1 // Validate AST before lowering it to HIR
3 // This pass is supposed to catch things that fit into AST data structures,
4 // but not permitted by the language. It runs after expansion when AST is frozen,
5 // so it can check for erroneous constructions produced by syntax extensions.
6 // This pass is supposed to perform only simple checks not requiring name resolution
7 // or type checking or some other kind of complex analysis.
10 use syntax::print::pprust;
12 use rustc::lint::builtin::{BuiltinLintDiagnostics, NESTED_IMPL_TRAIT};
13 use rustc::session::Session;
14 use rustc_data_structures::fx::FxHashMap;
17 use syntax::source_map::Spanned;
18 use syntax::symbol::keywords;
20 use syntax::visit::{self, Visitor};
21 use syntax::{span_err, struct_span_err, walk_list};
22 use syntax_ext::proc_macro_decls::is_proc_macro_attr;
24 use errors::Applicability;
27 #[derive(Copy, Clone, Debug)]
28 struct OuterImplTrait {
31 /// rust-lang/rust#57979: a bug in original implementation caused
32 /// us to fail sometimes to record an outer `impl Trait`.
33 /// Therefore, in order to reliably issue a warning (rather than
34 /// an error) in the *precise* places where we are newly injecting
35 /// the diagnostic, we have to distinguish between the places
36 /// where the outer `impl Trait` has always been recorded, versus
37 /// the places where it has only recently started being recorded.
38 only_recorded_since_pull_request_57730: bool,
42 /// This controls whether we should downgrade the nested impl
43 /// trait diagnostic to a warning rather than an error, based on
44 /// whether the outer impl trait had been improperly skipped in
45 /// earlier implementations of the analysis on the stable
47 fn should_warn_instead_of_error(&self) -> bool {
48 self.only_recorded_since_pull_request_57730
52 struct AstValidator<'a> {
54 has_proc_macro_decls: bool,
55 has_global_allocator: bool,
57 // Used to ban nested `impl Trait`, e.g., `impl Into<impl Debug>`.
58 // Nested `impl Trait` _is_ allowed in associated type position,
59 // e.g `impl Iterator<Item=impl Debug>`
60 outer_impl_trait: Option<OuterImplTrait>,
62 // Used to ban `impl Trait` in path projections like `<impl Iterator>::Item`
63 // or `Foo::Bar<impl Trait>`
64 is_impl_trait_banned: bool,
66 // rust-lang/rust#57979: the ban of nested `impl Trait` was buggy
67 // until PRs #57730 and #57981 landed: it would jump directly to
68 // walk_ty rather than visit_ty (or skip recurring entirely for
69 // impl trait in projections), and thus miss some cases. We track
70 // whether we should downgrade to a warning for short-term via
72 warning_period_57979_didnt_record_next_impl_trait: bool,
73 warning_period_57979_impl_trait_in_proj: bool,
76 impl<'a> AstValidator<'a> {
77 fn with_impl_trait_in_proj_warning<T>(&mut self, v: bool, f: impl FnOnce(&mut Self) -> T) -> T {
78 let old = mem::replace(&mut self.warning_period_57979_impl_trait_in_proj, v);
80 self.warning_period_57979_impl_trait_in_proj = old;
84 fn with_banned_impl_trait(&mut self, f: impl FnOnce(&mut Self)) {
85 let old = mem::replace(&mut self.is_impl_trait_banned, true);
87 self.is_impl_trait_banned = old;
90 fn with_impl_trait(&mut self, outer: Option<OuterImplTrait>, f: impl FnOnce(&mut Self)) {
91 let old = mem::replace(&mut self.outer_impl_trait, outer);
93 self.outer_impl_trait = old;
96 fn visit_assoc_type_binding_from_generic_args(&mut self, type_binding: &'a TypeBinding) {
97 // rust-lang/rust#57979: bug in old visit_generic_args called
98 // walk_ty rather than visit_ty, skipping outer `impl Trait`
99 // if it happened to occur at `type_binding.ty`
