src/librustc/front/feature_gate.rs

   1 // Copyright 2013 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 //! Feature gating
  12 //!
  13 //! This modules implements the gating necessary for preventing certain compiler
  14 //! features from being used by default. This module will crawl a pre-expanded
  15 //! AST to ensure that there are no features which are used that are not
  16 //! enabled.
  17 //!
  18 //! Features are enabled in programs via the crate-level attributes of
  19 //! `#![feature(...)]` with a comma-separated list of features.
  20
  21 use lint;
  22
  23 use syntax::abi::RustIntrinsic;
  24 use syntax::ast::NodeId;
  25 use syntax::ast;
  26 use syntax::attr;
  27 use syntax::attr::AttrMetaMethods;
  28 use syntax::codemap::Span;
  29 use syntax::visit;
  30 use syntax::visit::Visitor;
  31 use syntax::parse::token;
  32
  33 use driver::session::Session;
  34
  35 use std::cell::Cell;
  36
  37 /// This is a list of all known features since the beginning of time. This list
  38 /// can never shrink, it may only be expanded (in order to prevent old programs
  39 /// from failing to compile). The status of each feature may change, however.
  40 static KNOWN_FEATURES: &'static [(&'static str, Status)] = &[
  41     ("globs", Active),
  42     ("macro_rules", Active),
  43     ("struct_variant", Active),
  44     ("once_fns", Active),
  45     ("asm", Active),
  46     ("managed_boxes", Active),
  47     ("non_ascii_idents", Active),
  48     ("thread_local", Active),
  49     ("link_args", Active),
  50     ("phase", Active),
  51     ("plugin_registrar", Active),
  52     ("log_syntax", Active),
  53     ("trace_macros", Active),
  54     ("concat_idents", Active),
  55     ("unsafe_destructor", Active),
  56     ("intrinsics", Active),
  57     ("lang_items", Active),
  58
  59     ("simd", Active),
  60     ("default_type_params", Active),
  61     ("quote", Active),
  62     ("linkage", Active),
  63     ("struct_inherit", Active),
  64     ("overloaded_calls", Active),
  65     ("unboxed_closure_sugar", Active),
  66
  67     ("quad_precision_float", Removed),
  68
  69     ("rustc_diagnostic_macros", Active),
  70     ("unboxed_closures", Active),
  71     ("import_shadowing", Active),
  72
  73     // if you change this list without updating src/doc/rust.md, cmr will be sad
  74
  75     // A temporary feature gate used to enable parser extensions needed
  76     // to bootstrap fix for #5723.
  77     ("issue_5723_bootstrap", Accepted),
  78
  79     // These are used to test this portion of the compiler, they don't actually
  80     // mean anything
  81     ("test_accepted_feature", Accepted),
  82     ("test_removed_feature", Removed),
  83 ];
  84
  85 enum Status {
  86     /// Represents an active feature that is currently being implemented or
  87     /// currently being considered for addition/removal.
  88     Active,
  89
  90     /// Represents a feature which has since been removed (it was once Active)
  91     Removed,
  92
  93     /// This language feature has since been Accepted (it was once Active)
  94     Accepted,
  95 }
  96
  97 /// A set of features to be used by later passes.
