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, sym};
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;
23 use syntax_pos::{Span, MultiSpan};
24 use errors::{Applicability, FatalError};
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_visibility(&self, vis: &Visibility, note: Option<&str>) {
196 if let VisibilityKind::Inherited = vis.node {
200 let mut err = struct_span_err!(self.session,
203 "unnecessary visibility qualifier");
204 if vis.node.is_pub() {
205 err.span_label(vis.span, "`pub` not permitted here because it's implied");
207 if let Some(note) = note {
213 fn check_decl_no_pat<ReportFn: Fn(Span, bool)>(&self, decl: &FnDecl, report_err: ReportFn) {
214 for arg in &decl.inputs {
216 PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), _, None) |
218 PatKind::Ident(BindingMode::ByValue(Mutability::Mutable), _, None) =>
219 report_err(arg.pat.span, true),
220 _ => report_err(arg.pat.span, false),
225 fn check_trait_fn_not_async(&self, span: Span, asyncness: &IsAsync) {
226 if asyncness.is_async() {
227 struct_span_err!(self.session, span, E0706,
228 "trait fns cannot be declared `async`").emit()
232 fn check_trait_fn_not_const(&self, constness: Spanned<Constness>) {
233 if constness.node == Constness::Const {
234 struct_span_err!(self.session, constness.span, E0379,
235 "trait fns cannot be declared const")
236 .span_label(constness.span, "trait fns cannot be const")
241 fn no_questions_in_bounds(&self, bounds: &GenericBounds, where_: &str, is_trait: bool) {
242 for bound in bounds {
243 if let GenericBound::Trait(ref poly, TraitBoundModifier::Maybe) = *bound {
244 let mut err = self.err_handler().struct_span_err(poly.span,
245 &format!("`?Trait` is not permitted in {}", where_));
247 err.note(&format!("traits are `?{}` by default", poly.trait_ref.path));
254 /// Matches `'-' lit | lit (cf. parser::Parser::parse_literal_maybe_minus)`,
255 /// or paths for ranges.
257 // FIXME: do we want to allow `expr -> pattern` conversion to create path expressions?
258 // That means making this work:
260 // ```rust,ignore (FIXME)
269 fn check_expr_within_pat(&self, expr: &Expr, allow_paths: bool) {
271 ExprKind::Lit(..) => {}
272 ExprKind::Path(..) if allow_paths => {}
273 ExprKind::Unary(UnOp::Neg, ref inner)
274 if match inner.node { ExprKind::Lit(_) => true, _ => false } => {}
275 _ => self.err_handler().span_err(expr.span, "arbitrary expressions aren't allowed \
280 fn check_late_bound_lifetime_defs(&self, params: &[GenericParam]) {
281 // Check only lifetime parameters are present and that the lifetime
282 // parameters that are present have no bounds.
283 let non_lt_param_spans: Vec<_> = params.iter().filter_map(|param| match param.kind {
284 GenericParamKind::Lifetime { .. } => {
285 if !param.bounds.is_empty() {
286 let spans: Vec<_> = param.bounds.iter().map(|b| b.span()).collect();
288 .span_err(spans, "lifetime bounds cannot be used in this context");
292 _ => Some(param.ident.span),
294 if !non_lt_param_spans.is_empty() {
295 self.err_handler().span_err(non_lt_param_spans,
296 "only lifetime parameters can be used in this context");
300 /// With eRFC 2497, we need to check whether an expression is ambiguous and warn or error
301 /// depending on the edition, this function handles that.
302 fn while_if_let_ambiguity(&self, expr: &P<Expr>) {
303 if let Some((span, op_kind)) = self.while_if_let_expr_ambiguity(&expr) {
304 let mut err = self.err_handler().struct_span_err(
305 span, &format!("ambiguous use of `{}`", op_kind.to_string())
309 "this will be a error until the `let_chains` feature is stabilized"
312 "see rust-lang/rust#53668 for more information"
315 if let Ok(snippet) = self.session.source_map().span_to_snippet(span) {
317 span, "consider adding parentheses", format!("({})", snippet),
318 Applicability::MachineApplicable,
326 /// With eRFC 2497 adding if-let chains, there is a requirement that the parsing of
327 /// `&&` and `||` in a if-let statement be unambiguous. This function returns a span and
328 /// a `BinOpKind` (either `&&` or `||` depending on what was ambiguous) if it is determined
329 /// that the current expression parsed is ambiguous and will break in future.
