src/librustc_passes/ast_validation.rs

   1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // Validate AST before lowering it to HIR
  12 //
  13 // This pass is supposed to catch things that fit into AST data structures,
  14 // but not permitted by the language. It runs after expansion when AST is frozen,
  15 // so it can check for erroneous constructions produced by syntax extensions.
  16 // This pass is supposed to perform only simple checks not requiring name resolution
  17 // or type checking or some other kind of complex analysis.
  18
  19 use rustc::lint;
  20 use rustc::session::Session;
  21 use syntax::ast::*;
  22 use syntax::attr;
  23 use syntax::codemap::Spanned;
  24 use syntax::parse::token;
  25 use syntax::symbol::keywords;
  26 use syntax::visit::{self, Visitor};
  27 use syntax_pos::Span;
  28 use errors;
  29
  30 struct AstValidator<'a> {
  31     session: &'a Session,
  32 }
  33
  34 impl<'a> AstValidator<'a> {
  35     fn err_handler(&self) -> &errors::Handler {
  36         &self.session.parse_sess.span_diagnostic
  37     }
  38
  39     fn check_label(&self, label: Ident, span: Span, id: NodeId) {
  40         if label.name == keywords::StaticLifetime.name() {
  41             self.err_handler().span_err(span, &format!("invalid label name `{}`", label.name));
  42         }
  43         if label.name == "'_" {
  44             self.session.add_lint(lint::builtin::LIFETIME_UNDERSCORE,
  45                                   id,
  46                                   span,
  47                                   format!("invalid label name `{}`", label.name));
  48         }
  49     }
  50
  51     fn invalid_visibility(&self, vis: &Visibility, span: Span, note: Option<&str>) {
  52         if vis != &Visibility::Inherited {
  53             let mut err = struct_span_err!(self.session,
  54                                            span,
  55                                            E0449,
  56                                            "unnecessary visibility qualifier");
  57             if vis == &Visibility::Public {
  58                 err.span_label(span, &format!("`pub` not needed here"));
  59             }
  60             if let Some(note) = note {
  61                 err.note(note);
  62             }
  63             err.emit();
  64         }
  65     }
  66
  67     fn check_decl_no_pat<ReportFn: Fn(Span, bool)>(&self, decl: &FnDecl, report_err: ReportFn) {
  68         for arg in &decl.inputs {
  69             match arg.pat.node {
  70                 PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), _, None) |
  71                 PatKind::Wild => {}
  72                 PatKind::Ident(..) => report_err(arg.pat.span, true),
  73                 _ => report_err(arg.pat.span, false),
  74             }
  75         }
  76     }
  77
  78     fn check_trait_fn_not_const(&self, constness: Spanned<Constness>) {
  79         match constness.node {
  80             Constness::Const => {
  81                 struct_span_err!(self.session, constness.span, E0379,
  82                                  "trait fns cannot be declared const")
  83                     .span_label(constness.span, &format!("trait fns cannot be const"))
  84                     .emit();
  85             }
  86             _ => {}
  87         }
  88     }
  89
  90     fn no_questions_in_bounds(&self, bounds: &TyParamBounds, where_: &str, is_trait: bool) {
  91         for bound in bounds {
  92             if let TraitTyParamBound(ref poly, TraitBoundModifier::Maybe) = *bound {
  93                 let mut err = self.err_handler().struct_span_err(poly.span,
  94                                     &format!("`?Trait` is not permitted in {}", where_));
  95                 if is_trait {
  96                     err.note(&format!("traits are `?{}` by default", poly.trait_ref.path));
  97                 }
  98                 err.emit();
  99             }
 100         }
 101     }
 102 }
 103
 104 impl<'a> Visitor<'a> for AstValidator<'a> {
 105     fn visit_lifetime(&mut self, lt: &'a Lifetime) {
 106         if lt.name == "'_" {
 107             self.session.add_lint(lint::builtin::LIFETIME_UNDERSCORE,
 108                                   lt.id,
 109                                   lt.span,
 110                                   format!("invalid lifetime name `{}`", lt.name));
 111         }
 112
 113         visit::walk_lifetime(self, lt)
 114     }
 115
 116     fn visit_expr(&mut self, expr: &'a Expr) {
 117         match expr.node {
 118             ExprKind::While(.., Some(ident)) |
 119             ExprKind::Loop(_, Some(ident)) |
 120             ExprKind::WhileLet(.., Some(ident)) |
 121             ExprKind::ForLoop(.., Some(ident)) |
 122             ExprKind::Break(Some(ident), _) |
 123             ExprKind::Continue(Some(ident)) => {
 124                 self.check_label(ident.node, ident.span, expr.id);
 125             }
 126             _ => {}
 127         }
 128
 129         visit::walk_expr(self, expr)
 130     }
 131
 132     fn visit_ty(&mut self, ty: &'a Ty) {
 133         match ty.node {
 134             TyKind::BareFn(ref bfty) => {
 135                 self.check_decl_no_pat(&bfty.decl, |span, _| {
 136                     let mut err = struct_span_err!(self.session,
 137                                                    span,
 138                                                    E0561,
