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.
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.
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
18 //! Features are enabled in programs via the crate-level attributes of
19 //! `#![feature(...)]` with a comma-separated list of features.
23 use syntax::abi::RustIntrinsic;
24 use syntax::ast::NodeId;
27 use syntax::attr::AttrMetaMethods;
28 use syntax::codemap::Span;
30 use syntax::visit::Visitor;
31 use syntax::parse::token;
33 use driver::session::Session;
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)] = &[
42 ("macro_rules", Active),
43 ("struct_variant", Active),
46 ("managed_boxes", Active),
47 ("non_ascii_idents", Active),
48 ("thread_local", Active),
49 ("link_args", 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),
60 ("default_type_params", Active),
63 ("struct_inherit", Active),
64 ("overloaded_calls", Active),
65 ("unboxed_closure_sugar", Active),
67 ("quad_precision_float", Removed),
69 ("rustc_diagnostic_macros", Active),
70 ("unboxed_closures", Active),
71 ("import_shadowing", Active),
72 ("advanced_slice_patterns", Active),
73 ("tuple_indexing", Active),
75 // if you change this list without updating src/doc/rust.md, cmr will be sad
77 // A temporary feature gate used to enable parser extensions needed
78 // to bootstrap fix for #5723.
79 ("issue_5723_bootstrap", Accepted),
81 // These are used to test this portion of the compiler, they don't actually
83 ("test_accepted_feature", Accepted),
84 ("test_removed_feature", Removed),
88 /// Represents an active feature that is currently being implemented or
89 /// currently being considered for addition/removal.
92 /// Represents a feature which has since been removed (it was once Active)
95 /// This language feature has since been Accepted (it was once Active)
99 /// A set of features to be used by later passes.
100 pub struct Features {
101 pub default_type_params: Cell<bool>,
102 pub overloaded_calls: Cell<bool>,
103 pub rustc_diagnostic_macros: Cell<bool>,
104 pub import_shadowing: Cell<bool>,
108 pub fn new() -> Features {
110 default_type_params: Cell::new(false),
111 overloaded_calls: Cell::new(false),
112 rustc_diagnostic_macros: Cell::new(false),
113 import_shadowing: Cell::new(false),
119 features: Vec<&'static str>,
123 impl<'a> Context<'a> {
124 fn gate_feature(&self, feature: &str, span: Span, explain: &str) {
125 if !self.has_feature(feature) {
126 self.sess.span_err(span, explain);
127 self.sess.span_note(span, format!("add #![feature({})] to the \
128 crate attributes to enable",
129 feature).as_slice());
133 fn gate_box(&self, span: Span) {
134 self.gate_feature("managed_boxes", span,
135 "The managed box syntax is being replaced by the \
136 `std::gc::Gc` and `std::rc::Rc` types. Equivalent \
137 functionality to managed trait objects will be \
138 implemented but is currently missing.");
141 fn has_feature(&self, feature: &str) -> bool {
142 self.features.iter().any(|n| n.as_slice() == feature)
146 impl<'a, 'v> Visitor<'v> for Context<'a> {
147 fn visit_ident(&mut self, sp: Span, id: ast::Ident) {
148 if !token::get_ident(id).get().is_ascii() {
149 self.gate_feature("non_ascii_idents", sp,
150 "non-ascii idents are not fully supported.");
154 fn visit_view_item(&mut self, i: &ast::ViewItem) {
156 ast::ViewItemUse(ref path) => {
158 ast::ViewPathGlob(..) => {
159 self.gate_feature("globs", path.span,
160 "glob import statements are \
161 experimental and possibly buggy");
166 ast::ViewItemExternCrate(..) => {
167 for attr in i.attrs.iter() {
