src/libsyntax/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 use self::Status::*;
  21
  22 use abi::RustIntrinsic;
  23 use ast::NodeId;
  24 use ast;
  25 use attr;
  26 use attr::AttrMetaMethods;
  27 use codemap::{CodeMap, Span};
  28 use diagnostic::SpanHandler;
  29 use visit;
  30 use visit::Visitor;
  31 use parse::token;
  32
  33 use std::slice;
  34 use std::ascii::AsciiExt;
  35
  36
  37 // if you change this list without updating src/doc/reference.md, @cmr will be sad
  38 static KNOWN_FEATURES: &'static [(&'static str, Status)] = &[
  39     ("globs", Accepted),
  40     ("macro_rules", Active),
  41     ("struct_variant", Accepted),
  42     ("asm", Active),
  43     ("managed_boxes", Removed),
  44     ("non_ascii_idents", Active),
  45     ("thread_local", Active),
  46     ("link_args", Active),
  47     ("phase", Active),
  48     ("plugin_registrar", Active),
  49     ("log_syntax", Active),
  50     ("trace_macros", Active),
  51     ("concat_idents", Active),
  52     ("unsafe_destructor", Active),
  53     ("intrinsics", Active),
  54     ("lang_items", Active),
  55
  56     ("simd", Active),
  57     ("default_type_params", Accepted),
  58     ("quote", Active),
  59     ("link_llvm_intrinsics", Active),
  60     ("linkage", Active),
  61     ("struct_inherit", Removed),
  62
  63     ("quad_precision_float", Removed),
  64
  65     ("rustc_diagnostic_macros", Active),
  66     ("unboxed_closures", Active),
  67     ("import_shadowing", Active),
  68     ("advanced_slice_patterns", Active),
  69     ("tuple_indexing", Accepted),
  70     ("associated_types", Accepted),
  71     ("visible_private_types", Active),
  72     ("slicing_syntax", Active),
  73
  74     ("if_let", Accepted),
  75     ("while_let", Accepted),
  76
  77     // A temporary feature gate used to enable parser extensions needed
  78     // to bootstrap fix for #5723.
  79     ("issue_5723_bootstrap", Accepted),
  80
  81     // A way to temporarily opt out of opt in copy. This will *never* be accepted.
  82     ("opt_out_copy", Deprecated),
  83
  84     // A way to temporarily opt out of the new orphan rules. This will *never* be accepted.
  85     ("old_orphan_check", Deprecated),
  86
  87     // OIBIT specific features
  88     ("optin_builtin_traits", Active),
  89
  90     // These are used to test this portion of the compiler, they don't actually
  91     // mean anything
  92     ("test_accepted_feature", Accepted),
  93     ("test_removed_feature", Removed),
  94 ];
  95
  96 enum Status {
  97     /// Represents an active feature that is currently being implemented or
  98     /// currently being considered for addition/removal.
  99     Active,
 100
 101     /// Represents a feature gate that is temporarily enabling deprecated behavior.
 102     /// This gate will never be accepted.
 103     Deprecated,
 104
 105     /// Represents a feature which has since been removed (it was once Active)
 106     Removed,
 107
 108     /// This language feature has since been Accepted (it was once Active)
 109     Accepted,
 110 }
 111
 112 /// A set of features to be used by later passes.
