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_non_exhaustive_attribute(&self, variant: &Variant) {
  46         let has_non_exhaustive = variant.node.attrs.iter()
  47             .any(|attr| attr.check_name("non_exhaustive"));
  48         if has_non_exhaustive {
  49             self.err_handler().span_err(variant.span,
  50                                         "#[non_exhaustive] is not yet supported on variants");
  51         }
  52     }
  53
  54     fn invalid_visibility(&self, vis: &Visibility, span: Span, note: Option<&str>) {
  55         if vis != &Visibility::Inherited {
  56             let mut err = struct_span_err!(self.session,
  57                                            span,
  58                                            E0449,
  59                                            "unnecessary visibility qualifier");
  60             if vis == &Visibility::Public {
  61                 err.span_label(span, "`pub` not needed here");
  62             }
  63             if let Some(note) = note {
  64                 err.note(note);
  65             }
  66             err.emit();
  67         }
  68     }
  69
  70     fn check_decl_no_pat<ReportFn: Fn(Span, bool)>(&self, decl: &FnDecl, report_err: ReportFn) {
  71         for arg in &decl.inputs {
  72             match arg.pat.node {
  73                 PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), _, None) |
  74                 PatKind::Wild => {}
  75                 PatKind::Ident(BindingMode::ByValue(Mutability::Mutable), _, None) =>
  76                     report_err(arg.pat.span, true),
  77                 _ => report_err(arg.pat.span, false),
  78             }
  79         }
  80     }
  81
  82     fn check_trait_fn_not_const(&self, constness: Spanned<Constness>) {
  83         match constness.node {
  84             Constness::Const => {
  85                 struct_span_err!(self.session, constness.span, E0379,
  86                                  "trait fns cannot be declared const")
  87                     .span_label(constness.span, "trait fns cannot be const")
  88                     .emit();
  89             }
  90             _ => {}
  91         }
  92     }
  93
  94     fn no_questions_in_bounds(&self, bounds: &TyParamBounds, where_: &str, is_trait: bool) {
  95         for bound in bounds {
  96             if let TraitTyParamBound(ref poly, TraitBoundModifier::Maybe) = *bound {
  97                 let mut err = self.err_handler().struct_span_err(poly.span,
  98                                     &format!("`?Trait` is not permitted in {}", where_));
  99                 if is_trait {
 100                     err.note(&format!("traits are `?{}` by default", poly.trait_ref.path));
 101                 }
 102                 err.emit();
 103             }
 104         }
 105     }
 106
 107     /// matches '-' lit | lit (cf. parser::Parser::parse_pat_literal_maybe_minus),
 108     /// or path for ranges.
 109     ///
 110     /// FIXME: do we want to allow expr -> pattern conversion to create path expressions?
 111     /// That means making this work:
 112     ///
 113     /// ```rust,ignore (FIXME)
 114     ///     struct S;
 115     ///     macro_rules! m {
 116     ///         ($a:expr) => {
 117     ///             let $a = S;
 118     ///         }
 119     ///     }
 120     ///     m!(S);
 121     /// ```
 122     fn check_expr_within_pat(&self, expr: &Expr, allow_paths: bool) {
 123         match expr.node {
 124             ExprKind::Lit(..) => {}
 125             ExprKind::Path(..) if allow_paths => {}
 126             ExprKind::Unary(UnOp::Neg, ref inner)
 127                 if match inner.node { ExprKind::Lit(_) => true, _ => false } => {}
 128             _ => self.err_handler().span_err(expr.span, "arbitrary expressions aren't allowed \
 129                                                          in patterns")
 130         }
 131     }
 132 }
 133
 134 impl<'a> Visitor<'a> for AstValidator<'a> {
 135     fn visit_expr(&mut self, expr: &'a Expr) {
 136         match expr.node {
 137             ExprKind::While(.., Some(ident)) |
 138             ExprKind::Loop(_, Some(ident)) |
 139             ExprKind::WhileLet(.., Some(ident)) |
 140             ExprKind::ForLoop(.., Some(ident)) |
 141             ExprKind::Break(Some(ident), _) |
 142             ExprKind::Continue(Some(ident)) => {
 143                 self.check_label(ident.node, ident.span);
 144             }
 145             _ => {}
 146         }
 147
 148         visit::walk_expr(self, expr)