330 fn while_if_let_expr_ambiguity(&self, expr: &P<Expr>) -> Option<(Span, BinOpKind)> {
331 debug!("while_if_let_expr_ambiguity: expr.node: {:?}", expr.node);
333 ExprKind::Binary(op, _, _) if op.node == BinOpKind::And || op.node == BinOpKind::Or => {
334 Some((expr.span, op.node))
336 ExprKind::Range(ref lhs, ref rhs, _) => {
337 let lhs_ambiguous = lhs.as_ref()
338 .and_then(|lhs| self.while_if_let_expr_ambiguity(lhs));
339 let rhs_ambiguous = rhs.as_ref()
340 .and_then(|rhs| self.while_if_let_expr_ambiguity(rhs));
342 lhs_ambiguous.or(rhs_ambiguous)
349 enum GenericPosition {
354 fn validate_generics_order<'a>(
356 handler: &errors::Handler,
357 generics: impl Iterator<
360 Option<&'a [GenericBound]>,
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![];
371 let mut found_type = false;
372 let mut found_const = false;
374 for (kind, bounds, span, ident) in generics {
375 if let Some(ident) = ident {
376 param_idents.push((kind, bounds, param_idents.len(), ident));
378 let max_param = &mut max_param;
380 Some(max_param) if *max_param > kind => {
381 let entry = out_of_order.entry(kind).or_insert((*max_param, vec![]));
384 Some(_) | None => *max_param = Some(kind),
387 ParamKindOrd::Type => found_type = true,
388 ParamKindOrd::Const => found_const = true,
393 let mut ordered_params = "<".to_string();
394 if !out_of_order.is_empty() {
395 param_idents.sort_by_key(|&(po, _, i, _)| (po, i));
396 let mut first = true;
397 for (_, bounds, _, ident) in param_idents {
399 ordered_params += ", ";
401 ordered_params += &ident;
402 if let Some(bounds) = bounds {
403 if !bounds.is_empty() {
404 ordered_params += ": ";
405 ordered_params += &pprust::bounds_to_string(&bounds);
411 ordered_params += ">";
413 let pos_str = match pos {
414 GenericPosition::Param => "parameter",
415 GenericPosition::Arg => "argument",
418 for (param_ord, (max_param, spans)) in &out_of_order {
419 let mut err = handler.struct_span_err(spans.clone(),
421 "{} {pos}s must be declared prior to {} {pos}s",
426 if let GenericPosition::Param = pos {
430 "reorder the {}s: lifetimes, then types{}",
432 if sess.features_untracked().const_generics { ", then consts" } else { "" },
434 ordered_params.clone(),
435 Applicability::MachineApplicable,
441 // FIXME(const_generics): we shouldn't have to abort here at all, but we currently get ICEs
442 // if we don't. Const parameters and type parameters can currently conflict if they
444 if !out_of_order.is_empty() && found_type && found_const {
449 impl<'a> Visitor<'a> for AstValidator<'a> {
450 fn visit_expr(&mut self, expr: &'a Expr) {
452 ExprKind::IfLet(_, ref expr, _, _) | ExprKind::WhileLet(_, ref expr, _, _) =>
453 self.while_if_let_ambiguity(&expr),
454 ExprKind::InlineAsm(..) if !self.session.target.target.options.allow_asm => {
455 span_err!(self.session, expr.span, E0472, "asm! is unsupported on this target");
457 ExprKind::ObsoleteInPlace(ref place, ref val) => {
458 let mut err = self.err_handler().struct_span_err(
460 "emplacement syntax is obsolete (for now, anyway)",
463 "for more information, see \
464 <https://github.com/rust-lang/rust/issues/27779#issuecomment-378416911>"
467 ExprKind::Lit(ref v) if v.node.is_numeric() => {
469 place.span.between(val.span),
470 "if you meant to write a comparison against a negative value, add a \
471 space in between `<` and `-`",
473 Applicability::MaybeIncorrect
483 visit::walk_expr(self, expr)
486 fn visit_ty(&mut self, ty: &'a Ty) {
488 TyKind::BareFn(ref bfty) => {
489 self.check_decl_no_pat(&bfty.decl, |span, _| {
490 struct_span_err!(self.session, span, E0561,
491 "patterns aren't allowed in function pointer types").emit();
493 self.check_late_bound_lifetime_defs(&bfty.generic_params);
495 TyKind::TraitObject(ref bounds, ..) => {