  98 pub struct Features {
  99     pub default_type_params: Cell<bool>,
 100     pub overloaded_calls: Cell<bool>,
 101     pub rustc_diagnostic_macros: Cell<bool>,
 102     pub import_shadowing: Cell<bool>,
 103 }
 104
 105 impl Features {
 106     pub fn new() -> Features {
 107         Features {
 108             default_type_params: Cell::new(false),
 109             overloaded_calls: Cell::new(false),
 110             rustc_diagnostic_macros: Cell::new(false),
 111             import_shadowing: Cell::new(false),
 112         }
 113     }
 114 }
 115
 116 struct Context<'a> {
 117     features: Vec<&'static str>,
 118     sess: &'a Session,
 119 }
 120
 121 impl<'a> Context<'a> {
 122     fn gate_feature(&self, feature: &str, span: Span, explain: &str) {
 123         if !self.has_feature(feature) {
 124             self.sess.span_err(span, explain);
 125             self.sess.span_note(span, format!("add #![feature({})] to the \
 126                                                crate attributes to enable",
 127                                               feature).as_slice());
 128         }
 129     }
 130
 131     fn gate_box(&self, span: Span) {
 132         self.gate_feature("managed_boxes", span,
 133                           "The managed box syntax is being replaced by the \
 134                            `std::gc::Gc` and `std::rc::Rc` types. Equivalent \
 135                            functionality to managed trait objects will be \
 136                            implemented but is currently missing.");
 137     }
 138
 139     fn has_feature(&self, feature: &str) -> bool {
 140         self.features.iter().any(|n| n.as_slice() == feature)
 141     }
 142 }
 143
 144 impl<'a> Visitor<()> for Context<'a> {
 145     fn visit_ident(&mut self, sp: Span, id: ast::Ident, _: ()) {
 146         if !token::get_ident(id).get().is_ascii() {
 147             self.gate_feature("non_ascii_idents", sp,
 148                               "non-ascii idents are not fully supported.");
 149         }
 150     }
 151
 152     fn visit_view_item(&mut self, i: &ast::ViewItem, _: ()) {
 153         match i.node {
 154             ast::ViewItemUse(ref path) => {
 155                 match path.node {
 156                     ast::ViewPathGlob(..) => {
 157                         self.gate_feature("globs", path.span,
 158                                           "glob import statements are \
 159                                            experimental and possibly buggy");
 160                     }
 161                     _ => {}
 162                 }
 163             }
 164             ast::ViewItemExternCrate(..) => {
 165                 for attr in i.attrs.iter() {
 166                     if attr.name().get() == "phase"{
 167                         self.gate_feature("phase", attr.span,
 168                                           "compile time crate loading is \
 169                                            experimental and possibly buggy");
 170                     }
 171                 }
 172             }
 173         }
 174         visit::walk_view_item(self, i, ())
 175     }
 176
 177     fn visit_item(&mut self, i: &ast::Item, _:()) {
 178         for attr in i.attrs.iter() {
 179             if attr.name().equiv(&("thread_local")) {
 180                 self.gate_feature("thread_local", i.span,
 181                                   "`#[thread_local]` is an experimental feature, and does not \
 182                                   currently handle destructors. There is no corresponding \
 183                                   `#[task_local]` mapping to the task model");
 184             }
 185         }
 186         match i.node {
 187             ast::ItemEnum(ref def, _) => {
 188                 for variant in def.variants.iter() {
 189                     match variant.node.kind {
 190                         ast::StructVariantKind(..) => {
 191                             self.gate_feature("struct_variant", variant.span,
 192                                               "enum struct variants are \
 193                                                experimental and possibly buggy");
 194                         }
 195                         _ => {}
 196                     }
 197                 }
 198             }
 199
 200             ast::ItemForeignMod(ref foreign_module) => {
 201                 if attr::contains_name(i.attrs.as_slice(), "link_args") {
 202                     self.gate_feature("link_args", i.span,
 203                                       "the `link_args` attribute is not portable \
 204                                        across platforms, it is recommended to \
 205                                        use `#[link(name = \"foo\")]` instead")
 206                 }
 207                 if foreign_module.abi == RustIntrinsic {
 208                     self.gate_feature("intrinsics",
 209                                       i.span,
 210                                       "intrinsics are subject to change")
 211                 }