 149     }
 150
 151     fn visit_ty(&mut self, ty: &'a Ty) {
 152         match ty.node {
 153             TyKind::BareFn(ref bfty) => {
 154                 self.check_decl_no_pat(&bfty.decl, |span, _| {
 155                     struct_span_err!(self.session, span, E0561,
 156                                      "patterns aren't allowed in function pointer types").emit();
 157                 });
 158             }
 159             TyKind::TraitObject(ref bounds, ..) => {
 160                 let mut any_lifetime_bounds = false;
 161                 for bound in bounds {
 162                     if let RegionTyParamBound(ref lifetime) = *bound {
 163                         if any_lifetime_bounds {
 164                             span_err!(self.session, lifetime.span, E0226,
 165                                       "only a single explicit lifetime bound is permitted");
 166                             break;
 167                         }
 168                         any_lifetime_bounds = true;
 169                     }
 170                 }
 171                 self.no_questions_in_bounds(bounds, "trait object types", false);
 172             }
 173             TyKind::ImplTrait(ref bounds) => {
 174                 if !bounds.iter()
 175                           .any(|b| if let TraitTyParamBound(..) = *b { true } else { false }) {
 176                     self.err_handler().span_err(ty.span, "at least one trait must be specified");
 177                 }
 178             }
 179             _ => {}
 180         }
 181
 182         visit::walk_ty(self, ty)
 183     }
 184
 185     fn visit_path(&mut self, path: &'a Path, _: NodeId) {
 186         if path.segments.len() >= 2 && path.is_global() {
 187             let ident = path.segments[1].identifier;
 188             if token::Ident(ident).is_path_segment_keyword() {
 189                 self.err_handler()
 190                     .span_err(path.span, &format!("global paths cannot start with `{}`", ident));
 191             }
 192         }
 193
 194         visit::walk_path(self, path)
 195     }
 196
 197     fn visit_item(&mut self, item: &'a Item) {
 198         match item.node {
 199             ItemKind::Use(ref view_path) => {
 200                 let path = view_path.node.path();
 201                 path.segments.iter().find(|segment| segment.parameters.is_some()).map(|segment| {
 202                     self.err_handler().span_err(segment.parameters.as_ref().unwrap().span(),
 203                                                 "generic arguments in import path");
 204                 });
 205             }
 206             ItemKind::Impl(.., Some(..), _, ref impl_items) => {
 207                 self.invalid_visibility(&item.vis, item.span, None);
 208                 for impl_item in impl_items {
 209                     self.invalid_visibility(&impl_item.vis, impl_item.span, None);
 210                     if let ImplItemKind::Method(ref sig, _) = impl_item.node {
 211                         self.check_trait_fn_not_const(sig.constness);
 212                     }
 213                 }
 214             }
 215             ItemKind::Impl(.., None, _, _) => {
 216                 self.invalid_visibility(&item.vis,
 217                                         item.span,
 218                                         Some("place qualifiers on individual impl items instead"));
 219             }
 220             ItemKind::AutoImpl(..) => {
 221                 self.invalid_visibility(&item.vis, item.span, None);
 222             }
 223             ItemKind::ForeignMod(..) => {
 224                 self.invalid_visibility(&item.vis,
 225                                         item.span,
 226                                         Some("place qualifiers on individual foreign items \
 227                                               instead"));
 228             }
 229             ItemKind::Enum(ref def, _) => {
 230                 for variant in &def.variants {
 231                     self.invalid_non_exhaustive_attribute(variant);
 232                     for field in variant.node.data.fields() {
 233                         self.invalid_visibility(&field.vis, field.span, None);
 234                     }
 235                 }
 236             }
 237             ItemKind::Trait(is_auto, _, ref generics, ref bounds, ref trait_items) => {
 238                 if is_auto == IsAuto::Yes {
 239                     // Auto traits cannot have generics, super traits nor contain items.