168 if attr.name().get() == "phase"{
169 self.gate_feature("phase", attr.span,
170 "compile time crate loading is \
171 experimental and possibly buggy");
176 visit::walk_view_item(self, i)
179 fn visit_item(&mut self, i: &ast::Item) {
180 for attr in i.attrs.iter() {
181 if attr.name().equiv(&("thread_local")) {
182 self.gate_feature("thread_local", i.span,
183 "`#[thread_local]` is an experimental feature, and does not \
184 currently handle destructors. There is no corresponding \
185 `#[task_local]` mapping to the task model");
189 ast::ItemEnum(ref def, _) => {
190 for variant in def.variants.iter() {
191 match variant.node.kind {
192 ast::StructVariantKind(..) => {
193 self.gate_feature("struct_variant", variant.span,
194 "enum struct variants are \
195 experimental and possibly buggy");
202 ast::ItemForeignMod(ref foreign_module) => {
203 if attr::contains_name(i.attrs.as_slice(), "link_args") {
204 self.gate_feature("link_args", i.span,
205 "the `link_args` attribute is not portable \
206 across platforms, it is recommended to \
207 use `#[link(name = \"foo\")]` instead")
209 if foreign_module.abi == RustIntrinsic {
210 self.gate_feature("intrinsics",
212 "intrinsics are subject to change")
217 if attr::contains_name(i.attrs.as_slice(), "plugin_registrar") {
218 self.gate_feature("plugin_registrar", i.span,
219 "compiler plugins are experimental and possibly buggy");
223 ast::ItemStruct(struct_definition, _) => {
224 if attr::contains_name(i.attrs.as_slice(), "simd") {
225 self.gate_feature("simd", i.span,
226 "SIMD types are experimental and possibly buggy");
228 match struct_definition.super_struct {
229 Some(ref path) => self.gate_feature("struct_inherit", path.span,
230 "struct inheritance is experimental \
231 and possibly buggy"),
234 if struct_definition.is_virtual {
235 self.gate_feature("struct_inherit", i.span,
236 "struct inheritance (`virtual` keyword) is \
237 experimental and possibly buggy");
241 ast::ItemImpl(..) => {
242 if attr::contains_name(i.attrs.as_slice(),
243 "unsafe_destructor") {
244 self.gate_feature("unsafe_destructor",
246 "`#[unsafe_destructor]` allows too \
247 many unsafe patterns and may be \
248 removed in the future");
255 visit::walk_item(self, i);
258 fn visit_mac(&mut self, macro: &ast::Mac) {
259 let ast::MacInvocTT(ref path, _, _) = macro.node;
260 let id = path.segments.last().unwrap().identifier;
261 let quotes = ["quote_tokens", "quote_expr", "quote_ty",
262 "quote_item", "quote_pat", "quote_stmt"];
263 let msg = " is not stable enough for use and are subject to change";
266 if id == token::str_to_ident("macro_rules") {
267 self.gate_feature("macro_rules", path.span, "macro definitions are \
268 not stable enough for use and are subject to change");
271 else if id == token::str_to_ident("asm") {
272 self.gate_feature("asm", path.span, "inline assembly is not \
273 stable enough for use and is subject to change");
276 else if id == token::str_to_ident("log_syntax") {
277 self.gate_feature("log_syntax", path.span, "`log_syntax!` is not \
278 stable enough for use and is subject to change");
281 else if id == token::str_to_ident("trace_macros") {
282 self.gate_feature("trace_macros", path.span, "`trace_macros` is not \
283 stable enough for use and is subject to change");
286 else if id == token::str_to_ident("concat_idents") {
287 self.gate_feature("concat_idents", path.span, "`concat_idents` is not \
288 stable enough for use and is subject to change");
292 for "e in quotes.iter() {
293 if id == token::str_to_ident(quote) {
294 self.gate_feature("quote",
296 format!("{}{}", quote, msg).as_slice());