100 if let TyKind::ImplTrait(..) = type_binding.ty.node {
101 self.warning_period_57979_didnt_record_next_impl_trait = true;
103 self.visit_assoc_type_binding(type_binding);
106 fn visit_ty_from_generic_args(&mut self, ty: &'a Ty) {
107 // rust-lang/rust#57979: bug in old visit_generic_args called
108 // walk_ty rather than visit_ty, skippping outer `impl Trait`
109 // if it happened to occur at `ty`
110 if let TyKind::ImplTrait(..) = ty.node {
111 self.warning_period_57979_didnt_record_next_impl_trait = true;
116 fn outer_impl_trait(&mut self, span: Span) -> OuterImplTrait {
117 let only_recorded_since_pull_request_57730 =
118 self.warning_period_57979_didnt_record_next_impl_trait;
120 // (this flag is designed to be set to true and then only
121 // reach the construction point for the outer impl trait once,
122 // so its safe and easiest to unconditionally reset it to
124 self.warning_period_57979_didnt_record_next_impl_trait = false;
127 span, only_recorded_since_pull_request_57730,
131 // Mirrors visit::walk_ty, but tracks relevant state
132 fn walk_ty(&mut self, t: &'a Ty) {
134 TyKind::ImplTrait(..) => {
135 let outer_impl_trait = self.outer_impl_trait(t.span);
136 self.with_impl_trait(Some(outer_impl_trait), |this| visit::walk_ty(this, t))
138 TyKind::Path(ref qself, ref path) => {
140 // - `Option<impl Trait>`
141 // - `option::Option<impl Trait>`
142 // - `option::Option<T>::Foo<impl Trait>
145 // - `<impl Trait>::Foo`
146 // - `option::Option<impl Trait>::Foo`.
148 // To implement this, we disallow `impl Trait` from `qself`
149 // (for cases like `<impl Trait>::Foo>`)
150 // but we allow `impl Trait` in `GenericArgs`
151 // iff there are no more PathSegments.
152 if let Some(ref qself) = *qself {
153 // `impl Trait` in `qself` is always illegal
154 self.with_banned_impl_trait(|this| this.visit_ty(&qself.ty));
157 // Note that there should be a call to visit_path here,
158 // so if any logic is added to process `Path`s a call to it should be
159 // added both in visit_path and here. This code mirrors visit::walk_path.
160 for (i, segment) in path.segments.iter().enumerate() {
161 // Allow `impl Trait` iff we're on the final path segment
162 if i == path.segments.len() - 1 {
163 self.visit_path_segment(path.span, segment);
165 self.with_banned_impl_trait(|this| {
166 this.visit_path_segment(path.span, segment)
171 _ => visit::walk_ty(self, t),
175 fn err_handler(&self) -> &errors::Handler {
176 &self.session.diagnostic()
179 fn check_lifetime(&self, ident: Ident) {
180 let valid_names = [keywords::UnderscoreLifetime.name(),
181 keywords::StaticLifetime.name(),
182 keywords::Invalid.name()];
183 if !valid_names.contains(&ident.name) && ident.without_first_quote().is_reserved() {
184 self.err_handler().span_err(ident.span, "lifetimes cannot use keyword names");
188 fn check_label(&self, ident: Ident) {
189 if ident.without_first_quote().is_reserved() {
191 .span_err(ident.span, &format!("invalid label name `{}`", ident.name));
195 fn invalid_non_exhaustive_attribute(&self, variant: &Variant) {
196 let has_non_exhaustive = attr::contains_name(&variant.node.attrs, "non_exhaustive");
197 if has_non_exhaustive {
198 self.err_handler().span_err(variant.span,
199 "#[non_exhaustive] is not yet supported on variants");
203 fn invalid_visibility(&self, vis: &Visibility, note: Option<&str>) {
204 if let VisibilityKind::Inherited = vis.node {
208 let mut err = struct_span_err!(self.session,
211 "unnecessary visibility qualifier");
212 if vis.node.is_pub() {
213 err.span_label(vis.span, "`pub` not permitted here because it's implied");
