_let_expr_ambiguity: expr.node: {:?}", expr.node); |
| match &expr.node { |
| ExprKind::Binary(op, _, _) if op.node == BinOpKind::And || op.node == BinOpKind::Or => { |
| Some((expr.span, op.node)) |
| }, |
| ExprKind::Range(ref lhs, ref rhs, _) => { |
| let lhs_ambiguous = lhs.as_ref() |
| .and_then(|lhs| self.while_if_let_expr_ambiguity(lhs)); |
| let rhs_ambiguous = rhs.as_ref() |
| .and_then(|rhs| self.while_if_let_expr_ambiguity(rhs)); |
| |
| lhs_ambiguous.or(rhs_ambiguous) |
| } |
| _ => None, |
| } |
| } |
| |
| } |
| |
| impl<'a> Visitor<'a> for AstValidator<'a> { |
| fn visit_expr(&mut self, expr: &'a Expr) { |
| match expr.node { |
| ExprKind::IfLet(_, ref expr, _, _) | ExprKind::WhileLet(_, ref expr, _, _) => |
| self.while_if_let_ambiguity(&expr), |
| ExprKind::InlineAsm(..) if !self.session.target.target.options.allow_asm => { |
| span_err!(self.session, expr.span, E0472, "asm! is unsupported on this target"); |
| } |
| ExprKind::ObsoleteInPlace(ref place, ref val) => { |
| let mut err = self.err_handler().struct_span_err( |
| expr.span, |
| "emplacement syntax is obsolete (for now, anyway)", |
| ); |
| err.note( |
| "for more information, see \ |
| <https://github.com/rust-lang/rust/issues/27779#issuecomment-378416911>" |
| ); |
| match val.node { |
| ExprKind::Lit(ref v) if v.node.is_numeric() => { |
| err.span_suggestion_with_applicability( |
| place.span.between(val.span), |
| "if you meant to write a comparison against a negative value, add a \ |
| space in between `<` and `-`", |
| "< -".to_string(), |
| Applicability::MaybeIncorrect |
| ); |
| } |
| _ => {} |
| } |
| err.emit(); |
| } |
| _ => {} |
| } |
| |
| visit::walk_expr(self, expr) |
| } |
| |
| fn visit_ty(&mut self, ty: &'a Ty) { |
| match ty.node { |
| TyKind::BareFn(ref bfty) => { |
| 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 { |
| span_err!(self.session, lifetime.ident.span, E0226, |
| "only a single explicit lifetime bound is permitted"); |
| break; |
| } |
| any_lifetime_bounds = true; |
| } |
| } |
| self.no_questions_in_bounds(bounds, "trait object types", false); |
| } |
| TyKind::ImplTrait(_, ref bounds) => { |
| 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"); |
| } |
| } |
| _ => {} |
| } |
| |
| visit::walk_ty(self, 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) { |
| match item.node { |
| ItemKind::Impl(unsafety, polarity, _, _, Some(..), ref ty, ref impl_items) => { |
| self.invalid_visibility(&item.vis, None); |
| if let TyKind::Err = ty.node { |
| self.err_handler() |
| .struct_span_err(item.span, "`impl Trait for .. {}` is an obsolete syntax") |
| .help("use `auto trait Trait {}` instead").emit(); |
| } |
| if unsafety == Unsafety::Unsafe && polarity == ImplPolarity::Negative { |
| span_err!(self.session, item.span, E0198, "negative impls cannot be unsafe"); |
| } |
| for impl_item in impl_items { |
| self.invalid_visibility(&impl_item.vis, None); |
| if let ImplItemKind::Method(ref sig, _) = impl_item.node { |
| self.check_trait_fn_not_const(sig.header.constness); |
| self.check_trait_fn_not_async(impl_item.span, sig.header.asyncness); |
| } |
| } |
| } |
| ItemKind::Impl(unsafety, polarity, defaultness, _, None, _, _) => { |
| self.invalid_visibility(&item.vis, |
| Some("place qualifiers on individual impl items instead")); |
| if unsafety == Unsafety::Unsafe { |
| span_err!(self.session, item.span, E0197, "inherent impls cannot be unsafe"); |
| } |
| if polarity == ImplPolarity::Negative { |
| self.err_handler().span_err(item.span, "inherent impls cannot be negative"); |
| } |
| if defaultness == Defaultness::Default { |
| self.err_handler() |
| .struct_span_err(item.span, "inherent impls cannot be default") |
| .note("only trait implementations may be annotated with default").emit(); |
| } |
| } |
| ItemKind::ForeignMod(..) => { |
| self.invalid_visibility( |
| &item.vis, |
| Some("place qualifiers on individual foreign items instead"), |
| ); |
| } |