 212             }
 213
 214             ast::ItemFn(..) => {
 215                 if attr::contains_name(i.attrs.as_slice(), "plugin_registrar") {
 216                     self.gate_feature("plugin_registrar", i.span,
 217                                       "compiler plugins are experimental and possibly buggy");
 218                 }
 219             }
 220
 221             ast::ItemStruct(struct_definition, _) => {
 222                 if attr::contains_name(i.attrs.as_slice(), "simd") {
 223                     self.gate_feature("simd", i.span,
 224                                       "SIMD types are experimental and possibly buggy");
 225                 }
 226                 match struct_definition.super_struct {
 227                     Some(ref path) => self.gate_feature("struct_inherit", path.span,
 228                                                         "struct inheritance is experimental \
 229                                                          and possibly buggy"),
 230                     None => {}
 231                 }
 232                 if struct_definition.is_virtual {
 233                     self.gate_feature("struct_inherit", i.span,
 234                                       "struct inheritance (`virtual` keyword) is \
 235                                        experimental and possibly buggy");
 236                 }
 237             }
 238
 239             ast::ItemImpl(..) => {
 240                 if attr::contains_name(i.attrs.as_slice(),
 241                                        "unsafe_destructor") {
 242                     self.gate_feature("unsafe_destructor",
 243                                       i.span,
 244                                       "`#[unsafe_destructor]` allows too \
 245                                        many unsafe patterns and may be \
 246                                        removed in the future");
 247                 }
 248             }
 249
 250             _ => {}
 251         }
 252
 253         visit::walk_item(self, i, ());
 254     }
 255
 256     fn visit_mac(&mut self, macro: &ast::Mac, _: ()) {
 257         let ast::MacInvocTT(ref path, _, _) = macro.node;
 258         let id = path.segments.last().unwrap().identifier;
 259         let quotes = ["quote_tokens", "quote_expr", "quote_ty",
 260                       "quote_item", "quote_pat", "quote_stmt"];
 261         let msg = " is not stable enough for use and are subject to change";
 262
 263
 264         if id == token::str_to_ident("macro_rules") {
 265             self.gate_feature("macro_rules", path.span, "macro definitions are \
 266                 not stable enough for use and are subject to change");
 267         }
 268
 269         else if id == token::str_to_ident("asm") {
 270             self.gate_feature("asm", path.span, "inline assembly is not \
 271                 stable enough for use and is subject to change");
 272         }
 273
 274         else if id == token::str_to_ident("log_syntax") {
 275             self.gate_feature("log_syntax", path.span, "`log_syntax!` is not \
 276                 stable enough for use and is subject to change");
 277         }
 278
 279         else if id == token::str_to_ident("trace_macros") {
 280             self.gate_feature("trace_macros", path.span, "`trace_macros` is not \
 281                 stable enough for use and is subject to change");
 282         }
 283
 284         else if id == token::str_to_ident("concat_idents") {
 285             self.gate_feature("concat_idents", path.span, "`concat_idents` is not \
 286                 stable enough for use and is subject to change");
 287         }
 288
 289         else {
 290             for &quote in quotes.iter() {
 291                 if id == token::str_to_ident(quote) {
 292                   self.gate_feature("quote",
 293                                     path.span,
 294                                     format!("{}{}", quote, msg).as_slice());
 295                 }
 296             }
 297         }
 298     }
 299
 300     fn visit_foreign_item(&mut self, i: &ast::ForeignItem, _: ()) {
 301         if attr::contains_name(i.attrs.as_slice(), "linkage") {
 302             self.gate_feature("linkage", i.span,
 303                               "the `linkage` attribute is experimental \
 304                                and not portable across platforms")
 305         }
 306         visit::walk_foreign_item(self, i, ())
 307     }
 308
 309     fn visit_ty(&mut self, t: &ast::Ty, _: ()) {
 310         match t.node {
 311             ast::TyClosure(closure) if closure.onceness == ast::Once => {
 312                 self.gate_feature("once_fns", t.span,
 313                                   "once functions are \
 314                                    experimental and likely to be removed");
 315
 316             },
 317             ast::TyBox(_) => { self.gate_box(t.span); }
 318             ast::TyUnboxedFn(..) => {
 319                 self.gate_feature("unboxed_closure_sugar",
 320                                   t.span,