 240                     if !generics.ty_params.is_empty() {
 241                         self.err_handler().span_err(item.span,
 242                                                     "auto traits cannot have generics");
 243                     }
 244                     if !bounds.is_empty() {
 245                         self.err_handler().span_err(item.span,
 246                                                     "auto traits cannot have super traits");
 247                     }
 248                     if !trait_items.is_empty() {
 249                         self.err_handler().span_err(item.span,
 250                                                     "auto traits cannot contain items");
 251                     }
 252                 }
 253                 self.no_questions_in_bounds(bounds, "supertraits", true);
 254                 for trait_item in trait_items {
 255                     if let TraitItemKind::Method(ref sig, ref block) = trait_item.node {
 256                         self.check_trait_fn_not_const(sig.constness);
 257                         if block.is_none() {
 258                             self.check_decl_no_pat(&sig.decl, |span, mut_ident| {
 259                                 if mut_ident {
 260                                     self.session.buffer_lint(
 261                                         lint::builtin::PATTERNS_IN_FNS_WITHOUT_BODY,
 262                                         trait_item.id, span,
 263                                         "patterns aren't allowed in methods without bodies");
 264                                 } else {
 265                                     struct_span_err!(self.session, span, E0642,
 266                                         "patterns aren't allowed in methods without bodies").emit();
 267                                 }
 268                             });
 269                         }
 270                     }
 271                 }
 272             }
 273             ItemKind::Mod(_) => {
 274                 // Ensure that `path` attributes on modules are recorded as used (c.f. #35584).
 275                 attr::first_attr_value_str_by_name(&item.attrs, "path");
 276                 if item.attrs.iter().any(|attr| attr.check_name("warn_directory_ownership")) {
 277                     let lint = lint::builtin::LEGACY_DIRECTORY_OWNERSHIP;
 278                     let msg = "cannot declare a new module at this location";
 279                     self.session.buffer_lint(lint, item.id, item.span, msg);
 280                 }
 281             }
 282             ItemKind::Union(ref vdata, _) => {
 283                 if !vdata.is_struct() {
 284                     self.err_handler().span_err(item.span,
 285                                                 "tuple and unit unions are not permitted");
 286                 }
 287                 if vdata.fields().len() == 0 {
 288                     self.err_handler().span_err(item.span,
 289                                                 "unions cannot have zero fields");
 290                 }
 291             }
 292             _ => {}
 293         }
 294
 295         visit::walk_item(self, item)
 296     }
 297
 298     fn visit_foreign_item(&mut self, fi: &'a ForeignItem) {
 299         match fi.node {
 300             ForeignItemKind::Fn(ref decl, _) => {
 301                 self.check_decl_no_pat(decl, |span, _| {
 302                     struct_span_err!(self.session, span, E0130,
 303                                      "patterns aren't allowed in foreign function declarations")
 304                         .span_label(span, "pattern not allowed in foreign function").emit();
 305                 });
 306             }
 307             ForeignItemKind::Static(..) | ForeignItemKind::Ty => {}
 308         }
 309
 310         visit::walk_foreign_item(self, fi)
 311     }
 312
 313     fn visit_vis(&mut self, vis: &'a Visibility) {
 314         match *vis {
 315             Visibility::Restricted { ref path, .. } => {
 316                 path.segments.iter().find(|segment| segment.parameters.is_some()).map(|segment| {
 317                     self.err_handler().span_err(segment.parameters.as_ref().unwrap().span(),
 318                                                 "generic arguments in visibility path");
 319                 });
 320             }
 321             _ => {}
 322         }
 323
 324         visit::walk_vis(self, vis)
 325     }
 326
 327     fn visit_generics(&mut self, g: &'a Generics) {
 328         let mut seen_default = None;
 329         for ty_param in &g.ty_params {
 330             if ty_param.default.is_some() {
 331                 seen_default = Some(ty_param.span);
 332             } else if let Some(span) = seen_default {
 333                 self.err_handler()
 334                     .span_err(span, "type parameters with a default must be trailing");
 335                 break
 336             }
 337         }
 338         for predicate in &g.where_clause.predicates {
 339             if let WherePredicate::EqPredicate(ref predicate) = *predicate {
 340                 self.err_handler().span_err(predicate.span, "equality constraints are not yet \
 341                                                              supported in where clauses (#20041)");
 342             }
 343         }
 344         visit::walk_generics(self, g)
 345     }
 346
 347     fn visit_pat(&mut self, pat: &'a Pat) {
 348         match pat.node {
 349             PatKind::Lit(ref expr) => {
 350                 self.check_expr_within_pat(expr, false);
 351             }
 352             PatKind::Range(ref start, ref end, _) => {
 353                 self.check_expr_within_pat(start, true);
 354                 self.check_expr_within_pat(end, true);
 355             }
 356             _ => {}
 357         }
 358
 359         visit::walk_pat(self, pat)
 360     }
 361 }
 362
 363 pub fn check_crate(session: &Session, krate: &Crate) {
 364     visit::walk_crate(&mut AstValidator { session: session }, krate)
 365 }