| ItemKind::Enum(ref def, _) => { |
| for variant in &def.variants { |
| self.invalid_non_exhaustive_attribute(variant); |
| for field in variant.node.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. |
| if !generics.params.is_empty() { |
| struct_span_err!(self.session, item.span, E0567, |
| "auto traits cannot have generic parameters").emit(); |
| } |
| if !bounds.is_empty() { |
| struct_span_err!(self.session, item.span, E0568, |
| "auto traits cannot have super traits").emit(); |
| } |
| if !trait_items.is_empty() { |
| struct_span_err!(self.session, item.span, E0380, |
| "auto traits cannot have methods or associated items").emit(); |
| } |
| } |
| self.no_questions_in_bounds(bounds, "supertraits", true); |
| for trait_item in trait_items { |
| if let TraitItemKind::Method(ref sig, ref block) = trait_item.node { |
| self.check_trait_fn_not_async(trait_item.span, sig.header.asyncness); |
| self.check_trait_fn_not_const(sig.header.constness); |
| if block.is_none() { |
| self.check_decl_no_pat(&sig.decl, |span, mut_ident| { |
| if mut_ident { |
| self.session.buffer_lint( |
| lint::builtin::PATTERNS_IN_FNS_WITHOUT_BODY, |
| trait_item.id, span, |
| "patterns aren't allowed in methods without bodies"); |
| } else { |
| struct_span_err!(self.session, span, E0642, |
| "patterns aren't allowed in methods without bodies").emit(); |
| } |
| }); |
| } |
| } |
| } |
| } |
| ItemKind::Mod(_) => { |
| // Ensure that `path` attributes on modules are recorded as used (cf. issue #35584). |
| attr::first_attr_value_str_by_name(&item.attrs, "path"); |
| if attr::contains_name(&item.attrs, "warn_directory_ownership") { |
| let lint = lint::builtin::LEGACY_DIRECTORY_OWNERSHIP; |
| let msg = "cannot declare a new module at this location"; |
| self.session.buffer_lint(lint, item.id, item.span, msg); |
| } |
| } |
| ItemKind::Union(ref vdata, _) => { |
| if !vdata.is_struct() { |
| 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"); |
| } |
| } |
| _ => {} |
| } |
| |
| visit::walk_item(self, item) |
| } |
| |
| fn visit_foreign_item(&mut self, fi: &'a ForeignItem) { |
| match fi.node { |
| ForeignItemKind::Fn(ref decl, _) => { |
| self.check_decl_no_pat(decl, |span, _| { |
| struct_span_err!(self.session, span, E0130, |
| "patterns aren't allowed in foreign function declarations") |
| .span_label(span, "pattern not allowed in foreign function").emit(); |
| }); |
| } |
| ForeignItemKind::Static(..) | ForeignItemKind::Ty | ForeignItemKind::Macro(..) => {} |
| } |
| |
| visit::walk_foreign_item(self, fi) |
| } |
| |
| fn visit_generics(&mut self, generics: &'a Generics) { |
| let mut seen_non_lifetime_param = false; |
| let mut seen_default = None; |
| for param in &generics.params { |
| match (¶m.kind, seen_non_lifetime_param) { |
| (GenericParamKind::Lifetime { .. }, true) => { |
| self.err_handler() |
| .span_err(param.ident.span, "lifetime parameters must be leading"); |
| }, |
| (GenericParamKind::Lifetime { .. }, false) => {} |
| (GenericParamKind::Type { ref default, .. }, _) => { |
| seen_non_lifetime_param = true; |
| if default.is_some() { |
| seen_default = Some(param.ident.span); |
| } else if let Some(span) = seen_default { |
| self.err_handler() |
| .span_err(span, "type parameters with a default must be trailing"); |
| break; |
| } |
| } |
| } |
| } |
| for predicate in &generics.where_clause.predicates { |
| if let WherePredicate::EqPredicate(ref predicate) = *predicate { |
| self.err_handler() |
| .span_err(predicate.span, "equality constraints are not yet \ |
| supported in where clauses (see #20041)"); |
| } |
| } |
| 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_pat(&mut self, pat: &'a Pat) { |
| match pat.node { |
| PatKind::Lit(ref expr) => { |
| self.check_expr_within_pat(expr, false); |
| } |
| PatKind::Range(ref start, ref end, _) => { |
| self.check_expr_within_pat(start, true); |
| self.check_expr_within_pat(end, 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_mac(&mut self, mac: &Spanned<Mac_>) { |