 321                                   "unboxed closure trait sugar is experimental");
 322             }
 323             _ => {}
 324         }
 325
 326         visit::walk_ty(self, t, ());
 327     }
 328
 329     fn visit_expr(&mut self, e: &ast::Expr, _: ()) {
 330         match e.node {
 331             ast::ExprUnary(ast::UnBox, _) => {
 332                 self.gate_box(e.span);
 333             }
 334             ast::ExprUnboxedFn(..) => {
 335                 self.gate_feature("unboxed_closures",
 336                                   e.span,
 337                                   "unboxed closures are a work-in-progress \
 338                                    feature with known bugs");
 339             }
 340             _ => {}
 341         }
 342         visit::walk_expr(self, e, ());
 343     }
 344
 345     fn visit_generics(&mut self, generics: &ast::Generics, _: ()) {
 346         for type_parameter in generics.ty_params.iter() {
 347             match type_parameter.default {
 348                 Some(ty) => {
 349                     self.gate_feature("default_type_params", ty.span,
 350                                       "default type parameters are \
 351                                        experimental and possibly buggy");
 352                 }
 353                 None => {}
 354             }
 355         }
 356         visit::walk_generics(self, generics, ());
 357     }
 358
 359     fn visit_attribute(&mut self, attr: &ast::Attribute, _: ()) {
 360         if attr::contains_name([*attr], "lang") {
 361             self.gate_feature("lang_items",
 362                               attr.span,
 363                               "language items are subject to change");
 364         }
 365     }
 366
 367     fn visit_fn(&mut self,
 368                 fn_kind: &visit::FnKind,
 369                 fn_decl: &ast::FnDecl,
 370                 block: &ast::Block,
 371                 span: Span,
 372                 _: NodeId,
 373                 (): ()) {
 374         match *fn_kind {
 375             visit::FkItemFn(_, _, _, ref abi) if *abi == RustIntrinsic => {
 376                 self.gate_feature("intrinsics",
 377                                   span,
 378                                   "intrinsics are subject to change")
 379             }
 380             _ => {}
 381         }
 382         visit::walk_fn(self, fn_kind, fn_decl, block, span, ());
 383     }
 384 }
 385
 386 pub fn check_crate(sess: &Session, krate: &ast::Crate) {
 387     let mut cx = Context {
 388         features: Vec::new(),
 389         sess: sess,
 390     };
 391
 392     for attr in krate.attrs.iter() {
 393         if !attr.check_name("feature") {
 394             continue
 395         }
 396
 397         match attr.meta_item_list() {
 398             None => {
 399                 sess.span_err(attr.span, "malformed feature attribute, \
 400                                           expected #![feature(...)]");
 401             }
 402             Some(list) => {
 403                 for &mi in list.iter() {
 404                     let name = match mi.node {
 405                         ast::MetaWord(ref word) => (*word).clone(),
 406                         _ => {
 407                             sess.span_err(mi.span,
 408                                           "malformed feature, expected just \
 409                                            one word");
 410                             continue
 411                         }
 412                     };
 413                     match KNOWN_FEATURES.iter()
 414                                         .find(|& &(n, _)| name.equiv(&n)) {
 415                         Some(&(name, Active)) => { cx.features.push(name); }
 416                         Some(&(_, Removed)) => {
 417                             sess.span_err(mi.span, "feature has been removed");
 418                         }
 419                         Some(&(_, Accepted)) => {
 420                             sess.span_warn(mi.span, "feature has added to rust, \
 421                                                      directive not necessary");
 422                         }
 423                         None => {
 424                             sess.add_lint(lint::builtin::UNKNOWN_FEATURES,
 425                                           ast::CRATE_NODE_ID,
 426                                           mi.span,
 427                                           "unknown feature".to_string());
 428                         }
 429                     }
 430                 }
 431             }
 432         }
 433     }
 434
 435     visit::walk_crate(&mut cx, krate, ());
 436
 437     sess.abort_if_errors();
 438
 439     sess.features.default_type_params.set(cx.has_feature("default_type_params"));
 440     sess.features.overloaded_calls.set(cx.has_feature("overloaded_calls"));
 441     sess.features.rustc_diagnostic_macros.set(cx.has_feature("rustc_diagnostic_macros"));
 442     sess.features.import_shadowing.set(cx.has_feature("import_shadowing"));
 443 }
 444