496 let mut any_lifetime_bounds = false;
497 for bound in bounds {
498 if let GenericBound::Outlives(ref lifetime) = *bound {
499 if any_lifetime_bounds {
500 span_err!(self.session, lifetime.ident.span, E0226,
501 "only a single explicit lifetime bound is permitted");
504 any_lifetime_bounds = true;
507 self.no_questions_in_bounds(bounds, "trait object types", false);
509 TyKind::ImplTrait(_, ref bounds) => {
510 if self.is_impl_trait_banned {
511 if self.warning_period_57979_impl_trait_in_proj {
512 self.session.buffer_lint(
513 NESTED_IMPL_TRAIT, ty.id, ty.span,
514 "`impl Trait` is not allowed in path parameters");
516 struct_span_err!(self.session, ty.span, E0667,
517 "`impl Trait` is not allowed in path parameters").emit();
521 if let Some(outer_impl_trait) = self.outer_impl_trait {
522 if outer_impl_trait.should_warn_instead_of_error() {
523 self.session.buffer_lint_with_diagnostic(
524 NESTED_IMPL_TRAIT, ty.id, ty.span,
525 "nested `impl Trait` is not allowed",
526 BuiltinLintDiagnostics::NestedImplTrait {
527 outer_impl_trait_span: outer_impl_trait.span,
528 inner_impl_trait_span: ty.span,
531 struct_span_err!(self.session, ty.span, E0666,
532 "nested `impl Trait` is not allowed")
533 .span_label(outer_impl_trait.span, "outer `impl Trait`")
534 .span_label(ty.span, "nested `impl Trait` here")
540 .any(|b| if let GenericBound::Trait(..) = *b { true } else { false }) {
541 self.err_handler().span_err(ty.span, "at least one trait must be specified");
544 self.with_impl_trait_in_proj_warning(true, |this| this.walk_ty(ty));
553 fn visit_label(&mut self, label: &'a Label) {
554 self.check_label(label.ident);
555 visit::walk_label(self, label);
558 fn visit_lifetime(&mut self, lifetime: &'a Lifetime) {
559 self.check_lifetime(lifetime.ident);
560 visit::walk_lifetime(self, lifetime);
563 fn visit_item(&mut self, item: &'a Item) {
564 if item.attrs.iter().any(|attr| is_proc_macro_attr(attr) ) {
565 self.has_proc_macro_decls = true;
568 if attr::contains_name(&item.attrs, sym::global_allocator) {
569 self.has_global_allocator = true;
573 ItemKind::Impl(unsafety, polarity, _, _, Some(..), ref ty, ref impl_items) => {
574 self.invalid_visibility(&item.vis, None);
575 if let TyKind::Err = ty.node {
577 .struct_span_err(item.span, "`impl Trait for .. {}` is an obsolete syntax")
578 .help("use `auto trait Trait {}` instead").emit();
580 if unsafety == Unsafety::Unsafe && polarity == ImplPolarity::Negative {
581 span_err!(self.session, item.span, E0198, "negative impls cannot be unsafe");
583 for impl_item in impl_items {
584 self.invalid_visibility(&impl_item.vis, None);
585 if let ImplItemKind::Method(ref sig, _) = impl_item.node {
586 self.check_trait_fn_not_const(sig.header.constness);
587 self.check_trait_fn_not_async(impl_item.span, &sig.header.asyncness.node);
591 ItemKind::Impl(unsafety, polarity, defaultness, _, None, _, _) => {
592 self.invalid_visibility(&item.vis,
593 Some("place qualifiers on individual impl items instead"));
594 if unsafety == Unsafety::Unsafe {
595 span_err!(self.session, item.span, E0197, "inherent impls cannot be unsafe");
597 if polarity == ImplPolarity::Negative {
598 self.err_handler().span_err(item.span, "inherent impls cannot be negative");
600 if defaultness == Defaultness::Default {
602 .struct_span_err(item.span, "inherent impls cannot be default")
603 .note("only trait implementations may be annotated with default").emit();
606 ItemKind::Fn(_, ref header, ref generics, _) => {
607 // We currently do not permit const generics in `const fn`, as
608 // this is tantamount to allowing compile-time dependent typing.
609 self.visit_fn_header(header);
610 if header.constness.node == Constness::Const {
611 // Look for const generics and error if we find any.