215 if let Some(note) = note {
221 fn check_decl_no_pat<ReportFn: Fn(Span, bool)>(&self, decl: &FnDecl, report_err: ReportFn) {
222 for arg in &decl.inputs {
224 PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), _, None) |
226 PatKind::Ident(BindingMode::ByValue(Mutability::Mutable), _, None) =>
227 report_err(arg.pat.span, true),
228 _ => report_err(arg.pat.span, false),
233 fn check_trait_fn_not_async(&self, span: Span, asyncness: IsAsync) {
234 if asyncness.is_async() {
235 struct_span_err!(self.session, span, E0706,
236 "trait fns cannot be declared `async`").emit()
240 fn check_trait_fn_not_const(&self, constness: Spanned<Constness>) {
241 if constness.node == Constness::Const {
242 struct_span_err!(self.session, constness.span, E0379,
243 "trait fns cannot be declared const")
244 .span_label(constness.span, "trait fns cannot be const")
249 fn no_questions_in_bounds(&self, bounds: &GenericBounds, where_: &str, is_trait: bool) {
250 for bound in bounds {
251 if let GenericBound::Trait(ref poly, TraitBoundModifier::Maybe) = *bound {
252 let mut err = self.err_handler().struct_span_err(poly.span,
253 &format!("`?Trait` is not permitted in {}", where_));
255 err.note(&format!("traits are `?{}` by default", poly.trait_ref.path));
262 /// Matches `'-' lit | lit (cf. parser::Parser::parse_literal_maybe_minus)`,
263 /// or paths for ranges.
265 // FIXME: do we want to allow `expr -> pattern` conversion to create path expressions?
266 // That means making this work:
268 // ```rust,ignore (FIXME)
277 fn check_expr_within_pat(&self, expr: &Expr, allow_paths: bool) {
279 ExprKind::Lit(..) => {}
280 ExprKind::Path(..) if allow_paths => {}
281 ExprKind::Unary(UnOp::Neg, ref inner)
282 if match inner.node { ExprKind::Lit(_) => true, _ => false } => {}
283 _ => self.err_handler().span_err(expr.span, "arbitrary expressions aren't allowed \
288 fn check_late_bound_lifetime_defs(&self, params: &[GenericParam]) {
289 // Check only lifetime parameters are present and that the lifetime
290 // parameters that are present have no bounds.
291 let non_lt_param_spans: Vec<_> = params.iter().filter_map(|param| match param.kind {
292 GenericParamKind::Lifetime { .. } => {
293 if !param.bounds.is_empty() {
294 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
296 .span_err(spans, "lifetime bounds cannot be used in this context");
300 _ => Some(param.ident.span),
302 if !non_lt_param_spans.is_empty() {
303 self.err_handler().span_err(non_lt_param_spans,
304 "only lifetime parameters can be used in this context");
308 /// With eRFC 2497, we need to check whether an expression is ambiguous and warn or error
309 /// depending on the edition, this function handles that.
310 fn while_if_let_ambiguity(&self, expr: &P<Expr>) {
311 if let Some((span, op_kind)) = self.while_if_let_expr_ambiguity(&expr) {
312 let mut err = self.err_handler().struct_span_err(
313 span, &format!("ambiguous use of `{}`", op_kind.to_string())
317 "this will be a error until the `let_chains` feature is stabilized"
320 "see rust-lang/rust#53668 for more information"
323 if let Ok(snippet) = self.session.source_map().span_to_snippet(span) {
325 span, "consider adding parentheses", format!("({})", snippet),
326 Applicability::MachineApplicable,
334 /// With eRFC 2497 adding if-let chains, there is a requirement that the parsing of
335 /// `&&` and `||` in a if-let statement be unambiguous. This function returns a span and
336 /// a `BinOpKind` (either `&&` or `||` depending on what was ambiguous) if it is determined
337 /// that the current expression parsed is ambiguous and will break in future.
