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.
25 use syntax::attr::AttrMetaMethods;
26 use syntax::codemap::Span;
28 use syntax::visit::Visitor;
29 use syntax::parse::token;
31 use driver::session::Session;
35 /// This is a list of all known features since the beginning of time. This list
36 /// can never shrink, it may only be expanded (in order to prevent old programs
37 /// from failing to compile). The status of each feature may change, however.
38 static KNOWN_FEATURES: &'static [(&'static str, Status)] = &[
40 ("macro_rules", Active),
41 ("struct_variant", Active),
44 ("managed_boxes", Active),
45 ("non_ascii_idents", Active),
46 ("thread_local", Active),
47 ("link_args", Active),
49 ("plugin_registrar", Active),
50 ("log_syntax", Active),
51 ("trace_macros", Active),
52 ("concat_idents", Active),
53 ("unsafe_destructor", Active),
56 ("default_type_params", Active),
59 ("struct_inherit", Active),
60 ("overloaded_calls", Active),
61 ("unboxed_closure_sugar", Active),
63 ("quad_precision_float", Active),
65 // A temporary feature gate used to enable parser extensions needed
66 // to bootstrap fix for #5723.
67 ("issue_5723_bootstrap", Active),
69 // These are used to test this portion of the compiler, they don't actually
71 ("test_accepted_feature", Accepted),
72 ("test_removed_feature", Removed),
76 /// Represents an active feature that is currently being implemented or
77 /// currently being considered for addition/removal.
80 /// Represents a feature which has since been removed (it was once Active)
83 /// This language feature has since been Accepted (it was once Active)
87 /// A set of features to be used by later passes.
89 pub default_type_params: Cell<bool>,
90 pub quad_precision_float: Cell<bool>,
91 pub issue_5723_bootstrap: Cell<bool>,
92 pub overloaded_calls: Cell<bool>,
96 pub fn new() -> Features {
98 default_type_params: Cell::new(false),
99 quad_precision_float: Cell::new(false),
100 issue_5723_bootstrap: Cell::new(false),
101 overloaded_calls: Cell::new(false),
107 features: Vec<&'static str>,
111 impl<'a> Context<'a> {
112 fn gate_feature(&self, feature: &str, span: Span, explain: &str) {
113 if !self.has_feature(feature) {
114 self.sess.span_err(span, explain);
115 self.sess.span_note(span, format!("add #![feature({})] to the \
116 crate attributes to enable",
117 feature).as_slice());
121 fn gate_box(&self, span: Span) {
122 self.gate_feature("managed_boxes", span,
123 "The managed box syntax is being replaced by the \
124 `std::gc::Gc` and `std::rc::Rc` types. Equivalent \
125 functionality to managed trait objects will be \
126 implemented but is currently missing.");
129 fn has_feature(&self, feature: &str) -> bool {
130 self.features.iter().any(|n| n.as_slice() == feature)
134 impl<'a> Visitor<()> for Context<'a> {
135 fn visit_ident(&mut self, sp: Span, id: ast::Ident, _: ()) {
136 if !token::get_ident(id).get().is_ascii() {
137 self.gate_feature("non_ascii_idents", sp,
138 "non-ascii idents are not fully supported.");
142 fn visit_view_item(&mut self, i: &ast::ViewItem, _: ()) {
144 ast::ViewItemUse(ref path) => {
146 ast::ViewPathGlob(..) => {
147 self.gate_feature("globs", path.span,
148 "glob import statements are \
149 experimental and possibly buggy");
154 ast::ViewItemExternCrate(..) => {
155 for attr in i.attrs.iter() {
156 if attr.name().get() == "phase"{
157 self.gate_feature("phase", attr.span,
158 "compile time crate loading is \
159 experimental and possibly buggy");
164 visit::walk_view_item(self, i, ())
167 fn visit_item(&mut self, i: &ast::Item, _:()) {
168 for attr in i.attrs.iter() {
169 if attr.name().equiv(&("thread_local")) {
170 self.gate_feature("thread_local", i.span,
171 "`#[thread_local]` is an experimental feature, and does not \
172 currently handle destructors. There is no corresponding \
173 `#[task_local]` mapping to the task model");
177 ast::ItemEnum(ref def, _) => {
178 for variant in def.variants.iter() {
179 match variant.node.kind {
180 ast::StructVariantKind(..) => {
181 self.gate_feature("struct_variant", variant.span,
182 "enum struct variants are \
183 experimental and possibly buggy");
190 ast::ItemForeignMod(..) => {
191 if attr::contains_name(i.attrs.as_slice(), "link_args") {
192 self.gate_feature("link_args", i.span,
193 "the `link_args` attribute is not portable \
194 across platforms, it is recommended to \
195 use `#[link(name = \"foo\")]` instead")
200 if attr::contains_name(i.attrs.as_slice(), "plugin_registrar") {
201 self.gate_feature("plugin_registrar", i.span,
202 "compiler plugins are experimental and possibly buggy");
206 ast::ItemStruct(struct_definition, _) => {
207 if attr::contains_name(i.attrs.as_slice(), "simd") {
