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