338 fn while_if_let_expr_ambiguity(&self, expr: &P<Expr>) -> Option<(Span, BinOpKind)> {
339 debug!("while_if_let_expr_ambiguity: expr.node: {:?}", expr.node);
341 ExprKind::Binary(op, _, _) if op.node == BinOpKind::And || op.node == BinOpKind::Or => {
342 Some((expr.span, op.node))
344 ExprKind::Range(ref lhs, ref rhs, _) => {
345 let lhs_ambiguous = lhs.as_ref()
346 .and_then(|lhs| self.while_if_let_expr_ambiguity(lhs));
347 let rhs_ambiguous = rhs.as_ref()
348 .and_then(|rhs| self.while_if_let_expr_ambiguity(rhs));
350 lhs_ambiguous.or(rhs_ambiguous)
357 enum GenericPosition {
362 fn validate_generics_order<'a>(
363 handler: &errors::Handler,
364 generics: impl Iterator<Item = (ParamKindOrd, Span, Option<String>)>,
365 pos: GenericPosition,
368 let mut max_param: Option<ParamKindOrd> = None;
369 let mut out_of_order = FxHashMap::default();
370 let mut param_idents = vec![];
372 for (kind, span, ident) in generics {
373 if let Some(ident) = ident {
374 param_idents.push((kind, param_idents.len(), ident));
376 let max_param = &mut max_param;
378 Some(max_param) if *max_param > kind => {
379 let entry = out_of_order.entry(kind).or_insert((*max_param, vec![]));
382 Some(_) | None => *max_param = Some(kind),
386 let mut ordered_params = "<".to_string();
387 if !out_of_order.is_empty() {
388 param_idents.sort_by_key(|&(po, i, _)| (po, i));
389 let mut first = true;
390 for (_, _, ident) in param_idents {
392 ordered_params += ", ";
394 ordered_params += &ident;
398 ordered_params += ">";
400 let pos_str = match pos {
401 GenericPosition::Param => "parameter",
402 GenericPosition::Arg => "argument",
405 for (param_ord, (max_param, spans)) in out_of_order {
406 let mut err = handler.struct_span_err(spans,
408 "{} {pos}s must be declared prior to {} {pos}s",
413 if let GenericPosition::Param = pos {
416 &format!("reorder the {}s: lifetimes, then types, then consts", pos_str),
417 ordered_params.clone(),
418 Applicability::MachineApplicable,
425 impl<'a> Visitor<'a> for AstValidator<'a> {
426 fn visit_expr(&mut self, expr: &'a Expr) {
428 ExprKind::IfLet(_, ref expr, _, _) | ExprKind::WhileLet(_, ref expr, _, _) =>
429 self.while_if_let_ambiguity(&expr),
430 ExprKind::InlineAsm(..) if !self.session.target.target.options.allow_asm => {
431 span_err!(self.session, expr.span, E0472, "asm! is unsupported on this target");
433 ExprKind::ObsoleteInPlace(ref place, ref val) => {
434 let mut err = self.err_handler().struct_span_err(
436 "emplacement syntax is obsolete (for now, anyway)",
439 "for more information, see \
440 <https://github.com/rust-lang/rust/issues/27779#issuecomment-378416911>"
443 ExprKind::Lit(ref v) if v.node.is_numeric() => {
445 place.span.between(val.span),
446 "if you meant to write a comparison against a negative value, add a \
447 space in between `<` and `-`",
449 Applicability::MaybeIncorrect
459 visit::walk_expr(self, expr)
462 fn visit_ty(&mut self, ty: &'a Ty) {
464 TyKind::BareFn(ref bfty) => {
465 self.check_decl_no_pat(&bfty.decl, |span, _| {
466 struct_span_err!(self.session, span, E0561,
467 "patterns aren't allowed in function pointer types").emit();
469 self.check_late_bound_lifetime_defs(&bfty.generic_params);
471 TyKind::TraitObject(ref bounds, ..) => {
472 let mut any_lifetime_bounds = false;
473 for bound in bounds {
474 if let GenericBound::Outlives(ref lifetime) = *bound {
475 if any_lifetime_bounds {
476 span_err!(self.session, lifetime.ident.span, E0226,
477 "only a single explicit lifetime bound is permitted");