208 self.gate_feature("simd", i.span,
209 "SIMD types are experimental and possibly buggy");
211 match struct_definition.super_struct {
212 Some(ref path) => self.gate_feature("struct_inherit", path.span,
213 "struct inheritance is experimental \
214 and possibly buggy"),
217 if struct_definition.is_virtual {
218 self.gate_feature("struct_inherit", i.span,
219 "struct inheritance (`virtual` keyword) is \
220 experimental and possibly buggy");
224 ast::ItemImpl(..) => {
225 if attr::contains_name(i.attrs.as_slice(),
226 "unsafe_destructor") {
227 self.gate_feature("unsafe_destructor",
229 "`#[unsafe_destructor]` allows too \
230 many unsafe patterns and may be \
231 removed in the future");
238 visit::walk_item(self, i, ());
241 fn visit_mac(&mut self, macro: &ast::Mac, _: ()) {
242 let ast::MacInvocTT(ref path, _, _) = macro.node;
243 let id = path.segments.last().unwrap().identifier;
244 let quotes = ["quote_tokens", "quote_expr", "quote_ty",
245 "quote_item", "quote_pat", "quote_stmt"];
246 let msg = " is not stable enough for use and are subject to change";
249 if id == token::str_to_ident("macro_rules") {
250 self.gate_feature("macro_rules", path.span, "macro definitions are \
251 not stable enough for use and are subject to change");
254 else if id == token::str_to_ident("asm") {
255 self.gate_feature("asm", path.span, "inline assembly is not \
256 stable enough for use and is subject to change");
259 else if id == token::str_to_ident("log_syntax") {
260 self.gate_feature("log_syntax", path.span, "`log_syntax!` is not \
261 stable enough for use and is subject to change");
264 else if id == token::str_to_ident("trace_macros") {
265 self.gate_feature("trace_macros", path.span, "`trace_macros` is not \
266 stable enough for use and is subject to change");
269 else if id == token::str_to_ident("concat_idents") {
270 self.gate_feature("concat_idents", path.span, "`concat_idents` is not \
271 stable enough for use and is subject to change");
275 for "e in quotes.iter() {
276 if id == token::str_to_ident(quote) {
277 self.gate_feature("quote",
279 format!("{}{}", quote, msg).as_slice());
285 fn visit_foreign_item(&mut self, i: &ast::ForeignItem, _: ()) {
287 ast::ForeignItemFn(..) | ast::ForeignItemStatic(..) => {
288 if attr::contains_name(i.attrs.as_slice(), "linkage") {
289 self.gate_feature("linkage", i.span,
290 "the `linkage` attribute is experimental \
291 and not portable across platforms")
295 visit::walk_foreign_item(self, i, ())
298 fn visit_ty(&mut self, t: &ast::Ty, _: ()) {
300 ast::TyClosure(closure, _) if closure.onceness == ast::Once => {
301 self.gate_feature("once_fns", t.span,
302 "once functions are \
303 experimental and likely to be removed");
306 ast::TyBox(_) => { self.gate_box(t.span); }
307 ast::TyUnboxedFn(_) => {
308 self.gate_feature("unboxed_closure_sugar",
310 "unboxed closure trait sugar is experimental");
315 visit::walk_ty(self, t, ());
318 fn visit_expr(&mut self, e: &ast::Expr, _: ()) {
320 ast::ExprUnary(ast::UnBox, _) => {
321 self.gate_box(e.span);
325 visit::walk_expr(self, e, ());
328 fn visit_generics(&mut self, generics: &ast::Generics, _: ()) {
329 for type_parameter in generics.ty_params.iter() {
330 match type_parameter.default {
332 self.gate_feature("default_type_params", ty.span,
333 "default type parameters are \
334 experimental and possibly buggy");
339 visit::walk_generics(self, generics, ());
343 pub fn check_crate(sess: &Session, krate: &ast::Crate) {
344 let mut cx = Context {
345 features: Vec::new(),
349 for attr in krate.attrs.iter() {
350 if !attr.check_name("feature") {
354 match attr.meta_item_list() {
356 sess.span_err(attr.span, "malformed feature attribute, \
357 expected #![feature(...)]");
360 for &mi in list.iter() {
361 let name = match mi.node {
362 ast::MetaWord(ref word) => (*word).clone(),
364 sess.span_err(mi.span,
365 "malformed feature, expected just \
370 match KNOWN_FEATURES.iter()
371 .find(|& &(n, _)| name.equiv(&n)) {
372 Some(&(name, Active)) => { cx.features.push(name); }
373 Some(&(_, Removed)) => {
374 sess.span_err(mi.span, "feature has been removed");
376 Some(&(_, Accepted)) => {
377 sess.span_warn(mi.span, "feature has added to rust, \
378 directive not necessary");
381 sess.add_lint(lint::UnknownFeatures,
384 "unknown feature".to_string());
392 visit::walk_crate(&mut cx, krate, ());
394 sess.abort_if_errors();
396 sess.features.default_type_params.set(cx.has_feature("default_type_params"));
397 sess.features.quad_precision_float.set(cx.has_feature("quad_precision_float"));
398 sess.features.issue_5723_bootstrap.set(cx.has_feature("issue_5723_bootstrap"));
399 sess.features.overloaded_calls.set(cx.has_feature("overloaded_calls"));