 139                                                    "patterns aren't allowed in function pointer \
 140                                                     types");
 141                     err.span_note(span,
 142                                   "this is a recent error, see issue #35203 for more details");
 143                     err.emit();
 144                 });
 145             }
 146             TyKind::TraitObject(ref bounds) => {
 147                 let mut any_lifetime_bounds = false;
 148                 for bound in bounds {
 149                     if let RegionTyParamBound(ref lifetime) = *bound {
 150                         if any_lifetime_bounds {
 151                             span_err!(self.session, lifetime.span, E0226,
 152                                       "only a single explicit lifetime bound is permitted");
 153                             break;
 154                         }
 155                         any_lifetime_bounds = true;
 156                     }
 157                 }
 158                 self.no_questions_in_bounds(bounds, "trait object types", false);
 159             }
 160             TyKind::ImplTrait(ref bounds) => {
 161                 if !bounds.iter()
 162                           .any(|b| if let TraitTyParamBound(..) = *b { true } else { false }) {
 163                     self.err_handler().span_err(ty.span, "at least one trait must be specified");
 164                 }
 165             }
 166             _ => {}
 167         }
 168
 169         visit::walk_ty(self, ty)
 170     }
 171
 172     fn visit_path(&mut self, path: &'a Path, id: NodeId) {
 173         if path.segments.len() >= 2 && path.is_global() {
 174             let ident = path.segments[1].identifier;
 175             if token::Ident(ident).is_path_segment_keyword() {
 176                 self.session.add_lint(lint::builtin::SUPER_OR_SELF_IN_GLOBAL_PATH,
 177                                       id,
 178                                       path.span,
 179                                       format!("global paths cannot start with `{}`", ident));
 180             }
 181         }
 182
 183         visit::walk_path(self, path)
 184     }
 185
 186     fn visit_item(&mut self, item: &'a Item) {
 187         match item.node {
 188             ItemKind::Use(ref view_path) => {
 189                 let path = view_path.node.path();
 190                 if path.segments.iter().any(|segment| segment.parameters.is_some()) {
 191                     self.err_handler()
 192                         .span_err(path.span, "type or lifetime parameters in import path");
 193                 }
 194             }
 195             ItemKind::Impl(.., Some(..), _, ref impl_items) => {
 196                 self.invalid_visibility(&item.vis, item.span, None);
 197                 for impl_item in impl_items {
 198                     self.invalid_visibility(&impl_item.vis, impl_item.span, None);
 199                     if let ImplItemKind::Method(ref sig, _) = impl_item.node {
 200                         self.check_trait_fn_not_const(sig.constness);
 201                     }
 202                 }
 203             }
 204             ItemKind::Impl(.., None, _, _) => {
 205                 self.invalid_visibility(&item.vis,
 206                                         item.span,
 207                                         Some("place qualifiers on individual impl items instead"));
 208             }
 209             ItemKind::DefaultImpl(..) => {
 210                 self.invalid_visibility(&item.vis, item.span, None);
 211             }
 212             ItemKind::ForeignMod(..) => {
 213                 self.invalid_visibility(&item.vis,
 214                                         item.span,
 215                                         Some("place qualifiers on individual foreign items \
 216                                               instead"));
 217             }
 218             ItemKind::Enum(ref def, _) => {
 219                 for variant in &def.variants {
 220                     for field in variant.node.data.fields() {
 221                         self.invalid_visibility(&field.vis, field.span, None);
 222                     }
 223                 }
 224             }
 225             ItemKind::Trait(.., ref bounds, ref trait_items) => {
 226                 self.no_questions_in_bounds(bounds, "supertraits", true);
 227                 for trait_item in trait_items {
 228                     if let TraitItemKind::Method(ref sig, ref block) = trait_item.node {
 229                         self.check_trait_fn_not_const(sig.constness);
 230                         if block.is_none() {
 231                             self.check_decl_no_pat(&sig.decl, |span, _| {
 232                                 self.session.add_lint(lint::builtin::PATTERNS_IN_FNS_WITHOUT_BODY,
 233                                                       trait_item.id, span,
 234                                                       "patterns aren't allowed in methods \
 235                                                        without bodies".to_string());
 236                             });
 237                         }
 238                     }
 239                 }
 240             }
 241             ItemKind::Mod(_) => {
 242                 // Ensure that `path` attributes on modules are recorded as used (c.f. #35584).