302 fn visit_foreign_item(&mut self, i: &ast::ForeignItem) {
303 if attr::contains_name(i.attrs.as_slice(), "linkage") {
304 self.gate_feature("linkage", i.span,
305 "the `linkage` attribute is experimental \
306 and not portable across platforms")
308 visit::walk_foreign_item(self, i)
311 fn visit_ty(&mut self, t: &ast::Ty) {
313 ast::TyClosure(closure) if closure.onceness == ast::Once => {
314 self.gate_feature("once_fns", t.span,
315 "once functions are \
316 experimental and likely to be removed");
319 ast::TyBox(_) => { self.gate_box(t.span); }
320 ast::TyUnboxedFn(..) => {
321 self.gate_feature("unboxed_closure_sugar",
323 "unboxed closure trait sugar is experimental");
328 visit::walk_ty(self, t);
331 fn visit_expr(&mut self, e: &ast::Expr) {
333 ast::ExprUnary(ast::UnBox, _) => {
334 self.gate_box(e.span);
336 ast::ExprUnboxedFn(..) => {
337 self.gate_feature("unboxed_closures",
339 "unboxed closures are a work-in-progress \
340 feature with known bugs");
342 ast::ExprTupField(..) => {
343 self.gate_feature("tuple_indexing",
345 "tuple indexing is experimental");
349 visit::walk_expr(self, e);
352 fn visit_generics(&mut self, generics: &ast::Generics) {
353 for type_parameter in generics.ty_params.iter() {
354 match type_parameter.default {
356 self.gate_feature("default_type_params", ty.span,
357 "default type parameters are \
358 experimental and possibly buggy");
363 visit::walk_generics(self, generics);
366 fn visit_attribute(&mut self, attr: &ast::Attribute) {
367 if attr::contains_name([*attr], "lang") {
368 self.gate_feature("lang_items",
370 "language items are subject to change");
374 fn visit_pat(&mut self, pattern: &ast::Pat) {
376 ast::PatVec(_, Some(_), ref last) if !last.is_empty() => {
377 self.gate_feature("advanced_slice_patterns",
379 "multiple-element slice matches anywhere \
380 but at the end of a slice (e.g. \
381 `[0, ..xs, 0]` are experimental")
385 visit::walk_pat(self, pattern)
388 fn visit_fn(&mut self,
389 fn_kind: visit::FnKind<'v>,
390 fn_decl: &'v ast::FnDecl,
391 block: &'v ast::Block,
395 visit::FkItemFn(_, _, _, abi) if abi == RustIntrinsic => {
396 self.gate_feature("intrinsics",
398 "intrinsics are subject to change")
402 visit::walk_fn(self, fn_kind, fn_decl, block, span);
406 pub fn check_crate(sess: &Session, krate: &ast::Crate) {
407 let mut cx = Context {
408 features: Vec::new(),
412 for attr in krate.attrs.iter() {
413 if !attr.check_name("feature") {
417 match attr.meta_item_list() {
419 sess.span_err(attr.span, "malformed feature attribute, \
420 expected #![feature(...)]");
423 for &mi in list.iter() {
424 let name = match mi.node {
425 ast::MetaWord(ref word) => (*word).clone(),
427 sess.span_err(mi.span,
428 "malformed feature, expected just \
433 match KNOWN_FEATURES.iter()
434 .find(|& &(n, _)| name.equiv(&n)) {
435 Some(&(name, Active)) => { cx.features.push(name); }
436 Some(&(_, Removed)) => {
437 sess.span_err(mi.span, "feature has been removed");
439 Some(&(_, Accepted)) => {
440 sess.span_warn(mi.span, "feature has been added to Rust, \
441 directive not necessary");
444 sess.add_lint(lint::builtin::UNKNOWN_FEATURES,
447 "unknown feature".to_string());
455 visit::walk_crate(&mut cx, krate);
457 sess.abort_if_errors();
459 sess.features.default_type_params.set(cx.has_feature("default_type_params"));
460 sess.features.overloaded_calls.set(cx.has_feature("overloaded_calls"));
461 sess.features.rustc_diagnostic_macros.set(cx.has_feature("rustc_diagnostic_macros"));
462 sess.features.import_shadowing.set(cx.has_feature("import_shadowing"));