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