480 any_lifetime_bounds = true;
483 self.no_questions_in_bounds(bounds, "trait object types", false);
485 TyKind::ImplTrait(_, ref bounds) => {
486 if self.is_impl_trait_banned {
487 if self.warning_period_57979_impl_trait_in_proj {
488 self.session.buffer_lint(
489 NESTED_IMPL_TRAIT, ty.id, ty.span,
490 "`impl Trait` is not allowed in path parameters");
492 struct_span_err!(self.session, ty.span, E0667,
493 "`impl Trait` is not allowed in path parameters").emit();
497 if let Some(outer_impl_trait) = self.outer_impl_trait {
498 if outer_impl_trait.should_warn_instead_of_error() {
499 self.session.buffer_lint_with_diagnostic(
500 NESTED_IMPL_TRAIT, ty.id, ty.span,
501 "nested `impl Trait` is not allowed",
502 BuiltinLintDiagnostics::NestedImplTrait {
503 outer_impl_trait_span: outer_impl_trait.span,
504 inner_impl_trait_span: ty.span,
507 struct_span_err!(self.session, ty.span, E0666,
508 "nested `impl Trait` is not allowed")
509 .span_label(outer_impl_trait.span, "outer `impl Trait`")
510 .span_label(ty.span, "nested `impl Trait` here")
516 .any(|b| if let GenericBound::Trait(..) = *b { true } else { false }) {
517 self.err_handler().span_err(ty.span, "at least one trait must be specified");
520 self.with_impl_trait_in_proj_warning(true, |this| this.walk_ty(ty));
529 fn visit_label(&mut self, label: &'a Label) {
530 self.check_label(label.ident);
531 visit::walk_label(self, label);
534 fn visit_lifetime(&mut self, lifetime: &'a Lifetime) {
535 self.check_lifetime(lifetime.ident);
536 visit::walk_lifetime(self, lifetime);
539 fn visit_item(&mut self, item: &'a Item) {
540 if item.attrs.iter().any(|attr| is_proc_macro_attr(attr) ) {
541 self.has_proc_macro_decls = true;
544 if attr::contains_name(&item.attrs, "global_allocator") {
545 self.has_global_allocator = true;
549 ItemKind::Impl(unsafety, polarity, _, _, Some(..), ref ty, ref impl_items) => {
550 self.invalid_visibility(&item.vis, None);
551 if let TyKind::Err = ty.node {
553 .struct_span_err(item.span, "`impl Trait for .. {}` is an obsolete syntax")
554 .help("use `auto trait Trait {}` instead").emit();
556 if unsafety == Unsafety::Unsafe && polarity == ImplPolarity::Negative {
557 span_err!(self.session, item.span, E0198, "negative impls cannot be unsafe");
559 for impl_item in impl_items {
560 self.invalid_visibility(&impl_item.vis, None);
561 if let ImplItemKind::Method(ref sig, _) = impl_item.node {
562 self.check_trait_fn_not_const(sig.header.constness);
563 self.check_trait_fn_not_async(impl_item.span, sig.header.asyncness.node);
567 ItemKind::Impl(unsafety, polarity, defaultness, _, None, _, _) => {
568 self.invalid_visibility(&item.vis,
569 Some("place qualifiers on individual impl items instead"));
570 if unsafety == Unsafety::Unsafe {
571 span_err!(self.session, item.span, E0197, "inherent impls cannot be unsafe");
573 if polarity == ImplPolarity::Negative {
574 self.err_handler().span_err(item.span, "inherent impls cannot be negative");
576 if defaultness == Defaultness::Default {
578 .struct_span_err(item.span, "inherent impls cannot be default")
579 .note("only trait implementations may be annotated with default").emit();
582 ItemKind::Fn(_, ref header, ref generics, _) => {
583 // We currently do not permit const generics in `const fn`, as
584 // this is tantamount to allowing compile-time dependent typing.
585 self.visit_fn_header(header);
586 if header.constness.node == Constness::Const {
587 // Look for const generics and error if we find any.