 113 #[derive(Copy)]
 114 pub struct Features {
 115     pub unboxed_closures: bool,
 116     pub rustc_diagnostic_macros: bool,
 117     pub import_shadowing: bool,
 118     pub visible_private_types: bool,
 119     pub quote: bool,
 120     pub opt_out_copy: bool,
 121     pub old_orphan_check: bool,
 122 }
 123
 124 impl Features {
 125     pub fn new() -> Features {
 126         Features {
 127             unboxed_closures: false,
 128             rustc_diagnostic_macros: false,
 129             import_shadowing: false,
 130             visible_private_types: false,
 131             quote: false,
 132             opt_out_copy: false,
 133             old_orphan_check: false,
 134         }
 135     }
 136 }
 137
 138 struct Context<'a> {
 139     features: Vec<&'static str>,
 140     span_handler: &'a SpanHandler,
 141     cm: &'a CodeMap,
 142 }
 143
 144 impl<'a> Context<'a> {
 145     fn gate_feature(&self, feature: &str, span: Span, explain: &str) {
 146         if !self.has_feature(feature) {
 147             self.span_handler.span_err(span, explain);
 148             self.span_handler.span_help(span, format!("add #![feature({})] to the \
 149                                                        crate attributes to enable",
 150                                                       feature)[]);
 151         }
 152     }
 153
 154     fn has_feature(&self, feature: &str) -> bool {
 155         self.features.iter().any(|&n| n == feature)
 156     }
 157 }
 158
 159 struct MacroVisitor<'a> {
 160     context: &'a Context<'a>
 161 }
 162
 163 impl<'a, 'v> Visitor<'v> for MacroVisitor<'a> {
 164     fn visit_view_item(&mut self, i: &ast::ViewItem) {
 165         match i.node {
 166             ast::ViewItemExternCrate(..) => {
 167                 for attr in i.attrs.iter() {
 168                     if attr.name().get() == "phase"{
 169                         self.context.gate_feature("phase", attr.span,
 170                                           "compile time crate loading is \
 171                                            experimental and possibly buggy");
 172                     }
 173                 }
 174             },
 175             _ => { }
 176         }
 177         visit::walk_view_item(self, i)
 178     }
 179
 180     fn visit_mac(&mut self, macro: &ast::Mac) {
 181         let ast::MacInvocTT(ref path, _, _) = macro.node;
 182         let id = path.segments.last().unwrap().identifier;
 183
 184         if id == token::str_to_ident("macro_rules") {
 185             self.context.gate_feature("macro_rules", path.span, "macro definitions are \
 186                 not stable enough for use and are subject to change");
 187         }
 188
 189         else if id == token::str_to_ident("asm") {
 190             self.context.gate_feature("asm", path.span, "inline assembly is not \
 191                 stable enough for use and is subject to change");
 192         }
 193
 194         else if id == token::str_to_ident("log_syntax") {
 195             self.context.gate_feature("log_syntax", path.span, "`log_syntax!` is not \
 196                 stable enough for use and is subject to change");
 197         }
 198
 199         else if id == token::str_to_ident("trace_macros") {
 200             self.context.gate_feature("trace_macros", path.span, "`trace_macros` is not \
 201                 stable enough for use and is subject to change");
 202         }
 203
 204         else if id == token::str_to_ident("concat_idents") {
 205             self.context.gate_feature("concat_idents", path.span, "`concat_idents` is not \
 206                 stable enough for use and is subject to change");
 207         }
 208     }
 209 }
 210
 211 struct PostExpansionVisitor<'a> {
 212     context: &'a Context<'a>
 213 }
 214
 215 impl<'a> PostExpansionVisitor<'a> {
 216     fn gate_feature(&self, feature: &str, span: Span, explain: &str) {
 217         if !self.context.cm.span_is_internal(span) {
 218             self.context.gate_feature(feature, span, explain)
 219         }
 220     }
 221 }
 222
 223 impl<'a, 'v> Visitor<'v> for PostExpansionVisitor<'a> {
 224     fn visit_name(&mut self, sp: Span, name: ast::Name) {
 225         if !token::get_name(name).get().is_ascii() {
 226             self.gate_feature("non_ascii_idents", sp,
 227                               "non-ascii idents are not fully supported.");
 228         }
 229     }
 230
 231     fn visit_view_item(&mut self, i: &ast::ViewItem) {
 232         match i.node {
 233             ast::ViewItemUse(..) => {}
 234             ast::ViewItemExternCrate(..) => {
 235                 for attr in i.attrs.iter() {
 236                     if attr.name().get() == "phase"{
 237                         self.gate_feature("phase", attr.span,
 238                                           "compile time crate loading is \
 239                                            experimental and possibly buggy");
 240                     }
 241                 }
 242             }
 243         }
 244         visit::walk_view_item(self, i)
 245     }
 246
 247     fn visit_item(&mut self, i: &ast::Item) {
 248         for attr in i.attrs.iter() {
 249             if attr.name() == "thread_local" {
 250                 self.gate_feature("thread_local", i.span,
 251                                   "`#[thread_local]` is an experimental feature, and does not \
 252                                   currently handle destructors. There is no corresponding \