612 for param in &generics.params {
614 GenericParamKind::Const { .. } => {
618 "const parameters are not permitted in `const fn`",
627 ItemKind::ForeignMod(..) => {
628 self.invalid_visibility(
630 Some("place qualifiers on individual foreign items instead"),
633 ItemKind::Enum(ref def, _) => {
634 for variant in &def.variants {
635 for field in variant.node.data.fields() {
636 self.invalid_visibility(&field.vis, None);
640 ItemKind::Trait(is_auto, _, ref generics, ref bounds, ref trait_items) => {
641 if is_auto == IsAuto::Yes {
642 // Auto traits cannot have generics, super traits nor contain items.
643 if !generics.params.is_empty() {
644 struct_span_err!(self.session, item.span, E0567,
645 "auto traits cannot have generic parameters").emit();
647 if !bounds.is_empty() {
648 struct_span_err!(self.session, item.span, E0568,
649 "auto traits cannot have super traits").emit();
651 if !trait_items.is_empty() {
652 struct_span_err!(self.session, item.span, E0380,
653 "auto traits cannot have methods or associated items").emit();
656 self.no_questions_in_bounds(bounds, "supertraits", true);
657 for trait_item in trait_items {
658 if let TraitItemKind::Method(ref sig, ref block) = trait_item.node {
659 self.check_trait_fn_not_async(trait_item.span, &sig.header.asyncness.node);
660 self.check_trait_fn_not_const(sig.header.constness);
662 self.check_decl_no_pat(&sig.decl, |span, mut_ident| {
664 self.session.buffer_lint(
665 lint::builtin::PATTERNS_IN_FNS_WITHOUT_BODY,
667 "patterns aren't allowed in methods without bodies");
669 struct_span_err!(self.session, span, E0642,
670 "patterns aren't allowed in methods without bodies").emit();
677 ItemKind::Mod(_) => {
678 // Ensure that `path` attributes on modules are recorded as used (cf. issue #35584).
679 attr::first_attr_value_str_by_name(&item.attrs, sym::path);
680 if attr::contains_name(&item.attrs, sym::warn_directory_ownership) {
681 let lint = lint::builtin::LEGACY_DIRECTORY_OWNERSHIP;
682 let msg = "cannot declare a new module at this location";
683 self.session.buffer_lint(lint, item.id, item.span, msg);
686 ItemKind::Union(ref vdata, _) => {
687 if let VariantData::Tuple(..) | VariantData::Unit(..) = vdata {
688 self.err_handler().span_err(item.span,
689 "tuple and unit unions are not permitted");
691 if vdata.fields().is_empty() {
692 self.err_handler().span_err(item.span,
693 "unions cannot have zero fields");
696 ItemKind::Existential(ref bounds, _) => {
698 .any(|b| if let GenericBound::Trait(..) = *b { true } else { false }) {
699 let msp = MultiSpan::from_spans(bounds.iter()
700 .map(|bound| bound.span()).collect());
701 self.err_handler().span_err(msp, "at least one trait must be specified");
707 visit::walk_item(self, item)
710 fn visit_foreign_item(&mut self, fi: &'a ForeignItem) {
712 ForeignItemKind::Fn(ref decl, _) => {
713 self.check_decl_no_pat(decl, |span, _| {
714 struct_span_err!(self.session, span, E0130,
715 "patterns aren't allowed in foreign function declarations")
716 .span_label(span, "pattern not allowed in foreign function").emit();
719 ForeignItemKind::Static(..) | ForeignItemKind::Ty | ForeignItemKind::Macro(..) => {}
722 visit::walk_foreign_item(self, fi)
725 // Mirrors visit::walk_generic_args, but tracks relevant state
726 fn visit_generic_args(&mut self, _: Span, generic_args: &'a GenericArgs) {
727 match *generic_args {
728 GenericArgs::AngleBracketed(ref data) => {
729 walk_list!(self, visit_generic_arg, &data.args);
730 validate_generics_order(
733 data.args.iter().map(|arg| {
735 GenericArg::Lifetime(..) => ParamKindOrd::Lifetime,
736 GenericArg::Type(..) => ParamKindOrd::Type,
737 GenericArg::Const(..) => ParamKindOrd::Const,
738 }, None, arg.span(), None)
740 GenericPosition::Arg,
744 // Type bindings such as `Item=impl Debug` in `Iterator<Item=Debug>`
745 // are allowed to contain nested `impl Trait`.