 243                 attr::first_attr_value_str_by_name(&item.attrs, "path");
 244                 if item.attrs.iter().any(|attr| attr.check_name("warn_directory_ownership")) {
 245                     let lint = lint::builtin::LEGACY_DIRECTORY_OWNERSHIP;
 246                     let msg = "cannot declare a new module at this location";
 247                     self.session.add_lint(lint, item.id, item.span, msg.to_string());
 248                 }
 249             }
 250             ItemKind::Union(ref vdata, _) => {
 251                 if !vdata.is_struct() {
 252                     self.err_handler().span_err(item.span,
 253                                                 "tuple and unit unions are not permitted");
 254                 }
 255                 if vdata.fields().len() == 0 {
 256                     self.err_handler().span_err(item.span,
 257                                                 "unions cannot have zero fields");
 258                 }
 259             }
 260             _ => {}
 261         }
 262
 263         visit::walk_item(self, item)
 264     }
 265
 266     fn visit_foreign_item(&mut self, fi: &'a ForeignItem) {
 267         match fi.node {
 268             ForeignItemKind::Fn(ref decl, _) => {
 269                 self.check_decl_no_pat(decl, |span, is_recent| {
 270                     let mut err = struct_span_err!(self.session,
 271                                                    span,
 272                                                    E0130,
 273                                                    "patterns aren't allowed in foreign function \
 274                                                     declarations");
 275                     err.span_label(span, &format!("pattern not allowed in foreign function"));
 276                     if is_recent {
 277                         err.span_note(span,
 278                                       "this is a recent error, see issue #35203 for more details");
 279                     }
 280                     err.emit();
 281                 });
 282             }
 283             ForeignItemKind::Static(..) => {}
 284         }
 285
 286         visit::walk_foreign_item(self, fi)
 287     }
 288
 289     fn visit_vis(&mut self, vis: &'a Visibility) {
 290         match *vis {
 291             Visibility::Restricted { ref path, .. } => {
 292                 if !path.segments.iter().all(|segment| segment.parameters.is_none()) {
 293                     self.err_handler()
 294                         .span_err(path.span, "type or lifetime parameters in visibility path");
 295                 }
 296             }
 297             _ => {}
 298         }
 299
 300         visit::walk_vis(self, vis)
 301     }
 302
 303     fn visit_generics(&mut self, g: &'a Generics) {
 304         let mut seen_default = None;
 305         for ty_param in &g.ty_params {
 306             if ty_param.default.is_some() {
 307                 seen_default = Some(ty_param.span);
 308             } else if let Some(span) = seen_default {
 309                 self.err_handler()
 310                     .span_err(span, "type parameters with a default must be trailing");
 311                 break
 312             }
 313         }
 314         for predicate in &g.where_clause.predicates {
 315             if let WherePredicate::EqPredicate(ref predicate) = *predicate {
 316                 self.err_handler().span_err(predicate.span, "equality constraints are not yet \
 317                                                              supported in where clauses (#20041)");
 318             }
 319         }
 320         visit::walk_generics(self, g)
 321     }
 322 }
 323
 324 pub fn check_crate(session: &Session, krate: &Crate) {
 325     visit::walk_crate(&mut AstValidator { session: session }, krate)
 326 }