 253                                   `#[task_local]` mapping to the task model");
 254             } else if attr.name() == "linkage" {
 255                 self.gate_feature("linkage", i.span,
 256                                   "the `linkage` attribute is experimental \
 257                                    and not portable across platforms")
 258             }
 259         }
 260         match i.node {
 261             ast::ItemForeignMod(ref foreign_module) => {
 262                 if attr::contains_name(i.attrs[], "link_args") {
 263                     self.gate_feature("link_args", i.span,
 264                                       "the `link_args` attribute is not portable \
 265                                        across platforms, it is recommended to \
 266                                        use `#[link(name = \"foo\")]` instead")
 267                 }
 268                 if foreign_module.abi == RustIntrinsic {
 269                     self.gate_feature("intrinsics",
 270                                       i.span,
 271                                       "intrinsics are subject to change")
 272                 }
 273             }
 274
 275             ast::ItemFn(..) => {
 276                 if attr::contains_name(i.attrs[], "plugin_registrar") {
 277                     self.gate_feature("plugin_registrar", i.span,
 278                                       "compiler plugins are experimental and possibly buggy");
 279                 }
 280             }
 281
 282             ast::ItemStruct(..) => {
 283                 if attr::contains_name(i.attrs[], "simd") {
 284                     self.gate_feature("simd", i.span,
 285                                       "SIMD types are experimental and possibly buggy");
 286                 }
 287             }
 288
 289             ast::ItemImpl(_, polarity, _, _, _, ref items) => {
 290                 match polarity {
 291                     ast::ImplPolarity::Negative => {
 292                         self.gate_feature("optin_builtin_traits",
 293                                           i.span,
 294                                           "negative trait bounds are not yet fully implemented; \
 295                                           use marker types for now");
 296                     },
 297                     _ => {}
 298                 }
 299
 300                 if attr::contains_name(i.attrs[],
 301                                        "unsafe_destructor") {
 302                     self.gate_feature("unsafe_destructor",
 303                                       i.span,
 304                                       "`#[unsafe_destructor]` allows too \
 305                                        many unsafe patterns and may be \
 306                                        removed in the future");
 307                 }
 308
 309                 if attr::contains_name(i.attrs[],
 310                                        "old_orphan_check") {
 311                     self.gate_feature(
 312                         "old_orphan_check",
 313                         i.span,
 314                         "the new orphan check rules will eventually be strictly enforced");
 315                 }
 316
 317                 for item in items.iter() {
 318                     match *item {
 319                         ast::MethodImplItem(_) => {}
 320                         ast::TypeImplItem(ref typedef) => {
 321                             self.gate_feature("associated_types",
 322                                               typedef.span,
 323                                               "associated types are \
 324                                                experimental")
 325                         }
 326                     }
 327                 }
 328             }
 329
 330             _ => {}
 331         }
 332
 333         visit::walk_item(self, i);
 334     }
 335
 336     fn visit_foreign_item(&mut self, i: &ast::ForeignItem) {
 337         if attr::contains_name(i.attrs[], "linkage") {
 338             self.gate_feature("linkage", i.span,
 339                               "the `linkage` attribute is experimental \
 340                                and not portable across platforms")
 341         }
 342
 343         let links_to_llvm = match attr::first_attr_value_str_by_name(i.attrs[], "link_name") {
 344             Some(val) => val.get().starts_with("llvm."),
 345             _ => false
 346         };
 347         if links_to_llvm {
 348             self.gate_feature("link_llvm_intrinsics", i.span,
 349                               "linking to LLVM intrinsics is experimental");
 350         }
 351
 352         visit::walk_foreign_item(self, i)
 353     }
 354
 355     fn visit_ty(&mut self, t: &ast::Ty) {
 356         visit::walk_ty(self, t);
 357     }
 358
 359     fn visit_expr(&mut self, e: &ast::Expr) {
 360         match e.node {
 361             ast::ExprRange(..) => {
 362                 self.gate_feature("slicing_syntax",
 363                                   e.span,
 364                                   "range syntax is experimental");
 365             }
 366             _ => {}
 367         }
 368         visit::walk_expr(self, e);
 369     }
 370
 371     fn visit_attribute(&mut self, attr: &ast::Attribute) {
 372         if attr::contains_name(slice::ref_slice(attr), "lang") {
 373             self.gate_feature("lang_items",