| // when a new macro kind is added but the author forgets to set it up for expansion |
| // because that's the only part that won't cause a compiler error |
| self.session.diagnostic() |
| .span_bug(mac.span, "macro invocation missed in expansion; did you forget to override \ |
| the relevant `fold_*()` method in `PlaceholderExpander`?"); |
| } |
| } |
| |
| // Bans 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>` |
| struct NestedImplTraitVisitor<'a> { |
| session: &'a Session, |
| outer_impl_trait: Option<Span>, |
| } |
| |
| impl<'a> NestedImplTraitVisitor<'a> { |
| fn with_impl_trait<F>(&mut self, outer_impl_trait: Option<Span>, f: F) |
| where F: FnOnce(&mut NestedImplTraitVisitor<'a>) |
| { |
| let old_outer_impl_trait = self.outer_impl_trait; |
| self.outer_impl_trait = outer_impl_trait; |
| f(self); |
| self.outer_impl_trait = old_outer_impl_trait; |
| } |
| } |
| |
| |
| impl<'a> Visitor<'a> for NestedImplTraitVisitor<'a> { |
| fn visit_ty(&mut self, t: &'a Ty) { |
| if let TyKind::ImplTrait(..) = t.node { |
| if let Some(outer_impl_trait) = self.outer_impl_trait { |
| struct_span_err!(self.session, t.span, E0666, |
| "nested `impl Trait` is not allowed") |
| .span_label(outer_impl_trait, "outer `impl Trait`") |
| .span_label(t.span, "nested `impl Trait` here") |
| .emit(); |
| |
| } |
| self.with_impl_trait(Some(t.span), |this| visit::walk_ty(this, t)); |
| } else { |
| visit::walk_ty(self, t); |
| } |
| } |
| fn visit_generic_args(&mut self, _: Span, generic_args: &'a GenericArgs) { |
| match *generic_args { |
| GenericArgs::AngleBracketed(ref data) => { |
| for arg in &data.args { |
| self.visit_generic_arg(arg) |
| } |
| for type_binding in &data.bindings { |
| // Type bindings such as `Item=impl Debug` in `Iterator<Item=Debug>` |
| // are allowed to contain nested `impl Trait`. |
| self.with_impl_trait(None, |this| visit::walk_ty(this, &type_binding.ty)); |
| } |
| } |
| GenericArgs::Parenthesized(ref data) => { |
| for type_ in &data.inputs { |
| self.visit_ty(type_); |
| } |
| if let Some(ref type_) = 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| visit::walk_ty(this, type_)); |
| } |
| } |
| } |
| } |
| |
| fn visit_mac(&mut self, _mac: &Spanned<Mac_>) { |
| // covered in AstValidator |
| } |
| } |
| |
| // Bans `impl Trait` in path projections like `<impl Iterator>::Item` or `Foo::Bar<impl Trait>`. |
| struct ImplTraitProjectionVisitor<'a> { |
| session: &'a Session, |
| is_banned: bool, |
| } |
| |
| impl<'a> ImplTraitProjectionVisitor<'a> { |
| fn with_ban<F>(&mut self, f: F) |
| where F: FnOnce(&mut ImplTraitProjectionVisitor<'a>) |
| { |
| let old_is_banned = self.is_banned; |
| self.is_banned = true; |
| f(self); |
| self.is_banned = old_is_banned; |
| } |
| } |
| |
| impl<'a> Visitor<'a> for ImplTraitProjectionVisitor<'a> { |
| fn visit_ty(&mut self, t: &'a Ty) { |
| match t.node { |
| TyKind::ImplTrait(..) => { |
| if self.is_banned { |
| struct_span_err!(self.session, t.span, E0667, |
| "`impl Trait` is not allowed in path parameters").emit(); |
| } |
| } |
| 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_ban(|this| this.visit_ty(&qself.ty)); |
| } |
| |
| 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 { |
| visit::walk_path_segment(self, path.span, segment); |
| } else { |
| self.with_ban(|this| |
| visit::walk_path_segment(this, path.span, segment)); |
| } |
| } |
| } |
| _ => visit::walk_ty(self, t), |
| } |
| } |
| |
| fn visit_mac(&mut self, _mac: &Spanned<Mac_>) { |
| // covered in AstValidator |
| } |
| } |
| |
| pub fn check_crate(session: &Session, krate: &Crate) { |
| visit::walk_crate( |
| &mut NestedImplTraitVisitor { |
| session, |
| outer_impl_trait: None, |
| }, krate); |
| |
| visit::walk_crate( |
| &mut ImplTraitProjectionVisitor { |
| session, |
| is_banned: false, |
| }, krate); |
| |
| visit::walk_crate(&mut AstValidator { session }, krate) |
| } |