588 for param in &generics.params {
590 GenericParamKind::Const { .. } => {
594 "const parameters are not permitted in `const fn`",
603 ItemKind::ForeignMod(..) => {
604 self.invalid_visibility(
606 Some("place qualifiers on individual foreign items instead"),
609 ItemKind::Enum(ref def, _) => {
610 for variant in &def.variants {
611 self.invalid_non_exhaustive_attribute(variant);
612 for field in variant.node.data.fields() {
613 self.invalid_visibility(&field.vis, None);
617 ItemKind::Trait(is_auto, _, ref generics, ref bounds, ref trait_items) => {
618 if is_auto == IsAuto::Yes {
619 // Auto traits cannot have generics, super traits nor contain items.
620 if !generics.params.is_empty() {
621 struct_span_err!(self.session, item.span, E0567,
622 "auto traits cannot have generic parameters").emit();
624 if !bounds.is_empty() {
625 struct_span_err!(self.session, item.span, E0568,
626 "auto traits cannot have super traits").emit();
628 if !trait_items.is_empty() {
629 struct_span_err!(self.session, item.span, E0380,
630 "auto traits cannot have methods or associated items").emit();
633 self.no_questions_in_bounds(bounds, "supertraits", true);
634 for trait_item in trait_items {
635 if let TraitItemKind::Method(ref sig, ref block) = trait_item.node {
636 self.check_trait_fn_not_async(trait_item.span, sig.header.asyncness.node);
637 self.check_trait_fn_not_const(sig.header.constness);
639 self.check_decl_no_pat(&sig.decl, |span, mut_ident| {
641 self.session.buffer_lint(
642 lint::builtin::PATTERNS_IN_FNS_WITHOUT_BODY,
644 "patterns aren't allowed in methods without bodies");
646 struct_span_err!(self.session, span, E0642,
647 "patterns aren't allowed in methods without bodies").emit();
654 ItemKind::Mod(_) => {
655 // Ensure that `path` attributes on modules are recorded as used (cf. issue #35584).
656 attr::first_attr_value_str_by_name(&item.attrs, "path");
657 if attr::contains_name(&item.attrs, "warn_directory_ownership") {
658 let lint = lint::builtin::LEGACY_DIRECTORY_OWNERSHIP;
659 let msg = "cannot declare a new module at this location";
660 self.session.buffer_lint(lint, item.id, item.span, msg);
663 ItemKind::Union(ref vdata, _) => {
664 if let VariantData::Tuple(..) | VariantData::Unit(..) = vdata {
665 self.err_handler().span_err(item.span,
666 "tuple and unit unions are not permitted");
668 if vdata.fields().is_empty() {
669 self.err_handler().span_err(item.span,
670 "unions cannot have zero fields");
676 visit::walk_item(self, item)
679 fn visit_foreign_item(&mut self, fi: &'a ForeignItem) {
681 ForeignItemKind::Fn(ref decl, _) => {
682 self.check_decl_no_pat(decl, |span, _| {
683 struct_span_err!(self.session, span, E0130,
684 "patterns aren't allowed in foreign function declarations")
685 .span_label(span, "pattern not allowed in foreign function").emit();
688 ForeignItemKind::Static(..) | ForeignItemKind::Ty | ForeignItemKind::Macro(..) => {}
691 visit::walk_foreign_item(self, fi)
694 // Mirrors visit::walk_generic_args, but tracks relevant state
695 fn visit_generic_args(&mut self, _: Span, generic_args: &'a GenericArgs) {
696 match *generic_args {
697 GenericArgs::AngleBracketed(ref data) => {
698 walk_list!(self, visit_generic_arg, &data.args);
699 validate_generics_order(self.err_handler(), data.args.iter().map(|arg| {
701 GenericArg::Lifetime(..) => ParamKindOrd::Lifetime,
702 GenericArg::Type(..) => ParamKindOrd::Type,
703 GenericArg::Const(..) => ParamKindOrd::Const,
705 }), GenericPosition::Arg, generic_args.span());
707 // Type bindings such as `Item=impl Debug` in `Iterator<Item=Debug>`
708 // are allowed to contain nested `impl Trait`.
