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