 374                               attr.span,
 375                               "language items are subject to change");
 376         }
 377     }
 378
 379     fn visit_pat(&mut self, pattern: &ast::Pat) {
 380         match pattern.node {
 381             ast::PatVec(_, Some(_), ref last) if !last.is_empty() => {
 382                 self.gate_feature("advanced_slice_patterns",
 383                                   pattern.span,
 384                                   "multiple-element slice matches anywhere \
 385                                    but at the end of a slice (e.g. \
 386                                    `[0, ..xs, 0]` are experimental")
 387             }
 388             _ => {}
 389         }
 390         visit::walk_pat(self, pattern)
 391     }
 392
 393     fn visit_fn(&mut self,
 394                 fn_kind: visit::FnKind<'v>,
 395                 fn_decl: &'v ast::FnDecl,
 396                 block: &'v ast::Block,
 397                 span: Span,
 398                 _node_id: NodeId) {
 399         match fn_kind {
 400             visit::FkItemFn(_, _, _, abi) if abi == RustIntrinsic => {
 401                 self.gate_feature("intrinsics",
 402                                   span,
 403                                   "intrinsics are subject to change")
 404             }
 405             _ => {}
 406         }
 407         visit::walk_fn(self, fn_kind, fn_decl, block, span);
 408     }
 409 }
 410
 411 fn check_crate_inner<F>(cm: &CodeMap, span_handler: &SpanHandler, krate: &ast::Crate,
 412                         check: F)
 413                        -> (Features, Vec<Span>)
 414     where F: FnOnce(&mut Context, &ast::Crate)
 415 {
 416     let mut cx = Context {
 417         features: Vec::new(),
 418         span_handler: span_handler,
 419         cm: cm,
 420     };
 421
 422     let mut unknown_features = Vec::new();
 423
 424     for attr in krate.attrs.iter() {
 425         if !attr.check_name("feature") {
 426             continue
 427         }
 428
 429         match attr.meta_item_list() {
 430             None => {
 431                 span_handler.span_err(attr.span, "malformed feature attribute, \
 432                                                   expected #![feature(...)]");
 433             }
 434             Some(list) => {
 435                 for mi in list.iter() {
 436                     let name = match mi.node {
 437                         ast::MetaWord(ref word) => (*word).clone(),
 438                         _ => {
 439                             span_handler.span_err(mi.span,
 440                                                   "malformed feature, expected just \
 441                                                    one word");
 442                             continue
 443                         }
 444                     };
 445                     match KNOWN_FEATURES.iter()
 446                                         .find(|& &(n, _)| name == n) {
 447                         Some(&(name, Active)) => {
 448                             cx.features.push(name);
 449                         }
 450                         Some(&(name, Deprecated)) => {
 451                             cx.features.push(name);
 452                             span_handler.span_warn(
 453                                 mi.span,
 454                                 "feature is deprecated and will only be available \
 455                                  for a limited time, please rewrite code that relies on it");
 456                         }
 457                         Some(&(_, Removed)) => {
 458                             span_handler.span_err(mi.span, "feature has been removed");
 459                         }
 460                         Some(&(_, Accepted)) => {
 461                             span_handler.span_warn(mi.span, "feature has been added to Rust, \
 462                                                              directive not necessary");
 463                         }
 464                         None => {
 465                             unknown_features.push(mi.span);
 466                         }
 467                     }
 468                 }
 469             }
 470         }
 471     }
 472
 473     check(&mut cx, krate);
 474
 475     (Features {
 476         unboxed_closures: cx.has_feature("unboxed_closures"),
 477         rustc_diagnostic_macros: cx.has_feature("rustc_diagnostic_macros"),
 478         import_shadowing: cx.has_feature("import_shadowing"),
 479         visible_private_types: cx.has_feature("visible_private_types"),
 480         quote: cx.has_feature("quote"),
 481         opt_out_copy: cx.has_feature("opt_out_copy"),
 482         old_orphan_check: cx.has_feature("old_orphan_check"),
 483     },
 484     unknown_features)
 485 }
 486
 487 pub fn check_crate_macros(cm: &CodeMap, span_handler: &SpanHandler, krate: &ast::Crate)
 488 -> (Features, Vec<Span>) {
 489     check_crate_inner(cm, span_handler, krate,
 490                       |ctx, krate| visit::walk_crate(&mut MacroVisitor { context: ctx }, krate))
 491 }
 492
 493 pub fn check_crate(cm: &CodeMap, span_handler: &SpanHandler, krate: &ast::Crate)
 494 -> (Features, Vec<Span>) {
 495     check_crate_inner(cm, span_handler, krate,
 496                       |ctx, krate| visit::walk_crate(&mut PostExpansionVisitor { context: ctx },
 497                                                      krate))
 498 }