709 self.with_impl_trait(None, |this| {
710 walk_list!(this, visit_assoc_type_binding_from_generic_args, &data.bindings);
713 GenericArgs::Parenthesized(ref data) => {
714 walk_list!(self, visit_ty, &data.inputs);
715 if let Some(ref type_) = data.output {
716 // `-> Foo` syntax is essentially an associated type binding,
717 // so it is also allowed to contain nested `impl Trait`.
718 self.with_impl_trait(None, |this| this.visit_ty_from_generic_args(type_));
724 fn visit_generics(&mut self, generics: &'a Generics) {
725 let mut prev_ty_default = None;
726 for param in &generics.params {
727 if let GenericParamKind::Type { ref default, .. } = param.kind {
728 if default.is_some() {
729 prev_ty_default = Some(param.ident.span);
730 } else if let Some(span) = prev_ty_default {
732 .span_err(span, "type parameters with a default must be trailing");
738 validate_generics_order(self.err_handler(), generics.params.iter().map(|param| {
739 let span = param.ident.span;
740 let ident = Some(param.ident.to_string());
742 GenericParamKind::Lifetime { .. } => (ParamKindOrd::Lifetime, span, ident),
743 GenericParamKind::Type { .. } => (ParamKindOrd::Type, span, ident),
744 GenericParamKind::Const { ref ty } => {
745 let ty = pprust::ty_to_string(ty);
746 (ParamKindOrd::Const, span, Some(format!("const {}: {}", param.ident, ty)))
749 }), GenericPosition::Param, generics.span);
751 for predicate in &generics.where_clause.predicates {
752 if let WherePredicate::EqPredicate(ref predicate) = *predicate {
754 .span_err(predicate.span, "equality constraints are not yet \
755 supported in where clauses (see #20041)");
759 visit::walk_generics(self, generics)
762 fn visit_generic_param(&mut self, param: &'a GenericParam) {
763 if let GenericParamKind::Lifetime { .. } = param.kind {
764 self.check_lifetime(param.ident);
766 visit::walk_generic_param(self, param);
769 fn visit_pat(&mut self, pat: &'a Pat) {
771 PatKind::Lit(ref expr) => {
772 self.check_expr_within_pat(expr, false);
774 PatKind::Range(ref start, ref end, _) => {
775 self.check_expr_within_pat(start, true);
776 self.check_expr_within_pat(end, true);
781 visit::walk_pat(self, pat)
784 fn visit_where_predicate(&mut self, p: &'a WherePredicate) {
785 if let &WherePredicate::BoundPredicate(ref bound_predicate) = p {
786 // A type binding, eg `for<'c> Foo: Send+Clone+'c`
787 self.check_late_bound_lifetime_defs(&bound_predicate.bound_generic_params);
789 visit::walk_where_predicate(self, p);
792 fn visit_poly_trait_ref(&mut self, t: &'a PolyTraitRef, m: &'a TraitBoundModifier) {
793 self.check_late_bound_lifetime_defs(&t.bound_generic_params);
794 visit::walk_poly_trait_ref(self, t, m);
797 fn visit_mac(&mut self, mac: &Spanned<Mac_>) {
798 // when a new macro kind is added but the author forgets to set it up for expansion
799 // because that's the only part that won't cause a compiler error
800 self.session.diagnostic()
801 .span_bug(mac.span, "macro invocation missed in expansion; did you forget to override \
802 the relevant `fold_*()` method in `PlaceholderExpander`?");
805 fn visit_fn_header(&mut self, header: &'a FnHeader) {
806 if header.asyncness.node.is_async() && self.session.rust_2015() {
807 struct_span_err!(self.session, header.asyncness.span, E0670,
808 "`async fn` is not permitted in the 2015 edition").emit();
813 pub fn check_crate(session: &Session, krate: &Crate) -> (bool, bool) {
814 let mut validator = AstValidator {
816 has_proc_macro_decls: false,
817 has_global_allocator: false,
818 outer_impl_trait: None,
819 is_impl_trait_banned: false,
820 warning_period_57979_didnt_record_next_impl_trait: false,
821 warning_period_57979_impl_trait_in_proj: false,
823 visit::walk_crate(&mut validator, krate);
825 (validator.has_proc_macro_decls, validator.has_global_allocator)