746 self.with_impl_trait(None, |this| {
747 walk_list!(this, visit_assoc_type_binding_from_generic_args, &data.bindings);
750 GenericArgs::Parenthesized(ref data) => {
751 walk_list!(self, visit_ty, &data.inputs);
752 if let Some(ref type_) = data.output {
753 // `-> Foo` syntax is essentially an associated type binding,
754 // so it is also allowed to contain nested `impl Trait`.
755 self.with_impl_trait(None, |this| this.visit_ty_from_generic_args(type_));
761 fn visit_generics(&mut self, generics: &'a Generics) {
762 let mut prev_ty_default = None;
763 for param in &generics.params {
764 if let GenericParamKind::Type { ref default, .. } = param.kind {
765 if default.is_some() {
766 prev_ty_default = Some(param.ident.span);
767 } else if let Some(span) = prev_ty_default {
769 .span_err(span, "type parameters with a default must be trailing");
775 validate_generics_order(
778 generics.params.iter().map(|param| {
779 let ident = Some(param.ident.to_string());
780 let (kind, ident) = match ¶m.kind {
781 GenericParamKind::Lifetime { .. } => (ParamKindOrd::Lifetime, ident),
782 GenericParamKind::Type { .. } => (ParamKindOrd::Type, ident),
783 GenericParamKind::Const { ref ty } => {
784 let ty = pprust::ty_to_string(ty);
785 (ParamKindOrd::Const, Some(format!("const {}: {}", param.ident, ty)))
788 (kind, Some(&*param.bounds), param.ident.span, ident)
790 GenericPosition::Param,
794 for predicate in &generics.where_clause.predicates {
795 if let WherePredicate::EqPredicate(ref predicate) = *predicate {
797 .span_err(predicate.span, "equality constraints are not yet \
798 supported in where clauses (see #20041)");
802 visit::walk_generics(self, generics)
805 fn visit_generic_param(&mut self, param: &'a GenericParam) {
806 if let GenericParamKind::Lifetime { .. } = param.kind {
807 self.check_lifetime(param.ident);
809 visit::walk_generic_param(self, param);
812 fn visit_pat(&mut self, pat: &'a Pat) {
814 PatKind::Lit(ref expr) => {
815 self.check_expr_within_pat(expr, false);
817 PatKind::Range(ref start, ref end, _) => {
818 self.check_expr_within_pat(start, true);
819 self.check_expr_within_pat(end, true);
824 visit::walk_pat(self, pat)
827 fn visit_where_predicate(&mut self, p: &'a WherePredicate) {
828 if let &WherePredicate::BoundPredicate(ref bound_predicate) = p {
829 // A type binding, eg `for<'c> Foo: Send+Clone+'c`
830 self.check_late_bound_lifetime_defs(&bound_predicate.bound_generic_params);
832 visit::walk_where_predicate(self, p);
835 fn visit_poly_trait_ref(&mut self, t: &'a PolyTraitRef, m: &'a TraitBoundModifier) {
836 self.check_late_bound_lifetime_defs(&t.bound_generic_params);
837 visit::walk_poly_trait_ref(self, t, m);
840 fn visit_mac(&mut self, mac: &Spanned<Mac_>) {
841 // when a new macro kind is added but the author forgets to set it up for expansion
842 // because that's the only part that won't cause a compiler error
843 self.session.diagnostic()
844 .span_bug(mac.span, "macro invocation missed in expansion; did you forget to override \
845 the relevant `fold_*()` method in `PlaceholderExpander`?");
848 fn visit_fn_header(&mut self, header: &'a FnHeader) {
849 if header.asyncness.node.is_async() && self.session.rust_2015() {
850 struct_span_err!(self.session, header.asyncness.span, E0670,
851 "`async fn` is not permitted in the 2015 edition").emit();
856 pub fn check_crate(session: &Session, krate: &Crate) -> (bool, bool) {
857 let mut validator = AstValidator {
859 has_proc_macro_decls: false,
860 has_global_allocator: false,
861 outer_impl_trait: None,
862 is_impl_trait_banned: false,
863 warning_period_57979_didnt_record_next_impl_trait: false,
864 warning_period_57979_impl_trait_in_proj: false,
866 visit::walk_crate(&mut validator, krate);
868 (validator.has_proc_macro_decls, validator.has_global_allocator)